A method of determining a content of an element

Abstract

A method of determining a content of an element by mass of a selected substance. The method comprises preparing a reference density calibration data-group and applying the reference density calibration data-group for determining the content of the element by mass of the selected substance. The preparation of the reference density calibration data-group comprises providing a number of primary reference samples from one or more primary reference substance(s) determining an NMR intensity of at least one reference isotope for each of the primary reference samples, and generating the reference density calibration data-group. The determination of the content of the element by mass of the selected substance comprises determining an NMR intensity of at least one sample isotope of the sample and a density of the sample, and based on the determined NMR intensity and density of the sample, determining a second parameter representing the content of the element by mass of the selected substance.

Description

[0001] A METHOD OF DETERMINING A CONTENT OF AN ELEMENT

[0002] TECHNICAL FIELD

[0003] The invention relates to a method of determining a content of an element by mass of a substance, for example a complex substance, such as a food product or a biorefinery product. The invention also relates to a computer-readable storage device for generating a reference density calibration data-group.

[0004] BACKGROUND ART

[0005] Substances, in particular complex substances comprising a plurality of different elements, such as fat and / or water and / or protein and / or nucleic acids and / or carbohydrates and / or vitamins and / or minerals and / or nutrients, are typically analysed in laboratory using expensive equipment, such as laser scanning confocal microscopy, Inductive Coupled Plasma (ICP), chromatography, mass spectrometry and immunoassays, and / or time consuming wet chemistry laboratory methods. Depending on the specific application, such method may meet desired accuracy of measurement, but it is not uncommon that compromises have to be made between accuracy and time / price of measurement. Content determination of elements in a substance is of interest across many industries. For example, in the food industry it is in many jurisdictions required by law to label the food item with a nutrition declaration, wherein the amounts of for example fat, saturated, carbohydrate, sugars, protein, and / or salt by mass of the substance must be included. In other industries, it may not be regulated by law, but may still be of interest to determine the amount of specific elements of a substance being processed to monitor specific parameters, access environmental impact, health impact, and quality of the processing. To an increasing extent, environmental and health impact parameters may be required and subject to legal restriction.

[0006] Content determinations of elements in a substance are very often performed using analytical methods involving chemical analysis techniques, such as wet chemistry. Such methods are usually cumbersome and time consuming and are often based on very small amounts of samples to make a determination e.g. because the analysis involves destructive tests. Therefore, such chemical analyses are often rather inaccurate. Knowing how variable products it may be difficult to ensure that such small sample size is actually representative of the product tested.

[0007] For example, a Kjeldahl analysis technique is often applied for determining protein content. The carbohydrate content may often be estimated by taking the total mass of a product and subtracting all the other components (fats, protein, water, ash, etc.).

[0008] The fat content may often be determined by a wet chemistry extraction process. The amount of atomic elements may often be determined using ICP spectroscopy.

[0009] There is a substantial need for alternative or improved methods for determining a content of an element of a substance and in particular a method that is very efficient and / or a method which is suitable for generating valuable information of a substance even for a complex substance having a complex composition.

[0010] DISCLOSURE OF THE INVENTION

[0011] An objective of the invention is to provide a method for characterising a selected substance by determining a content of an element in the selected substance to characterise the composition of the selected substance, which method is relatively fast and provide a determination with a desired high accuracy.

[0012] In an embodiment, it is an objective to provide a method for determining a content of an element by mass of the selected substance to provide valuable information about the composition of the selected substance wherein the method may be performed as a nondestructive method with a relatively low workload.

[0013] In an embodiment, it is an objective to provide a cost-efficient method for controlling a content of an element in a selected substance e.g. in a production process for producing the selected substance to provide the selected substance to have a selected content of an element.

[0014] In an embodiment, it is an objective to provide a computer-readable storage device having encoded instructions enabling a fast and effective determination of an element in the selected substance. These and other objects have been solved by the invention or embodiments thereof as defined in the claims and / or as described herein below.

[0015] It has been found that the invention or embodiments thereof have a number of additional advantages, which will be clear to the skilled person from the following description.

[0016] The inventors of the present invention have realized and enabled the use of NMR technique for providing a very attractive solution of the abovementioned objective. While being applicable at any field, the invention demonstrates capability of the method using low-field NMR sensor technology without demanding high-resolution (sub-ppm) NMR capabilities as typically used in high-field instrumentation.

[0017] The use of nuclear magnetic resonance (NMR) for performing chemical analysis of substances is well known.

[0018] In general, nuclear magnetic resonance (NMR) has shown to be an excellent non-invasive technique for performing quantitative and qualitative determinations of isotopes and elements containing such isotopes in small volumes of a substance.

[0019] The method of the invention comprises a method of determining a content of an element by mass of a selected substance.

[0020] The fact that the method of the invention may be applied for determining the content of an element of a selected substance by mass has been found to be highly beneficial since declaration of contents of elements often is required by users or by governments. For example, it is required to provide information of contents of certain elements in foodstuff produced or sold in EU.

[0021] The method of the invention has shown to be both fast and cost effective and in addition, the determination of the element by mass may be obtained with a desired high accuracy.

[0022] The method of the invention comprises preparing a reference density calibration data- group and applying the reference density calibration data-group for determining the content of the element by mass of the selected substance. In an embodiment, the method of the invention comprises preparing a reference density calibration data-group and applying the reference density calibration data-group for determining the density of the selected substance.

[0023] The preparation of the reference density calibration data-group comprises

[0024] • providing a number of primary reference samples from one or more primary reference substance(s)

[0025] • determining an NMR intensity of at least one reference isotope for each of the primary reference samples, and

[0026] • generating the reference density calibration data-group based on the determined NMR intensities for the at least one reference isotope.

[0027] The determination of the content of the element by mass of the selected substance comprises

[0028] • obtaining a sample of the selected substance comprising the element,

[0029] • determining an NMR intensity of at least one sample isotope of the sample,

[0030] • determining a density of the selected substance by correlating the determined NMR intensity of the at least one sample isotope of the sample to the reference density calibration data-group,

[0031] • determining a first parameter representing a content of the element by volume of the selected substance, and

[0032] • determining the content of an element by mass of the selected substance by converting the first parameter representing the content of the element by volume of the selected substance to a second parameter representing the content of the element by mass of the selected substance based on the determined density. The determining of the density of the selected substance and the determining of the first parameter may be performed in any order.

[0033] Each of the primary reference samples may have different known densities, and the number of primary reference samples is at least 2.

[0034] In an embodiment, the number of the primary reference samples is at least 4, such as at least 6. The number of primary reference samples may in principle be any number from 2 and higher. However, it has been found that even a relative low number of primary reference samples may be sufficient to ensure a relatively high accuracy of the determination of the content of the element by mass. Therefore, the number of the primary reference samples may conveniently be from 2 to 20, such as from 4 to 10.

[0035] The at least two primary reference samples, may be obtained from a common basic reference substance e.g. in the form of a dilution series, wherein the respective primary reference samples are diluted e.g. using demineralized water, to different content of basic reference substance, including one optional undiluted primary reference sample.

[0036] The reference density calibration data-group may comprise one or more reference datasets of the determined NMR intensity and the known density of each of the respective primary reference samples. Each of the respective primary reference samples may conveniently be applied for generating one of the reference datasets, wherein this reference dataset comprises an NMR intensity e.g. obtained as a derivative, such as an average of one or more determined NMR intensities from a plurality of NMR readings the known density of the primary reference sample.

[0037] The inventors have found that the method of the invention provides a very effective tool for characterising a selected substance by determining the content of one or more elements in the selected substance using NMR intensity data. Especially, it has been found that there is a correlation between the NMR intensity of one or more selected isotopes related to an element in a selected substance and the density of the selected substance, which can be used to determine the content by mass of the element in the selected substance. Thus, the method may provide a very detailed analysis of the selected substance, which may be demonstrated, embedded in or even directly revealed by the content determination(s). Thus, in an embodiment the method may even provide determinations of the content(s) of one or more elements providing a unique characteristic, such as a biometric equivalent or analogous characteristic of the substance, such as fingerprint characteristic of the selected substance.

[0038] The fingerprint characteristic may advantageously encompass content by mass of one or more elements and / or the combination of elements of the selected substance that may contribute to an overall identification and / or quality of the substance.

[0039] In an embodiment, the fingerprint characteristic comprises a characteristic comprising content by mass of salt; trace elements, such as Iron (Fe), Zinc (Zn), Copper (Cu), Manganese (Mn), Iodine (I), Selenium (Se), Fluoride (F), Molybdenum (Mo) and / or Chromium (Cr); vitamins, such as Vitamin A (Retinol, Beta-carotene), Vitamin D (Calciferol), Vitamin E (Tocopherols and Tocotrienols), Vitamin K (Phylloquinone, Menaquinones), Vitamin B1 (Thiamine), Vitamin B2 (Riboflavin), Vitamin B3 (Niacin), Vitamin B5 (Pantothenic Acid), Vitamin B6 (Pyridoxine), Vitamin B7 (Biotin), Vitamin B9 (Folate, Folic Acid), Vitamin B12 (Cobalamin) and / or Vitamin C (Ascorbic Acid); phytonutrients and / or antioxidants, such as Flavonoids, Carotenoids, Polyphenols, Anthocyanins, Lignans and / or Glucosinolates; other micronutrients, such as Choline, Inositol, Carnitine and / or Taurine; and / or electrolytes, such as Potassium (K), Magnesium (Mg), Calcium (Ca) and / or Phosphorus (P).

[0040] In an embodiment, the fingerprint characteristic comprises a characteristic comprising content by mass of at least 1 wt. % of the selected substance, such as at least 10 wt. %, such as at least 25 wt. %, such as at least 50 wt. %, such as least 90 wt. % of the content of the selected substance, such as comprising a content by mass of at least 99 wt. % of the selected substance.

[0041] The method of the invention thereby provides a highly valuable tool for examining selected substances, e.g. for comparing with production or laboratory standards with a known composition, e.g. for determining if a quality parameter is fulfilled, such as a specific content of an element, e.g. for determining a composition of a selected substance, such as to provide information for labelling.

[0042] Thus, the method of the invention has been found to provide a valuable tool for use in productions for example for controlling a quality parameter of a raw material, a precursor material, and / or a produced material, such as a food selected substance for example as a part of a process control.

[0043] Thus, the method of the invention has been found to provide a valuable tool for use in productions for example for evaluating a composition of a selected substance by determining the content of the composition by mass of the selected substance.

[0044] The term “selected substance” means herein the substance, which is selected to be analysed by an embodiment of the method according to the invention by determining the content of at least one element.

[0045] The term “element” is herein used to mean any component or group of components of the selected substance. Examples of components and group of components comprises one or more nutrients, one or more chemical elements and / or one or more additives, such as content of fat, content of carbohydrate, content of protein, content of salt and / or content of one or more additives.

[0046] In an embodiment, the method comprises determining an element selected from salt; trace elements, such as Iron (Fe), Zinc (Zn), Copper (Cu), Manganese (Mn), Iodine (I), Selenium (Se), Fluoride (F), Molybdenum (Mo) and / or Chromium (Cr); vitamins, such as Vitamin A (Retinol, Beta-carotene), Vitamin D (Calciferol), Vitamin E (Tocopherols and Tocotrienols), Vitamin K (Phylloquinone, Menaquinones), Vitamin B1 (Thiamine), Vitamin B2 (Riboflavin), Vitamin B3 (Niacin), Vitamin B5 (Pantothenic Acid), Vitamin B6 (Pyridoxine), Vitamin B7 (Biotin), Vitamin B9 (Folate, Folic Acid), Vitamin B12 (Cobalamin) and / or Vitamin C (Ascorbic Acid); phytonutrients and / or antioxidants, such as Flavonoids, Carotenoids, Polyphenols, Anthocyanins, Lignans and / or Glucosinolates; other micronutrients, such as Choline, Inositol, Carnitine and / or Taurine; and / or electrolytes, such as Potassium (K), Magnesium (Mg), Calcium (Ca) and / or Phosphorus (P).

[0047] The term “wt. %” means herein percent in weight by weight of total unless otherwise specified.

[0048] The term “reference isotope” is herein used to mean an isotope present in the primary reference substance and / or the secondary reference substance for which the NMR intensity is determined. Thus, a reference isotope of a sample of the primary reference substance is a reference isotope for which the NMR intensity is determined of the sample of the primary reference substance and a reference isotope of a sample of the secondary reference substance is a reference isotope for which the NMR intensity is determined of the sample of the secondary reference substance. The reference isotope is present in the primary reference substance and / or the secondary reference substance, preferably in an amount of at least 0.001 mmol / kg, such as in an amount of at least 0.01 mmol / kg I, such as in an amount of at least 0.05 mmol / kg, such as in an amount of at least 0.1 mmol / kg, such as in an amount of at least 1 mmol / kg.

[0049] The term “sample isotope” is herein used to mean an isotope of the sample of the selected substance for which the NMR intensity is determined. The isotope should be an NMR detectable isotope, i.e., containing a nuclear spin. The terms “sample isotope” and “selected substance isotope” are used interchangeable.

[0050] The sample isotope is present in the selected substance and in the sample(s) thereof, preferably in an amount of at least 0.001 mmol / kg, such as in an amount of at least 0.01 mmol / kg I, such as in an amount of at least 0.05 mmol / kg, such as in an amount of at least 0.1 mmol / kg, such as in an amount of at least 1 mmol / kg. Advantageously, the sample isotope is an isotope of the element to be determined.

[0051] To ensure a very accurate determination of the density the at least one reference isotope and the at least one sample isotope comprises at least one identical isotope, such as any of the isotopes disclosed below.

[0052] The term “element isotope” is herein used to mean an isotope of the element of the sample of the selected substance or which the NMR intensity is determined.

[0053] The element isotope may be present in the selected substance and in the sample(s) thereof in any amount.

[0054] The term “primary reference substance(s)” is herein used to mean any substances having a composition that is representative for the selected substance. The primary reference substances may for example be representative for the selected substance, in that it comprises at least 25 wt. % of the components present in the selected substance, such as at least 50 wt. % of the components present in the selected substance, such as at least 90 wt. % of the components present in the selected substance. Advantageously, the primary reference substances comprise the element to be determined. The primary reference substances may comprise a group of primary reference substances, where all the primary reference substances are representative for the selected substance.

[0055] The primary reference substance may conveniently comprise a mass content of the element to be determined of 10 pg or more, such as 0.1 mg or more, such as 1 mg or more per 100 g of substance. In an embodiment, the primary reference substance comprises a mass content of the element to be determined, which may be as low as 0.001 wt.% or even lower, such as at least 0.01 wt. %, such as 0.1 wt. % of the mass content of the element to be determined of the selected substance.

[0056] It should be emphasized that the term “comprises / comprising” when used herein is to be interpreted as an open term, i.e. it should be taken to specify the presence of specifically stated feature(s), such as element(s), unit(s), integer(s), step(s), component(s), and combination(s) thereof, but does not preclude the presence or addition of one or more other features.

[0057] Throughout the description or claims, the singular encompasses the plural, and the plural encompasses the singular unless otherwise specified or required by the context.

[0058] The “an embodiment” should be interpreted to include examples of the invention comprising the feature(s) of the mentioned embodiment.

[0059] The term “substantially” should herein be taken to mean that ordinary product variances and tolerances are comprised. All features of the invention and embodiments of the invention as described herein, including ranges and preferred ranges, may be combined in various ways within the scope of the invention, unless there are specific reasons not to combine such features.

[0060] All features of the invention and embodiments of the invention as described herein including ranges and preferred ranges may be combined in various ways within the scope of the invention, unless there are specific reasons not to combine such features. Nuclear magnetic resonance (NMR) spectroscopy is a well-known analytical technique for structure elucidation of small and macromolecules for both quantitative and qualitative analysis.

[0061] When performing an NMR analysis, the analysis is usually performed on a given volume. Quantitative NMR analysis is therefore determined per volume unit.

[0062] Embodiments of the present invention provides an analysis tool that may result in a characterisation of a selected substance that may comprise several different elements and not merely a single element. Thus, the characterisation of the selected substance may be in the form of a content by mass of one or more elements in the selected substance and thereby a determination of a part of the composition or the entire composition of the selected substance.

[0063] In addition, it has been found that embodiments of the method of the present invention may be performed using a low-field NMR spectrometer.

[0064] It has been found that determinations of chemical shifts and distinguishing between isotopes in different environments e.g. isotopes bound in different molecules are not required.

[0065] Using a low-field spectrometer without chemical shift determinations has been found to be highly beneficial in the present invention in particular for cost reasons but also for obtaining a high accuracy of the content by mass of the element to be determined.

[0066] It is obviously cheaper to build magnets not being shimmed to high resolution, but there are also other practical issues: High-resolution typically requires a very good temperature control - as chemical shifts are highly temperature dependent. For permanent magnets the field moves if the temperature of the magnet changes. In addition, for production control flow measurements it is practically much easier to work without demand for chemical shift information. Another issue is that chemical shifts also are pH dependent, which mean that it may require samples be buffered to a particular pH.

[0067] A low-field NMR spectrometer is herein defined as an NMR spectrometer having a magnetic field homogeneity of at least 50 ppm, such as at least 100 ppm, such as at least 200 ppm. Preferably, the low-field NMR spectrometer has a magnetic field homogeneity of from 50 ppm to 150 ppm.

[0068] The magnetic field homogeneity is an indication for the uniformity of the magnetic field. A lower ppm value signifies that the variations or deviations in the magnetic field are smaller relative to the average field strength.

[0069] For many determinations, a high field homogeneity is crucial to ensure precise resonance frequencies. However, NMR spectrometers with a high homogeneity (high-field NMR spectrometers) are usually very expensive, requires large space, and are susceptible to environmental parameters such as room temperature, sample temperature, pH etc. In addition, such high field NMR spectrometers are very sensitive to mechanical disturbance and are not suitable for being movable.

[0070] Thus, it is highly beneficial that the method of the present invention may be performed using a low-field NMR spectrometer.

[0071] In an embodiment, the method comprises performing the NMR determinations of the respective isotopes using a low-field NMR spectrometer.

[0072] Preferably, the low-field NMR spectrometer comprises a permanent magnet generating the magnetic field. Advantageously, the low-field NMR spectrometer has a magnetic flux density of up to 2 Tesla, such as up to 1 Tesla, such as from about 0.1 to 3 Tesla, such as less than 1 Tesla, such as less than 0.8 Tesla, such as from 0.3 to 0.5 Tesla.

[0073] The low-field NMR spectrometer may advantageously be a movable NMR spectrometer, thereby measurements may be performed at any desired locations e.g. at any locations in a factory and not only as laboratory measurements.

[0074] By determining an NMR intensity of at least one sample isotope and / or element isotope(s) of the selected substance sample, one or more contents of a plurality of elements in the selected substance may be determined concurrently.

[0075] In an embodiment, the content determined by mass, is in the form of a mass fraction of the element of the selected substance, such as a mass percentage of the element in the selected substance. The phrases “content by mass” and “content by weight” are herein used interchangeable.

[0076] In an embodiment, the preparing of the reference density calibration data-group comprises fitting the reference datasets of the determined NMR intensity and the known density of the respective primary reference samples to a calibration curve, preferably a standard curve sometimes also referred to as a linear regression curve. It has been found that in some embodiments it may be favourable to fit the reference datasets of the determined NMR intensity and the known density of the respective primary reference samples to a calibration curve to obtain the reference density calibration data-group in the form of a linear or non-linear function describing a relationship between the density and the NMR intensity.

[0077] In an embodiment, the reference density calibration data-group is in the form of a linear function describing a linear relationship between the density and the determined NMR intensity.

[0078] In an embodiment, the reference density calibration data-group is in the form of a nonlinear function describing a polynomial and / or an exponential relationship between the density and the determined NMR intensity.

[0079] Where the measured isotope is bound in solid material and / or large molecules, it may be “invisible” for the NMR spectrometer. Thus, where the reference samples differ in solid mass and / or are digested to a different stage the reference density calibration data-group may conveniently be selected to comprise a non-linear function describing a polynomial and / or an exponential relationship between the density and the determined NMR intensity.

[0080] Where the reference density calibration data-group comprises a non-linear function describing a polynomial and / or an exponential relationship between the density and the determined NMR intensity, the number of primary reference samples and thereby the number of sets of the determined NMR intensity and the known density is conveniently 3 or more, preferably at least 8, such as at least 15.

[0081] The determining of the NMR intensity of the at least one sample isotope of the selected substance sample is conveniently a determination of the NMR intensity of the at least one sample isotope by volume. In the same way the determining of the NMR intensity of the at least one element isotope of the selected substance sample is conveniently a determination of the NMR intensity of the at least one sample isotope by volume.

[0082] In an embodiment, the determining of the first parameter comprises obtaining an NMR intensity of an element isotope, such as at least one element isotope of the sample of the selected substance. The element isotope may be identical to the sample isotope or different from the sample isotope. Thereby several different elements may be determined once the density of the selected substance has been determined using the reference density calibration data-group.

[0083] In an embodiment, where the element isotope is identical to the sample isotope, the obtaining of the NMR intensity of the element isotope of the sample of the selected substance may comprise obtaining the NMR intensity of the element isotope of the sample of the selected substance from a previously determined NMR intensity of the sample isotope of the sample of the selected substance. The NMR intensity of the sample isotope may for example be determined for the determination of the density of the selected substance, and then reused as NMR intensity of the element isotope for determining of the element content.

[0084] In an embodiment, the first parameter comprises the NMR intensity and / or the molar content of the element isotope by volume of the selected substance.

[0085] In an embodiment, the second parameter comprises the NMR intensity and / or the molar content of the element isotope by weight of the selected substance.

[0086] The content of the element may in as simple way be determined from the molar content of the element isotope.

[0087] In an embodiment, the first parameter is determined from the determination of the NMR intensity by volume of the selected substance. The first parameter comprises a content of the element by volume of the selected substance, such as a concentration of the element by volume. In an embodiment, the second parameter comprises the NMR intensity by weight of the selected substance.

[0088] In an embodiment, the content of the element by volume is determined by correlating the NMR intensity of the element isotope with a calibration parameter, preferably in the form of a NMR spectrometer calibration.

[0089] Preferably, an NMR spectrometer used for performing the NMR used for performing the NMR readings is calibrated with respect to one or more isotopes, preferably comprising the sample isotope(s), such that a specific NMR intensity relates to a known concentration of the sample isotope and / or a known concentration of the element by volume. Where the NMR intensity relates to a known concentration of the element isotope the concentration of the element may be determined by a correlation factor e.g. relating to the molar mass of the element and the element isotope.

[0090] In some embodiments, a calibration parameter may be relevant to correlate a specific NMR intensity to a concentration by volume. In an embodiment, the calibration parameter is based on a relationship between a known concentration of the element isotope and / element by volume and a corresponding NMR intensity of a specific isotope, such as an isotope of an atom present in the element.

[0091] In an embodiment, the method comprises performing at least one NMR reading to obtain the at least one NMR intensity of the at least one sample isotope, and generating a sample dataset comprising the at least one isotope intensity of each NMR reading.

[0092] In an embodiment, a plurality of NMR readings are performed of the at least one sample isotope is obtained and thereby a plurality of NMR intensities is obtained by the plurality of NMR readings.

[0093] The sample dataset preferably comprises the plurality of NMR intensities of said at least one sample isotope.

[0094] Advantageously, the at least one NMR reading comprises performing a plurality of NMR readings and preferably determining an average NMR intensity of the plurality of NMR intensities obtained by the plurality of NMR readings. Advantageously, the at least one sample isotope may be identical to the at least one reference isotope. In an embodiment, the at least one sample isotope comprises at least two different sample isotopes, wherein one of the two or more sample isotopes is identical to the at least one reference isotope.

[0095] In an embodiment, the sample dataset comprises the isotope intensities of each NMR reading of the at least one sample isotope, wherein at least one of the two or more sample isotopes is identical to the at least one reference isotope. In an embodiment, the sample dataset comprises an isotope intensity derived e.g. as an average from the isotope intensities of the NMR readings of the at least one sample isotope.

[0096] In an embodiment, the sample isotope and the element isotope are identical.

[0097] Preferably, the Isotope intensity or intensities in the sample dataset is / are associated with a concentration by volume of one or more elements in the selected substance.

[0098] In an embodiment, the NMR intensity of the at least one sample isotope, is determined by determining an average of the one or more NMR intensities in said sample dataset from the respective sample isotopes.

[0099] In an embodiment, the NMR intensity of the at least one element isotope, is determined by determining a derivative, such as an average of the one or more NMR intensities of the at least one element isotope.

[0100] In an embodiment, the density of the selected substance is determined based on the determined NMR intensity or intensities in said sample dataset.

[0101] In an embodiment, the method comprises determining an NMR intensity of each of at least two sample isotopes and / or element isotopes of the sample of the selected substance, wherein the NMR intensity of each of the at least one or at least two sample isotope(s) and / or each of the at least one or at least two element isotope(s) conveniently may be determined from a plurality of NMR intensities obtained by a plurality of NMR readings. In the same way the NMR intensity of the at least one reference isotope may conveniently be determined from a plurality of NMR intensities obtained by a plurality of NMR readings of the at least one reference isotope.

[0102] In an embodiment, a plurality of NMR readings is performed on each of at least two different sample isotopes by recording signals from one isotope during one or more of the delay periods of a recording from another isotope. This is herein referred to as interleaved NMR recording.

[0103] The providing of the number of reference samples may comprise providing at least one, preferably a plurality of the two or more primary reference samples to be subjected to a digestion, such as an enzymatic digestion. In the same way, the obtaining of the sample of the selected substance may conveniently comprise subjecting the sample to an enzymatic digestion.

[0104] The digesting may especially be suitable where the reference substance and / or selected substance and samples thereof comprises a substantial amount of large molecules and or where the isotope(s) for which the intensity is to be determined is bound in solid material.

[0105] Appropriate digestive enzymes comprise pepsin, trypsin, amylase, lipase and combinations thereof.

[0106] In an embodiment, the preparation of the liquid sample comprises digestion of proteins by enzymatic digestion or by chemical hydrolysis, optionally catalysed by acidic or alkaline conditions. After the digestion, the pH value may be adjusted if desired.

[0107] The digestion of protein is in particular desired where the selected material comprises large proteins, such as about 40.000 Dalton or larger or large quantities of other macromolecular species, such as carbohydrates. The protein digestion may increase the solubility or accessibility of the proteins, thereby increasing the accuracy.

[0108] The determining of the NMR intensities of the reference isotope(s), the sample isotope(s) and the element isotope(s) comprises measuring the NMR intensities may conveniently be performed using an NMR spectrometer, such as a low-field NMR spectrometer as described above comprising one or more NMR readings.

[0109] It has been found that the relaxation parameters of the isotopes may have influence if the measured NMR intensity. For each of at least one of the NMR intensities of at least one of the reference isotope(s), the sample isotope(s) and / or the element isotope(s) the method may therefore comprise determining at least one of the relaxation data T1 and / or T2 and compensating the measured NMR intensity with the T1 and / or T2 data.

[0110] It has been found, that where the repetition time (time between successive pulses) in an NMR reading may be too short to allow the magnetization to fully recover, leading to a lower signal intensity than the full intensity signal. Therefore, if the repetition time is shorter than Ti, the system may not reach equilibrium magnetization, resulting in partially saturated spins and reduced NMR signal intensity. For accurate determination of the NMR intensity, the repetition time is advantageously selected to be at least 5 times the longest Tl of the isotope being observed. Thus, if it is determined that the repetition time is shorter than Tl, the repetition time may conveniently be increased or the measured NMR intensity may be compensated, e.g. by a calibrated factor in dependence of the difference between the used repetition time and the determined Tl,

[0111] Short T2 times generally results in broader NMR lines and faster decay of the FID signal, which can decrease signal intensity and resolution. Molecules in solids or in highly concentrated environments have restricted motion, leading to more efficient dipole-dipole interactions and hence, a shorter T2 value.

[0112] Thus, where the T2 value is relative short, it may be beneficial to dilute the reference sample and / or primary sample analysed to increase the T2 value for obtaining a more accurate NMR intensity or to compensate the measured NMT intensity e.g. by a calibrated factor in dependence of the determined short T2 value.

[0113] In an embodiment, the determining of the NMR intensities of the reference isotope(s), the sample isotope(s) and the element isotope(s) comprises using the relaxation times T1 and / or T2 as filters to selectively observe particular isotopes or elements in a reference sample and / or a primary sample. This technique may be applied to enhance the detection of specific molecules based on their relaxation properties.

[0114] In an embodiment, the NMR intensity is measured using an inversion recovery experiment comprising applying a 180° pulse followed by a selected delay time and a 90° detection pulse. Different components of the sample analysed may have different T1 relaxation times, and by selecting the appropriate delay time, signals from components with certain T1 values may be suppressed while enhancing others. In an embodiment, the NMR intensity is measured using saturation recovery involving repeated application of pulses to saturate the spins followed by a selected recovery period. Components with different T 1 times will recover at different rates. By adjusting the selected recovery period, signals from specific components may be enhanced or suppressed based on their T1 relaxation times.

[0115] In an embodiment, the NMR intensity is measured using Spin Echo and CPMG Sequence. Spin echo sequences (Hahn echo) or Carr-Purcell-Meiboom-Gill (CPMG) sequences may be used to filter out components based on T2 relaxation times. In these sequences, the decay of the echo amplitude is dependent on T2 relaxation. By adjusting the echo time (TE) or the spacing between pulses in a CPMG sequence, signals from components with longer T2 times may be enhanced and signals with shorter T2 times may be suppressed, as the latter may dephase more rapidly and contribute less to the echo signal.

[0116] In an embodiment, the NMR intensity is measured using Relaxation-Edited Spectra. Relaxation-edited NMR techniques involve acquiring spectra with different relaxation delays and subtracting them to highlight components with specific T2characteristics. For instance, subtracting a spectrum with a short relaxation delay from one with a longer delay can reveal components with longer T2 times.

[0117] In an embodiment, the method comprises determining two or more first parameters, wherein each first parameter is based on the NMR intensities of a respective of the two or more sample isotopes. Advantageously, each first parameter determined based on the NMR intensities from the respective of the two or more sample isotopes may provide or represent a concentration by volume of the respective of each of two or more different elements of the selected substance.

[0118] Advantageously, the determining of the first parameter is performed by correlating the determined NMR intensity of the at least one element isotope to an element calibration data-group and / or to the fitted the element calibration data-group as further described below.

[0119] Examples of suitable isotopes for the at least one reference isotope and / or the at least one sample isotope and / or the at least one element isotope is selected from the group of isotopes comprising1H,10B,11B,13C,14N,15N,16O,19F23Na,27AI,29Si31P,33S,35CI,37CI,39K,41K,43Ca,47Ti,49Ti,50V,51V,53Cr,55Mn,57Fe,59Co,61Ni,63Cu,65Cu,67Zn,69Ga,71Ga,75As,77Se,79Br,81Br,83Kr,85Rb,87Rb,87Sr,89Y,91Zr,93Nb,95Mo,97Mo,105Pd,107Ag,109Ag,111Cd,113Cd,117Sn,119Sn,115Sn,121Sb,135Ba,137Ba177Pb,199Hg,201Hg,207Pb.

[0120] The at least one reference and / or sample isotope and / or element isotope applied is / are preferably selected to comprise one or more isotopes expected to be present in the selected substance, preferably, comprising one or more isotopes with a high presence in the substance. Examples of preferred isotopes comprise1H,2H,7Li,11B,14N,15N,23Na,31P,39K,41K,25Mg,19F,35CI,37CI,127l,13C or17O.

[0121] In an embodiment, the reference isotope is or comprises13C. In an embodiment, the sample isotope is or comprises23Na.

[0122] In an embodiment, the reference isotope is or comprises13C and the sample isotope is or comprises13C.

[0123] In an embodiment, the reference isotope is or comprises23Na and the sample isotope is or comprises23Na.

[0124] In an embodiment, the reference isotope is or comprises a first isotope and the sample isotope is or comprises a different isotope from the at least one reference isotope.

[0125] In an embodiment, the reference isotope is or comprises13C and the sample isotope is or comprises23Na.

[0126] In an embodiment it is preferred that the reference isotope is present in at least one of the at least two primary reference substance in a molar concentration, which differs less than 25% from a molar concentration of the sample isotope in the sample of the selected substance, such as in a molar concentration which differs less than 50%, such as less than 75 %, such as less than 90 %, such as less than 95 % from a molar concentration of the sample isotope in the sample of the selected substance.

[0127] In an embodiment it is preferred that the reference isotope is present in at least one of the at least two primary reference substance in a molar concentration, which is larger than a molar concentration of the sample isotope in the sample of the selected substance and that the reference isotope is present in at least one other of the at least two primary reference substance in a molar concentration, which is lower than a molar concentration of the sample isotope in the sample of the selected substance,

[0128] In an embodiment, the method comprises preparing two or more reference density calibration data-groups and herein the determining of the density of the selected substance may comprise correlating the determined NMR intensity of the at least one sample isotope of the sample to each of the two or more reference density calibration data-groups and obtaining for each correlation a preliminary density and deeming the average of the preliminary densities to be the density of the selected substance.

[0129] In an embodiment, the method comprises preparing an element calibration data-group comprises the following steps:

[0130] - providing a number of secondary reference element sample(s) based on at least one secondary reference substance, wherein the secondary reference substance comprises the element and wherein the number of the secondary reference sample(s) is at least 1. The secondary reference element sample(s) have / has known concentration(s) of the element. Where the number of secondary reference samples is 2 or more, the secondary reference samples may advantageously have different known concentrations of the element, and

[0131] - Determining a NMR intensity of at least one reference isotope for each of the reference element samples, and generating the element calibration data-group, wherein the element calibration data-group comprises one or more data sets of the determined NMR intensity and the known concentrations of the respective reference element samples.

[0132] The term “secondary reference substance” is used to mean any composition that is representative for the selected substance by comprising the element. The secondary reference substance may for example correspond to the selected substance, in that it comprises at least 25 wt. % of the components present in the selected substance, such as at least 50 wt. % of the components present in the selected substance, such as at least 90 wt. % of the components present in the selected substance. The secondary reference substance may be a group of reference substances, where all the secondary reference substances are representative for the selected substance by comprising the element.

[0133] The element calibration data-group may advantageously provide a calibration of the content of an element, which may especially be beneficial where the selected substance is a very complex substance, such as a very complex substance with many different elements and / or with many chemical interactions.

[0134] In an embodiment, the preparing of the element calibration data-group comprises fitting the element calibration data-group to a calibration curve, preferably a standard curve. The element calibration data-group may thereby be in the form of or comprising a fitted element calibration data-group.

[0135] In an embodiment, the one or more primary reference substance(s) comprises a plurality of primary reference substances, wherein each of the primary reference substances advantageously having a different density compared to each other.

[0136] In an embodiment, the one or more primary reference substance(s) comprises one or more primary reference substance(s) with at least 30 wt. % similarity between a composition of the respective primary reference substance and the selected substance, such as at least 50 wt. %, such as at least 75 wt. %.

[0137] In an embodiment, the step of providing a number of primary reference samples comprises preparing a number of primary reference samples by withdrawing samples from a first of the primary and preferably diluting said withdrawn samples to with different amounts of a solvent, such as water.

[0138] In an embodiment, the one or more secondary reference substance(s) comprises a plurality of secondary reference substances, wherein each of the secondary reference substances advantageously has a different concentration of the element compared to each other.

[0139] In an embodiment, the one or more secondary reference substance(s) comprises one or more secondary reference substance(s) with at least 30 wt. % similarity between a composition of the respective secondary reference substance and the selected substance, such as at least 50 wt. %, such as at least 75 wt. %.

[0140] The term “similarity” is herein used to mean a molecule content similarity relative to the molecule content of the selected substance.

[0141] In an embodiment, the step of providing a number of secondary reference samples comprises preparing a number of secondary reference samples by withdrawing samples from a first of the secondary reference samples and preferably diluting said withdrawn samples to with different amounts of a solvent, such as water.

[0142] In an embodiment, the method comprises correlating the second parameter to a target parameter, and identifying or determining a difference between the second parameter and the target parameter.

[0143] In an embodiment, the method comprises communicating the identified difference, e.g. to a display and / or by wire or wireless to an external computer, a tablet a smartphone or similar device.

[0144] In an embodiment, the target parameter comprises an NMR intensity by mass of the selected substance, an element density by mass of the selected substance, a target nutrient density by mass of the selected substance, and / or a target mass fraction of the selected substance.

[0145] In an embodiment, the selected substance is a food item. In an embodiment, the selected substance is a liquid, a paste, a semi-solid, or a solid.

[0146] The term “item” is used herein to mean any product independently of whether it has been processed or not.

[0147] In an embodiment, the selected substance and the primary reference substances are selected from a substance group, such as a substance group of food items.

[0148] In an embodiment, the substance group is a group of fruit, a group of vegetables, a group of seafood, a group of meat, a group of milk products and / or a group of fermented foods. It has been found that very accurate content by weight of the element may be determined where at least one, preferably a plurality of the two or more primary reference samples comprises a content of least one of fat, protein and / or carbohydrate, which is within the range of 50 wt.% to 150 wt.% of fat, protein and / or carbohydrate of the content of selected substance, such as within 75 wt.% to 125 wt.%, such as within 85 wt.% to 115 wt.%, such as within 95 wt.% to 105 wt.% of the content of selected substance.

[0149] Advantageously, at least one, preferably a plurality of the two or more primary reference samples comprises a solid content, which is within the range of 50 wt. % to 150 wt. % relative to the solid content of the content of selected substance, such as within 75 wt. % to 125 wt. %, such as within 85 wt. % to 115 wt. %, such as within 95 wt. % to 105 wt. % of the content of selected substance.

[0150] In an embodiment, the substance group comprises ready meals.

[0151] In an embodiment, the selected substance is an inorganic item. In an embodiment, the selected substance is an organic item.

[0152] In an embodiment, the element is nutrient, preferably a macronutrient and / or a micronutrient or an additive, such as salt.

[0153] In an embodiment, the element comprises one or more of fat, protein, carbohydrates, sugar and salt.

[0154] The invention also comprises a method of controlling such as quality controlling a selected substance by determining a content of an element of the selected substance. The method comprises determining the content of the element of the selected substance as detailed above, and comparing the determined content of the element to a selected range. Preferably, the selected range is selected based on one or more quality parameters or production requirements.

[0155] The invention also comprises a method for generating a primary reference density calibration data-group. The method comprises providing a number N of primary reference samples from one or more primary reference substance(s), wherein the primary reference samples have different known densities, and wherein the number N is at least 2, determining a NMR intensity of at least one reference isotope for each of the primary reference samples, and generating the reference density calibration data-group, wherein the reference density calibration data-group comprises reference datasets of the determined NMR intensity and the known density of the respective primary reference samples.

[0156] The term “primary reference substance(s)” is herein used to mean any substance having a composition that is representative for the selected substance. The primary reference substance(s) may for example be representative for the selected substance, in that it comprises at least 25 wt. % of the components present in the selected substance, such as at least 50 wt. % of the components present in the selected substance, such as at least 90 wt. % of the components present in the selected substance. Advantageously, the primary reference substance(s) comprises the element to be determined. The primary reference substance(s) may comprise a group of primary reference substances, where all the primary reference substances are representative for the selected substance.

[0157] In an embodiment, the primary and / or the secondary reference substance(s) is / are the same.

[0158] The invention also comprises a computer-readable storage device comprising executable encoded instructions thereon, wherein when executed by at least one processor, the computer-readable executable instructions cause the at least one processor to generate a reference density calibration data-group obtainable by the method as described above.

[0159] The computer-readable storage device may comprise encoded instructions thereon for determining the density of a sample of a selected substance by correlating a determined NMR intensity of the at least one reference isotope of the sample to the reference density calibration data-group.

[0160] The computer-readable storage device may comprise encoded instructions thereon for converting a first parameter representing a content of an element by volume of the selected substance to a second parameter representing a content of the element by mass of the selected substance. In an embodiment, the computer-readable storage device comprises encoded instructions thereon for determining a content of an element by mass according to a method of an embodiment of the invention as described above.

[0161] BRIEF DESCRIPTIONS OF EMBODIMENTS AND EXAMPLES

[0162] In the following, the invention will be further illustrated by the description of a number of illustrative and non-limiting embodiments and examples of the present invention, with reference to the appended drawings.

[0163] The figures are schematic, are not drawn to scale, and may be simplified for clarity. Throughout, the same reference numerals are used for identical or corresponding parts.

[0164] Figure 1 illustrates a calibration of density on two primary reference samples as obtained in example 1.

[0165] Figure 2 illustrates that the calibration in example 1 works for a plurality of primary reference substances as obtained in example 2.

[0166] Figure 3 illustrates that the method of the invention can be used to determine the content of salt per mass as obtained in example 3.

[0167] Figure 4 is a process diagram illustrating an embodiment of the method of the invention comprising generating a reference density calibration data-group.

[0168] Figure 5 is a process diagram illustrating an embodiment of the method of the invention comprising determining a content of an element by mass of a selected substance.

[0169] With reference to Figure 4, an embodiment of the method of the invention will now be detailed.

[0170] In step 20, a number N of primary reference samples from one or more primary reference substance(s) is provided, such as two primary reference samples as used in Example 1. The provided primary reference samples have different known densities. The primary reference substance may be as described above. In step 21 , NMR intensity of at least one reference isotope, for example one of the above described isotopes, is determined for each of the primary reference samples. In step 22, the reference density calibration data- group is generated. The reference density calibration data-group comprises reference datasets of the determined NMR intensity from step 21 and the known density of the respective primary reference sample.

[0171] The process diagram of Figure 4 illustrates an embodiment comprising generating a reference density calibration for determining a density of a selected substance.

[0172] With reference to Figure 5, one embodiment of the method of the invention will now be detailed.

[0173] The process comprises generating a reference density calibration data-group based on two or more primary reference substances and thereafter determining a first and second parameter of an element in a selected substance based on the reference density calibration data-group.

[0174] In step 30, a number of primary reference samples from one or more primary reference substance(s) is provided, such as two primary reference samples as used in Example 1. The provided primary reference samples have different known densities. The primary reference substance(s) may be as described above. In step 31 , NMR intensity of at least one reference isotope, for example one of the above-described isotopes, is determined for each of the primary reference samples. In step 32, the reference density calibration data- group is generated. The reference density calibration data-group comprises reference datasets of the determined NMR intensity from step 31 and the known density of the respective primary reference sample.

[0175] In step 33, a sample of the selected substance comprising the element is obtained. The selected substance may be as described above. In step 34, NMR intensity of at least one sample isotope of the sample, for example one of the above described isotopes, is determined. In step 35, a density of the selected substance is determined by correlating the determined NMR intensity from step 34 with the reference density calibration data- group from step 32. In step 36, a first parameter representing a content of the element by volume of the selected substance is determined. This first parameter may for example be a concentration measured in weight per volume. This first parameter may for example be an intensity per volume.

[0176] In step 37, the content of the element by mass of the selected substance is determined by converting the first parameter to a second parameter representing the content of the element by mass of the selected substance based on the determined density from step 35. This second parameter may for example be a content measure in weight per weight of the selected substance.

[0177] The process diagram in Figure 5 illustrates an embodiment for determining a content of an element by weight of the selected substance. The embodiment may for example be applied for determining a composition of a selected substance during a production, or may for example be applied for determining a composition of a food product, which then may be used for labelling.

[0178] EXAMPLE 1

[0179] Preparing of a reference density calibration data-group based on two primary reference samples

[0180] This example illustrates the use of NMR intensity data to preparing a reference density calibration data-group for determine the density of selected samples.

[0181] Two different commercial ketchup food products with different known densities were provided. A primary reference sample was taken from each of the tubes.

[0182] A portion of each of the primary reference samples was subject to an NMR analysis obtaining NMR intensity of the13C reference isotope.

[0183] The NMR intensity was obtained using a low-field NMR spectrometer in a standard calibrated state. Since the NMR spectrometer was calibrated, the NMR intensity output was proportional to total carbon content or the content of carbon of (a) specific type(s) such as in mobile constituents in the primary reference sample per volume (^). The obtained NMR intensity value for each of the primary reference samples was organised in reference datasets together with the known densities of the commercial ketchup food products as illustrated in the second and third column of the below Table 1.

[0184] The reference density calibration data-group in the form of a linear function was then obtained by fitting the NMR intensity values and the known density of the two primary reference samples to a linear regression model to obtain the coefficients m, c in p( ) = m ■ x + c, where x is the NMR intensity value.

[0185] The density of the two primary reference samples was also determined by dividing the NMR intensity with the identified coefficients m, c and a conversion factor to obtain the density in grams per millilitre, as illustrated in fourth column in Table 1.

[0186] Table 1

[0187] Figure 1 compares the values of the known density and the density determined by the calibration using the prepared reference density calibration data-group in this example, and the coefficient of determination, R2, approves that there is a true fit between the known and the determined density values. Thus, the procedure in Example 1 proves to be an effective procedure for determining a density of a sample based on NMR intensity.

[0188] EXAMPLE 2

[0189] Demonstration of determining density based on NMR using the reference density calibration data-group prepared in Example 1 across samples of selected substances with different compositions Ten different commercial ketchup food products with different compositions (sugar, no sugar, no salt, salt, and barbecue) and known densities were provided. A sample was taken from each of the tubes.

[0190] A portion of each of the samples was subject to an NMR analysis obtaining NMR intensity of the13C isotope.

[0191] The NMR intensity was obtained using a low-field NMR spectrometer in a standard calibrated state. Since the NMR spectrometer was calibrated, the NMR intensity output was proportional to total carbon content per volume (^).

[0192] The density of each of the samples of the selected substances was determined by correlating the determined NMR13C sample isotope with the reference density calibration data-group of Example 1 . The determined density based on NMR is illustrated in column 3 of Table 2. Samples 1 and 8 are the same samples as in Example 1.

[0193] Table 2

[0194] Figure 2 compares the values of the known density and the density determined by NMR intensity, and from the coefficient of determination, R2, it can be seen that there is a statistically significant relationship within a 95 % confidence interval. Thus, it is illustrated that the reference density calibration data-group of Example 1 using two primary reference samples with different densities can be used to determine density for a plurality of samples with different compositions.

[0195] EXAMPLE 3

[0196] Determination of salt content per mass of selected substance

[0197] Ten different commercial ketchup food products with different compositions (sugar, no sugar, no salt, salt, and barbecue), known densities and with known salt declaration were provided. A sample was taken from each of the tubes. The ten different commercial ketchup food products are the same as in Example 2.

[0198] A portion of each of the samples was subject to an NMR analysis obtaining NMR intensity of the23Na element isotope.

[0199] The NMR intensity was obtained using a low-field NMR spectrometer in a standard calibrated state. Since the NMR spectrometer was calibrated, the NMR intensity output was proportional to total sodium content per volume (^).

[0200] The obtained23Na element isotope intensity values for each sample is not shown.

[0201] From the obtained23Na element isotope intensity of each sample, a first parameter representing the content of the salt by volume it was determined. The first parameter was converted to a second parameter representing the content of salt by mass of the sample based on the determined density (as found in Example 2). From column 3 in Table 3, the mass fraction for each of the samples is illustrated.

[0202] Table 3

[0203] Figure 3 compares the values of the declared salt mass fraction and the determined salt mass fraction using NMR, and from the coefficient of determination, R2=0,965, there is a statistically significant relationship within a 95 % confidence interval. Thus, it is illustrated that by using the reference density calibration data-group of Example 1 , and the determined density of Example 2, relatively accurate content of salt by mass of ketchup may be determiner in a fast and effective way using NMR.

[0204] EXAMPLE 4

[0205] Preparing of a reference density calibration data-group based on of a plurality of primary reference samples

[0206] A ready meal in the form of a beef burger is obtained. 25 wt. % (based on the weight of the burger) of demineralized water is added. The burger and the added water are blended and homogenized to obtain a paste. The paste is mixed with a digesting enzyme, such as Trypsin, Pepsin or Papain. The mixture is pH adjusted and incubated at 37 °C for 2 hours, where after the enzymatic cleaving is terminated by heating. Thereafter, 6 primary reference samples, each of a volume of 1 ml, is obtained from the paste in the form of a dilution series using demineralized water, wherein the respective primary reference samples are diluted to different content of the paste, such that the 6 reference samples has a different content by weight of the paste. The density of each reference sample is determined by determining the weight of the respective reference samples. A portion of each of the primary reference samples is subject to an NMR analysis obtaining NMR intensity of the13C isotope using a low-field NMR spectrometer as in example 1.

[0207] The obtained NMR intensity value for each of the primary reference samples is organised in reference datasets together with the determined densities of the respective reference samples.

[0208] The reference density calibration data-group in the form of a linear function is then obtained by fitting the NMR intensity values and the known density of the two primary reference samples to a linear regression model to obtain the coefficients m, c in p( ) = m ■ x + c, where x is the NMR intensity value.

[0209] EXAMPLE 5

[0210] Determining the density of a ready meal by volume

[0211] A ready meal in the form of a beef lasagne is obtained from a supermarket. A sample of the ready meal is mixed with 25 wt. % (based on the weight of the lasagne) of demineralized water is added. The lasagne and the added water are blended and homogenized to obtain a paste and the paste is subjected to a digesting as described in example 5, and a portion thereof is subject to an NMR analysis obtaining NMR intensity of the13C isotope using a low-field NMR spectrometer as in example 1.

[0212] The density of the paste of the ready meal (i.e. the selected substance) is determined by correlating the determined NMR13C sample isotope with the reference density calibration data-group of Example 4.

[0213] EXAMPLE 6

[0214] Determining the protein content of a ready meal by volume

[0215] The samples (or a paste or enzymatically digested samples) are subject to an NMR analysis obtaining NMR intensity of the14N element isotope. The NMR intensity is obtained using a low-field NMR spectrometer of example 4.

[0216] From the obtained14N element isotope intensity of the sample, a first parameter representing the content of protein by volume is determined. The first parameter is converted to a second parameter representing the content of protein by mass of the paste of the ready meal in the form of a beef lasagne.

[0217] EXAMPLE 7

[0218] Determining the salt content of a ready meal by volume

[0219] The sample is subject to an NMR analysis obtaining NMR intensity of the23Na element isotope.

[0220] The NMR intensity is obtained using a low-field NMR spectrometer of example 4.

[0221] From the obtained23Na element isotope intensity of the sample, a first parameter representing the content of salt by volume it is determined. The first parameter is converted to a second parameter representing the content of salt by mass of the paste of the ready meal in the form of a beef lasagne.

Claims

CLAIMS1 . A method of determining a content of an element by mass of a selected substance, the method comprising- preparing a reference density calibration data-group comprising- providing a number of primary reference samples from one or more primary reference substances, wherein the primary reference samples have different known densities, and wherein the number of primary reference samples is at least 2,- determining an NMR intensity of at least one reference isotope for each of the primary reference samples, and generating the reference density calibration data-group, wherein the reference density calibration data-group comprises data sets of the determined NMR intensity and the known density of the respective primary reference samples,- obtaining a sample of the selected substance comprising the element,- determining at least one NMR intensity of at least one sample isotope of the sample of the selected substance,- determining a density of the selected substance by correlating the determined NMR intensity of the at least one sample isotope of the sample of the selected substance to the reference density calibration data-group,- determining a first parameter representing a content of the element by volume of the selected substance, and- determining the content of an element by mass of the selected substance by converting the first parameter representing the content of the element by volume of the selected substance to a second parameter representing the content of the element by mass of the selected substance based on the determined density.

2. The method of claim 1 , wherein the at least one reference isotope and the at least one sample isotope comprises at least one identical isotope.

3. The method of claim 1 or claim 2, wherein the content determined by mass is a mass fraction of the element of the selected substance.

4. The method of any one of the preceding claims, wherein the preparing of the reference density calibration data-group comprises fitting the sets of the determined NMRintensity and the known density of the respective primary reference samples to a calibration curve, preferably a standard curve.

5. The method of any one of the preceding claims, wherein the preparing of the reference density calibration data-group comprises fitting the sets of the determined NMR intensity and the known density of the respective primary reference samples to a linear regression curve.

6. The method of any one of the preceding claims, wherein the reference density calibration data-group is in the form of a linear function describing a linear relationship between the density and the determined NMR intensity.

7. The method of any one of the preceding claims, wherein the reference density calibration data-group is in the form of a non-linear function describing a polynomial and / or an exponential relationship between the density and the determined NMR intensity.

8. The method of any one of the preceding claims, wherein the determining of the first parameter comprises obtaining an NMR intensity of at least one element isotope of the sample of the selected substance, wherein the at least one element isotope is identical to the sample isotope and / or different from the sample isotope.

9. The method of claim 8, wherein the element isotope is identical to the sample isotope and wherein the obtaining of the NMR intensity of the element isotope of the sample of the selected substance comprises obtaining the NMR intensity of the element isotope of the sample of the selected substance from the previously determined NMR intensity of the sample isotope of the sample of the selected substance.

10. The method of any one of the preceding claims, wherein the first parameter comprises the NMR intensity and / or the molar content of the element isotope by volume of the selected substance.11 . The method of any one of the preceding claims, wherein the second parameter comprises the NMR intensity and / or the molar content of the element isotope by weight of the selected substance.

12. The method of any one of the preceding claims, wherein the first parameter comprises a content of the element by volume of the selected substance.

13. The method of any one of the preceding claims, wherein the second parameter comprises a content of the element by weight of the selected substance.

14. The method according to claim 12 or claim 13, wherein the content of the element by volume is determined by correlating the NMR intensity of the element isotope with a calibration parameter.

15. The method according to claim 14, wherein the calibration parameter is based on a relationship between a known concentration of the element and a corresponding NMR intensity of said at least one element isotope.

16. The method according to any one of the preceding claims, wherein the selected substance is a liquid, a paste, a semi-solid, or a solid.

17. The method according to any one of the preceding claims, wherein the at least one sample isotope is identical to the reference isotope.

18. The method according to any one of the preceding claims, wherein the at least one sample isotope comprises at least two different sample isotopes, wherein one of the two sample isotopes is identical to the reference isotope.

19. The method according to any one of the preceding claims, the method comprises performing at least one NMR reading of the at least one sample isotope to obtaining at least one NMR intensity of the at least one sample isotope, and generating a sample dataset comprising the at least one NMR intensity of the sample isotope of each NMR reading.

20. The method of claim 19, wherein the sample dataset comprises the isotope intensities of each NMR reading of the at least one sample isotope and / or an NMR intensity derived from the plurality of NMR intensities of said at least one sample isotope.21 . The method of any one of the claims 18-20, wherein a plurality of NMR readings are performed on each of the at least two different sample isotopes by recording signals from one isotope during one or more of the delay periods of a recording from another isotope.

22. The method of any one of the claims 18-21 , wherein the NMR intensity of the at least one sample isotope, is determined by determining an average of the plurality of NMR intensities in said sample dataset from the respective isotope.

23. The method of any one of the claims 18-22, wherein the density of the selected substance is determined based on the determined NMR intensities in said sample dataset.

24. The method of any one of the preceding claims, the method further comprises determining an NMR intensity of at least two sample isotopes and / or element isotopes of the sample.

25. The method of claim 24, wherein a first parameter is determined based on each of the NMR intensities of the two sample isotopes and / or element isotopes.

26. The method according to any one of the preceding claims, wherein the at least one reference isotope and / or the at least one sample isotope and / or the at least one element isotope is / are selected from the isotopes1H,10B,11B,13C,14N,15N,16O,19F23Na,27AI,29Si31P,33S,35CI,37CI, and39K,41K,43Ca,47Ti,49Ti,50V,51V,53Cr,55Mn,57Fe,59Co,61Ni,63Cu,65Cu,67Zn,69Ga,71Ga,75As,77Se,79Br,81Br,83Kr,85Rb,87Rb,87Sr,89Y,91Zr,93Nb,95Mo,97Mo,105Pd,107Ag,109Ag,111Cd,113Cd,117Sn,119Sn,115Sn,121Sb,135Ba,137Ba177Pb,199Hg,201Hg,207Pb.

27. The method according to any one the preceding claims, wherein the at least one reference isotope and / or the at least one sample isotope and / or the at least one element isotope is one or more of1H,2H,7Li,31B,14N,15N,23Na,31P,39K,41K,25Mg,19F,35CI,37CI,127l,13C or17O.

28. The method of any one of the preceding claims, wherein the reference isotope is29. The method of any one of the preceding claims, wherein the sample isotope is23Na.

30. The method of any one of the preceding claims, wherein the element isotope is an isotope of the element to be determined, preferably the element isotope is selected from1H,13C,23Na,31P, and14N.31 . The method of any one of the preceding claims, further comprising preparing an element calibration data-group comprising- providing a number of secondary reference element samples from one or more secondary reference substances comprising the element, wherein the reference element samples have different known concentrations of the element, and wherein the number is at least 1 ,- determining an NMR intensity of at least one reference isotope for each of the secondary reference element samples, and generating the element calibration data-group, wherein the element calibration data-group comprises one or more data sets of the determined NMR intensity and the known concentrations of the respective secondary reference element samples.

32. The method of claim 31 , wherein the preparing of the element calibration data- group comprises fitting one or more data sets of the determined NMR intensity and the known concentrations of the respective secondary reference element samples to a calibration curve, preferably a standard curve.

33. The method of claim 31 or claim 32, wherein the determining of the first parameter is performed by correlating the determined NMR intensity of the at least one sample isotope to the element calibration data-group, wherein the element calibration data-group optionally is in the form of a fitted element calibration data-group.

34. The method of any one of the preceding claims, wherein the step of providing a number of primary and / or secondary reference samples of the primary and / or the secondary reference substance with different known densities comprises preparing a number of samples by withdrawing samples from the primary and / or the secondaryreference substance and preferably diluting said each sample with a solvent, such as water.

35. The method of any one of the preceding claims, wherein the one or more primary and reference substances comprises a plurality of primary reference substances, each of the primary reference substances having a different density compared to each other.

36. The method of any one of the preceding claims, wherein the one or more primary reference substances comprises one or more primary reference substances with at least 30 wt. % similarity between a composition of the reference substance and the selected substance, such as at least 50 wt. %, such as at least 75 wt. %.

37. The method of any one of the preceding claims, wherein the two or more primary reference samples are obtained from one or more reference substances, e.g. comprising diluting the one or more reference substances, such as comprising a dilution series.

38. The method of any one of the preceding claims, wherein at least one, preferably a plurality of the two or more primary reference samples comprises a content of least one of fat, protein and / or carbohydrate, which is within the range of 50 wt.% to 150 wt.% of fat, protein and / or carbohydrate of the content of selected substance, such as within 75 wt.% to 125 wt.%, such as within 85 wt.% to 115 wt.%, such as within 95 wt.% to 105 wt.% of the content of selected substance.

39. The method of any one of the preceding claims, wherein at least one, preferably a plurality of the two or more primary reference samples comprises a solid content, which is within the range of 50 wt. % to 150 wt. % relative to the solid content of the content of selected substance, such as within 75 wt. % to 125 wt. %, such as within 85 wt. % to 115 wt. %, such as within 95 wt. % to 105 wt. % of the content of selected substance.

40. The method of any one of the preceding claims, wherein the providing of the number of reference samples comprises providing at least one, preferably a plurality of the two or more primary reference samples to be subjected to a digestion, such as an enzymatic digestion, preferably the obtaining of the sample of the selected substance comprises subjecting the sample to an enzymatic digestion.41 . The method of any one of the preceding claims, wherein the determining of the NMR intensities of the reference isotope(s), the sample isotope(s) and the element isotope(s) comprises measuring the NMR intensities using an NMR spectrometer, such as a low-field NMR spectrometer.

42. The method of claim 41 , wherein the determination for each of at least one of the NMR intensities of at least one of the reference isotope(s), the sample isotope(s) and / or the element isotope(s) comprises determining at least one of the relaxation data T1 and / or T2 and compensating the measured NMR intensity with the T1 and / or T2 data.

43. The method of any one of the preceding claims, wherein the one or more secondary reference substances comprises a plurality of secondary reference substances, each of the second reference substances having a different content of the element compared to each other.

44. The method of any one of the preceding claims, wherein the one or more secondary reference substances comprises one or more secondary reference substances with at least 30 % similarity between a composition of the reference substance and the selected substance, such as at least 50 %, such as at least 75 %.

45. The method of any one of the preceding claims, wherein the method further comprises correlating the second parameter to a target parameter, and identifying a difference between the second parameter and the target parameter.

46. The method according to claim 45, wherein the method further comprises communicating the identified difference.

47. The method according to any of claims 44 or 45, wherein the target parameter comprises an NMR intensity by mass of the selected substance, an element density by mass of the selected substance, a target nutrient density by mass of the selected substance, and / or a target mass fraction of the selected substance.

48. The method of any one of the preceding claims, wherein the selected substance is a food item.

49. The method of any one of the preceding claims, wherein the selected substance is an inorganic item.

50. The method of any one of the preceding claims, wherein the selected substance is an organic item.51 . The method of any one of the preceding claims, wherein the element is nutrient, preferably a macronutrient and / or a micronutrient or an additive, selected such as salt.

52. The method of any one of the preceding claims, wherein the number of primary reference samples is at least 4, such as at least 6.

53. The method of any one of the preceding claims, wherein the method comprises performing the NMR determinations of the respective isotopes using a low-field NMR spectrometer having a magnetic field homogeneity below 50 ppm, such as below 100 ppm, such as below 200 ppm, such as below 1000 ppm, such as below 2000 ppm.

54. The method of any one of the preceding claims, wherein the method comprises performing the NMR determinations of the respective isotopes using a low-field NMR spectrometer comprising at least one permanent magnet preferably adapted for generating a magnetic flux density of up to 2 Tesla, such as up to 1 Tesla, such as up to 0.8 Tesla, such as up to 0.5 Tesla.

55. A method of controlling a selected substance comprising determining a content of an element of the selected substance, the method comprises determining the content of the element using the method of any one of the preceding claims, and comparing the determined content of the element to a selected range.

56. A method for generating a primary reference calibration data-group comprising- providing a number N of primary reference samples from one or more primary reference substances, wherein the primary reference samples have different and known densities, and wherein the number N is at least 2,- determining an NMR intensity of at least one reference isotope for each of the primary reference samples, and generating the primary reference calibration data-group, wherein the reference calibration data-group comprises data sets of the determined NMR intensity and the known density of the respective primary reference samples.

57. A computer-readable storage device comprising executable encoded instructions thereon, wherein when executed by at least one processor, the computer-readable executable instructions cause the at least one processor to generate a reference density calibration data-group obtainable by the method of any one of the preceding claims.

58. The computer-readable storage device of claim 57, wherein the computer- readable storage device comprises encoded instructions thereon for determining the density of a sample of a selected substance by correlating a determined NMR intensity of the at least one reference isotope of the sample to the reference density calibration data- group.

59. The computer-readable storage device of claim 57 or claim 58, wherein the computer-readable storage device comprises encoded instructions thereon for converting a parameter representing a content of an element by volume of the selected substance to a parameter representing a content of the element by mass of the selected substance.

60. The computer-readable storage device of any one of claims 57-59, wherein the computer-readable storage device comprises encoded instructions thereon for determining a content of an element by mass according to any one of claims 1-54.

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