Study On The Gelation Process And Mechanism Of Collichthys Lucidus Surimi Gel Induced By Ultra-High Pressure

With the development of aquatic products processing, people's demand for the quality of aquatic products is also increasing especially the surimi-based products. However, the traditional thermal processing has a large thermal damage, such as the loose structure, leading to the decline of texture and color. It is not conducive to high-quality products.Ultra-high pressure (UHP) is a non-thermal technology and it can affect high-grade structure of protein, leading to protein denaturation, aggregation or gelation. Collichthys lucidus is a small-size economical fish in the costal. In this study, it was chosen as the raw material. Gelation process of surimi gel induced by UHP was optimized. The comparison of UHP and heat treatment on gel property and its change during storage were investigated. Gelation mechanism of UHP was researched at the same time.The effect of pressure (100-600 MPa), holding time (5-30 min) and co-temperature (10-60℃) on gel property were carried out. Surimi gel had been formed under 200 MPa; holding time on gel property was no significant impact; gel property reduced significantly with the raising co-temperature. The optimum UHP processing condition was obtained with orthogonal test as following:pressure of 300 MPa, holding time of 15 min and co-temperature of 20℃.Compared with heat-induced gel, we found that the gel strength of pressure-induced gel was 2.2 times better, but the hardness was only 67% of heat-induced gel. To springiness, cohesiveness, chewiness, water holding capability and whiteness, the effects of UHP were better, the springiness was especially 1.6 times of heat treatment. From the two cooperative processing methods of UHP and heat treatment, it showed that the effect of heat treatment after UHP was similar to the two-stage heat treatment while UHP treatment after heat treatment could damage gel structure obviously.Gel property such as gel strength, texture, pH, color, moisture and micro-structure improved while adding TGase, carrageenan or gellan gum under UHP, especially for the usage of TGase resulting a high quality.The change of surimi gel phy-chenmical quality during storage was investigated. The results showed that, gel structure was strongly destroyed under storage of-18℃, leading to a significant decrease of hardness, springiness and chewiness. It is more conducive to maintain the stability of gel property for UHP than heat treatment during storage.The effect of UHP on structure of myofibrils extracted from collichthys lucidus surimi was studied, including protein sulfhydryl groups, protein aggregation and secondary structure, to find the relationship between gelation process and mechanism. The results showed that, as pressure increasing, the active sulfhydryl content increased, while the total sulfhydryl content decreased gradually. The intensity of myosin heavy chain and actin band declined under UHP, while the macromolecular protein band (MW>200 kDa) appeared. The main secondary structure element of myofibrils wasβ-sheet, and the rearrangement of secondary structure was happened under UHP, leading to the reduction of helix, increase of disordered structure and stretching of molecular chain.In summary, UHP can promote the formation of collichthys lucidus surimi gel and obtain a high quality. It suggests that UHP processing exhibits a good potential for surimi processing.