A method for incubating rapeseed meal endogenous myrosinase to hydrolyze glucosinolates

Abstract

The present invention relates to a method for incubating rapeseed meal endogenous myrosinase to hydrolyze glucosinolates, and belongs to the technical field of agricultural product processing. The method is characterized in that rapeseed meal after low-temperature pressing and oil extraction is used as raw material, the rapeseed meal is crushed and sieved, and its endogenous myrosinase is activated under appropriate incubation conditions, so as to hydrolyze glucosinolates to form products such as isothiocyanates, and then the glucosinolate degradation products are removed by heat treatment.

Description

1. Technical Field

[0001] The invention relates to a method for hydrolyzing glucosinolates (short for glucosinolates) by incubating endogenous myrosinase in rapeseed meal, and belongs to the technical field of agricultural product processing. 2. Technical Background

[0002] Rapeseed meal is a byproduct obtained after rapeseed oil is pressed, with an annual output of about 9 million tons. Rapeseed meal contains a large amount of protein, mineral elements and vitamins, as well as rich functional ingredients such as polyphenols, polysaccharides, alkaloids, saponins and sterols, with anti-inflammatory, antioxidant and anti-cancer functions. However, the anti-nutritional factors such as glucosinolates contained in rapeseed meal greatly limit its application as a raw material in feed. Among them, glucosinolates are the largest anti-nutritional factor in rapeseed meal, accounting for 4% to 8% of the total mass. When animals eat rapeseed meal, the black mustard enzyme produced by microorganisms in their intestines will hydrolyze glucosinolates to produce harmful products such as isothiocyanates. At present, the main methods to reduce the glucosinolate content in rapeseed meal include heating and enzymatic hydrolysis. Among them, the heating method is simple and effective, but high temperature will denature the protein, seriously affecting the nutritional value of the protein; the enzymatic hydrolysis method is efficient and specific, but the cost is high and the use conditions are relatively strict; when the microbial fermentation method decomposes glucosinolates, it will also decompose the protein and cause nutrient loss, and there are many influencing factors, so the practical application is limited; mechanical processing methods such as crushing, shelling, and seed coat removal are cumbersome, and the waste seed coats produced are difficult to handle; the chemical method uses acid and alkali treatment, ammonia treatment, solvent leaching and ferrous sulfate treatment, but there will be residual chemical substances.

[0003] In view of the shortcomings of the prior art, the present invention uses bioconversion combined with thermal processing technology to reduce the glucosinolate content in rapeseed meal. In the present invention, under appropriate conditions, the partially passivated myrosinase contained in rapeseed meal is activated, thereby degrading glucosinolates to form products such as isothiocyanates, and then removing volatile toxic degradation products by thermal treatment, which can effectively reduce the glucosinolate content in rapeseed meal and improve the utilization value and economic benefits of rapeseed meal. In particular, low-temperature cold pressing technology is the development trend of rapeseed oil industry, and the myrosinase activity retention in the rapeseed meal produced by it is higher, which makes the present invention have broad application prospects. The present invention has low cost, simple process, strong operability, high retention of original nutrients, and is environmentally friendly. III. Summary of the invention

[0004] Technical issues:

[0005] The invention provides a method for hydrolyzing glucosinolates by incubating endogenous myrosinase in rapeseed meal, which solves the problems of existing methods for reducing the glucosinolate content in rapeseed meal, such as destruction of nutrient substances in rapeseed meal, complicated procedures, high energy consumption, and large amounts of waste discharged, and has the advantages of simple operation, high glucosinolate degradation rate, no three wastes generated during the treatment process, and is easy for industrial production.

[0006] Technical solution:

[0007] A method for incubating rapeseed meal endogenous myrosinase to hydrolyze glucosinolates, characterized in that rapeseed meal after low-temperature pressing and oil extraction is used as a raw material, the rapeseed meal is crushed and sieved, and its endogenous myrosinase is activated under appropriate incubation conditions to hydrolyze glucosinolates to form products such as isothiocyanates, and then the glucosinolate degradation products are volatilized and removed by heat treatment, and specifically comprises the following steps:

[0008] (1) Rapeseed meal pretreatment: crush the rapeseed meal according to a known method and pass it through a 60-120 mesh sieve;

[0009] (2) Rapeseed meal incubation: adding a citric acid buffer solution of pH 2.0 to 8.0 to the rapeseed meal at a feed-liquid ratio of 1:3 to 10 (g / mL), and then placing the rapeseed meal in a constant temperature shaker and incubating at 25 to 50° C. and 200 to 300 rpm for 0.5 to 6 h;

[0010] (3) Rapeseed meal heat treatment and reflux condensation treatment: The rapeseed meal after enzymatic hydrolysis is treated by microwave combined with hot air heating to volatilize and remove toxic glucosinolate degradation products; the vapor volatilized by heating is collected by a condensing device and extracted with ethyl acetate to obtain isothiocyanate;

[0011] (4) Rapeseed meal drying: The heat-treated rapeseed meal is dried using the well-known hot air drying technology.

[0012] Beneficial effects:

[0013] Compared with the prior art, the method for incubating rapeseed meal endogenous myrosinase to hydrolyze glucosinolates has the following advantages:

[0014] (1) The present invention uses an incubation method to activate the activity of endogenous myrosinase in rapeseed meal, thereby degrading glucosinolates in rapeseed meal, which is simple to operate, highly efficient, and environmentally friendly;

[0015] (2) In the present invention, heat treatment is used to volatilize and remove glucosinolate degradation products, and reflux condensation treatment is used to recover isothiocyanate, which can significantly reduce the content of glucosinolate and its degradation products in rapeseed meal and improve the added value of rapeseed meal. 4. Specific implementation methods

[0016] Example 1

[0017] The rapeseed meal is crushed and passed through a 60-mesh sieve; clean water is added to the rapeseed meal according to a material-liquid ratio of 1:4 (g / mL), and the pH value of the rapeseed meal is adjusted to 7 with a citric acid buffer solution, and then the rapeseed meal is placed in a constant temperature shaker and incubated at 25°C and 200rpm for 5 hours; the rapeseed meal after enzymatic hydrolysis is treated by microwave combined with hot air heating to volatilize and remove toxic glucosinolate degradation products, and the rapeseed meal heat treatment conditions are as follows: microwave power of 500W / kg, hot air temperature of 40°C, gradient heating, and moisture conversion point of 20%; the steam volatilized by heating is collected by a condensing device, and the condensation recovery conditions are as follows: the condensing tube is 1m long, the inner diameter is 2.4cm, and the condensed water temperature is 4°C, and the isothiocyanate is extracted with ethyl acetate to obtain the isothiocyanate; the rapeseed meal after heat treatment is dried by a known hot air drying technology; the glucosinolate degradation rate in the rapeseed meal is 70%, and the isothiocyanate conversion rate is 50%.

[0018] Example 2

[0019] The rapeseed meal is crushed and passed through a 70-mesh sieve; clean water is added to the rapeseed meal according to a material-liquid ratio of 1:5 (g / mL), and the pH value of the rapeseed meal is adjusted to 6 with a citric acid buffer solution, and then the rapeseed meal is placed in a constant temperature shaker and incubated at 30°C and 200rpm for 6 hours; the rapeseed meal after enzymatic hydrolysis is treated by microwave combined with hot air heating to volatilize and remove toxic glucosinolate degradation products, and the rapeseed meal heat treatment conditions are as follows: microwave power of 600W / kg, hot air temperature of 40°C, gradient heating, and moisture conversion point of 30%; the steam volatilized by heating is collected by a condensing device, and the condensation recovery conditions are as follows: the condensing tube is 1.5m long, the inner diameter is 2.4cm, the condensed water temperature is 5°C, and the isothiocyanate is extracted with ethyl acetate to obtain the isothiocyanate; the rapeseed meal after heat treatment is dried by a known hot air drying technology; the glucosinolate degradation rate in the rapeseed meal is 75%, and the isothiocyanate conversion rate is 55%.

[0020] Example 3

[0021] The rapeseed meal is crushed and passed through an 80-mesh sieve; clean water is added to the rapeseed meal according to a material-liquid ratio of 1:7 (g / mL), and the pH value of the rapeseed meal is adjusted to 6 with a citric acid buffer solution, and then the rapeseed meal is placed in a constant temperature shaker and incubated at 35°C and 250rpm for 7 hours; the rapeseed meal after enzymatic hydrolysis is treated by microwave combined with hot air heating to volatilize and remove toxic glucosinolate degradation products, and the rapeseed meal heat treatment conditions are as follows: microwave power of 800W / kg, hot air temperature of 40°C, gradient heating, and moisture conversion point of 35%; the steam volatilized by heating is collected by a condensing device, and the condensation recovery conditions are as follows: the condensing tube is 2m long, the inner diameter is 2.4cm, and the condensed water temperature is 5°C, and the isothiocyanate is extracted with ethyl acetate to obtain the isothiocyanate; the rapeseed meal after heat treatment is dried by a known hot air drying technology; the glucosinolate degradation rate in the rapeseed meal is 80%, and the isothiocyanate conversion rate is 60%.

[0022] The above detailed description of the embodiments of the present invention is only for the sake of understanding and should not be regarded as limiting the scope of the present invention. Similarly, any person skilled in the art can make various possible equivalent changes or substitutions based on the technical solution of the present invention and the description of its preferred embodiments, but all these changes or substitutions should fall within the scope of protection of the claims of the present invention.

Claims

1. A method for incubating rapeseed meal endogenous myrosinase to hydrolyze glucosinolates, characterized in that: The method uses rapeseed meal after low-temperature pressing and oil extraction as raw material, crushes and sieves it, activates its endogenous myrosinase under appropriate incubation conditions, thereby hydrolyzing glucosinolates to form isothiocyanate products, and then removes glucosinolate degradation products through heat treatment, which specifically includes the following steps: (1) Rapeseed meal pretreatment: crush the rapeseed meal according to a known method and pass it through a 60-120 mesh sieve; (2) Rapeseed meal incubation: adding a citric acid buffer solution of pH 6.0 to 8.0 to the rapeseed meal at a mass volume ratio of 1:3 to 10 g / mL; then placing the rapeseed meal in a constant temperature shaker and incubating at 25 to 35°C and 200 to 300 rpm for 5 to 6 hours; (3) Rapeseed meal heat treatment and reflux condensation treatment: The rapeseed meal after enzymatic hydrolysis is treated by microwave combined with hot air heating to volatilize and remove glucosinolate degradation products; the steam volatilized by heating is collected by a condensation device and extracted with ethyl acetate to obtain isothiocyanate; the microwave power is 300 to 3000 W / kg, the hot air temperature is 30 to 80° C., the temperature is increased in a gradient, and the moisture conversion point is 20% to 50%; the condensation recovery conditions are that the condenser tube is 1 to 5 m long, the inner diameter is 5 to 15 cm, and the condensed water temperature is 4 to 15° C.; (4) Rapeseed meal drying: The heat-treated rapeseed meal is concentrated and dried using the well-known hot air drying technology.

2. The method for hydrolyzing glucosinolates by incubating endogenous myrosinase in rapeseed meal according to claim 1, characterized in that: After incubation and hydrolysis, the degradation rate of glucosinolate in rapeseed meal is 70% to 90%, and the conversion rate of isothiocyanate is 50% to 80%.