Secoisolariciresinol diglucoside pyrolysis product for improving stability and bioavailability of alpha-linolenic acid in emulsion system as well as preparation method and application of secoisolariciresinol diglucoside pyrolysis product

Abstract

The invention belongs to the technical field of food processing, and particularly relates to a secoisolariciresinol diglucoside pyrolysis product for improving the stability and bioavailability of alpha-linolenic acid in an emulsion system, and a preparation method and application of the secoisolariciresinol diglucoside pyrolysis product. The FLM hot processing product with efficient antioxidant activity is obtained by carrying out heat treatment on natural-form flax lignan (FLM) at 150 DEG C, and the FLM hot processing product can be directly applied to an emulsion system so as to improve the stability and bioavailability of alpha-linolenic acid. When the FLM hot processing product and the ALA are subjected to co-nanocrystallization to form the emulsion, the FLM hot processing product spontaneously adsorbs on an oil drop interface to improve the density of the emulsion drop interface, and the storage physical and chemical stability of the ALA emulsion is further improved based on the interface anti-oxidation effect. The FLM hot processing product and the gastrointestinal tract digestion product of the FLM further participate in synthesis of ALA micelles, ALA absorption is promoted by improving expression of protein related to absorption of ALA in small intestine epithelial cells, so that the bioavailability of ALA is improved, and efficient ingestion of plant-derived ALA is realized based on'total ingestion chain type regulation '.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of biotechnology, and specifically relates to a flax lignan pyrolysis product for improving the stability and bioavailability of alpha-linolenic acid in an emulsion system, a preparation method and application. BACKGROUND

[0002] Lignans are important drug candidates in the field of medicinal chemistry, and have biological activities such as antioxidant activity, tumor activity, anti-inflammatory activity, etc. Research has found that flax lignans can improve the storage stability of whey protein / phospholipid stabilized flaxseed oil emulsion and promote the release of ALA. In addition, lignans can also improve the absorption of free fatty acids in the epithelial cells of the emulsion system by stimulating bile secretion, increasing the production of micelles, and increasing the expression of apolipoprotein to promote chylomicron synthesis, and are currently the most polyphenolic compounds that can reduce ALA oxidation and improve its bioavailability. In flaxseed, lignans usually exist in the form of SDG oligomers, also known as flax lignan macromolecules (FLM), and the highest molecular weight of FLM is about 4000 Da, mainly composed of five SDG residues connected by HMGA residues. 4-O-β-d-glucopyranosyl coumaric acid (CouAG) and 4-O-β-d-glucopyranosyl ferulic acid (FerAG) and other phenolic acid glycosides are connected to SDG through ester bonds and exist at both ends of the SDG-HMGA chain to form the side chain of FLM, and determine the degree of polymerization in the process of biosynthesis. In addition, pinoresinol diglucoside (PDG) and flavonoid plant gossypetin diglucoside (HDG) may also participate in the formation of the FLM skeleton. FLM has been found to have the ability to release small molecule phenolic acids and flavonoids, and SDG and other polyphenolic compounds may have synergistic antioxidant effects, which further helps them to enhance antioxidant effects in vivo and in vitro.

[0003] Heat processing is a common processing method for lignan-related products, such as pasteurization, boiling, cooking and baking. Studies have found that moderate heat input can significantly affect the content and structure of food polyphenols, and promote their dissolution during digestion and further interaction with other food ingredients. For example, for sesamin and sesame meal rich in sesamin, the release of lignans after in vitro digestion increased to 19.6% after 240℃ heat treatment for 20min due to the degradation of aglycone and glycoside. SDG has excellent thermal stability in dried flaxseed meal even under baking conditions. Intermittent pasteurization (85℃, 20min) does not affect the content of SDG in SDG-rich whey beverage, but after 6 months of storage at 8℃, the concentration of SDG decreases by 25%. At present, in-depth research on the structure and function changes of flax lignans under different heat treatment conditions, especially the structure-function (antioxidant activity) relationship and the changes in microbehavior in emulsions is still blank. Therefore, it is urgent to explore the structure-function evolution law of FLM in different heat processing processes, and to screen out heat decomposition products with high antioxidant activity and synchronous improvement of polyunsaturated fatty acid bioavailability, in order to realize the optimal utilization of flax lignans in food industry. SUMMARY

[0004] Therefore, the present application provides a flax lignan pyrolysis product for improving the stability and bioavailability of alpha-linolenic acid in an emulsion system, a preparation method and application.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] The first technical purpose of the present application is to provide a preparation method of a flax lignan pyrolysis product for improving the stability and bioavailability of alpha-linolenic acid in an emulsion system. The flax lignan pyrolysis product is a high-temperature heat treatment decomposition product, the heat treatment temperature is 150℃, and the time is 30 minutes.

[0007] Alternatively, the flax lignan is obtained by defatting and extracting flaxseed shell powder.

[0008] Further, the specific preparation of the flax lignan is as follows:

[0009] Flaxseed hull powder (FHP, 20 g) was defatted by incubation with 100 mL of n-hexane at 25℃ for 24 hours; 20 g of defatted FHP sample was extracted with 100 mL of 70% ethanol solution (v / v) for three times, each time for 24 hours; after each extraction, the mixture was centrifuged at 10000 x g for 40 minutes, and the supernatant enriched with FLM was collected, and the polar small molecule polyphenols were purified by a C18 solid phase extraction column (Waters, C18, 5 cm), followed by concentration of the purified FLM extract using a rotary evaporator (IKAR V10D, Germany), and then vacuum freeze-drying treatment to obtain the FLM.

[0010] Further, the pyrolysis conditions of the flax lignan include low-temperature heat treatment decomposition and high-temperature heat treatment decomposition; wherein,

[0011] The low-temperature heat treatment decomposition temperature includes a digestion temperature of 37℃, a low-temperature sterilization temperature of 55℃, and a pasteurization temperature of 70℃; and the high-temperature heat treatment decomposition temperature includes a boiling temperature of 100℃ and a baking temperature of 150℃.

[0012] The second technical purpose of the present application is to disclose a flax lignan pyrolysis product prepared by the above method, and the FLM retention rate is 50% after moderate heat treatment (150℃, 30 min); although the FLM is degraded under the condition of high-temperature moderate heat treatment (baking temperature 150℃), no other small molecule polyphenols are generated after degradation, indicating that the degree of degradation is limited and only exists in the oxidation of the internal hydroxyl group of FLM.

[0013] Further, the flax lignan pyrolysis product can improve the stability and bioavailability of alpha-linolenic acid in an emulsion system, the FLM retention rate of flax lignan FLM is 50%, the degradation rate of total phenolic acid at the chain end of FLM is 45%, and the antioxidant capacity of the mixture FLM150 is improved by more than 70% (DPPH free radical scavenging rate).

[0014] The third technical purpose of the present application is to disclose the application of the flax lignan pyrolysis product prepared by the above method in improving the stability and bioavailability of alpha-linolenic acid in an emulsion system in food processing.

[0015] Compared with the prior art, the beneficial effects of the present application are:

[0016] The application obtains a FLM heat-processed product with high-efficiency antioxidant activity by heat treating natural-form flax lignan (FLM) at 150 DEG C, which can be directly applied in emulsion systems to improve the stability and bioavailability of alpha-linolenic acid (ALA). When the FLM heat-processed product and ALA are co-nanoized to form an emulsion, the FLM heat-processed product improves the interface density of the emulsion droplets by spontaneously adsorbing on the interface of the oil droplets, and further improves the storage physicochemical stability of the ALA emulsion based on the interface antioxidant effect. The FLM heat-processed product and its gastrointestinal digestion product further participate in the synthesis of ALA micelles, promote the absorption of ALA by improving the expression of proteins related to the absorption of ALA in small intestinal epithelial cells, thereby improving the bioavailability of ALA, and realize the efficient intake of plant-sourced ALA based on the "whole intake chain regulation". BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the 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 only embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the provided drawings.

[0018] Figure 1 is the stability (concentration and retention rate) of FLM under different heat processing conditions.

[0019] Figure 2 is the structural change (FT-IR) of FLM product after heat processing.

[0020] Figure 3 is the change of main component content of FLM product after heat processing (1-6 are FLM, FLM 37, FLM 55, FLM 70, FLM 100, FLM 150, mg / mL, respectively).

[0021] Figure 4 is a schematic diagram of the structural change of FLM under acid, alkali and heat processing conditions (ChemDraw Ultra 14.0).

[0022] Figure 5 is the change of antioxidant performance of FLM under different processing conditions (DPPH and ABTS free radical scavenging capacity).

[0023] Figure 6 is the effect of FLM, FLM 37, FLM 55, FLM 70, FLM 100 or FLM 150 on the release of free fatty acids (FFA%) and micellization of ALA of phospholipid-ALA emulsion in different simulated digestion stages.

[0024] Figure 7is the maximum loading of ALA in micelles that can be formed after FLM and its thermally processed products are simulated to be digested in small intestine.

[0025] Figure 8 is the absorption kinetics of ALA by Caco-2 model simulated small intestinal epithelial cells.

[0026] Figure 9 is the storage stability of emulsion system (multiple light scattering analysis) introduced FLM and its thermally processed products.

[0027] Figure 10 is the effect of FLM and its thermally processed products on oil-water interfacial tension. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0029] Herein, the term "embodiment" as "exemplary" explained in any embodiment is not necessarily interpreted as superior or better than other embodiments. In the performance index test of the embodiments of the present application, unless otherwise specified, the conventional test method in the art is adopted. It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the disclosure of the present application.

[0030] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as generally understood by those skilled in the art to which the present application belongs; as the test methods and technical means not specially noted in the present application are all the experimental methods and technical means generally used by those skilled in the art.

[0031] In the description of the present application, it should be understood that the terms "middle", "upper", "lower", "rise", "fall", "vertical", "surface", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and are not intended to indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0032] In order to better illustrate the content of the present application, a large number of specific details are given in the specific embodiments below. Those skilled in the art should understand that the present application can also be implemented without some specific details. In the embodiments, some methods, means, instruments, devices and the like which are well known to those skilled in the art are not described in detail, in order to highlight the main idea of the present application.

[0033] In the case of no conflict, the technical features disclosed in the embodiments of the present application can be combined arbitrarily, and the technical solutions obtained belong to the disclosure of the present application.

[0034] The application discloses a kind of flax lignan pyrolysis product for improving the stability and bioavailability of α-linolenic acid in emulsion system and a preparation method thereof.

[0035] To better understand the present application, the following examples are further described below, but can not be understood as limiting the present application, some non-essential improvements and adjustments made by the skilled in the art according to the above invention are also regarded as falling within the scope of the present application.

[0036] Example 1

[0037] A kind of flax lignan pyrolysis product and a preparation method thereof, as follows:

[0038] Defatting treatment was carried out by incubating flaxseed hull powder (FHP, 20 g) with 100 mL of n-hexane at 25°C for 24 hours; 20 g of defatted FHP sample was taken and extracted with 100 mL of 70% ethanol solution (v / v) for three times, each time for 24 hours; after each extraction, the mixture was centrifuged at 10000 x g for 40 minutes, and the supernatant enriched with FLM obtained from each extraction was collected and purified by a C18 solid-phase extraction column (Waters, C18, 5 cm). The purified FLM extract was then concentrated using a rotary evaporator (IKAR V10D, Germany) and freeze-dried under vacuum to obtain the product.

[0039] After the FLM sample was redissolved in 0.5 mL of 70% ethanol aqueous solution (v / v), it was diluted with distilled water to 10 mL (concentration 5 mg / mL, w / v). The FLM solution was heated in a water bath at 37°C, 55°C, 70°C and 100°C for 30 minutes to simulate low-temperature drying (55°C), pasteurization (70°C) and boiling (100°C) processes. An oil bath at 150°C was also set to heat for 30 minutes to simulate the baking process of FLM. Immediately after heat treatment, the sample was placed in ice water to terminate the reaction, and then freeze-dried for later use. The FLM samples prepared at different temperatures were labeled as FLM-37, FLM-55, FLM-70, FLM-100 and FLM-150, respectively.

[0040] To further demonstrate the beneficial effects of the present application and better understand the present application, the technical features disclosed in the present application are further illustrated by the following test examples and application examples, but can not be understood as limiting the present application. Other improvements without creative work made by the skilled in the art according to the above invention are also regarded as falling within the scope of the present application.

[0041] 1. FLM heat-treated product structure

[0042] To clarify the structural changes of FLM during heat treatment, the commonly used heat conditions were set as follows: simulated digestion temperature 37℃ (FLM 37), low-temperature sterilization temperature 55℃ (FLM 55), pasteurization temperature 70℃ (FLM 70), simulated boiling temperature 100℃ (FLM 100) and baking temperature 150℃ (FLM 150) to conduct FLM heat treatment for experimental exploration.

[0043] Figure 1 To compare the FLM retention rate after FLM treatment under different heat processing conditions with the untreated FLM group (FLM), the FLM retention rate in FLM 37 and FLM 55 groups was as high as 100%, but the FLM retention rate in FLM 70, FLM 100 and FLM 150 groups was significantly reduced (p<0.05), and the degradation rate in FLM 150 group reached 50%.

[0044] The above results all show that FLM has strong thermal stability under low-temperature heat treatment conditions (simulated digestion temperature 37℃ and low-temperature sterilization temperature 55℃). However, under high-temperature heat treatment conditions (simulated boiling temperature 100℃, baking temperature 150℃), FLM degrades, but no other small molecule polyphenols are produced after degradation, indicating that the degradation is limited and may only exist in the oxidation of the internal hydroxyl groups of FLM.

[0045] To further analyze the structural changes of FLM during high-temperature heat treatment, infrared was used to identify the structure of FLM, and the composition changes of FLM were determined by hydrolysis reaction.

[0046] The changes in the structure of FLM and its heat-treated products were analyzed by Fourier transform infrared spectroscopy, and the results are shown in Fig. Figure 2 a. FLM and its heat-treated products (FLM 37, FLM 55, FLM 70, FLM 100 and FLM 150) all have absorption peaks of the typical structure of lignan in FT-IR spectrum: C-O single bond stretching vibration of phenolic hydroxyl (Ar-OH) at 3369.36 cm -1 , C single bond stretching vibration of Ar-OH at 1218 cm -1 , C-H single bond bending vibration of methyl (-CH3) at 1458 cm -1 , Calkyl-O stretching vibration of methoxyl (Ar-OCH3) at 1120 cm -1 , and 1900-1650 cm -1occurred. The C=0 stretching vibration (Wen, Song, Zhuang, et al., 2022) occurred. The FLM and its heat-treated product structures had characteristic peaks at wave numbers of 3369 cm -1 , 1726 cm -1 , and 1458 cm -1 , further indicating that they contained hydroxyl, carbonyl, and benzene ring characteristic structures in their structures. Compared with FLM, the groups -OH (3369.36 cm -1 ) of FLM 37, FLM 55, FLM 70, FLM 100, and FLM 150 groups had a blue shift, and the C=0 group (1726 cm -1 ) had a red shift, indicating that the phenolic hydroxyl and C=0 groups changed in structure under high-temperature heat treatment.

[0047] The O single bond stretching signal of -OH at 3369.36 cm -1 was further normalized ( Figure 2 b) to evaluate the changes in the relative contents of -OH and C=0 groups. The results showed that the intensity of the O single bond stretching vibration signal (3369.36 cm -1 ) of the phenolic hydroxyl gradually decreased after heat treatment, and the signal intensity of the C=0 stretching vibration (1726 cm -1 ) correspondingly increased, thus confirming that -OH was oxidized and further converted to carbonyl C=0 during the high-temperature treatment of FLM, and the product was likely to be a quinone compound. This process also conforms to the oxidation rules of polyphenolic compounds.

[0048] 2. Changes in the composition of FLM heat-treated products

[0049] Further qualitative and quantitative analysis of the components of FLM, FLM 37, FLM 55, FLM 70, FLM 100, and FLM 150 after complete hydrolysis was performed to confirm the changes in the structural composition of FLM after different heat treatments. Figure 3 The concentrations of the main components released after complete hydrolysis of FLM, FLM 37, FLM 55, FLM 70, FLM 100, and FLM 150 (p-coumaric acid and its glycosides, ferulic acid and its glycosides, caffeic acid, and lignan SDG, flavonoid PDG and its monoglucoside, gossypol glucoside, dihydroferulic acid dimer monoglucoside, and its aglycone).

[0050] Compared with the unheated FLM group, the FLM 37 group showed depletion of CouAG, FerAG, SDG, PDG, HDG, and dihydroferulic acid dimer and its glycosides, with depletion rates less than 1% (p < 0.05). The major components SDG, PDG, HDG, CouAG, FerAG, and dihydroferulic acid were significantly different between the FLM 37, FLM 55, and FLM 70 groups. Compared with the unheated FLM group, the FLM 100 and FLM 150 groups showed decreased levels of CouAG, FerAG, CarA, SDG, PDG, HDG, and dihydroferulic acid dimer. The depletion rates of SDG, PDG, and HDG were all less than 1%, with no significant differences. The depletion rates of CouAG, FerAG and its isomers, and dihydroferulic acid dimer glycosides were significantly higher, at 14%, 10%, and 21%, respectively (p < 0.05). FLM exhibits strong thermal stability under low-temperature heat treatment. However, high-temperature heat treatment (>100°C) oxidizes the hydroxyl groups on the phenolic acid glycosides at both ends of the FLM long chain, resulting in a significant loss of phenolic acid glycosides in the composition. The results showed that the FerAG content in the FLM 150 group increased significantly compared to the FLM 100 group (p<0.05), indicating that isomerization between FerAG and its isomers may occur under high-temperature conditions.

[0051] 3. Mechanism prediction

[0052] Based on the above research results, the degradation mechanism of FLM under thermal processing conditions is speculated. Figure 4 As shown in the figure, under thermal processing conditions, low heat has no effect on the FLM structure. However, under high heat (>100°C), the phenolic acids at both ends of the FLM molecular chain undergo cis-trans isomerization, and the phenolic hydroxyl groups are oxidized to form quinone compounds. Furthermore, molecular depolymerization may occur under high heat conditions due to ester bond cleavage.

[0053] 4. Analysis of antioxidant effect

[0054] On the basis of the degradation rule of FLM in the hot processing environment, the antioxidant properties of FLM hot processing products were further analyzed from the perspective of free radical scavenging (ABTS·+and DPPH·), respectively. By calculation, the ratio of the number of hydroxyl groups of SDG, SECO, and FLM under the same molar concentration is 1:1.9:0.64 (at this time the average molecular weight of FLM is Mw=4641). By calculation, when the mass concentration of FLM is 1 mg / mL, the mass concentration of SDG containing the same number of hydroxyl groups is 0.1 mg / mL, and the mass concentration of SECO is 0.025 mg / mL. Therefore, the mass concentrations of FLM, SDG, and SECO in the experimental group are set to 1 mg / mL, 0.1 mg / mL, and 0.025 mg / mL, respectively, aiming to compare the differences in antioxidant capacity of the three under the condition of the same number of hydroxyl groups.

[0055] The scavenging effects of FLM, SDG, and SECO on different free radicals (0.01 μmol DPPH·or ABTS / 20 μL FLM) were compared, where DPPH·represents the antioxidant properties of the three lignans in alcohol systems, mainly involving the HAT mechanism of polyphenol antioxidant, and ABTS·+represents the antioxidant properties of the three lignans in water systems, mainly involving the SPLET mechanism. The results are shown in Figure 4 As shown in the figures, there is no significant difference in the ABTS·+( Figure 5 a) and DPPH·( Figure 5 b) scavenging capacity between untreated FLM and its hot processing products. The ABTS·+and DPPH·scavenging capacity of SDG and SECO with the same number of hydroxyl groups is significantly lower than that of FLM and its hot processing products, where the ABTS·+and DPPH·scavenging capacity of SDG is 18.8% and 8.6% lower than that of FLM, respectively, and the ABTS·+and DPPH·scavenging capacity of SECO is 75.2% and 50% lower than that of FLM, respectively (p<0.05). In addition, the ABTS·+and DPPH·scavenging rates of SDG are 66.7% and 50% higher than those of SECO, respectively (p<0.05).

[0056] The antioxidant properties of FLM and FLM hot processing products were compared, and it was found that there was no significant difference in the reducing capacity of FLM and its hot processing products. Compared with untreated FLM, higher temperature hot treatment (FLM 70, FLM 100, and FLM 150) significantly reduced the total phenol content of FLM by 5% (p<0.05), indicating the degradation of hydroxyl groups. In addition, there is no significant difference in total phenol content between FLM and its hot processing products and SDG under the same number of hydroxyl groups, which are all between 30-35 μg SA / mL.

[0057] The above experimental results suggest that FLM and its heat-processed products have good antioxidant thermal stability, and represent two different antioxidant mechanisms for two different free radicals, DPPH· and ABTS·+. The results show that, under the same number of hydroxyl groups, the scavenging ability of FLM and its heat-processed products for the two free radicals is better than that of SDG and SECO, indicating that the hydroxyl groups in FLM have higher free radical scavenging efficiency, and the reason for this phenomenon may be the free radical scavenging effect of the phenolic hydroxyl groups of HDG, PDG and other flavonoid polyphenol compounds in FLM.

[0058] 5. Digestive stability and antioxidant analysis

[0059] The digestion process simulates the emptying process of gastric digestion. During the simulated gastric digestion, the supernatant was taken at 1 h, 2 h and 3 h and labeled as G1, G2 and G3, respectively. The remaining sample was subjected to simulated intestinal digestion, and samples were also taken at 1 h, 2 h and 3 h during the digestion process and labeled as I1, I2 and I3, respectively.

[0060] Antioxidant capacity of FLM at different digestion stages. The total phenol content, ferrous ion reducing capacity, and free radical scavenging capacity (polar system ABTS and weakly polar system DPPH) in the supernatant after initial, oral, gastric (G1, G2, G3), and intestinal (I1, I2, I3) digestion were determined. During the simulated oral digestion stage, the total phenol content of FLM was at a low level (<75 μg sinapinic acid / mL), the FRAP reducing capacity of each group was about 5 μg sinapinic acid / mL, and it had strong ABTS free radical scavenging capacity (~100%) and DPPH free radical scavenging capacity (~40%); during the simulated gastric digestion stage, the total phenol content of FLM increased significantly to 200 μg sinapinic acid / mL, at this time the FRAP reducing capacity of each group had no significant difference compared with that after oral simulation digestion, about 5 μg sinapinic acid / mL, the DPPH free radical scavenging capacity had no significant change except for FLM 150 group (increased by 15%, P<0.05), but the ABTS free radical scavenging capacity was significantly reduced (~40%, P<0.05); during the simulated intestinal digestion stage, the total phenol content of FLM increased significantly to 350-400 μg sinapinic acid / mL, at this time the FRAP reducing capacity of each group was significantly improved, especially in the I3 stage (+3.4 times, P<0.05), the ABTS free radical scavenging capacity was increased to 100% (P<0.05), but the DPPH free radical scavenging capacity was reduced by 50% (P<0.05).

[0061] For FLMs treated with different heat treatments, the difference between groups mainly existed in FLM 150 group, and there was no significant difference in the change of antioxidant resistance during the digestion process in other groups. Compared with the untreated FLM group, the total phenol content of the FLM 150 treated group was significantly increased by 30.8% (P<0.05) at the small intestine I1 stage, the reducing power was also increased by 60% (P<0.05) at the small intestine I1 stage, the ABTS free radical scavenging capacity was increased by 70% (P<0.05) at the small intestine I2 and I3 stages, and the DPPH free radical scavenging capacity was significantly increased by 50% (P<0.05) at the stomach G1 stage. This may be due to the unfolding of FLM structure caused by high temperature heat treatment, which makes it easier to contact with digestive enzymes and thus hydrolysis, releasing more phenolic hydroxyl groups. In addition, the total phenol content and FRAP reducing power of FLM and its heat treated products are produced in the small intestine simulation stage, and the FLM reducing power in the I3 stage is 1.2 times that of I1 and I2 (P<0.05), indicating that the small intestine is the main digestion depolymerization site of FLM, indicating that the depolymerization and solubilization of FLM during digestion process causes the further exposure of phenolic hydroxyl groups, improving its antioxidant capacity. Therefore, FLM treated at 150°C under simulated baking conditions can improve its solubility in the small intestine stage and improve its antioxidant performance. The main mechanism may be that high temperature heat treatment causes the unfolding of FLM structure, which makes it easier to contact with digestive enzymes and thus hydrolysis and release of phenolic hydroxyl groups.

[0062] In summary, under high temperature conditions (100°C and 150°C), the phenolic hydroxyl groups of CouAG, FerAG and their isomers and dihydroferulic acid dimers, etc. located at both ends of FLM molecule are oxidized to carbonyl C=O, resulting in a decrease of 14%, 10% and 21% respectively. The results of simulated digestion antioxidant activity show that FLM high temperature pyrolysis products have improved antioxidant capacity during in vivo digestion process, and FLM and its heat treated products have antioxidant capacity throughout the digestion stage, and their antioxidant capacity gradually increases with the progress of digestion. In addition, the highest total phenol content and FRAP reducing power of FLM and its heat treated products are produced in the small intestine simulation stage, and the FLM reducing power in the I3 stage is 1.2 times that of I1 and I2 (P<0.05), indicating that the small intestine is the main digestion depolymerization site of FLM and its pyrolysis products, and the depolymerization and solubilization of FLM during the digestion process causes the further exposure of phenolic hydroxyl groups, improving its antioxidant capacity. For FLMs treated with different heat treatments, the difference between groups mainly exists in FLM 150 group, and shows more excellent antioxidant properties.

[0063] Application Example 1: FLM 150 for improving the physicochemical stability of ALA in emulsion system

[0064] Emulsion preparation: The emulsions were prepared with 20% linseed oil as oil phase, 2% sunflower phospholipid Sunlipon 90 (S90, PC > 90%) as water phase, and 0.5 mg / mL FLM or its heat-processed products as antioxidant. The specific preparation method is as follows: 5 mM phosphate buffer (PBS, pH = 7, potassium phosphate dibasic and potassium phosphate monobasic) was prepared for emulsifier solution. The emulsifier S90 was dissolved in PBS to a concentration of 2.5%, and stirred overnight to completely dissolve. FLM and its heat-processed products were weighed and added to the emulsifier solution after being dissolved with 100 μL of 70% ethanol to a concentration of 6.25 mg / mL. The 80% emulsifier solution containing antioxidants was sheared with 20% linseed oil by a high-speed shearing machine at 10,000 rpm for 5 min to complete the pre-emulsification step, and at this time the concentration of emulsifier S90 in the whole system was 2% and the concentration of antioxidant was 0.5 mg / mL. The pre-emulsified ALA-rich emulsion was further prepared using a microfluidizer at a pressure of 12,000 psi for 4 cycles. To prevent microbial contamination during the storage experiment, 0.02% sodium azide was added to the emulsion after the emulsion was prepared to inhibit the growth of microorganisms. The emulsion was divided into 15 mL test tubes and sealed with silica gel plugs, and stored at 37°C in the dark for 15 days. The samples were taken regularly to determine the relevant indicators.

[0065] The backscattering light change curve during emulsion storage is as follows Figure 9 The results show that in the bottom part of the sample (0-8 cm), the ΔBS curve of all emulsions shows a continuous downward trend with the change of storage time, which indicates that the droplets at the bottom of the bottle have aggregated or floated upwards. In the middle of the sample (10-16 cm), the ΔBS of all emulsions has a whole upward or downward shift in the whole interval, indicating that the droplets are floating upwards while the particle size is increasing during storage. In the top of the sample (40-44 cm), the ΔBS of all emulsion systems except FLM 55 and FLM 150 groups is less than 0, indicating that sedimentation, demulsification or oil separation may occur in the top layer, resulting in a lower backscattering light than the initial value. However, the ΔBS of FLM 55 and FLM 150 emulsion groups is greater than 0, but the ΔBS value of FLM 55 emulsion group is as high as 40%, and the ΔBS value of FLM 150 emulsion group is about 35%, indicating that the emulsion group added with FLM 150 has better physical stability.

[0066] The change of stability index (Turbiscan Stability Index, TSI) over time showed that the TSI values were in the order of FLM 55 > FLM 37 > FLM > FLM 100 ≈ FLM 70 ≈ control > FLM 150. Therefore, the results showed that the emulsion group with FLM 150 had the best thermodynamic stability. Comprehensive evaluation of particle size, micro-morphology, stability index and dynamic stability during emulsion storage showed that compared with the untreated and other heat treatment methods, FLM 150 could promote the formation of S90 emulsion interface and significantly improve the storage stability of S90 stabilized ALA emulsion.

[0067] The results of primary (lipid hydroperoxide) and secondary reaction products (TBARS) produced by lipid oxidation during storage showed that FLM 100 and FLM 150 had the ability to significantly reduce the concentration of hydroperoxide and TBARS in the emulsion system, with the highest reduction of 26.7% for hydroperoxide concentration and 80% for TBARS concentration. Therefore, the results of this study showed that FLM 100 and FLM 150 had the effect of inhibiting lipid oxidation in S90 stabilized emulsion system.

[0068] The adsorption kinetics of S90 on the FO-water interface showed that the interfacial tension of all groups of flaxseed oil-water decreased rapidly from 12.7 mN / m to 6.5-7.5 mN / m, among which the emulsifier S90 group had the lowest flaxseed oil-water interfacial tension value of 6.5 mN / m. Compared with the blank control group (oil-water), the addition of FLM and its heat processed products all led to an increase in flaxseed oil-water interfacial tension, especially FLM 100 and FLM 150. The interfacial pressure π was converted to γ sample -γ control , and the function of interfacial pressure π-t 1 / 2 was plotted. As Figure 10 shown, the function of π-t 1 / 2 was linear in the initial adsorption process, and previous studies have shown that when the interfacial pressure π is linear with t 1 / 2 , the interfacial adsorption process of emulsifiers on the oil-water interface in the initial stage is formed by free diffusion. In addition, the slope of the curve (K diff ) was calculated, which can be used to quantify the diffusion rate, and FLM 100 and FLM 150 showed higher K diffThe results showed that FLM 150 and its thermally processed products competed with S90 for adsorption, inhibiting S90's interfacial adsorption but accelerating the formation of an emulsifier film at the oil-water interface. Furthermore, the study found that FLM 150 increased the oil-water interfacial tension by 13.2%, indicating that FLM 150 positively impacted the interfacial properties of S90 films. This is likely due to the increased hydrophilicity after thermal treatment, which facilitates its adsorption at the oil-water interface.

[0069] Application Example 2: FLM 150 is used to improve the digestion and absorption of ALA in emulsion systems

[0070] Emulsion preparation is the same as application 1

[0071] During the digestion process in the small intestine, lipase is adsorbed and activated at the oil-water interface, hydrolyzing triglycerides and releasing free fatty acids (FFA). Figure 6 As shown, after simulated intestinal digestion of phospholipid-flaxseed oil emulsions, free fatty acids were rapidly released within 25 minutes in the flaxseed oil emulsion group, followed by a slower release rate until reaching relative equilibrium. However, the emulsion group supplemented with FLM and its thermally processed products did not reach relative equilibrium until approximately 50 minutes later. The FFA release rates of the flaxseed oil emulsion, FLM, FLM 37, FLM 55, FLM 70, FLM 100, and FLM 150 emulsion groups were 90.4%, 92.88%, 87.52%, 82.62%, 94.06%, 100%, and 99%, respectively. Compared with the flaxseed oil emulsion group, FLM 100 and FLM 150 increased FFA release by 10.6%.

[0072] In the FFA absorption stage, it is generally believed that only FFA that enters the bile salt micelles can pass through the small intestinal mucus layer and be absorbed by the small intestinal epithelial cells, such as Figure 7 The results showed that compared with the flaxseed oil emulsion group (ALA maximum loading 0.84±0.07 mg / mL), the maximum ALA loading in the small intestinal digestive juices of FLM 70, FLM 100, and FLM 150 increased by 9.5%, 7.1%, and 17.8%, respectively.

[0073] The results of ALA absorption kinetics are as follows Figure 8ALA absorption was detected in the S90 group (sunflower phospholipids without added SECO) in the first 30 min of absorption, with the highest amount of ALA in the lower chamber, about 2.8 μg, and no significant difference between the Control and SDG groups. The amount of ALA in the lower chamber was about 1.3-1.5 μg in the SECO, FLM and FLM 150 groups, and there was no significant difference between the three groups. The lowest amount of ALA in the lower chamber was about 0.57 μg in the sunflower phospholipid group (S90). After 120 min of absorption, the highest amount of ALA in the lower chamber was about 9.5 μg in the FLM 150 and SDG groups, and there was no significant difference between the two groups. The amount of ALA in the lower chamber was about 4.8-6.1 μg in the Control, SECO and FLM groups, and there was no significant difference between the three groups. The lowest amount of ALA in the lower chamber was about 1.3 μg in the sunflower phospholipid group (S90).

[0074] Due to the presence of a small amount of ALA in the sunflower phospholipids, ALA absorption was detected in the sunflower phospholipid group (S90 group) without added SECO. In the SECO, FLM and FLM 150 emulsion groups, the results of the ALA absorption kinetics showed that the amount of ALA absorbed in the early stage of ALA absorption (first 30 min) was significantly lower than in the Control group and the group with added SDG (p<0.05). After 120 min of absorption by the small intestinal epithelial cells, the introduction of FLM 150 significantly increased the amount of ALA absorbed in the emulsion system, with an increase of 95% in the amount of ALA absorbed compared to the control (Control).

[0075] The above description of disclosed embodiments enables one skilled in the art to make or use the application. Numerous modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Therefore, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of preparing a pyrolysis product of a lignan of flax to enhance the stability and bioavailability of α-linolenic acid in an emulsion system, characterized by, The flax lignan pyrolysis product is a flax lignan pyrolysis product obtained by high-temperature heat treatment decomposition, and the heat treatment temperature is 150 DEG C and the heat treatment time is 30 min.

2. The production method according to claim 1, characterized by, The flax lignan is obtained by defatting and extracting flaxseed shell powder.

3. The production method according to claim 1 or 2, characterized by, The flax lignan is prepared as follows: The flaxseed shell powder (FHP, 20 g) is defatted by incubating with 100 mL of n-hexane at 25 DEG C for 24 hours; 20 g of the defatted FHP sample is extracted with 100 mL of 70% ethanol solution (v / v) for three times, each time for 24 hours; after each extraction, the mixture is centrifuged at 10000xg for 40 min, and the supernatant enriched with FLM is collected, and the polar small molecule polyphenols are purified by a C18 solid-phase extraction column (Waters, C18, 5 cm), and then the purified FLM extract is concentrated by a rotary evaporator (IKAR V10D, Germany), and then vacuum freeze-dried to obtain the flax lignan.

4. The preparation method according to claim 1, characterized in that The pyrolysis conditions of the flax lignan include low-temperature heat treatment decomposition and high-temperature heat treatment decomposition; wherein, The low-temperature heat treatment decomposition temperature includes a digestion temperature of 37 DEG C, a low-temperature sterilization temperature of 55 DEG C, and a pasteurization temperature of 70 DEG C; and the high-temperature heat treatment decomposition temperature includes a boiling temperature of 100 DEG C and a baking temperature of 150 DEG C.

5. The flax lignan pyrolysis product for improving the stability and bioavailability of alpha-linolenic acid in an emulsion system, which is prepared by the method of claim 1.

6. The pyrolysis product of a lignan according to claim 5, characterized in that, The flax lignan pyrolysis product can improve the stability and bioavailability of alpha-linolenic acid in an emulsion system, the retention rate of flax lignan FLM is 50%, the degradation rate of total phenolic acid at the chain end of FLM is greater than or equal to 45%, and the antioxidant capacity of the mixture FLM150 is improved by more than 70% (DPPH free radical scavenging rate).

7. The flax lignan pyrolysis product for improving the stability and bioavailability of alpha-linolenic acid in an emulsion system, which is prepared by the method of claim 1, in food processing.

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