| Loach(Misgurnus anguillicaudatus) is widely distributed in natural freshwater regions all over the country, It’s a typical fish with high protein and low fat. In Recent year, loach in domestic demand is increasing because of its high nutritional value and fresh taste. The functional properties of loach myofibrillar protein largely determines the gel properties of loach products, But the loach myofibrillar protein gel ability is not strong. The soy protein isolate(SPI) often used in process of surimi products as a functional food additive. But in practice, the processing temperature used in cryogenic surimi products was lower than the denaturation temperature of SPI, it didn’t cause effective change in structure of SPI, it wouldn’t be good for SPI provide a function of auxiliary and improvement for gel properties in muscle protein. Therefore, this paper studied on different systems of environmental conditions on properties of functional and gel in myofibrillar proteins(MP), and effect of addition of SPI on the gel properties of MP extracted from loach, and the effect of SPI treated during the gel process of loach surimi. The findings for SPI rational used in fish products provide high value. The main conclusions of this paper are as follows:(1)Study on different factors of environment on the properties of function and gel in loach MP, results show:With the increase of pH value, solubility increased gradually, EAI and ESI showed a upward trend first and then decreased in loach MP, and surface hydrophobicity showed a downward trend; The water retention property of MP was gradually increased, but the hardness and whiteness of the gel decreased significantly,thus, the heat-induced gelation shouldn’t prepare in high pH.In the 0.3-0.6 mol/L range, with the increase of NaCl concentration, the solubility,EAI, and ESI enlarged,the surface hydrophobicity showed a downward trend; the gel strength significantly increased in heat-induced gelation of extracted MP, waterretention increased first and then decreased, whiteness showed a decreased, but not significantly. For process of loach MP, It may be appropriate to increase the concentration of NaCI MP to improve properties of function and gel.Within the concentration in range of 0.00% to 0.45%, solubility, EAI and ESI showed a upward trend first and then decreased in loach MP, surface hydrophobicity show a downward trend first and then increased; the gel strength, water retention and whiteness increased first and then decreased in extracted MP. The suitable concentration of TPP was 0.15%.(2)Study on effect of the addition of SPI on gel properties in loach MP, results show:SPI is beneficial to increase the hardness, water retention property and gel whiteness of the compound gel after heat treatment. With the increase of heat treatment temperature and heat treatment time, the effect of SPI on the gel properties of the mixed system is more obvious. Among them, adding the SPI effect of heat treatment 180 min was the best. Compared with the natural SPI, the gel hardness of the mixed protein was increased by 92.56%, and the water retention increased by 11.67%. Heating method of mixed protein gel hardness and water also has a significant effect: SPI and MP were mixed with protein by slowly heating the formed gel hardness and water retention were higher than that of gel hardness and water retention induced by 80℃, the constant temperature heating.SPI in different pH conditions after acid treatment, and mixed with MP, can also serve to enhance the objective MP gel hardness and water, which add the effect of pH3 treated SPI is the most significant and add natural SPI mixed protein system compared to the hardness of gel increased 106% and water retention rose 19.67% and gel whiteness changed little.SPI treated by Alcalase hydrolysis and MP mixed gel and significantly reduce the composite gel hardness and water holding, but when the hydrolysis degree reaches a certain value DH=5. The increase of degree of hydrolysis, won’t cause gel hardness significantly reduced. The increase of hydrolysis degree will increase the whiteness of the gel, but the hydrolysis degree of DH=5 will not change significantly after the hydrolysis degree.(3) Study on different concentration of SPI, concentration of NaCl, sodium tripolyphosphate(TPP) concentration, SPI pre-processing conditions on surimi gel elasticity and hardness, water retention and cooking loss and whiteness of the impact.The results showed that:With the increase of content of SPI, gel strength and elasticity significantly increased;the concentration of SPI hadn’t significantly influence on water retention and cooking loss in gel, it showed a upward trend first and then decreased for gel whiteness,whiteness got the highest value when concentration of SPI was 3%.The texture property showed a upward trend first and then decreased in gel of loach surimi with the increase of concentration of NaCl, however, water retention increased, cooking loss and whiteness decreased gradually, but, the value of whiteness hadn’t significantly difference.With the increase of the concentration of TPP, the hardness of the gel increased gradually, and the hardness increased by 14.29% when the concentration was 0.15%.But concentrations continue to increase, the gel hardness not increased significantly;elastic gel increases gradually, When the concentration is 0.45%, the gel elasticity 0.67,than without the addition of TPP gel elastic lifting 14.14; the water retention property of the gel increases gradually, cooking loss decreases; the whiteness of gel increases gradually, and in the range of 0.0%-0.3% exist a significant difference.The effect of different SPI on gel properties in loach surimi: compared to control group(without adding SPI), it would improve hardness and elasticity in surimi gel with the addition of heated SPI, also it increased water retention. The sample added SPI which DH was 3, it showed higher hardness and elasticity than the sample added SPI without hydrolyzing, but all of these showed a downward trend. The SPI of different treatment had no significantly influence on whiteness in gel of loach surimi. |
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