What is the progress of research on rice enzymatic proteins？

Rice is mainly composed of starch and protein, of which, starch accounts for about 80% of the total weight of rice, and protein accounts for only about 8% of the total weight.

Rice proteins can be divided into four categories according to their solubility: 1. water-soluble proteins, clear proteins 2. salt-soluble proteins, globulins 3. alcohol-soluble proteins 4. alkali-soluble proteins, gluten; gluten and alcohol proteins are also known as storage proteins, and they are the main components of rice proteins.

Rice protein extraction process

1.Enzymatic preparation:

Enzymatic extraction of an idea is the use of proteases on the degradation and modification of rice protein, making it into a soluble peptide and be extracted. This method of reaction conditions are mild, protein peptide chains can be hydrolyzed to short peptide chains, improving the solubility of protein.

Enzymatic hydrolysis increases the hydrophobicity of proteins, which can effectively improve their solubility, emulsification and foaming properties. The disadvantages of this method are that the production cost is high and the extraction rate varies greatly depending on the enzyme used. According to the different conditions of protease action, can be divided into acid protease, neutral protease and alkaline protease and so on.

2, alkali acid precipitation method:

Lye can make the rice in the tight starch structure becomes loose, while lye on the protein molecules of the secondary bond, especially the hydrogen bond has a destructive effect, and can make some of the polar groups to dissociate, so that the surface of protein molecules have the same charge. Thus, it has a solubilizing effect on protein molecules and promotes the separation of starch and protein.

Enzymatic action of protease on rice protein

Based on the poor water solubility of rice protein and the fact that the non-protein components are mainly carbohydrates, the extracted protein should be further purified (Purification). It can also be treated with cellulase, pectinase and isoamylase to promote the solubilization of more carbohydrates.

1, alkaline protease modified rice protein process

Crushed rice → soaking → wet milling → rice slurry liquid → mixing slurry

Rice flour: alkali (0.06mol / L) = 1:8 → room temperature stirring extraction 2h → 3500r/min centrifugation 20min → take the supernatant → adjust the pH to 4.8 isoelectric point acid precipitation → 3500r/min centrifugation 10min → precipitation → freeze-drying → alkaline extraction of rice protein

Alkaline extraction of rice protein powder → 5% (w/v) rice protein suspension → hydration and dissolution at room temperature for 1h → 55 ℃ super-constant temperature water bath → according to the different amount of enzyme, substrate concentration, pH enzyme (pH-Stat [76] method to stabilize the pH of the system, the measurement of the degree of hydrolysis) → 3500r/min centrifugation for 20min → the supernatant → 85 ℃ /10min inactivation of enzymes → vacuum concentration → freeze-drying → rice protein powder → 3500r/min centrifugation for 20min → the supernatant → 85 ℃ /10min inactivation → vacuum concentration Freeze-drying → rice protein digests

Compared with the rice protein modified by alkaline protease Alcalase, the solubility increased 13.92 times, emulsification increased 3.07 times, emulsification stability increased 2.26 times, foaming increased 1.07 times, foam stability increased 1.21 times, and the functional properties of rice protein proteolytic products were improved to different degrees.

Compared with the hydrolysis of rice protein with Protease N by Ji Wei et al, the improvement of solubility of Alcalase enzyme digestion product was more significant; it was close to the improvement of protein solubility by acid deamidation of modified protein by Jiang Tianyan; and it was in agreement with the conclusions of the research of enzyme digestion on the improvement of solubility of rice protein by Xuan Guodong, Guo Rongrong, and Peng Qinghui that the solubility of the protein had reached more than 90%.

 

2, pepsin modified rice protein process

Process: rice protein → pepsin hydrolysis → enzyme inactivation → measurement of protein concentration in the supernatant → pH value to 7.0 → dialysis → freeze-drying → determination of the functional properties of proteins.

Pepsin has a certain effect on the solubility of rice protein, and the influencing factors are pH value > enzyme addition > hydrolysis time > temperature. The optimal parameters were enzyme addition of 7.0 U/g, pH 1.5, hydrolysis time of 5 h, and temperature of 3 0 ℃. The functional properties of hydrolyzed rice protein were higher than those of untreated rice protein.

Among them, the emulsion stability and emulsification were 3 3 . 2 8mi n , and 0.456, which were even higher than soy protein and egg white protein. Foaming stability and foaming stability were 25.0% and 82.4%, and water holding and oil holding properties were 2.80 and 3.30 g/g, which were 2.09 and 2.92 times higher than those of untreated rice protein, respectively.

Summary

In summary, rice protein has a reasonable amino acid composition, high biological potency, hypoallergenic, and high nutritional value. By means of enzymatic digestion, the solubility of rice protein is increased, emulsification, emulsion stability, water holding and oil holding are improved, and the quality of rice protein is improved so that it can be more easily absorbed and utilized by animals.

China is a large rice-producing country, with abundant rice resources, which provides a basis for the development and utilization of rice protein, rice protein as a very valuable plant protein resources, to solve the problem of insufficient feed protein resources in China provides a feasible way.