Structural characteristics and removal measures of anti-nutritional factors in soybean protein raw materials
Protein raw materials are rising and in short supply. The industry generally adopts reducing protein or replacing protein raw materials with miscellaneous meal to control feed costs; the premise of cost reduction is to ensure the quality of feed, and the most important thing is to ensure the efficient utilization of protein in feed.
Efficient utilization of feed protein is related to the digestibility of raw protein on the one hand (refer to “Analysis of raw materials (3)”Analysis of raw protein structure and its influence on protein digestibility), and on the other hand, it is related to the digestibility of the animal itself.
Anti-nutritional factors in protein raw materials will damage the intestinal structure of animals, reduce the ability of digestion and absorption, and reduce the efficient utilization of protein. Among them, soybean-derived protein raw materials have many types and high content of anti-nutritional factors, and the antigen content varies greatly after different processes, which directly affects the efficient utilization of feed protein.
In this issue,we will analyze the structural characteristics and removal methods of anti-nutritional factors of soybean raw materials to help you optimize feed protein nutrition and achieve cost reduction and increase benefits.
General introduction
Types of anti-nutritional factors, physicochemical properties and anti-nutritional mechanisms in soybean protein raw materials
Soy protein is widely used in the current feed, usually the proportion reaches 10-25%. However, soybean contains a variety of anti-nutritional factors, which also limits the use amount of soybean protein. Let’s take a look at the types, contents, physicochemical properties and anti-nutritional mechanisms of anti-nutritional factors in soybeans. After understanding the structural characteristics and anti-nutritional mechanisms, we can take corresponding measures to remove or reduce them.
Table 1 Types, physicochemical properties and anti-nutritional mechanisms of anti-nutritional factors in soybean protein raw materials
It can be seen from the analysis of the above table that the anti-nutritional factors with high content and great harm to animals in soybean protein raw materials are mainly antigenic protein and trypsin inhibitor. Next, we will analyze in detail the structural characteristics of these two types of anti-nutritional factors and the effective measures to remove them.
1.Antigenic protein
(1) Structural features
Among the antigenic proteins, glycinin and β-conglycinin have the highest content, and they have special allergenic subunits of quaternary and tertiary structures. Among them, glycinin consists of 6 subunits, and there are 5 combinations of subunits; β-conglycinin consists of 3 subunits, and there are 6 combinations of subunits, all of which are potential allergens.
Table 2 Composition and spatial structure characteristics of antigenic proteins
(2) Measures to remove
There are two main ways to remove or reduce antigens:
Destruction of the tertiary and quaternary spatial structure of the allergic subunit of the antigenic protein;
Destruction of the amino acid primary structure of the allergic subunit of the antigenic protein.
High pressure/high temperature changes the quaternary and tertiary spatial structures of antigenic proteins; enzymatic hydrolysis/fermentation destroys the quaternary and tertiary structures of proteins, and even degrades the secondary and primary structures.
Through high temperature and high pressure treatment of puffed soybean and soybean protein concentrate, the clearance rate of antigenic protein reaches 50%-70%; the average clearance rate of antigenic protein is 50% for fermented soybean meal due to different strains and fermentation conditions; combined liquid enzymolysis selects certain enzymes and control conditions according to protein structure characteristics, and the clearance rate of antigen protein is more than 90%.
Table 3 Effects of different treatment methods on antigenic proteins
2.Trypsin inhibitor
(1) Structural features
There are 7-10 trypsin inhibitors, but only 2 trypsin inhibitors have been studied extensively and in detail, namely Kunitz trypsin inhibitor (KTI) and Bowman.Birk trypsin inhibitor (BBI). They all have active centers that bind to proteases, inhibiting protease activity, and destroying the active centers can reduce anti-nutritional effects.
Table 4 Composition, physicochemical properties and spatial structure characteristics of trypsin inhibitor
(2) Measures to remove
High temperature can destroy the conformation of the active center of trypsin inhibitor, and enzymatic hydrolysis/fermentation can change the spatial structure of trypsin inhibitor, and even degrade the secondary and primary structures, thereby destroying its active center.
The high temperature clearance rate is 75-95%, and the clearance rate is 50-90% due to differences in fermentation strains and conditions; the combined liquid protease hydrolysis clearance rate is 90%.
Table 5 Effects of different treatment methods on trypsin inhibitor
Conclusion
The main components of anti-nutritional factors in soy protein raw materials are antigenic protein and trypsin inhibitor, which need to be eliminated as much as possible to reduce intestinal damage to animals and ensure intestinal digestion and absorption capacity.
In actual production, high temperature, high pressure, fermentation and enzymatic hydrolysis can remove antigenic proteins and trypsin inhibitors to varying degrees.
Enzymatic hydrolysis removes more than 90% of anti-nutritional factors in soybean protein, effectively improving the efficient utilization of protein.
(For the anti-nutrient content of soybean raw materials of different processes, please refer to "Analysis of Raw Materials (II) Quality Analysis of Feed Protein Raw Materials for Suckling Pigs")
The fifth issue of "Analysis of Raw Materials" will share with you our detection and evaluation of protein digestion rate in the nutritional value of protein, so stay tuned!
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