The use of modern biotechnology to transform soybean meal into high-quality protein feed raw materials is a hotspot of international research and development. The product is less than ten years old, and the technology and industrialization level are the most prominent in the world, with Denmark as the leading country. In our country in this research began in the late 1990 s, the current domestic still in the early stage of large-scale industrialization, nearly hundred enterprises producing fermented soybean meal, but the quality is uneven, and many manufacturers one-sided propaganda, intentionally or unintentionally mislead, make the products on the market caused great confusion, user. How to evaluate and detect the quality of fermented soybean meal has become a big problem for various feed manufacturers and even some fermented soybean meal manufacturers (small factories).
1、Purpose of soybean meal fermentation
Only by clarifying the purpose of soybean meal fermentation can the main indexes of fermented soybean meal quality be determined. The main purpose of soybean meal after fermentation is as follows:
1.1 Destroy the anti - nutrient factor in soybean meal
Soybean meal contains trypsin inhibitor, oligosaccharide, lectin, phytic acid, urease and other antitrophic factors. During the fermentation process, through the action of microorganisms, enzymes and organic acids produced by fermentation, the antitrophic factors are degraded or inactivated and thus destroyed.
1.2 Eliminate antigenicity of soybean meal protein
The 7S and 11S proteins in soybean meal have strong antigenicity, and young animals are especially sensitive to them. During fermentation, the antigenicity is lost mainly by degrading the antigenicity.
1.3 Degradation of macromolecular proteins
The molecular weights of 11S and 7S proteins in soybean meal are 350KD and 180KD respectively, which are degraded into amino acids and various polypeptides by fermentation enzymatic hydrolysis, which are beneficial to the absorption and utilization of animals.
1.4 The formation of various beneficial fermentation products
At present, safe strains such as Bacillus subtilis, yeast and lactobacillus are used in the fermentation of soybean meal, and the products often contain a high number of beneficial bacteria, organic acids, proteases and other metabolites after fermentation.
2、Evaluation procedure for fermented soybean meal
The evaluation of fermented soybean meal can be carried out in four steps. The indexes to be tested are as follows:
2.1 Sensory evaluation
Including color, odor, fineness. After fermentation and drying, the color of soybean meal becomes darker, and the high-quality fermented soybean meal is brownish yellow or light yellow brown. If the color is light and consistent with the soybean meal, the fermentation degree may be insufficient or mixed with other light protein raw materials; If the color is too dark (e.g., dark brown), it indicates excessive dryness and maillard reaction. The smell of fermented soybean meal is slightly different according to different strains and production techniques, but there should be no bean-odor or mildew taste. Generally, the products with strong sour flavor are mainly lactic acid bacteria fermentation. Such products have low loss, low cost, high organic acid content, good food inducing effect, partial degradation of anti-nutrient factors, and generally can increase 4-5% of crude protein, with high digestibility and absorption rate. The grain size of fermented soybean meal should not be too fine. The finer the granularity, the more the loss of active ingredients in the product, and the harder it is for the eye to judge maternity leave.
2.2 Conventional physical and chemical analysis
Conventional physical and chemical indexes (protein content, water content, ash content, acidity, etc.) can be completed in the laboratory of most feed mills. According to these indexes and sensory indexes, the quality and stability of fermented soybean meal can be preliminarily determined. The protein content can generally meet the standard. It is suggested that all manufacturers detect the content of true protein in fermented soybean meal and simply judge whether to take maternity leave. The true protein of fermented soybean meal produced by using peeled soybean meal as raw material is generally between 44% and 49%, but this is also related to the content of free amino acid in the fermented product. High free amino acid content makes the true protein lower correspondingly. Manufacturers generally do not pay too much attention to the moisture content of fermented soybean meal, as long as it does not exceed the standard. In fact, there are great differences between different manufacturers in the formulation of moisture content standards for fermented soybean meal, which may cause misunderstanding to some users. Some manufacturers instill the concept of "low water content means more effective substances", which is actually not the case. For example, there are two products: A with 12% water content and 50% protein content; B 8% water, 50% protein. If A reduced the water content to 8%, the protein was 52.27%. B raised the water to 12% and the protein to 47.83%. From this example, we can see that high water content does not mean that there are fewer effective substances in the product. On the contrary, low water content means that drying temperature should be further increased or drying time should be prolonged, which will inevitably cause damage to the active substances. Fermentation technology is not mature or improper selection of strains of manufacturers, generally will be this method to improve the protein content. Soybean meal usually contains 5.5% ~ 6.5% total ash. Because there is a certain loss in the fermentation process, the crude ash content of fermented soybean meal is usually higher than that of raw soybean meal. Generally, the pH value of fermented soybean meal from various manufacturers is around 5, which is not the lower the pH of the product, the better.
2.3 Acidity
The method of titration is simple and fast. The acidity of fermented soybean meal is more than 2%, and if the acidity is too low, ammonia may be produced due to insufficient fermentation degree or improper fermentation control.
2.4 Antinutritional factors
2.4.1 Antigen protein
Soybean antigen protein is a kind of heat-stable antitrophic factor, which has the greatest influence on animals (especially young animals) in soybean. Soybean protein can be divided into 11S globulin (soybean globulin) and 7S globulin (and with globulin) according to sedimentation coefficient and immunological method, among which soybean globulin and -with soybean globulin are the most immunogenic soybean antigen proteins, accounting for 65% ~ 80% of total soybean seed protein. According to the characteristics of antigen proteins, many methods for the separation and determination of 7S globulin and 11S globulin have been established, including isoelectric point precipitation, cold precipitation, salting out, precipitation according to different ionic strength and immunoassay. At present, the method of SDS-PAGE polyacrylamide gel electrophoresis is used to determine the molecular weight distribution of the protein. By comparing the standard molecular weight map, the removal degree of antitrophic factors can be reflected to some extent. The antigen protein was quantitatively determined by ELISA and immunodiffusion. One of the main purposes of fermented soybean meal is to degrade soybean antigen, but for feed mills, it is basically impossible to detect, and can only be judged by the data provided by the manufacturers. As far as the production process of fermented soybean meal is concerned, it is impossible for antigen protein to be completely degraded. However, many manufacturers claim that their fermented soybean meal is "antigen-free" or "antigen-free", and the nominal antigen content is less than 1mg/kg, which is not consistent with the actual situation. In addition, some of the fermented soybean meal as the drying temperature is too high, the protein can't extract, sample on the protein concentration is low, there will be a sds-page shows that protein degradation of good appearance, we can be improved through the forint phenol method or Lorry method to detect the content of water soluble protein, if water soluble protein content is low, the product has a problem.
2.4.2. Trypsin ihhibitor
Although the trypsin inhibitor in soybean meal is a heat-sensitive factor, the activity of trypsin inhibitor in soybean meal can still reach about 2000TIU/g, and the high quality fermented soybean meal can reach below 400TIU/g. Generally, trypsin inhibitor can be quantitatively analyzed by NY/T1103.2-2006 method.
2.5 Determination of small molecular protein in fermented soybean meal
Another main purpose of fermented soybean meal is to degrade the large molecular proteins in soybean meal into small molecular proteins, or even into peptides and small peptides, so as to improve the absorption rate of digestion and immunity of the body in animals. At present, all manufacturers use tCA-N method for the determination of small molecular protein, while some fermented soybean meal manufacturers use this method for the determination of small molecular protein is claimed to be "small peptide" (less than 1000 Dalton), and did not deduct non-protein nitrogen (NPN) and free amino acid, which is confusing concept. Generally, tCA-N method is used to determine the small molecular protein substances whose molecular weight is less than 10000Da in fermented soybean meal, but not the peptide substances that have the significance of "small peptide" in biologist and animal nutrition. Between molecular weight of da in 5000 ~ 180 da, called "peptide molecular weight peptide between da 5000 ~ 3000 da referred to as the" big peptide, "da in 3000 ~ 1000 da between molecular weight peptide called" peptides, "molecular weight periods of da in 1000 ~ 180 da called" small peptide ", "oligopeptide", "low poly peptide", also known as small molecules active peptides, generally consists of 2 ~ 6 amino acids. In order to increase the crude protein content and reduce the cost, some manufacturers add some non-protein nitrogen (such as urea, protein essence) before fermentation. If this method is used to detect the content of small molecule protein, it is necessary to pay attention to the detection of non-protein nitrogen content.
2.6 Detection of microbial species and quantity
As the main raw material of fermented soybean meal, aflatoxin may be produced in soybean meal. Aflatoxin so far found pollution of agricultural products is the strongest type of biological toxins, belongs to the strong carcinogenic substances, can be in the growth of soybean, harvest, drying, processing and storage of any part, and can directly enter the food chain, in soybean as the pollution of aquatic animal feed ingredients, the variety of products can be found in the aflatoxin residue, resulting in aquatic animals, even one chain of pollution. Therefore, it is necessary to detect the microbial species and quantity in fermented soybean meal. Aflatoxin was detected against national standard GB 8381-87.
To sum up, the author suggests that if you want to fermentation soybean meal quality stable and reliable, you need to choose the regular manufacturers of starter, control the key points in the fermentation process, in order to get high quality fermentation products! Polaris, for example, which has a 19 year advantage in fermentation technology, is trustworthy. For the theme, Polaris conventional feed raw material starter culture can be selected. It can not only effectively degrade the harmful substances and anti-nutrient factors in soybean meal, cotton meal and rapeseed meal, but also significantly improve its feeding value.
