Flaxseed oil with high content of antioxidant nutrient linolenol and without bitter taste and preparation method of flaxseed oil

Abstract

The invention relates to the field of food processing, and discloses bitter-free linseed oil with high content of antioxidant nutrient linolenol and a preparation method thereof, and the method comprises the following steps: (1) carrying out germination treatment on linseeds to obtain germinated linseeds; (2) performing squeezing treatment on the flaxseeds subjected to germination treatment to obtain crude flaxseed oil; and (3) mixing the linseed crude oil with a debitterizing agent. According to the method, the degummed linseeds are germinated and then treated with the debitterizing agent, so that the prepared linseed oil has high oil yield and is rich in antioxidant nutrient linol, bitter substances (cyclopeptide E) and bitter precursor substances (cyclopeptide P) in the linseed oil can be efficiently removed, the content of cyclopeptide E in the linseed oil is reduced to 5 ppm or below, and the debitterizing agent is used for debitterizing the linseed oil. The content of the cyclopeptide P is reduced to be below 7ppm, so that the flaxseed oil does not return bitter in the shelf life.

Description

Technical Field

[0001] The invention relates to the field of food processing, and in particular to a flaxseed oil with a high content of antioxidant nutrient linolein and no bitterness and a preparation method thereof. Background Art

[0002] Flaxseed oil is rich in polyunsaturated fatty acids, of which linolenic acid content is about 50%, and is a healthy oil that is popular among consumers. However, after flaxseed oil is squeezed and stored for a short time, bitter substances will be generated, which seriously affects the taste.

[0003] The bitter substances in flaxseed oil are mainly divided into three categories: the first is cyanogenic glycosides, such as linamarin, which are endogenous substances contained in flaxseed; the second is lignans and polyphenols, which are separated from sesame seed skins; the third is cyclopeptides, which are produced during the processing of flaxseed, among which cyclopeptide E is the main substance that contributes to bitterness. At the same time, non-bitter cyclopeptides such as cyclopeptides A / C / F / G / P will be generated during the processing. During the storage process, cyclopeptide P will be oxidized to generate cyclopeptide E, which will also enhance the bitterness of the product and make the flaxseed oil product bitter again.

[0004] "Preparation of refined cold-pressed flaxseed oil rich in cyclopeptides and digestion and absorption of cyclopeptides; Zeng Junpeng, Nanchang University, 2022" explored the effects of different refining processes on cyclopeptides in flaxseed oil. The results showed that after degumming, alkali refining, decolorization and deodorization, the bitter substances in flaxseed oil were reduced by 20%, 10%, 50% and 6%, respectively. The content of bitter peptides in flaxseed oil after refining was still high (500-600ppm), and the content of bitter precursor cyclopeptide A+P was still above 60ppm, posing a risk of bitterness reversion during the shelf life.

[0005] CN107619716A discloses a method for removing bitter substances from linseed oil, which includes subjecting winterized linseed oil to tangential flow membrane separation and column chromatography purification, and finally obtaining linseed oil without bitterness; CN111394170A discloses a method for preparing detoxified linseed powder and debittered linseed oil, which includes subjecting linseed to low-temperature pressing and high-voltage pulse electric field pretreatment to obtain virgin linseed oil, and then finely filtering after adsorption by an adsorbent to obtain debittered linseed oil. Although both methods can remove bitter substances from linseed oil, they are cumbersome to operate, costly, and difficult to industrialize.

[0006] In summary, the existing methods such as refining, membrane separation, silica gel adsorption, and high-voltage pulsed electric field are mainly used to remove the bitter substances produced in linseed oil. The debittering methods are complicated and cannot effectively remove the bitter precursors in the oil, and cannot solve the problem of bitterness of products during the shelf life.

[0007] Therefore, there is an urgent need to find a method for preparing flaxseed oil that can efficiently remove bitter substances (cyclopeptide E) and bitter precursors (cyclopeptide P) in flaxseed oil, thereby improving product quality, ensuring that the product does not return to bitterness during the shelf life, and at the same time increasing the content of linolenic acid, an antioxidant nutrient in flaxseed oil. Summary of the invention

[0008] The purpose of the present invention is to overcome the problem in the prior art that linseed oil products become bitter due to oxidation of cyclopeptide P to generate cyclopeptide E during storage, and to provide a linseed oil with a high content of the antioxidant nutrient linseed phenol and no bitterness and a preparation method thereof. The method can efficiently remove bitter substances and bitter precursors in the linseed oil while obtaining a high oil yield, thereby ensuring that the product does not become bitter during the shelf life, and can further increase the content of the antioxidant nutrient linseed phenol in the product.

[0009] The inventors of the present invention have found that by subjecting degummed flaxseed to germination treatment and then treating it with a debittering agent, bitter substances (especially cyclopeptide E) and bitter precursor substances (especially cyclopeptide P) in flaxseed oil can be efficiently removed while obtaining a high oil yield, so that the content of cyclopeptide E in flaxseed oil is reduced to below 5ppm, and the content of cyclopeptide P is reduced to below 7ppm, thereby ensuring that the flaxseed oil product does not return to bitterness during the shelf life. Therefore, in order to achieve the above-mentioned purpose, the first aspect of the present invention provides a method for preparing flaxseed oil, wherein the method comprises the following steps:

[0010] (1) subjecting flax seeds to a germination treatment to obtain flax seeds after the germination treatment;

[0011] (2) pressing the linseed after the germination treatment to obtain crude linseed oil;

[0012] (3) Mixing the crude linseed oil with a debittering agent.

[0013] A second aspect of the present invention provides linseed oil, wherein the linseed oil is prepared by the method of the present invention.

[0014] Preferably, the content of cyclopeptide E in the linseed oil is ≤5ppm, the content of cyclopeptide P is ≤7ppm, and the content of linolenic acid is ≥300ppm.

[0015] Through the above technical solution, the present invention achieves at least the following beneficial technical effects:

[0016] (1) The present invention can target the transformation of bitter precursors in flaxseed, reduce the migration of bitter precursors into flaxseed oil, and significantly reduce the content of bitter precursors (such as cyclopeptide P) in flaxseed oil.

[0017] (2) In a preferred embodiment, the debittering agent used in the present invention can effectively remove the bitter cyclopeptide E and the bitter precursor cyclopeptide P in linseed oil, so that the content of cyclopeptide E in linseed oil is reduced to below 5 ppm, and the content of cyclopeptide P is reduced to below 7 ppm, thereby ensuring that the linseed oil product does not become bitter during the shelf life.

[0018] (3) The flaxseed oil prepared by the method of the present invention has a high oil yield and is rich in the antioxidant nutrient linolenic acid. In a preferred embodiment, the content of linolenic acid in the flaxseed oil is as high as 567.5 ppm. DETAILED DESCRIPTION

[0019] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0020] A first aspect of the present invention provides a method for preparing linseed oil, wherein the method comprises the following steps:

[0021] (1) subjecting flax seeds to a germination treatment to obtain flax seeds after the germination treatment;

[0022] (2) pressing the linseed after the germination treatment to obtain crude linseed oil;

[0023] (3) Mixing the crude linseed oil with a debittering agent.

[0024] According to some implementation methods of the present invention, the method further comprises degumming the flax seeds before the germination treatment, wherein the degumming treatment makes the degumming rate of the degummed flax seeds greater than 0.08%, preferably 0.1%-5%.

[0025] In the present invention, degumming the flax seeds can remove part of the phospholipids in the flax seeds, destroy the colloid layer on the surface of the flax seeds, facilitate the entry of water into the flax seeds, promote the germination of the flax seeds, and shorten the germination treatment time.

[0026] In the present invention, the degumming rate of degummed flax seeds is determined by the difference method, and the degumming rate of degummed flax seeds (%) = 100% × (mass of untreated flax seeds - mass of flax seeds after degumming) / mass of untreated flax seeds.

[0027] Preferably, the degumming treatment method includes a dry grinding degumming method and / or a wet grinding degumming method.

[0028] In the present invention, the degumming process can be carried out in a sand-disc rice husker. The sand-disc rice husker is purchased from Zhejiang Grain Industry Machinery Technology Co., Ltd., and the instrument model is MLGQ25B rice husker.

[0029] Specifically, the dry grinding and degumming method includes: pouring flax seeds into a sand disk rice husker (the sand disk rice husker is divided into an upper disk and a lower disk, the upper disk is fixed, and the lower disk rotates), adjusting the upper and lower disk linear speeds to 20-25 m / s, adjusting the rolling distance between the upper and lower sand disks to 6-9 mm, sanding for 5s-60s, peeling the surface glue from the flax seeds, and the glue powder is sprayed out from the sieve holes and sent to the glue powder collector through a fan for collection. The flax seeds are gradually pushed to the other end of the cylindrical glue powder screen under the push of the sand roller guide groove to flow out, so as to obtain degummed flax seeds.

[0030] Specifically, the wet grinding and degumming method comprises: adding 2-10 times the mass of phosphoric acid solution (pH 4-6) to flax seeds, stirring at a rotation speed of 100-300 rpm for 1-4 hours, centrifuging to remove the extract, and repeating the extraction process 2-3 times; pouring the extracted flax seeds into a sand tray rice husker, grinding and degumming according to the dry grinding and degumming method, to obtain degummed flax seeds.

[0031] According to some embodiments of the present invention, the conditions of the germination treatment are such that the flax seeds after the germination treatment include sprouted flax seeds and unsprouted flax seeds.

[0032] Preferably, based on the total mass of the germination treated flax seeds, the sprouted flax seeds account for 5wt%-45wt%, more preferably 8wt%-25wt%; the unsprouted flax seeds account for 55wt%-95wt%, more preferably 75wt%-92wt%.

[0033] In the present invention, the proportion of sprouted flax seeds and unsprouted flax seeds in the flax seeds after germination treatment is determined by weight method, and the specific determination method includes: selecting 100 flax seeds that have not been subjected to germination treatment, and after germination treatment according to the above method, weighing and recording as M, and dividing the 100 flax seeds into piles according to unsprouted, sprouted flax seeds with a sprout length of less than 0.1 mm, sprouted flax seeds with a sprout length of 0.1-2 mm, and sprouted flax seeds with a sprout length of more than 2 mm, and weighing and recording as m respectively. 0 、m 1 、m 2 、m 3 By dividing the weight of different sprout lengths by the weight M after germination, the proportion of sprouted flax seeds and unsprouted flax seeds in the flax seeds after germination treatment can be calculated.

[0034] In the present invention, the proportion of sprouted flax seeds and unsprouted flax seeds in the flax seeds after the germination treatment meets the above-mentioned limited range, which can avoid excessive consumption of oil in the flax seeds and further ensure the oil yield of the flax seeds.

[0035] Preferably, the sprouted flax seeds include flax seeds with a sprout length of <0.1 mm, flax seeds with a sprout length in the range of 0.1-2 mm and flax seeds with a sprout length of >2 mm.

[0036] More preferably, based on the total mass of the flax seeds after the germination treatment, the flax seeds with a sprout length of less than 0.1 mm account for 1wt%-10wt%, the flax seeds with a sprout length in the range of 0.1-2mm account for 2wt%-15wt%, and the flax seeds with a sprout length greater than 2mm account for 2wt%-20wt%.

[0037] In the present invention, by controlling the proportion of flax seeds with a sprout length in the range of 0.1-2 mm and flax seeds with a sprout length greater than 2 mm in the sprouted flax seeds, the germination degree of flax seeds can be further improved, thereby further reducing the concentration of the bitter precursor cyclic peptide P.

[0038] In the present invention, before the degummed flax seeds are subjected to the germination treatment, preferably, the degummed flax seeds are subjected to the swelling treatment. Specifically, the swelling treatment method comprises: mixing the degummed flax seeds with water, wherein the amount of water used is 5wt%-50wt% of the mass of the degummed flax seeds, and stirring for 20-40 minutes, so that the degummed flax seeds fully absorb water. The swelling treatment softens or breaks the seed coat of the degummed flax seeds, increases the permeability of the seed coat, and promotes the germination of the flax seeds.

[0039] According to some embodiments of the present invention, the conditions of the germination treatment include: relative humidity of 60-100% and temperature of 10-40°C.

[0040] Preferably, the conditions for the germination treatment include: relative humidity of 65-95% and temperature of 15-35°C.

[0041] In the present invention, there is no particular requirement for the duration of the germination treatment, but preferably, the duration of the germination treatment is sufficient to make the proportion of germinated flax seeds within the above range, and the duration of the germination treatment may be 6-120 hours, preferably, the duration of the germination treatment is 15-95 hours.

[0042] In the present invention, the germination treatment can be carried out in a constant temperature and humidity chamber. For example, the constant temperature and humidity chamber is purchased from Yiheng Instrument Equipment Co., Ltd., and the product model is LHS-50CH.

[0043] The inventors of the present invention have discovered that germination treatment of degummed flaxseeds can mobilize the flaxseed's own enzyme system, regulate the composition of proteins in flaxseeds through biotechnology, transform the content of bitter substances and bitter precursors, and reduce the migration of bitter substances and bitter precursors in flaxseed oil into finished oils and fats.

[0044] According to some embodiments of the present invention, the method further comprises frying the flax seeds after the germination treatment before the pressing treatment, and the frying temperature is 35-120° C. and the time is 20-40 minutes.

[0045] In the present invention, the pressing process is divided into cold pressing and moderate temperature pressing according to different frying temperatures. For example, frying temperature of 35-90°C is cold pressing, and frying temperature of 90-120°C is moderate temperature pressing.

[0046] In the present invention, the flax seeds after the germination treatment are fried before the pressing treatment, which is beneficial to protein denaturation and oil coagulation, and can also improve the fluidity of the oil, so as to obtain a higher oil yield.

[0047] In the present invention, high-temperature pressing easily leads to oxidation and deterioration of linseed oil, and the obtained linseed oil has a strong bitter taste; the linseed oil obtained by low-temperature and moderate-temperature pressing has a lighter bitter taste.

[0048] In the present invention, there is no particular limitation on the method of squeezing, and any method that can achieve physical squeezing is acceptable. For example, a screw press can be used for squeezing, and the screw press is purchased from Guangxin Grain and Oil Machinery Co., Ltd., and the instrument model is YZYX168.

[0049] According to some embodiments of the present invention, the debittering agent is an enzyme preparation.

[0050] Preferably, compared to 1g of the crude linseed oil, the amount of the enzyme preparation is 1-45U; more preferably, compared to 1g of the crude linseed oil, the amount of the enzyme preparation is 1-30U.

[0051] Preferably, the enzyme preparation comprises a protease and a non-protease.

[0052] More preferably, the ratio of the enzyme activity units of the protease and the non-protease is 1:(0.2-9).

[0053] According to some embodiments of the present invention, the protease is selected from at least one of trypsin, chymotrypsin, an exoprotease derived from Aspergillus niger and an endoprotease derived from Aspergillus niger, preferably trypsin and / or chymotrypsin.

[0054] In the present invention, the exoprotease derived from Aspergillus niger and the endoprotease derived from Aspergillus niger refer to the proteases prepared using Aspergillus niger as a donor as recorded in "Table C.3 (Continued) of the Applicable Standards for Food Additives GB2760-2024".

[0055] The enzyme activity unit of trypsin is defined as the amount of enzyme required to convert 1 micromole of substrate in 1 minute at 35-50°C. The enzyme activity unit of chymotrypsin is defined as the amount of enzyme required to convert 1 micromole of substrate (protein) in 1 minute at 35-50°C.

[0056] In the present invention, in order to fully mix the debittering agent with the crude linseed oil, the debittering agent may be prepared into a solution and then added to the crude linseed oil.

[0057] According to some embodiments of the present invention, the non-protease is selected from at least one of carboxypeptidase, deaminase and aminopeptidase, preferably carboxypeptidase and / or deaminase. The enzymatic activity unit of carboxypeptidase is defined as the amount of enzyme that can convert 1 micromole of substrate (polypeptide) within 1 minute at 35-50°C. The enzymatic activity unit of deaminase is defined as the amount of enzyme that can convert 1 micromole of substrate (amino acid) within 1 minute at 35-50°C.

[0058] In the present invention, when the type and ratio of the enzyme preparation meet the above-mentioned limited range, the bitter cyclopeptide E and the bitter precursor cyclopeptide P in the linseed oil can be more significantly removed, ensuring that the linseed oil does not return to bitterness during the shelf life.

[0059] According to some embodiments of the present invention, the mixing conditions may include: a temperature of 10-60° C. and a time of 0.5-4 h.

[0060] Preferably, the mixing conditions include: temperature of 20-50° C. and time of 1-3.5 h.

[0061] In the present invention, preferably, the method further comprises: after the crude linseed oil and the enzyme preparation are mixed, the water phase in the obtained oil product is separated, and the obtained clear oil is filtered to obtain the linseed oil. The separation of the water phase can be carried out by centrifugal separation, such as centrifugal separation using a horizontal screw centrifuge; the filtration can be carried out by plate and frame filtration to further remove impurities such as residual enzymes in the oil, gum formed by hydration of phospholipids, and residues after linseed pressing.

[0062] A second aspect of the present invention provides linseed oil, wherein the linseed oil is prepared by the method of the present invention.

[0063] Preferably, the content of cyclopeptide E in the linseed oil is ≤5ppm, the content of cyclopeptide P is ≤7ppm, and the content of linolenic acid is ≥300ppm.

[0064] According to a particularly preferred embodiment of the present invention, a method for preparing linseed oil is provided, the method comprising the following steps:

[0065] (1) subjecting flax seeds to a germination treatment to obtain flax seeds after the germination treatment;

[0066] Wherein, the degumming rate of the flaxseed is 0.2%-4%;

[0067] The conditions of the germination treatment include: relative humidity of 65-95%, temperature of 15-35°C, and time of 15-95h;

[0068] Among the flax seeds after the germination treatment, the proportion of sprouted flax seeds is 8wt%-25wt%, and the proportion of unsprouted flax seeds is 75wt%-92wt%;

[0069] (2) pressing the linseed after the germination treatment to obtain crude linseed oil;

[0070] (3) mixing the crude linseed oil with a debittering agent;

[0071] Wherein, the debittering agent is an enzyme preparation; compared with 1g of the crude linseed oil, the dosage of the enzyme preparation is 1-27U;

[0072] The enzyme preparation comprises trypsin and carboxypeptidase, and the ratio of the enzyme activity units of trypsin and carboxypeptidase is 1:(1-9).

[0073] The present invention will be described in detail below through examples.

[0074] Trypsin was purchased from Amano Enzyme Co., Ltd. with the product model AXH2; carboxypeptidase was purchased from Amano Enzyme Co., Ltd. with the product model CPPs.

[0075] The sand disc rice husker was purchased from Zhejiang Lianggong Machinery Technology Co., Ltd., and the product model is MLGQ25B rice husker.

[0076] The screw press was purchased from Guangxin Grain and Oil Machinery Co., Ltd., product model is YZYX168.

[0077] The constant temperature and humidity chamber was purchased from Yiheng Instrument Equipment Co., Ltd., and the product model is LHS-50CH.

[0078] The degumming rate of degummed flaxseed was determined by differential method.

[0079] Degumming rate (%) of degummed flax seeds = 100% x (mass of untreated flax seeds - mass of flax seeds after degumming) / mass of untreated flax seeds.

[0080] The proportion of sprouted flax seeds and unsprouted flax seeds in the flax seeds after germination treatment is determined by weight method. The specific determination method includes: selecting 100 flax seeds that have not been subjected to germination treatment, weighing and recording as M, performing germination treatment according to the above method, and dividing the 100 flax seeds into piles according to unsprouted, sprouted flax seeds with a sprout length of less than 0.1 mm, sprouted flax seeds with a sprout length of 0.1-2 mm, and sprouted flax seeds with a sprout length of more than 2 mm, and weighing and recording as m respectively. 0 、m 1 、m 2 、m 3 By dividing the weight of different sprout lengths by the original weight M, the proportion of sprouted flax seeds and unsprouted flax seeds in the flax seeds after germination treatment can be calculated.

[0081] Example 1

[0082] This example is used to illustrate the preparation of linseed oil by the method described in the present invention.

[0083] (1) Pour 1000 g of flax seeds into a sand tray rice husker (the sand tray rice husker is divided into an upper tray and a lower tray, the upper tray is fixed, and the lower tray rotates), adjust the rolling distance between the upper and lower trays to 6 mm, adjust the linear speed of the upper and lower trays to 20 m / s, and after sanding for 10 seconds, peel off the surface glue from the flax seeds, and the glue powder is sprayed out from the sieve holes and sent to the glue powder collector by a fan. The flax seeds are gradually pushed to the other end of the cylindrical glue powder screen under the push of the sand roller guide groove to flow out, thereby obtaining degummed flax seeds;

[0084] Among them, the degumming rate of degummed flaxseed is 0.2%;

[0085] (2) adding water of 15% of the mass of the degummed flax seeds to the degummed flax seeds, mixing and stirring for 30 minutes to allow the degummed flax seeds to fully absorb water; germinating the degummed flax seeds in a constant temperature and humidity chamber at a relative humidity of 65% and a temperature of 15° C. for 15 hours to obtain germination-treated flax seeds;

[0086] Among them, the flax seeds after the germination treatment account for 8wt% of the flax seeds that have sprouted, and the flax seeds that have not sprouted account for 92wt%; among the flax seeds after the germination treatment, the flax seeds with a sprout length of 0.1-2mm account for 3wt%, the flax seeds with a sprout length greater than 2mm account for 2wt%, and the flax seeds with a sprout length less than 1mm account for 3wt%;

[0087] (3) pouring the flax seeds after germination treatment, which were roasted at 55° C. for 40 minutes, into a screw press for pressing to obtain crude flax seed oil;

[0088] (4) adding 20 U of trypsin and carboxypeptidase to each gram of the crude linseed oil, stirring at 20° C. for 1 h, separating the aqueous phase by decanter centrifugation after the reaction, and filtering the clear oil by plate and frame filtration to obtain linseed oil A1;

[0089] Among them, the ratio of the enzyme activity units of trypsin and carboxypeptidase is 1:9.

[0090] Example 2

[0091] This example is used to illustrate the preparation of linseed oil by the method described in the present invention.

[0092] (1) Pour 1000 g of flax seeds into a sand tray rice husker (the sand tray rice husker is divided into an upper tray and a lower tray, the upper tray is fixed, and the lower tray rotates), adjust the rolling distance between the upper and lower trays to 8.5 mm, adjust the linear speed of the upper and lower trays to 25 m / s, and after sanding for 20 seconds, peel off the surface glue from the flax seeds, and the glue powder is sprayed out from the sieve holes and sent to the glue powder collector by a fan. The flax seeds are gradually pushed to the other end of the cylindrical glue powder screen under the push of the sand roller guide groove to flow out, thereby obtaining degummed flax seeds;

[0093] Among them, the degumming rate of degummed flaxseed is 2.5%;

[0094] (2) adding 30% water of the mass of the degummed flax seeds to the degummed flax seeds, mixing and stirring for 30 minutes to allow the degummed flax seeds to fully absorb water; germinating the degummed flax seeds in a constant temperature and humidity chamber at a relative humidity of 75% and a temperature of 30° C. for 60 hours to obtain germination-treated flax seeds;

[0095] Among them, the flax seeds after the germination treatment account for 30wt% of the flax seeds that have sprouted, and the flax seeds that have not sprouted account for 70wt%; among the flax seeds after the germination treatment, the flax seeds with a sprout length of 0.1-2mm account for 10wt%, the flax seeds with a sprout length greater than 2mm account for 18wt%, and the flax seeds with a sprout length less than 1mm account for 2wt%;

[0096] (3) pouring the flax seeds after germination treatment, which have been roasted at 80° C. for 40 minutes, into a screw press for pressing to obtain crude flax seed oil;

[0097] (4) adding 40 U of trypsin and carboxypeptidase to each gram of the crude linseed oil, stirring at 50° C. for 2.5 h, separating the aqueous phase by horizontal screw centrifugation after the reaction, and filtering the clear oil by plate and frame filtration to obtain linseed oil A2;

[0098] Among them, the ratio of the enzyme activity units of trypsin and carboxypeptidase is 2:1.

[0099] Example 3

[0100] This example is used to illustrate the preparation of linseed oil by the method described in the present invention.

[0101] (1) Pour 1000 g of flax seeds into a sand tray rice husker (the sand tray rice husker is divided into an upper tray and a lower tray, the upper tray is fixed, and the lower tray rotates), adjust the rolling distance between the upper and lower trays to 9 mm, adjust the linear speed of the upper and lower trays to 25 m / s, and after sanding for 40 seconds, peel off the surface glue from the flax seeds, and the glue powder is sprayed out from the sieve holes and sent to the glue powder collector by a fan. The flax seeds are gradually pushed to the other end of the cylindrical glue powder screen under the push of the sand roller guide groove to flow out, thereby obtaining degummed flax seeds;

[0102] Among them, the degumming rate of degummed flaxseed is 4.5%;

[0103] (2) adding 50% water by weight of the degummed flax seeds to the degummed flax seeds, mixing and stirring for 30 minutes to allow the degummed flax seeds to fully absorb water; germinating the degummed flax seeds in a constant temperature and humidity chamber at a relative humidity of 95% and a temperature of 35° C. for 80 hours to obtain germination-treated flax seeds;

[0104] Among them, the flax seeds after the germination treatment accounted for 37wt% of the flax seeds that had sprouted, and the flax seeds that had not sprouted accounted for 63wt%; among the flax seeds after the germination treatment, the flax seeds with a sprout length of 0.1-2mm accounted for 9wt%, and the flax seeds with a sprout length greater than 2mm accounted for 28wt%;

[0105] (3) pouring the flax seeds after germination treatment, which were roasted at 115° C. for 30 minutes, into a screw press for pressing to obtain crude flax seed oil;

[0106] (4) adding 35 U of trypsin and carboxypeptidase to each gram of the crude linseed oil, stirring at 50° C. for 3.5 h, separating the aqueous phase by horizontal screw centrifugation after the reaction, and filtering the clear oil by plate and frame filtration to obtain linseed oil A3;

[0107] Among them, the ratio of the enzyme activity units of trypsin and carboxypeptidase is 1:3.

[0108] Example 4

[0109] This example is used to illustrate the preparation of linseed oil by the method described in the present invention.

[0110] (1) Add 5 times the mass of phosphoric acid solution (pH=5) to 1000 g of flax seeds, stir at 100 rpm for 1 hour, centrifuge to remove the extract, repeat the extraction process twice, and obtain extracted flax seeds; pour the extracted flax seeds into a sand plate rice husker (the sand plate rice husker is divided into an upper plate and a lower plate, the upper plate is fixed, and the lower plate is rotating), adjust the rolling distance between the upper and lower plates to 6 mm, adjust the linear speed of the upper and lower plates to 20 m / s, and after sanding for 50 seconds, peel off the surface glue from the flax seeds, and the glue powder is sprayed out from the sieve holes and sent to the glue powder collector by a fan. The flax seeds are gradually pushed to the other end of the cylindrical glue powder screen by the guide groove of the sand roller to flow out, and obtain degummed flax seeds;

[0111] Among them, the degumming rate of degummed flaxseed is 3.3%;

[0112] (2) adding 40% water of the mass of the degummed flax seeds to the degummed flax seeds, mixing and stirring for 30 minutes to allow the degummed flax seeds to fully absorb water; germinating the degummed flax seeds in a constant temperature and humidity chamber at a relative humidity of 80% and a temperature of 25° C. for 24 hours to obtain germination-treated flax seeds;

[0113] Among them, the flax seeds after the germination treatment account for 25wt% of the flax seeds that have sprouted, and the flax seeds that have not sprouted account for 75wt%; among the flax seeds after the germination treatment, the flax seeds with a sprout length of 0.1-2mm account for 8wt%, the flax seeds with a sprout length of more than 2mm account for 15wt%, and the flax seeds with a sprout length of less than 0.1mm account for 2wt%;

[0114] (3) pouring the flax seeds after germination treatment, which were roasted at 115° C. for 20 minutes, into a screw press for pressing to obtain crude flax seed oil;

[0115] (4) adding 27 U of trypsin and carboxypeptidase to each gram of the crude linseed oil, stirring at 40° C. for 2 h, separating the aqueous phase by horizontal screw centrifugation after the reaction, and filtering the clear oil by plate and frame filtration to obtain linseed oil A4;

[0116] Among them, the ratio of the enzyme activity units of trypsin and carboxypeptidase is 3:1.

[0117] Example 5

[0118] This example is used to illustrate the preparation of linseed oil by the method described in the present invention.

[0119] (1) Add 5 times the mass of phosphoric acid solution (pH=5) to 1000 g of flax seeds, stir at 100 rpm for 1 hour, centrifuge to remove the extract, repeat the extraction process twice, and obtain extracted flax seeds; pour the extracted flax seeds into a sand plate rice husker (the sand plate rice husker is divided into an upper plate and a lower plate, the upper plate is fixed, and the lower plate is rotating), adjust the rolling distance between the upper and lower plates to 6 mm, adjust the linear speed of the upper and lower plates to 20 m / s, and after sanding for 50 seconds, peel off the surface glue from the flax seeds, and the glue powder is sprayed out from the sieve holes and sent to the glue powder collector by a fan. The flax seeds are gradually pushed to the other end of the cylindrical glue powder screen by the guide groove of the sand roller to flow out, and obtain degummed flax seeds;

[0120] Among them, the degumming rate of degummed flaxseed is 3%;

[0121] (2) adding 40% water of the mass of the degummed flax seeds to the degummed flax seeds, mixing and stirring for 30 minutes to allow the degummed flax seeds to fully absorb water; germinating the degummed flax seeds in a constant temperature and humidity chamber at a relative humidity of 80% and a temperature of 25° C. for 12 hours to obtain germination-treated flax seeds;

[0122] Among them, the flax seeds after the germination treatment account for 15wt% of the flax seeds that have sprouted, and the flax seeds that have not sprouted account for 85wt%; among the flax seeds after the germination treatment, the flax seeds with a sprout length of 0.1-2mm account for 5wt%, the flax seeds with a sprout length greater than 2mm account for 9wt%, and the flax seeds with a sprout length less than 0.1mm account for 1wt%;

[0123] (3) pouring the flax seeds after germination treatment, which were roasted at 115° C. for 20 minutes, into a screw press for pressing to obtain crude flax seed oil;

[0124] (4) adding 1 U of trypsin and carboxypeptidase to each gram of the crude linseed oil, stirring at 40° C. for 2 h, separating the aqueous phase by horizontal screw centrifugation after the reaction, and filtering the clear oil by plate and frame filtration to obtain linseed oil A5;

[0125] Among them, the ratio of the enzyme activity units of trypsin and carboxypeptidase is 3:1.

[0126] Example 6

[0127] Linseed oil was prepared according to the method of Example 2, except that in step (4), the enzyme preparation was only trypsin, to obtain linseed oil A6.

[0128] Example 7

[0129] Linseed oil was prepared according to the method of Example 2, except that in step (4), the enzyme preparation was only carboxypeptidase, to obtain linseed oil A7.

[0130] Example 8

[0131] Linseed oil was prepared according to the method of Example 2, except that in step (3), the linseeds after germination treatment, which were roasted at 200° C. for 20 min, were poured into a screw press for pressing to obtain linseed oil A8.

[0132] Example 9

[0133] Flaxseed oil was prepared according to the method of Example 2, except that in step (2), the germination treatment was carried out in a constant temperature and humidity chamber at a relative humidity of 50% and a temperature of 25° C. for 168 h, and the flax seeds after the germination treatment contained 59 wt % of sprouted flax seeds and 41 wt % of unsprouted flax seeds, thereby obtaining flaxseed oil A9.

[0134] Example 10

[0135] Linseed oil was prepared according to the method of Example 2, except that in step (2), the germination treatment time was 1 h, and the sprouted linseeds in the linseeds after the germination treatment accounted for 0 wt %, thereby obtaining linseed oil A10.

[0136] Embodiment 11

[0137] Linseed oil was prepared according to the method of Example 2, except that in step (4), the ratio of the enzyme activity units of trypsin and carboxypeptidase was 1:10, to obtain linseed oil A11.

[0138] Example 12

[0139] Linseed oil was prepared according to the method of Example 2, except that in step (1), the rolling distance between the upper and lower plates of the sand disk huller was 12 mm, the degumming rate of the degummed linseed was 0.01%, the linseeds after the germination treatment had 1 wt% of linseeds with a sprout length of 0.1-2 mm, and the ungerminated linseeds accounted for 99 wt%, thereby obtaining linseed oil A12.

[0140] Example 13

[0141] Flaxseed oil was prepared according to the method of Example 2, except that in step (1), the germination treatment time was 0.5 h, and the sprouted flax seeds in the germination treatment accounted for 0 wt %; in step (2), the amount of enzyme preparation used was 0.05 U per gram of crude flaxseed oil, to obtain flaxseed oil A13.

[0142] Comparative Example 1

[0143] Linseed oil was prepared according to the method of Example 2, except that in step (4), no enzyme preparation was added to the crude linseed oil, to obtain linseed oil B1.

[0144] Comparative Example 2

[0145] The flax seeds roasted at 80° C. for 40 minutes were poured into a screw press for pressing to obtain flax seed oil B2.

[0146] Test Example 1

[0147] The cyclopeptide P, cyclopeptide E, oil yield and bitter substance score in the linseed oil of the above examples and comparative examples were measured respectively. The results are shown in Table 2.

[0148] The contents of cyclopeptide P and cyclopeptide E were determined by high performance liquid chromatography-mass spectrometry (HPLC-MS / MS) using the 6495D instrument.

[0149] The oil yield was determined by the weight method, oil yield (%) = 100% × (weight of crude oil after filtration / weight of flaxseed before pressing).

[0150] The method for determining the bitterness score is as follows: the undebittered linseed oil is used as a control, and the debittered linseed oil is provided to 10 tasters (5 males and 5 females, aged 20-30 years old, healthy, no smoking or spicy food two hours before tasting, no disease) to score the debittered linseed oil according to the proposed scoring criteria after training. The average value of the 10 tasters is used to represent the intensity of bitterness, and the scoring criteria are shown in Table 1 below.

[0151] Table 1. Bitterness rating standard for linseed oil

[0152] standard Score (points) Bitter taste of blank control group 10 No bitter taste 1-2 Slightly bitter 3-4 Bitter taste 5-6 Bitter taste 7-8 Strong bitter taste 9-10

[0153] Note: The scoring criteria in Table 1 do not include values ​​such as 2.3, 2.5, 4.3, 4.5, 6.3, 6.5, 8.3, 8.5, etc. Such data are rounded to the nearest integer. For example, when the score is 2.5, it is rounded to the nearest integer and recorded as 3. When the score is 2.3, it is rounded to the nearest integer and recorded as 2, and so on.

[0154] Test Example 2

[0155] The contents of linolenic acid and linolenic acid in the linseed oil of the above examples and comparative examples were measured respectively. The results are shown in Table 3.

[0156] The linolenic acid content was determined by gas chromatography using the instrument model 7890B.

[0157] Flaxenol refers to the general term for tocopherols and polyphenols. Tocopherols refer to the sum of tocopherol, tocotrienols, PC-8 (Plastochromanol-8, a natural compound with a similar structure to γ-tocopherol) and their series of derivatives; polyphenols refer to the sum of free and bound polyphenols including flaxenol lignans.

[0158] The tocopherol content is determined according to the method of "GB 5009.82-2016 National Food Safety Standard Determination of Vitamin A, D and E in Food Method 2".

[0159] The content of PC-8 is determined in accordance with "GB / T 26635-2011 Determination of Tocopherol and Tocotrienol Content in Animal and Plant Oils and Fats - High Performance Liquid Chromatography".

[0160] The content of polyphenols is determined in accordance with “LS / T 6119-2017 Grain and Oil Inspection-Determination of Polyphenols in Vegetable Oils-Spectrophotometric Method”.

[0161] Table 2

[0162]

[0163]

[0164] Table 3

[0165]

[0166] By comparing Examples 1-5 with Examples 6-13, it can be seen that the linseed oil prepared by the preferred method has a high oil yield, a high content of the antioxidant nutrient linolenic acid in the linseed oil, and further removes the bitter cyclic peptide E and the bitter precursor cyclic peptide P in the linseed oil, thereby improving product quality and ensuring that the product does not return to bitterness during the shelf life.

[0167] Compared with the examples, comparative example 1 does not use an enzyme preparation, resulting in high contents of bitter cyclopeptide E and bitter precursor cyclopeptide P in the linseed oil, and a strong bitter taste of the linseed oil; comparative example 2 uses a conventional pressing process to prepare linseed oil, and the contents of bitter cyclopeptide E and bitter precursor cyclopeptide P in the linseed oil are very high, resulting in a strong bitter taste of the linseed oil.

[0168] In summary, the method of the present invention can obtain flaxseed oil with high oil yield and high antioxidant nutrient linolenic acid, and can also efficiently remove bitter substances and bitter precursors in flaxseed oil, thereby ensuring that the oil does not return to bitterness during the shelf life.

[0169] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing linseed oil, characterized in that: The method comprises the following steps: (1) subjecting flax seeds to a germination treatment to obtain flax seeds after the germination treatment; (2) pressing the linseed after the germination treatment to obtain crude linseed oil; (3) Mixing the crude linseed oil with a debittering agent.

2. The method according to claim 1, wherein: The method further comprises degumming the flaxseed before the germination treatment, wherein the degumming treatment makes the degumming rate of the degummed flaxseed greater than 0.08%, preferably 0.1%-5%; Preferably, the degumming treatment method includes a dry grinding degumming method and / or a wet grinding degumming method.

3. The method according to claim 1 or 2, wherein: The germination treatment is carried out under conditions such that the flax seeds after the germination treatment include sprouted flax seeds and unsprouted flax seeds; Preferably, based on the total mass of the flax seeds subjected to the germination treatment, the proportion of the sprouted flax seeds is 5wt%-45wt%, more preferably 8wt%-25wt%; the proportion of the unsprouted flax seeds is 55wt%-95wt%, more preferably 75wt%-92wt%; Preferably, the sprouted flax seeds include flax seeds with a sprout length of <0.1 mm, flax seeds with a sprout length in the range of 0.1-2 mm, and flax seeds with a sprout length of >2 mm; More preferably, based on the total mass of the flax seeds after the germination treatment, the flax seeds with a sprout length of less than 0.1 mm account for 1wt%-10wt%, the flax seeds with a sprout length in the range of 0.1-2mm account for 2wt%-15wt%, and the flax seeds with a sprout length greater than 2mm account for 2wt%-20wt%.

4. The method according to any one of claims 1 to 3, wherein: The conditions of the germination treatment include: relative humidity of 60-100% and temperature of 10-40°C.

5. The method according to claim 4, wherein: The conditions of the germination treatment include: relative humidity of 65-95% and temperature of 15-35°C.

6. The method according to any one of claims 1 to 3, wherein: The method further comprises frying the flax seeds after the germination treatment before the pressing treatment, wherein the frying temperature is 35-120° C. and the time is 20-40 minutes.

7. The method according to claim 1, wherein: The debittering agent is an enzyme preparation; Preferably, compared to 1g of the crude linseed oil, the amount of the enzyme preparation is 1-45U; Preferably, the enzyme preparation comprises a protease and a non-protease; More preferably, the ratio of the enzyme activity units of the protease and the non-protease is 1:(0.2-9).

8. The method according to claim 7, wherein: The protease is selected from at least one of trypsin, chymotrypsin, an exoprotease derived from Aspergillus niger, and an endoprotease derived from Aspergillus niger, preferably trypsin and / or chymotrypsin; and / or, the non-protease is selected from at least one of carboxypeptidase, deaminase and aminopeptidase, preferably carboxypeptidase and / or deaminase; Preferably, the enzyme preparations are trypsin and carboxypeptidase.

9. The method according to any one of claims 1 to 3, wherein: The mixing conditions include: temperature of 10-60°C and time of 0.5-4h; Preferably, the mixing conditions include: temperature of 20-50° C. and time of 1-3.5 h.

10. A linseed oil, characterized in that: The linseed oil is prepared by the method according to any one of claims 1 to 9; Preferably, the content of cyclopeptide E in the linseed oil is ≤5ppm, the content of cyclopeptide P is ≤7ppm, and the content of linolenic acid is ≥300ppm.

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