3.1 Protein content of soy protein isolate
Using the semi-micro Kjeldahl method, the protein content of the soybean protein isolate used in the experiment was 90.58%, which met the relevant quality requirements.
3.2 The effect of soy protein isolate on sausage yield
It can be seen from Figure 1 that as the amount of soy protein isolate added increases, the yield of sausage also increases. This is mainly because of the good water and oil retention of soy protein isolate, which enhances the water and oil retention of sausages; during the cooking process of sausages, soy protein isolate has its gelling effect before muscle fiber contraction, at the periphery of muscle fiber. A dense covering film is formed, which greatly reduces the loss of juice due to muscle fiber contraction. The interaction of soy protein isolate and meat protein can also form a gel with a certain strength and elasticity and a chewy feel. This gel is better than the gel formed by the meat protein itself. After gelling, water and fat are fixed in the gel. In the network. As the amount of soy protein isolate added increases, the absorbed water and fat also increase, and the gelation effect is also enhanced, so the yield rate is significantly improved. However, the amount of soy protein isolate added is not as high as possible. Although my country has not yet stipulated the maximum amount of soy protein isolate added in sausages, the effect of adding soy protein isolate on the texture characteristics of sausages should also be considered.
3.3 The effect of soy protein isolate addition on the physical properties of sausages
From Figures 2 to 4, it can be seen that the hardness, elasticity and cohesion of sausages all have a tendency to increase first and then decrease as the content of soy protein isolate increases. The hardness and cohesiveness of sausage reach the maximum when the soy protein isolate is added at 2%, and the elasticity of the sausage reaches the maximum when the soy protein isolate is added at 3%.
This may be due to the increase in the amount of soy protein isolate added at the beginning, the number of molecules per unit volume increased, and the interaction between protein molecules increased, from the hardness, elasticity and cohesion of the sausage. However, as the added amount of soy protein isolate continues to increase, it decreases, which may be related to the water absorption of soy protein isolate. The soy protein isolate absorbs more water, and the more water in the sausage offsets the enhancement of the gel effect caused by the increase of the soy protein isolate content. Therefore, it is shown when the soy protein isolate is added at 3% to 5%. , The hardness, elasticity and cohesion of sausages are all reduced.