Creamy fat rich in concentrated chain triglyceride as well as preparation method and application thereof

Abstract

The invention provides milk fat rich in concentrated chain triglyceride as well as a preparation method and application of the milk fat. The method for preparing the milk fat rich in the concentrated chain triglyceride comprises the following steps: (1) completely melting anhydrous milk fat in a water bath, preserving heat in the water bath, growing crystal at the temperature of 20-30 DEG C, and carrying out crystal separation to obtain soft fat and stearin; and (2) carrying out single-stage short-path molecular distillation on the molten soft fat at 175-185 DEG C to obtain a heavy-phase component and a light-phase component, and the light-phase component is the milk fat rich in the concentrated-chain triglyceride. The method is simple to operate and low in cost, and the MCT-rich soft fat is obtained through crystal growing separation and then is subjected to short-path molecular distillation, so that MCT can be effectively enriched, and the flavor quality of the milk fat is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of dairy processing, and particularly relates to a milk fat rich in medium-chain triglycerides and a preparation method and application thereof. BACKGROUND

[0002] At present, medium-chain triglycerides (MCT) are mainly derived from coconut oil and palm kernel oil, and other common animal and plant oils are mainly long-chain triglycerides (LCT). However, the refining process of plant oil may produce trans fatty acids, and excessive intake of trans fatty acids may increase the risk of cardiovascular diseases and diabetes, and may also affect the growth and development of infants and the health of the nervous system. Meanwhile, the extraction of MCT from coconut oil and palm kernel oil has the problems of great geographical limitations of raw material supply and easy influence by climate and market fluctuations.

[0003] For example, Tong Yinying uses octanoic acid and glycerol as raw materials and an acidic ionic liquid as a catalyst to synthesize MCT. Although chemical synthesis can improve the content of MCT, it is difficult to separate by-products and easy to contaminate the product, which may destroy the natural flavor components in the oil and cannot improve the flavor of milk fat, and even introduce irritating odor. Norulaini et al. used supercritical extraction of coconut oil, and the results showed that the content of MCT increased with the increase of temperature, and decreased with the increase of pressure, but the change of flavor was not explored. Ma Chuan-guo et al. used lipase Lipozyme 435 as a catalyst to catalyze the reaction of glycerol and a mixture of octanoic acid and decanoic acid in a solvent-free system to generate medium-chain triglycerides, but the enzyme catalyst is expensive and the total cost is high, which is difficult to realize large-scale production.

[0004] If MCT is enriched from animal fat, not only can the health risks of trans fatty acids be avoided to ensure product safety, but also the raw material source of MCT can be broadened, the dependence on single plant fat raw material can be reduced, and the stability of the supply chain can be enhanced. Milk fat is a kind of animal fat, which has a wide source, but the retention effect of original flavor substances in milk fat is poor, and deep processing may easily lead to undesirable flavor. As a core element of dairy product quality, milk fat flavor directly affects the acceptance of consumers, and therefore improving the flavor of milk fat helps to improve the market competitiveness of products. In addition, how to maximize the enrichment of MCT in milk fat is also a key problem. SUMMARY

[0005] The present application aims to at least partially solve one of the problems of the prior art. To this end, one object of the present application is to propose a milk fat rich in medium-chain triglycerides and a preparation method and application thereof.

[0006] In a first aspect, the present application proposes a preparation method of a milk fat rich in medium-chain triglycerides, which comprises: (1) After the anhydrous milk fat is completely melted in a water bath and kept in the water bath, it is placed at 20-30℃ for crystal growth, and soft fat and hard fat are obtained by crystallization separation; (2) The melted soft fat is subjected to single-stage short-path molecular distillation at 175-185℃ to obtain a heavy phase component and a light phase component, and the light phase component is the milk fat rich in medium-chain triglycerides.

[0007] According to the method for preparing milk fat rich in medium-chain triglycerides provided in the application, the anhydrous milk fat is first completely melted in a water bath and kept in the water bath, and then placed at 20-30℃ for crystal growth, so that soft fat rich in MCT is obtained. Then the soft fat rich in MCT is melted and subjected to single-stage short-path molecular distillation at 175-185℃. By controlling the distillation temperature, MCT is efficiently volatilized into the light phase component, ensuring the efficiency and stability of the whole process. Not only is the enrichment of MCT significantly improved, but also the flavor of the milk fat is improved and the impact on the quality of the milk fat is reduced at this temperature range. The method is simple in operation and low in cost. The dry separation (crystal growth separation) is used to obtain soft fat rich in MCT, and then short-path molecular distillation is performed, so that MCT can be effectively enriched, and the flavor and quality of the milk fat are also improved.

[0008] Specifically, the inventors found that in step (1), if the crystal growth temperature is too high, the crystal structure of the milk fat is irregular, forming uneven crystals, affecting the consistency of the product. A too high temperature also leads to the loss of volatile flavor components in the soft fat, affecting the quality of the final product. If the crystal growth temperature is too low, the crystallization rate of the fatty acids in the milk fat is slowed down, and the crystallization time is prolonged. A lower temperature also leads to incomplete crystallization, and part of the fatty acids still exist in the milk fat in an amorphous state, affecting the subsequent separation effect. In step (1), if the distillation temperature is too low or too high, not only is the content of MCT enrichment less, but also the flavor of the milk fat is poor.

[0009] For example, the crystal growth temperature is 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, or a range between any two of the above values, and preferably the crystal growth temperature is 24-26℃. For example, the distillation temperature is 175℃, 176℃, 178℃, 180℃, 181℃, 182℃, 183℃, 184℃, 185℃, or a range between any two of the above values. Preferably, the distillation temperature is 180℃.

[0010] It should be noted that the soft fat refers to the liquid or semi-liquid milk fat component obtained after crystal growth, and the hard fat refers to the solid milk fat component obtained after crystal growth. The light phase component refers to the volatile component obtained after distillation, and the heavy phase component refers to the other component obtained after distillation of the volatile component.

[0011] Further, the medium-chain triglyceride is a fatty acid with a carbon chain length of 8-14.

[0012] In some embodiments of the present application, in step (1), the solid-liquid separation uses an oil press and a nylon mesh. Specifically, the temperature of the separation is room temperature (20-30℃).

[0013] In some embodiments of the present application, in step (1), the temperature of the water bath is 70-90℃.

[0014] The temperature of the water bath in the above range can completely destroy the original crystal structure, eliminate the difference in thermal history, and ensure the reproducibility of the separation process.

[0015] In some embodiments of the present application, the water bath incubation time is 5-20 min. The water bath incubation time in the above range can ensure that all components in the AMF are fully heated, avoiding the situation that partial melting is not complete, thereby improving the consistency and reliability of subsequent operations.

[0016] In some embodiments of the present application, in step (1), the time for crystal growth is 15-20 h. For example, the time for crystal growth is 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, or a range between any two of the above values. Controlling the time for crystal growth in the above range can make the triglyceride in the AMF fully crystallize to form a clear crystalline phase, which can effectively control the production cost and improve the separation efficiency while ensuring the quality of the crystal.

[0017] In some embodiments of the present application, in step (2), the working pressure of the single-stage short-path molecular distillation is 0.007-0.01 mbar. The working pressure of the single-stage short-path molecular distillation in the above range can ensure effective separation while taking into account the feasibility of operation and the stability of the equipment. This pressure range can effectively separate different components in the soft fat, improve the purity of the light phase component and the heavy phase component, and at the same time avoid equipment failure or operation difficulty caused by too low or too high pressure.

[0018] In some embodiments of the present application, the rotating speed of the thin film blade in the single-stage short-path molecular distillation is 130-200 r / min.

[0019] In some embodiments of the present application, in step (2), the feeding rate of the feed inlet of the single-stage short-path molecular distillation is 1.5-2.5 mL / min, and the temperature is 60-65℃.

[0020] In some embodiments of the present application, before the single-stage short-path molecular distillation, the soft fat is melted in a water bath at 60-65℃.

[0021] In a second aspect, the present application provides a milk fat rich in medium-chain triglycerides, which is prepared by the method described above.

[0022] In some embodiments of the present application, the mass fraction of medium-chain triglycerides in the milk fat rich in medium-chain triglycerides is 3.7%-4.8%.

[0023] In some embodiments of the present application, the characteristic flavor substances of the milk fat rich in medium-chain triglycerides include one or more of hexanal, 2-propanone and 1-pentene-3-ol.

[0024] In a third aspect, the present application provides the use of the milk fat rich in medium-chain triglycerides described above in food and health products.

[0025] In some embodiments of the present application, the food includes high-end baking fat, infant formula, sports nutrition supplements, etc. The present application has at least the following beneficial effects: (1) The method for preparing the milk fat rich in medium-chain triglycerides is simple in operation and low in cost. The soft fat rich in MCT is obtained by dry fractionation (crystallization separation), and then short-path molecular distillation is performed, so that the MCT can be effectively enriched, and the flavor quality of the milk fat is also improved.

[0026] (2) The milk fat rich in medium-chain triglycerides can be widely used in the fields of high-end baking fat, infant formula, sports nutrition supplements, etc. It provides high-quality raw materials for food enterprises to develop differentiated products, and improves the market competitiveness and added value of products. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0028] Figure 1 is a test result chart of the flavor substances of each component of the examples and comparative examples of the present application. DETAILED DESCRIPTION

[0029] Based on the examples in the present application, all other examples obtained by those skilled in the art without any creative effort are within the scope of protection of the present application. The present application will be described below with reference to specific examples. It should be noted that these examples are merely descriptive, and do not limit the present application in any way.

[0030] Example 1 (1) The chilled anhydrous milk fat (AMF) was completely melted (destroyed the original crystal structure) in 80 °C water bath and kept at this temperature for 10 min, then placed in 25 °C crystal tank for 18 h, and then separated the components using oil press and nylon net to obtain hard fat (S25) and soft fat (L25), which were stored at 4 °C for standby.

[0031] (2) The fractionation component L25 was subjected to single-stage short-path molecular distillation to obtain heavy phase (R) and light phase (D) components. The distillation temperature was set at 180 °C. The prepared L25 was completely melted at 60 °C water bath and then added to the feed bottle of the distillation instrument. The rate and temperature of the feed inlet (oil bath) were set at 2.0 mL / min and 60 °C, respectively. The working pressure of the distillation was 0.008 mbar, and the rotation speed of the thin film blade was 150 r / min. After distillation, two fractions were obtained, namely heavy phase component (180R) and light phase component (180D).

[0032] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is: The distillation temperature was set at 170 °C. After distillation, two fractions were obtained, namely heavy phase component (170R) and light phase component (170D).

[0033] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is: The distillation temperature was set at 160 °C. After distillation, two fractions were obtained, namely heavy phase component (160R) and light phase component (160D).

[0034] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is: The distillation temperature was set at 190 °C. After distillation, two fractions were obtained, namely heavy phase component (190R) and light phase component (190D).

[0035] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is: The chilled anhydrous milk fat (AMF) was completely melted (destroyed the original crystal structure) in 80 °C water bath and kept at this temperature for 10 min, then placed in 15 °C crystal tank for 18 h, and then separated the components using oil press and nylon net to obtain hard fat (S15) and soft fat (L15).

[0036] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is: The chilled anhydrous milk fat (AMF) was completely melted (destroying the original crystal structure) in a water bath at 80℃, and kept at this temperature for 10 min, then placed in a 35℃ crystal growing tank for 18 h. The components were separated by using an oil press and nylon mesh to obtain stearin (S35) and olein (L35).

[0037] (1) The yield and sliding melting point of each component obtained from the examples and comparative examples were determined. Yield (%) = mass of fraction / mass of AMF x 100.

[0038] The sliding melting point in each component refers to GB / T 24892-2010 "Determination of melting point (slip point) of animal and vegetable fats and oils in open capillary".

[0039] The yield determination results of each component obtained from the examples and comparative examples are shown in Table 1.

[0040] As can be seen from Table 1, after dry fractionation of AMF, the yield of L25 is relatively high, which is 61.57%. As the distillation temperature increases, the yield of the light phase component continuously increases to 7.71%, but the overall sliding melting point is lower than that of AMF. This is because more low melting point fatty acids and triglycerides are distilled out into the light phase, and the proportion and purity of low melting point substances in the light phase component increase. In addition, in Comparative Example 4 and Comparative Example 5, when AMF is fractionated at 15℃, the yield of L15 is very low, only 3.88%, and the sliding melting point is 12.05℃. This indicates that L15 contains less medium and high melting point components, which means that the content of medium and long chain fatty acids contained therein is relatively low, resulting in the need to invest more AMF raw materials to obtain the same yield of MCT in the subsequent short path molecular distillation process, increasing the production cost. Although the yield of L35 is relatively high (86.04%), due to the higher dry fractionation temperature, the components are complex, resulting in a higher sliding melting point. In the subsequent short path molecular distillation, higher temperature or stronger vacuum is needed to effectively separate MCT. In addition, L35 contains more medium and high melting point components, and even after short path molecular distillation, a small amount of fatty acids greater than C14 may still be mixed in the light phase component, reducing the purity of MCT.

[0041] (2) Gas chromatography for detecting fatty acid composition and content of components The sample was heated to complete melting, 20 μL of the sample was taken in a 10 mL centrifuge tube, 1 mL of n-hexane and 1 mL of 1 mol / L KOH-methanol solution were added, vortexed for 8 min, then 2 mL of distilled water was added, vortexed for 2 min, and then centrifuged at 4000 r / min for 5 min to obtain the supernatant. The supernatant was filtered through a 0.22 organic filter membrane and transferred to a gas chromatography bottle. The fatty acid composition of each component was analyzed using an Agilent 8890A chromatograph equipped with a flame ionization detector.

[0042] The fatty acid composition and the fatty acid content of each component of the examples and the comparative examples are shown in Table 2.

[0043] Table 2 fatty acid composition and content (%) Note: short-chain fatty acids, SCFA (C4-C6); medium-chain fatty acids, MCFA, (C8-C14); long-chain fatty acids, LCFA, (C15-C18); total saturated fatty acids, SFA; monounsaturated fatty acids, MUFA; polyunsaturated fatty acids, PUFA; unsaturated fatty acids, UFA; L25 and S25 are components of Example 1.

[0044] As can be seen from Table 2, dry fractionation and short-path molecular distillation do not change the fatty acid composition, but affect the fatty acid content. After dry fractionation, the SCFA, MCFA, and LCFA contents in AMF and L25 are similar. After short-path molecular distillation, compared with L25, the SCFA and MCFA contents in the light phase component increase as the temperature increases, that is, as the distillation temperature increases, the light phase component has better aggregation for medium and short-chain fatty acids.

[0045] (3) Determination of triglyceride types and contents of each component of the examples and the comparative examples by high performance liquid chromatography-mass spectrometry About 5 mg of sample was weighed and dissolved in 1 mL of chloroform / methanol mixed solution (1:2, v / v) and vortexed for 30 s until the sample was completely dissolved. Then the sample was diluted 50 times with a methanol solution containing 10 mmol / L ammonium formate and 0.1% formic acid and 1 mmol / L internal standard (12:0 LPC), and the diluted sample was transferred to a chromatographic vial and vortexed again.

[0046] High performance liquid chromatography conditions: BEH C18 (1.7 μm, 2.1 mm ID x 100 mm) was used to transfer the sample solution. The column temperature was maintained at 60°C throughout the process. The mobile phase A was a mixture of isopropyl alcohol-acetonitrile (9:1, v / v), and the mobile phase B was acetonitrile-water (1:1, v / v), both containing 10 mmol / L ammonium formate and 0.1% formic acid. Elution conditions: flow rate 0.3 mL / min; injection volume 3 μL; 0 min, 75% A; 28 min, 90% A; 28.1 min, 75% B; 30 min, 75% B.

[0047] Mass spectrometry conditions: gas curtain gas (CPU) 25; collision gas CAD medium; ion source gas 1 (GS1) 45; ion source gas 2 (GS2) 50; electrospray voltage 5500 V; temperature 550℃; set EMS-EPI mode to obtain parent ions, MRM-IDA-EPI method, Q1=Q3, for identification.

[0048] The triglyceride species and content determination results of the components of the examples and comparative examples are shown in Table 3.

[0049] Table 3 Triglyceride species and content (%) of each component Note: Low molecular weight triglyceride, LMW-TAG (C26-C34); medium molecular weight triglyceride, MMW-TAG (C35-C40); high molecular weight triglyceride, HMW-TAG (C41-C54); saturated triglyceride, STAG; unsaturated triglyceride, UTAG. Medium long chain triglyceride, MLCT; medium chain triglyceride, MCT; L25 and S25 are components of Example 1.

[0050] As can be seen from Table 3, after dry fractionation, the MCT content of the L25 component is higher than that of the AMF, and after further distillation, the MCT content of 170D, 180D and 190D is all relatively high, significantly higher than that of the AMF. Specifically, when the distillation temperature reaches above 180℃, the MCT content (>4.55%) is more than twice that of the AMF (1.98%), effectively realizing the enrichment of MCT.

[0051] (4) Flavor determination The flavor of each component was determined by gas chromatography-ion mobility chromatography (HS-GC-IMS). 1 g of sample was accurately weighed into a 20 mL headspace bottle, incubated at 65℃ for 15 min, and then the sample was tested. The specific setting process is as follows: the headspace sampling conditions use an incubation temperature of 65℃; the incubation time is 15 min; the sampling needle temperature is 85℃; the sampling volume is 500 μL; and the incubation rotation speed is 500 r / min.

[0052] GC conditions: chromatographic column: MXT-WAX (30 m x 0.53 mm x 1.0 μm) was used; the column temperature was set to 60℃; the initial flow rate was 2 mL / min, maintained for 2 min; linearly increased to 10 mL / min within 8 min, and then linearly increased to 100 mL / min within 10 min, maintained for 30 min; the chromatographic run time was 50 min; the injection port temperature was 80℃.

[0053] IMS conditions: drift gas flow rate 150 mL / min; both carrier gas and drift gas are high-purity nitrogen (purity ≥99.999%); carrier gas flow rate is 2 mL / min from 0 to 2 min; IMS temperature is 45℃.

[0054] L25 and S25 are components of Example 1.

[0055] The flavor determination results for the examples and comparative examples are shown in the figure. Figure 1 .

[0056] from Figure 1 It is known that pentanal, propionaldehyde, butyraldehyde, and acetic acid account for a relatively high proportion of flavor compounds in the 160D fraction and the heavy phase. These substances are the main sources of pungent odors. At low concentrations, they can add a certain flavor profile to milk fat, but at higher concentrations, they can impart unpleasant flavors. Hexanal, 2-propanone, and 1-penten-3-ol not only account for a relatively high proportion in the 180D fraction but are also higher than in other light phase fractions. They mainly contribute flavor characteristics such as green aroma, fatty flavor, fruity aroma, and apple flavor. Ethanol has the highest content in the 170D and 190D fractions, which can impart pungent or alcoholic odors to the milk fat fraction, affecting the overall flavor balance. The 180D fraction of Example 1 can efficiently enrich MCTs and also improve the flavor of milk fat, enhancing its overall flavor quality.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for the preparation of milk fat enriched in medium-chain triglycerides, characterized in that, The method comprises: (1) after completely melting the anhydrous milk fat in a water bath and keeping the water bath warm, placing it at 20-30℃ for crystallization, and separating soft fat and hard fat through crystallization; (2) performing single-stage short-path molecular distillation on the melted soft fat at 175-185℃ to obtain a heavy phase component and a light phase component, wherein the light phase component is the milk fat rich in medium-chain triglycerides.

2. The method of claim 1, wherein, In step (1), the temperature of the water bath is 70-90℃.

3. The method of claim 1, wherein, In step (1), the time for keeping the water bath warm is 5-20min.

4. The method of claim 1, wherein, In step (1), the time for crystallization is 15h-20h.

5. The method of claim 1, wherein, In step (2), the working pressure of the single-stage short-path molecular distillation is 0.007-0.01mbar. And / or, the rotating speed of the thin-film knife in the single-stage short-path molecular distillation is 130-200r / min.

6. The method of claim 1, wherein, In step (2), the feeding rate of the feeding port of the single-stage short-path molecular distillation is 1.5-2.5mL / min, and the temperature is 60-65℃. And / or, before the single-stage short-path molecular distillation, the soft fat is melted in a water bath at 60-65℃.

7. A milk fat enriched in medium-chain triglycerides, characterized in that, Prepared by the method of any one of claims 1-6.

8. The milk fat enriched in medium-chain triglycerides according to claim 7, characterized in that, The mass fraction of medium-chain triglycerides in the milk fat rich in medium-chain triglycerides is 3.7%-4.8%.

9. The milk fat enriched in medium-chain triglycerides according to claim 7, characterized in that, The characteristic flavor substances of the milk fat rich in medium-chain triglycerides include one or more of hexanal, 2-propanone and 1-pentene-3-ol.

10. The milk fat rich in medium-chain triglycerides of any one of claims 7-9 is used in food and health products.

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