Preparation method of peanut oil with high nutritional value and sweet fried fragrance

Abstract

The invention provides the preparation method of the peanut oil with high nutritional value and sweet fried fragrance. Specifically, the invention provides a peanut raw material pretreatment method, the method comprises the steps of moistening and freeze thawing peanut raw materials, in the moistening step, water accounting for 4-12% of the mass of the peanut raw materials is uniformly mixed with the peanut raw materials, and the mixture is placed for 30-60 minutes; the color L value of the frozen and thawed peanut raw material after red skin removal is 48.0-60.0, and the value a is 2.10-3.80. The invention also provides a preparation method of the fried sweet fragrant peanut oil. The preparation method comprises the step of pretreating the peanut raw material by adopting the pretreatment method disclosed by the invention. Peanut oil prepared from the peanut raw materials treated by the method is rich in sweet flavor and high in nutritional value, the caramelized flavor compound product content, the VE total amount and the PV stability are all improved, smoothbore does not occur or basically does not occur in the squeezing process, and the residual oil amount is low.

Description

Technical Field

[0001] This invention belongs to the field of edible vegetable oil processing technology, specifically relating to a method for preparing peanut oil with high nutritional value and a sweet roasted aroma. Background Technology

[0002] Peanut oil, a traditional edible oil, is rich in nutrients and easily digested and absorbed by the human body. During the roasting process, peanuts produce various aroma components, resulting in peanut oil with a rich peanut aroma that provides consumers with a pleasant sensory experience.

[0003] Currently, the main methods for preparing peanut oil include high-temperature pressing, solvent extraction, and hydro-enzyme extraction. Pressing mainly involves roasting peanuts and then pressing them, which is the main processing technology for fragrant peanut oil. The production process of fragrant peanut oil mainly involves rolling, steaming, roasting and mechanical pressing. Among these, roasting the seeds (about 200℃) has a significant impact on the flavor of peanut oil [Li Pengfei, "Hydro-enzyme Extraction of Peanut Oil and Protein", Food Science and Engineering, Jiangnan University, 2016], but its oil yield is low and the cake residue is as high as 7-15%. In contrast, the solvent extraction method has a high oil yield, but the unique flavor substances of peanut oil are removed during processing, losing the characteristics of peanut oil itself. The hydro-enzyme extraction process is expensive and immature, and cannot be industrialized at present. Moreover, its flavor is far weaker than that of pressing [Wei Zhencheng et al., "Research Progress and Prospect of Peanut Oil Processing and Related Technologies", Journal of China Cereals and Oils, 2021, 26(6):118-121].

[0004] In the preparation of aromatic peanut oil, amino acids and reducing sugars are important aroma precursors. Newell et al. [Newell JA, Mason ME, Matlock R S., Precursors of typical and atypical roasted peanut flavor, Journal of Agricultural and Food Chemistry, 1967, 15(5):767-772] analyzed that some amino acids in peanuts, such as aspartic acid, asparagine, glutamic acid, phenylalanine and histidine, are precursors of the characteristic peanut flavor of roasted peanuts and play a key role.

[0005] Meanwhile, there are also many patent applications for the preparation of fragrant peanut oil. For example, CN 202010290336.1 mainly uses the step of heating peanut powder in the presence of enzymatic hydrolysate, wherein the enzymatic hydrolysate is the reaction product of the enzymatic raw material under the action of water and enzymes, and the enzymatic raw material includes peanut powder; the peanut oil obtained according to this method has a richer flavor, significantly increased oxidative stability, and significantly extended shelf life. CN 201911408519.2 discloses peanut oil and its preparation method using a steaming process, including soaking in a buffer solution and then steaming, followed by cooling and freezing steps to obtain a pure peanut oil product. CN 201710246681.3 discloses a preparation process for health-promoting peanut oil, which increases the nutritional components of peanut oil by adding evening primrose to granular peanuts, ultimately giving the peanut oil health benefits and making it suitable for various groups of people.

[0006] Existing technologies mainly focus on enhancing the flavor of peanut oil or improving its nutritional content by adding special exogenous substances. There is a lack of processes that can directly produce peanut oil with specific flavor and nutrients using traditional methods without adding exogenous substances. Summary of the Invention

[0007] This application mainly involves repeatedly freezing and thawing peanuts after moistening them with water, followed by roasting and pressing to obtain peanut oil. The peanut oil prepared using this method has a rich sweet aroma and high nutritional value.

[0008] Specifically, the present invention provides a method for pre-treatment of peanut raw materials, which includes the steps of wetting and freezing-thawing the peanut raw materials. In the wetting step, 4-12% of the peanut raw material mass of water is used to mix the peanut raw material with the raw material and let it stand for 30-60 minutes. After the peanut raw material is frozen and thawed and the red skin is removed, the color L value is 48.0-60.0 and the a value is 2.10-3.80.

[0009] In some implementations, the color L value of the frozen and thawed peanut raw material after removing the red skin is 50.0-60.0, preferably 50.0-55.0.

[0010] In some implementations, the color α value of the frozen-thawed peanut raw material after removing the red skin is 2.10-3.50, preferably 2.30-3.50, and more preferably 2.30-3.30.

[0011] In some embodiments, the peanut raw material is whole peanut kernels that have not been crushed.

[0012] In some implementations, the peanuts are frozen at a freezing rate of 0.030-0.150 °C / (min / kg), where kg refers to the mass of the peanuts.

[0013] In some implementations, the freezing start temperature can be room temperature, such as 20 to 25°C; after freezing to -5°C to -55°C, the following step (2) is performed for thawing.

[0014] In some implementations, thawing is carried out at a thawing rate of 0.15-0.50℃ / (min / kg), where kg refers to the mass of the peanuts; the next round of freezing is carried out when the temperature of the peanuts reaches 50-80℃.

[0015] In some implementation schemes, one freezing and one thawing constitutes one freeze-thaw cycle, and 2-3 freeze-thaw cycles are carried out.

[0016] In some embodiments, the freezing rate is 0.050 to 0.120 °C / (min / kg), preferably 0.070 to 0.120 °C / (min / kg).

[0017] In some implementations, the freezer is thawed after being frozen to -8°C to -30°C, preferably -10°C to -25°C.

[0018] In some embodiments, the thawing rate is 0.20 to 0.50 °C / (min / kg), preferably 0.20 to 0.45 °C / (min / kg), and more preferably 0.20 to 0.40 °C / (min / kg).

[0019] In some implementations, the food is thawed to 55–80°C or 55–65°C before freezing.

[0020] A second aspect of the present invention provides a method for preparing sweet roasted peanut oil or a method for increasing the caramel flavor compounds and total vitamin E content in peanut oil, the method comprising the steps of wetting and freeze-thawing peanut raw materials using the pretreatment method described in any embodiment of the present invention, and roasting and pressing steps.

[0021] In some implementation schemes, the roasting temperature is 180-200℃ and the discharge temperature is 140-145℃ during the roasting step.

[0022] In some implementations, the pressing temperature is 100–120°C during the pressing step.

[0023] In some implementations, the method further includes a purification step prior to wetting treatment.

[0024] In some embodiments, the method further includes a step of refining the pressed peanut oil, preferably including filtration and crystal growth.

[0025] A third aspect of the present invention provides a method for reducing or avoiding slippage during the pressing process of peanut oil preparation, while simultaneously increasing the total vitamin E and caramel flavor compounds in the obtained peanut oil. The method includes steps of applying water-wetting and freeze-thaw treatment to the peanut raw material using the pretreatment method described in any embodiment of the present invention.

[0026] A fourth aspect of the present invention provides peanut raw materials obtained using the pretreatment method described in any embodiment herein.

[0027] The fifth aspect of the present invention provides an oil prepared by means of any embodiment of the present invention, and a blended oil containing the oil.

[0028] The sixth aspect of the present invention provides applications selected from the following:

[0029] (1) The application of the peanut raw material pretreatment method described in any embodiment of the present invention in the preparation of sweet roasted peanut oil or in enhancing the caramel flavor compounds and total VE content of peanut oil;

[0030] (2) The peanut raw material pretreatment method described in any embodiment of the present invention reduces or avoids slippage when preparing peanut oil by pressing, and at the same time increases the total VE content and caramel flavor compounds in the obtained peanut oil.

[0031] (3) The application of the peanut raw material described in any embodiment of the present invention in the preparation of sweet roasted peanut oil or in enhancing the caramel flavor compounds and total VE content of peanut oil;

[0032] (4) The peanut raw material described in any embodiment of the present invention reduces or avoids slippage when preparing peanut oil by pressing, while increasing the total amount of vitamin E and caramel flavor compounds in the obtained peanut oil. Detailed Implementation

[0033] To enable those skilled in the art to understand the features and effects of this invention, the terms and expressions used herein are explained and defined in general terms below. Unless otherwise specified, all technical and scientific terms used herein have the common meaning understood by those skilled in the art regarding this invention, and in case of conflict, the definitions herein shall prevail.

[0034] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0035] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0036] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0037] Unless otherwise specified, percentages refer to mass percentages and proportions refer to mass ratios in this article.

[0038] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0039] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0040] This invention aims to provide a method for preparing peanut oil using traditional processes without adding any special exogenous substances, and the peanut oil obtained thereby. Specifically, this invention pre-treats peanut raw materials, namely, wetting and freeze-thaw treatment. The peanut oil obtained from the pre-treated peanut raw materials has a rich sweet aroma and high nutritional value. The content of caramelized flavor compounds, total vitamin E, and the stability of polyphenol oxidase (PV) are all improved. Furthermore, using the method of this invention, slippage does not occur or is virtually eliminated during the pressing process, and the residual oil content is low.

[0041] Moisturizing

[0042] In this invention, "moistening with water" refers to soaking peanuts in water.

[0043] In this invention, the peanuts can be any variety of peanuts known in the art for preparing peanut oil. Preferably, the peanuts used for wetting and freeze-thawing in this invention are whole peanut kernels that have not been crushed.

[0044] In this invention, the water used for wetting treatment can be drinking water. The water temperature can be room temperature.

[0045] In this invention, the amount of water added can be 4-12% of the weight of the peanuts, such as 4-10% or 5-8%. This invention does not require the peanuts to be completely soaked in water; it is sufficient to moisten them.

[0046] In this invention, after adding water, the peanuts are mixed evenly and then left to stand. The standing time can be 30-60 minutes.

[0047] In some embodiments, the moistening step of the present invention includes: adding 4-12% water by weight of the peanut raw material to the peanut raw material and letting it stand for 30-60 minutes.

[0048] freeze-thaw

[0049] After moistening with water, the peanut raw materials can be freeze-thawed.

[0050] In some embodiments, the present invention freezes and thaws the moistened peanut raw material so that the color L value of the freeze-thawed peanut raw material after removing the red skin is 48.0-60.0 and the a value is 2.10-3.80.

[0051] In some embodiments, the L value of the color of the freeze-thawed peanut raw material after removing the red skin is 50.0-60.0. In some embodiments, the L value of the color of the freeze-thawed peanut raw material after removing the red skin is 50.0-55.0.

[0052] In some embodiments, the color α value of the freeze-thawed peanut raw material after removing the red skin is 2.10-3.50. In some embodiments, the color α value of the freeze-thawed peanut raw material after removing the red skin is 2.30-3.50. In some embodiments, the color α value of the freeze-thawed peanut raw material after removing the red skin is 2.30-3.30.

[0053] In some implementations, the above-mentioned color L and a values ​​can be obtained in the following ways:

[0054] (1) Freeze at a freezing rate of 0.030-0.150℃ / (min / kg), wherein the kg refers to the mass of peanuts;

[0055] The freezing start temperature can be room temperature, such as 20-25℃; after freezing to -5℃ to -55℃ (i.e. freezing end temperature), the following step (2) can be carried out immediately for thawing;

[0056] (2) Thaw at a rate of 0.15-0.50℃ / (min / kg), where kg refers to the mass of peanuts; once the temperature of the peanuts reaches 50-80℃ (i.e., the thawing termination temperature), the next round of freezing can be carried out immediately;

[0057] (3) A freeze-thaw cycle consists of one freezing and one thawing, and 2-3 freeze-thaw cycles are carried out.

[0058] In some embodiments, the freezing rate is preferably 0.050–0.120 °C / (min / kg). In some embodiments, the freezing rate is preferably 0.070–0.120 °C / (min / kg). In some embodiments, the freezing termination temperature is preferably -8 °C to -30 °C. In some embodiments, the freezing termination temperature is preferably -10 °C to -25 °C. In some embodiments, the freezing termination temperature is 20 ± 5 °C.

[0059] In some embodiments, the thawing rate is preferably 0.20–0.50 °C / (min / kg). In some embodiments, the thawing rate is preferably 0.20–0.45 °C / (min / kg). In some embodiments, the thawing rate is preferably 0.20–0.40 °C / (min / kg). In some embodiments, the thawing termination temperature is 55–80 °C, or 55–65 °C.

[0060] Freeze-thaw cycles can be performed using equipment and techniques conventional in the art. Exemplary equipment includes, but is not limited to, freezers, ice baths, vacuum freezers, and refrigerators.

[0061] After the final thawing, the peanut raw material can be used directly for roasting or roasting, or it can be roasted or roasted after it has cooled down appropriately (such as to room temperature).

[0062] roasting

[0063] After freeze-thaw, the peanut raw materials can be roasted. Roasting is a conventional technique in this field, and the roasting temperature can vary depending on the type of oilseed. For example, the roasting temperature for peanuts can be 180–200℃. The discharge temperature can be 140–145℃. The roasting time can be determined by those skilled in the art based on the actual situation. For example, for peanuts, roasting is sufficient until the peanut kernels are golden in color and there is no white core inside when the kernels are broken open.

[0064] Oil pressing

[0065] After roasting, the peanut kernels can be pressed for oil. Oil pressing can be performed using processes and equipment well-known in the art. For example, the pressing temperature can be 100–120℃, such as 110±5℃. For example, a screw press can be used for oil pressing. After pressing, crude peanut oil is obtained.

[0066] Oil refining

[0067] The crude oil obtained from the pressing process can be refined to obtain the final peanut oil product. Refining steps may include filtration and crystal formation.

[0068] For crystal growth, techniques known in the art can be followed. For example, crystal growth can be carried out at temperatures below 20°C, such as 18–20°C. There is no specific choice regarding the crystal growth time; it can be selected based on actual conditions. Typically, the crystal growth time can be 0.5–5 hours.

[0069] There are no particular restrictions on the filtration method; it is sufficient to remove large impurities such as oil residue, for example, a plate and frame filter.

[0070] After crystal growth, filtration yields the finished peanut oil of this invention. It should be understood that the filtration and crystal growth processes described herein can employ any existing technology.

[0071] Preprocessing

[0072] In some preferred embodiments of the present invention, the peanut raw material may be pre-treated before wetting. There are no particular limitations on the means of pre-treatment; it can be carried out according to the actual quality, state, and needs of the peanut raw material. Optionally, such pre-treatment in the present invention may include impurity removal and stone removal steps, and optionally also includes metal removal steps. The impurity removal step mainly removes large impurities, stones, and metallic substances from the peanut raw material. Large impurities in the peanut raw material can be removed by one or more (e.g., two) vibrating screens. Stones in the peanut raw material can be removed by one or more (e.g., two) gravity separation. Metallic substances in the peanut raw material can be removed using a magnetic separator and a metal detector.

[0073] Methods and Applications

[0074] In some embodiments, the present invention provides a peanut raw material pretreatment method, which includes the wetting and freeze-thaw steps described in any of the embodiments herein.

[0075] In some embodiments, the present invention provides a method for reducing or avoiding slippage during the pressing process of peanut oil preparation, while simultaneously increasing the total vitamin E and caramel flavor compounds in the obtained peanut oil. The method is characterized by comprising a step of pretreating the peanut raw material using the peanut raw material pretreatment method described in any embodiment of this invention.

[0076] In some embodiments, the present invention provides a method for preparing peanut oil, the method comprising the moistening and freeze-thaw steps described in any embodiment herein. The method further comprises roasting and pressing steps. Optionally, the method further comprises an oil refining step, such as including crystal growth and filtration steps. It should be understood that the present invention can be implemented using roasting, pressing, and oil refining techniques well known in the art. In some embodiments, the roasting, pressing, and oil refining are as described in any embodiment herein. In some embodiments, the method further comprises a pretreatment step, as described in this application.

[0077] In some embodiments, the present invention provides a method for increasing the caramel flavor compounds and total vitamin E in peanut oil, the method comprising the wetting and freeze-thaw steps described in any embodiment herein. Optionally, the method further comprises an oil refining step, such as including crystal growth and filtration steps. It should be understood that the present invention can be implemented using roasting, pressing, and oil refining techniques well known in the art. In some embodiments, the roasting, pressing, and oil refining are as described in any embodiment herein. In some embodiments, the method further comprises a pretreatment step, as described in this application.

[0078] In this invention, caramel flavor compounds generally include flavor substances and caramel compounds. Flavor substances include, but are not limited to, alcohols, phenols, aldehydes, ketones, acids, and esters. Exemplary flavor substances include pyrazines, other N / S heterocyclic compounds (pyridine, pyrrole, pyran, pyrimidine), furanones, pyranones, and maltol. Caramel compounds include, but are not limited to, alcohols, phenols, and ketones. Exemplary caramel compounds include furanones, pyranones, and maltol.

[0079] In some embodiments, the present invention provides the application of the wetting and freeze-thaw techniques described in any of the embodiments herein in enhancing the caramel flavor compounds and total vitamin E content in peanut oil, and in the preparation of peanut oil with enhanced caramel flavor compounds and total vitamin E content.

[0080] When peanut oil is prepared using the method of this invention, slippage or only slight slippage occurs, meaning that the following situation does not occur or substantially does not occur: oilseeds slipping from the pressing chamber during operation, preventing effective oil extraction and reducing pressing efficiency. The residual oil content in the peanut meal after pressing is low, such as below 20.0%, preferably below 15.0%, more preferably below 13.5%. Meanwhile, the peanut oil prepared using the method of this application contains a high total vitamin E content and a high content of caramelized flavor compounds.

[0081] Pre-processing peanut raw materials and oil

[0082] In some embodiments, the present invention also provides a peanut raw material obtained using the pretreatment method of the present invention. In some embodiments, the peanut raw material is characterized by at least the following: a color L value of 48.0-60.0 and an a value of 2.10-3.80 after removing the red skin. In some embodiments, the color L value of the peanut raw material after removing the red skin is 50.0-60.0. In some embodiments, the color L value of the peanut raw material after removing the red skin is 50.0-55.0. In some embodiments, the color a value of the peanut raw material after removing the red skin is 2.10-3.50. In some embodiments, the color a value of the peanut raw material after removing the red skin is 2.30-3.50. In some embodiments, the color a value of the peanut raw material after removing the red skin is 2.30-3.30. When peanut oil is prepared using this peanut raw material via pressing, no slippage or only slight slippage occurs, and the resulting peanut oil has a higher total vitamin E content and caramel flavor compound content compared to peanut raw material not treated with this pretreatment method. In some embodiments, the total VE content and the caramel flavor compound content are as described in any embodiment of the present invention.

[0083] In some embodiments, the present invention provides peanut oil obtained by the method described in any embodiment herein. Preferably, the peanut oil contains more than 19.5% caramelized flavor compounds, such as 19.5-30.0% or 19.5-25.0%. Preferably, the peanut oil contains more than 310 mg / kg of vitamin E, such as 310-360 mg / kg. In some embodiments, the peanut oil of the present invention has a PV ≤ 0.18 mmol / kg.

[0084] In some embodiments, the present invention provides an oil (blended oil) containing peanut oil prepared by the method described in any embodiment of the present invention. The blended oil may also contain other edible oils well known in the art, including but not limited to vegetable oils and / or animal fats. Exemplary vegetable oils include any mixture of one or more of the following: rice bran oil, sunflower seed oil, palm oil, palm kernel oil, sesame oil, rapeseed oil, safflower seed oil, perilla seed oil, tea seed oil, coconut oil, olive oil, cocoa bean oil, almond oil, apricot kernel oil, rice bran oil, corn germ oil, wheat germ oil, sesame seed oil, flaxseed oil, evening primrose seed oil, hazelnut oil, walnut oil, grapeseed oil, borage seed oil, sea buckthorn seed oil, tomato seed oil, pumpkin seed oil, macadamia nut oil, and algae oil. Exemplary animal fats include any mixture of one or more of the following: beef tallow, lard, mutton tallow, chicken fat, fish oil, seal oil, whale oil, dolphin oil, and oyster sauce. In the blended oil, the content of peanut oil in this invention can be any amount, which can be determined by those skilled in the art according to actual needs.

[0085] In some embodiments, the present invention provides a seasoning containing peanut oil or blended oil prepared by the method described in any embodiment of the present invention.

[0086] The present invention also provides a method for preparing blended oil, the method comprising A) obtaining peanut oil using the method described in any embodiment of the present invention, and B) mixing the peanut oil obtained in step A) with other edible oils to prepare blended oil.

[0087] The present invention will be described below by way of specific embodiments. It should be understood that these embodiments are merely illustrative and are not intended to limit the scope of the invention. The methods, reagents, and materials used in the embodiments are conventional methods, reagents, and materials in the art, unless otherwise stated. The raw material compounds in the embodiments are all commercially available.

[0088] The implementation process of Comparative Examples 1-10 and Examples 1-7 is as follows:

[0089] 1. Peanuts undergo a process of removing impurities and stones;

[0090] 2. After soaking or adding 4-13% water, let stand for 30-60 minutes, then freeze at a freezing rate of 0.02℃ / (min / kg)-0.16℃ / (min / kg) to 0℃~-60℃. After reaching the set freezing stop temperature, immediately raise the temperature to 60-90℃ at a thawing rate of 0.15-0.6℃ / (min / kg) to thaw; repeat 1-4 times; after the freeze-thaw treatment is completed, remove the red skin from the peanuts.

[0091] 3. The peanuts obtained in step 2 are roasted at 185℃, and the discharge temperature is 145℃;

[0092] 4. Pressing: After the material is discharged, it is pressed at 110℃±5℃ using a screw press to produce crude peanut oil;

[0093] 5. Crystallization and Filtration: The peanut oil is crystallized at 18-20℃ and then filtered to obtain the finished peanut oil.

[0094] The specific process is shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] Note: Comparative Example 10 used broken peanut kernels, while the other examples and comparative examples used whole peanut kernels.

[0099] The following methods were used to detect peanut color, total free amino acid content, reducing sugar content, PV and PE content, and the proportion of caramelized flavor compounds:

[0100] 1. Total amount of free amino acids

[0101] Sample pretreatment: Peanut samples were extracted using Soxhlet extraction to obtain peanut meal. Approximately 0.5 g of sample was accurately weighed into a 25 mL volumetric flask, diluted to volume with 5 g / 100 mL trichloroacetic acid solution, allowed to stand for 1 hour, and then filtered through double-layered filter paper. 1 mL of the filtrate was transferred to a 2 mL centrifuge tube and centrifuged at 10000 rpm for 10 minutes for use in an amino acid analyzer.

[0102] Free amino acid analysis: ODS HYPERSIL column (Φ4.6×250mm, 5μm); column temperature 40℃; gradient elution; flow rate 1.0mL / min; UV detection wavelengths 338nm and 262nm; injection volume 10μL; external standard method for quantification.

[0103] 2. Reducing sugar content

[0104] Sample pretreatment: Weigh approximately 0.50 g of defatted peanut meal into a centrifuge tube, add 10 mL of 70% ethanol solution, sonicate for 20 min, centrifuge at 2000 rpm for 10 min to separate the supernatant. Add 10 mL of 70% ethanol to the lower layer, sonicate for 20 min, and centrifuge to separate the supernatant. Combine the two supernatants and filter. Evaporate the filtrate under vacuum at 50℃, bring the volume to 2 mL with 70% ethanol, and centrifuge at 10000 rpm for 10 min for HPLC analysis.

[0105] HPLC analysis: Spherisorb NH2 column (Φ4.6×250mm, 5μm); column temperature 30℃; mobile phase 70% acetonitrile solution; flow rate 1.0mL / min; differential refractive index detector; injection volume 5μL; external standard method for quantification.

[0106] 3. Flavor testing:

[0107] Equipment requirements: 7890A-5975C gas chromatograph-coupled analyzer, HP-5 column (60m×0.25mm×0.25μm) and 25ml headspace vials with threaded caps were purchased from Agilent Technologies; multi-functional injector with solid-phase microextraction was purchased from Co-Chemistry; extraction head: 50 / 30μm DVB / Carboxen / PDMS, purchased from Amperex Technology Co., Ltd.

[0108] Flavor compounds: pyrazines, other NS heterocyclic compounds (pyridine, pyrrole, pyran, pyrimidine), furanones, pyranones, maltol and other alcohols and phenols, alcohols, phenols, aldehydes, ketones, acids, esters. Among them, caramel compounds include furanones, pyranones, maltol and other alcohols and phenols.

[0109] Detection method:

[0110] Chromatography: Injector temperature: 250℃; Splitless mode; Temperature program: Hold at 40℃ for 1 min, increase to 250℃ at 5℃ / min, and hold for 5 min;

[0111] Mass spectrometry: transfer line temperature 280℃; ionization method: electron impact source (EI); ionization energy: 70eV; electron multiplication voltage: 1600V; ion source temperature: 230℃; quadrupole temperature: 150℃; monitoring method: full scan;

[0112] Mass spectrometry analysis: The components were qualitatively analyzed using the NIST.L mass spectrometry database, and the ratio of flavor compounds was expressed as the peak area response ratio.

[0113] 4. Vitamin E detection: Dissolve 5g of sample in acetone and bring the volume to 100mL, then directly inject into the liquid chromatography system for detection. Liquid chromatography conditions: a) Column: C18 column, column length 150mm or equivalent; b) Mobile phase: methanol; c) Flow rate: 1mL / min, analysis time 30min; d) UV detector, detection wavelength 294nm; e) Injection volume: 5μL.

[0114] 5. Peanut color detection: After removing the red skin from the peanuts, they are crushed using a grinder and then quickly tested using a color flex EZ instrument.

[0115] 6. PV detection:

[0116] GB 5009.227-2023 National Food Safety Standard: Determination of Peroxide Value in Food.

[0117] The results are shown in Table 2 below.

[0118] Table 2

[0119]

[0120]

[0121] Note: (1) Comparative Example 2 uses soaking to treat peanuts, resulting in a lower content of free amino acids and reducing sugars; other comparative examples and examples all use water addition, and the content of free amino acids and reducing sugars does not change much. Therefore, only the content of free amino acids and reducing sugars in a few examples and comparative examples is provided.

[0122] (2) The peroxide value of Comparative Example 10 is about 10 times that of normal peanut oil, and the oil has a distinct oxidized smell.

[0123] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for pretreating peanut raw materials, the method comprising the steps of wetting the peanut raw materials and freeze-thawing, wherein, In the hydration step, use 4-12% water by weight of the peanut raw material to mix with the peanut raw material and let it stand for 30-60 minutes; the color L value of the peanut raw material after freezing and thawing and removing the red skin is 48.0-60.0 and the a value is 2.10-3.

80.

2. The preprocessing method as described in claim 1, characterized in that: The color L value of peanut raw materials after freeze-thaw processing and removal of the red skin is 50.0-60.0, preferably 50.0-55.0; and / or The color a value of peanut raw material after freeze-thaw processing and removal of red skin is 2.10-3.50, preferably 2.30-3.50, more preferably 2.30-3.30; and / or The peanut raw material is whole peanut kernels, which have not been crushed.

3. The method according to any one of claims 1 to 2, characterized in that, The freeze-thaw step includes: (1) Freeze at a freezing rate of 0.030-0.150℃ / (min / kg), wherein the kg refers to the mass of peanuts; The freezing start temperature is room temperature; after freezing to -5℃ to -55℃, proceed with the thawing step (2) below; (2) Thaw at a rate of 0.15-0.50℃ / (min / kg), where kg refers to the mass of peanuts; after the temperature of the peanuts reaches 50-80℃, carry out the next round of freezing; (3) A freeze-thaw cycle consists of one freezing and one thawing, and 2-3 freeze-thaw cycles are carried out.

4. The method as described in claim 3, characterized in that: The freezing rate is 0.050–0.120 °C / (min / kg), preferably 0.070–0.120 °C / (min / kg); and / or Thawing is performed after freezing to -8°C to -30°C, preferably -10°C to -25°C; and / or The thawing rate is 0.20–0.50 °C / (min / kg), preferably 0.20–0.45 °C / (min / kg), more preferably 0.20–0.40 °C / (min / kg); and / or Thaw to 55–80°C or 55–65°C and then freeze.

5. A method for preparing sweet roasted peanut oil or a method for increasing the caramel flavor compounds and total vitamin E content in peanut oil, characterized in that, The method includes the steps of moistening and freeze-thawing the peanut raw material using the method of any one of claims 1 to 4, and the steps of roasting and pressing.

6. The method as described in claim 5, characterized in that: In the roasting step, the roasting temperature is 180-200℃, and the discharge temperature is 140-145℃; and / or In the pressing step, the pressing temperature is 100–120℃, preferably 110±5℃; and / or The method further includes a purification step prior to wetting treatment; and / or The method further includes a step of refining the crude peanut oil obtained by pressing, preferably including filtration and crystal growth.

7. A method for reducing or avoiding slippage during the pressing process of peanut oil preparation, while simultaneously increasing the total vitamin E and caramel flavor compounds in the obtained peanut oil, characterized in that, The method includes a step of pretreating peanut raw materials using the method described in any one of claims 1 to 4.

8. Peanut raw material obtained by the method described in any one of claims 1 to 4.

9. The oil prepared by any one of claims 5 to 6, and the blended oil containing the oil.

10. Selected from the following applications: (1) The method of any one of claims 1 to 4 is used in the preparation of sweet roasted peanut oil or in enhancing the caramel flavor compounds and total vitamin E content of peanut oil; (2) The method of any one of claims 1 to 4 is used to reduce or avoid slippage when preparing peanut oil by pressing, and to increase the total amount of vitamin E and caramel flavor compounds in the obtained peanut oil. (3) The application of the peanut raw material according to claim 8 in the preparation of sweet roasted peanut oil or in enhancing the caramel flavor compounds and total VE content of peanut oil; (4) The peanut raw material of claim 8 is used to reduce or avoid slippage when preparing peanut oil by pressing, and at the same time to increase the total amount of vitamin E and caramel flavor compounds in the obtained peanut oil.

Images