Study On The Gel-forming Properties Of Frozen Horse Mackerel

Horse mackerel (Trachurus trachurus) is a species of abundant warm waters fish. Its annual landings in the world were around 5 million tons in the past ten years. 55% of the horse mackerel catches were used for fish meal and fish oil processing, most of the rest were chilled and frozen, and the others were for fillet processing. In China, horse mackerel is an underutilized fish species. Therefore, manufacturing surimi using frozen horse mackerel as raw materials is expected to be an available means for enhancing the value of the fish.This work deals with the assessment of frozen horse mackerel as a resource for surimi gels, studying its chemical components, characteristics of its myofibril protein, and its gel characteristics with different washing methods to develop a good surimi processing. Besides, to improve the gels obtained, the effect of the addition of some protein additives (Egg white protein, Pork plasma protein, Soybean protein and Whey protein concentrate) on the surimi gel from frozen horse mackerel was investigated.The main research content and conclusions are as follows:1. The biochemical component of horse mackerel and its surimi, and the changes of Ca2+-ATPase activity and myofibril heavy chains (MHC) under different temperature were investigated, in order to understand the effect of temperature on the protein of frozen horse mackerel.The results showed the contents of crude protein and fat were high. The content of myofibrils in the protein (68.85%) was the highest, which was nearly to the content of Pollock. It was proved that horse mackerel was good material for surimi manufacture. However, the protein of frozen horse mackerel was easy to be denaturalized. The KD of Ca2+-ATPase at 25℃was 9.31×10-5. The degradation of ATPase and MHC with higher temperature or longer setting time was heavy. The change of MHC with temperature pointed that the fish was rich in proteinase, and the proteinase activity became higher with temperature increasing.2. The gel-forming characteristics of frozen horse mackerel under different washing processing (unwashed, washed, CaCl2 washed) during heating at elevated temperature were investigated. Effects of setting at 30℃and 40℃on textural properties and cross-linking of myofibrillar protein in surimi produced from horse mackerel were also investigated.The results showed that washed meat pastes from frozen horse mackerel belonged to the easy-setting and easy-disintegrating group, which performs obvious gel-forming phenomenon at 30°C, and shows heavy modori around 65°C. So the two-step heating would be suitable for the horse mackerel surimi processing. The caloium chloride (CaCl2) washing processing can improve the quality of the surimi gelation from frozen horse mackerel. It can postpone the modori phenomenon, but won't change the gel-forming characteristics of frozen horse mackerel. Setting at 30℃or 40℃would improve the gel strength of surimi. The rate of gel forming at 40℃was faster than at 30℃. However, there was no obvious increase in the gel strength with longer setting time (>2h), at both temperatures. The gel-forming characteristics of unwashed surimi showed that there was some proteolytic enzyme in sarcoplasmic fraction of frozen horse mackerel, which had activity in myosin heavy chain degradation at 40℃and could be removed by washing.3. In view of the gel-forming characteristics of frozen horse mackerel, to improve the mechanical properties of surimi gels concentration of protein additives (Egg white protein, Pork plasma protein, Soybean protein and Whey protein concentrate), temperature and time were studied.The result showed that egg white protein (EW), pork plasma protein (PPP), soybean protein (SP) and whey protein concentrate (WPC) all improved the gel strength of surimi from frozen horse mackerel with no obvious effect on whiteness of surimi gels. The proteinase inhibitory activity of PPP was the best, followed by EW, WPC and SP. The best concentration of the PPP, EW, WPC and SP were 1%, 5%, 5% and 2% respectively. The effect of 5% addition of EW and WPC on the gel improvement was equal to 1% PPP. EW and PPP (1%) could strength the suwari ability of surimi.