Research On Processing Technology Of Canned Tuna And By-products

Tuna is called "submarine gold", which is delicious and has abundance of nutrients and active substances. Katsuwonus pelamis is one kind of low-value tunas with a high level of commercial value. Katsuwonus pelamis are mainly processed to be dried products, cans and frozen products and production of cans take up a large proportion, but there are no reports on shelf life prediction of canned tuna, which is usefull to improve performance of enterprises. In addition, a large number of by-products, taking up half of total quality of tuna, like bones, skins, heads, viscera, etc., will be produced in processing, which was made to be fish meal with a low value. In order to utilize Katsuwonus pelamis reasonably and achieve a high value of processing of by-products.This thesis studied processing technology of canned tuna and by-products based on meat and bones of tunas.Firstly, taking tuna (Katsuwonus pelamis) as materials, the optimal sauce formulation (vinegar8.5%, bean paste2.5%, sugar13.5%, salt3.0%) was obtained through single factor and orthogonal experiment, on the basis of which, adding10.0%mushroom could cover fishy smell. In addition, taking121℃and55mins as sterilization conditions, the canned tuna could achieve one state of commercial sterilization. In this condition, TVC, TSS, pH value, POV, acid value, histamine contents of caned tuna were7CFU/mL,16.65%,5.33,0.0041g/100g,0.495mg/g,6.39mg/100g, respectively, Which were accord with DB11/617-2009Hygienic requirement for cooked aquatic products and GB14939-2005Hygienic standard for canned fish.Secondly, in order to study shelf-life of canned tuna, accelerated storage tests were used to explore the kinetics of quality in canned tuna. Physicochemical and microbial sensory index were detected at different temperatures (30℃、40℃、50℃) during storage. It was found that the dates of TVC, POV, acid value, TSS were accord with first-order reaction model and pH value fitted zero-order reaction model.On the basis of result of sensory index, Weibull model was built to predict shelf-life in30℃,40℃,50℃, where the shelf-life was300,240,149days, recpectively. It was found that Parameterβ of weibull model had no connection with temperature and the relationship of shelf-life and temperature was accord with Arrhenius equation by T-test method.what’s more, this model could predict shelf-life in25℃, which is365days. On the basis of results of TVC, POV and acid value, multiple index ex could be transformed to be a overall index though GSI theory, which could help to build a shelf-life model. It also could predicted shelf-life in25℃, being365days. Thirdly, taking DPPH radical scavenging rate and degree of hydrolysis as response value. Antioxidant substance was extracted respectively with Neutras, Alcalase, Papain, Pepsin, among which Neutras was showed to be a kind of best proteases.The test showed that the optimal hydrolysis conditions were as follows:hydrolysis temperature of56.22℃, enzyme dose of1.5%, hydrolysis time of1.88h, pH of6.15, liquid-material ratio of20.19:1. Under this condition, the protein concentration of enzymatic hydrolysates, the hydrolysis degree, the scavenging rate on DPPH free radicals and hydroxyl free radicals were9.30mg/mL,12.34%,94.97%,97.21%respectively. The antioxidant activity of enzymatic hydrolysates was higher than that of ascorbic acid at the same concentration.Fourthly, taking bones of Katsuwonus pelamis as a object.The effects of liquid-solid, alkali concentration, alkali extraction time, alkali extraction temperature, hydrolysis temperature on the extraction rate was studied.On the basis of single-factor, these parameters of extraction process was optimized by response surface methodology. It can build a model by regression analysis, which is Y=2.70+0.183A-0.026B-0.077C-0.18D-0.1AB+0.090AC-0.11AD-0.087BC+0.16BD-0.01CD-0.14A2-0.11B2-0.18C2-0.36D2(A is liquid-solid; B is alkali concentration; C is alkali extraction time; D is alkali extraction temperature). The results showed that the optimal conditions were as follows:the liquid-solid ratio of42.76:1, the alkali concentration of3.31%, the alkali extraction time of3.25h and the alkali extraction temperature of52.36℃.Under this condition, the extraction rate of chondroitin sulfate could reach2.80%.