Abstract: Soybean peptide is a polypeptide that hydrolyzes soybean protein into 3 ~ 6 amino acids, with a molecular weight of about 1000Da. Soybean peptides are produced by fermentation from soybean meal. Some bitter peptide groups are modified and reorganized through microbial action, so that the small peptides, small peptides and amino acids can be shifted and rearranged. The obtained soybean peptides have better physiological and processing characteristics, and overcome the shortcomings of enzymatic hydrolysis products such as large bitter taste and poor taste.
Key words: soybean peptide; Fermentation; Soybean protein; protease
CLC Number :TS201.2 Document Identification Code :A Article Number :1007-6395(2007)02-0055-02
Functional properties of soybean peptides
Soybean polypeptide is the basic raw material of soybean. Soybean globulin is converted into small molecule peptide by modern biotechnology. Small molecule soybean polypeptides not only have good solubility, low viscosity and anti-gel formation, but also can be digested and absorbed quickly in the body. Low peptides composed of 2 to 3 amino acids have better absorption performance than free amino acids, and can be absorbed completely through the intestine as bioactive peptides at the tissue level to cause biological effects in the body. Soybean peptide protein is highly available, but also has low antigenicity, will not produce allergic reaction. In addition, it also has physiological activities such as promoting myocyte recovery and fat metabolism. Soybean peptide overcomes the weakness of soybean protein in nutrition and has richer nutritional and functional properties than soybean protein. It is a potential functional food base.
Production of soybean peptides
The main methods for the production of soybean peptides are enzymatic hydrolysis and microbial fermentation. Enzymatic hydrolysis has the advantages of high product safety, mild production conditions, easy hydrolysis control, and positioning for the production of specific soybean peptides, but its disadvantage is that the utilization rate of soybean protein is not high, limited to a few microbial proteases, animal proteases and plant proteases, the enzymatic hydrolysis of peptide production rate is relatively low, and the cost is high, and the price of peptidase and the cost of bitter removal increase the production cost accordingly. At present, researchers are exploring the fermentation of soybean meal to produce soybean peptides, among which the strains are used to produce protease Aspergillus Niger. Active microbial bodies directly participate in biochemical metabolism, act on macromolecular soybean protein, and modify some functional groups. The active microorganism can synthesize and secrete small peptide substances, the protein hydrolysis degree of fermentation liquid is higher, the yield of soybean peptide is higher, and the sensory properties such as flavor and color are better than the products of enzymatic hydrolysis. In addition, the application of microbial direct bitter removal effect is good, very promising. There are a wide range of peptidase lineages in the endogenous enzymes of black mold, which are cheap and come from a wide range of sources, and have a promising development prospect.
Process for producing soybean peptides by fermentation
3. Process flow:
Steps:
(1) strain activation: After preparation of liquid medium, sterilization and cooling, adding strain activation, oscillating culture for 12-24h,120r/min,30℃.
(2) Crushing and dosing: using soybean meal as raw material, crushing particles with fineness of 100/m. After the measurement, add water and mix to prepare the mixed liquid, the concentration of soybean meal powder is 4% ~ 6%, and add a small amount of auxiliary ingredients
Figured. Stir until the mixture is even.
(3) Sterilization: the prepared mixture is divided and sterilized by wet heat, the temperature is 121℃, the pressure is 0.1MPa, and the time is 20min.
(4) Cooling and inoculation: the sterilized mixture is cooled to 25 ~ 28℃, and 10% of the total mixture is added to the bacteria and shaken.
(5) Fermentation: The mixed liquid after accessing the strain is fermented in the fermenter, the fermentation temperature is controlled at 25 ~ 28℃, the fermentation time is 72h, and the compressed air is passed into the fermentation liquid according to a certain proportion during the fermentation process to provide the oxygen required in the fermentation process, and constantly stirring, so that the material liquid fermentation is full and uniform. During the fermentation process, the pH value of the fermentation liquid should be maintained in the range of 6.5 ~ 7, and when abnormal, HCL and Ca(OH)2 should be used to adjust.
6) Separation: The slurry residue in the fermentation liquid is separated by centrifugation, and the supernatant is used to produce soybean peptides.
(7) Vacuum concentration: the filtrate is pumped into the three-effect low-temperature vacuum concentration, drying part of the water in the liquid to meet the requirements of spray drying, the concentration after concentration is 40% to 50%, the purpose of low-temperature drying is not to change the properties of protein and the activity of soybean peptides.
(8) Spray drying: The concentrated liquid is granular after spray drying by the spray drying tower air flow, and its moisture content is 8%.
(9) Screening: the powder and large particles are separated and crushed, and qualified products are quantitatively packaged after screening.
(10) Finished product: The product can be stored in the warehouse after quantitative packaging and inspection. In terms of separation and purification, most of them are separated by membrane method. The use of ultrafiltration membrane and nanofiltration membrane can effectively remove biological macromolecules and inorganic salts, and obtain the required molecular weight peptide chains. There are also high performance capillary electrophoresis and high pressure liquid chromatography for separation and purification, these methods are high efficiency, but expensive, only suitable for separation analysis or high value product separation, not suitable for large-scale industrial production.
In terms of separation and purification, most of them are separated by membrane method. The use of ultrafiltration membrane and nanofiltration membrane can effectively remove biological macromolecules and inorganic salts, and obtain the required molecular weight peptide chains. There are also high performance capillary electrophoresis and high pressure liquid chromatography for separation and purification, these methods are high efficiency, but expensive, only suitable for separation analysis or high value product separation, not suitable for large-scale industrial production.
Characteristics of soybean peptide production by fermentation
3.3.1 Improve the taste
The soybean protein active peptide was produced by microbial fermentation. Some bitter peptide groups were modified and recombined by microbial action, and the small peptides and amino acids were shifted and rearranged. The prepared soybean protein active peptide has no bitter taste and odor, and has good taste. It overcomes the disadvantages of the enzymatic hydrolysis product, such as big bitter taste and poor taste. The product can be widely used in food and pharmaceutical industry, and the content of soybean protein mixed peptide obtained by this method can reach more than 60%.
3.3.2 Full utilization of raw materials
Generally, oil refineries only treat soybean meal meal as animal feed after oil extraction, which causes pollution and waste to a certain extent. Soybean peptides can be produced by fermentation with a certain concentration of soybean meal meal as liquid fermentation medium, which can not only make full use of the cheap soybean meal meal, but also obtain soybean peptides with good functional and nutritional properties through further production and processing.
3.3.3 Reduce the production cost of soybean peptides
Abundant protease was produced in the process of microbial fermentation of soybean meal, which decomposed soybean protein into polypeptide. The two hydrophobic amino acids at the end of the hydrophobic polypeptide can be cut off specifically, and the bitter value of the polypeptide solution can be reduced. Therefore, the production of soybean peptide by fermentation combines the hydrolysis of soybean protein with the debitter step of soybean peptide, which saves time and reduces cost to a great extent.
foreground
As a kind of degradation of soybean protein, soybean peptide can effectively improve the physicochemical properties of raw protein (no bean smell, no protein denaturation, easy to dissolve in water, good fluidity, etc.), and at the same time can give the product special physiological activity function, is a very promising functional food raw material, is currently the focus of research at home and abroad. In recent years, alternative medicine, natural medicine, natural therapy has begun to be recognized by Western society, the United States FDA1999 began to allow soy protein products can prevent cardiovascular disease function, which means that health and health products will be re-recognized by human society, and the commercial development of polypeptide biochemical health products will be the most exciting chapter of this industry.
Fermentation is a hot spot in the production of soybean peptides at home and abroad, the use of gene technology to improve and improve the fermentation capacity of the strain, improve the fermentation process conditions, can make full use of soybean meal, reduce waste of resources, and constantly improve the separation and extraction technology of soybean peptides, improve the purity of soybean peptides, can also use chemical means to modify soybean peptides, so that it can be used in the pharmaceutical industry, to be more widely Widely used in other fields.
