Ice Temperature Preservation Of Large Yellow Croaker And Its Application In Industry

Ice temperature preservation on large yellow croaker was studied in the study toovercome the problem by using traditional preservation methods. The detail researchs wereas follows:1) Researching the freezing features of large yellow croaker;2) Developing thefreezing point regulator of large yellow croaker;3) Studying the bactericidal efficiency ofstrongly acidic electrolyzed water on large yellow croaker;4) Evaluating the shelf life oflarge yellow croaker during ice temperature preservation storage.5) Developing the icetemperature preservation machine for large yellow croaker. The data obtained from theresearch were as follows:Temperature, freezing medium, water content and size of fish cakes influencing thefreezing process of large yellow croaker were investigated systematically. Result showsthat the center temperature of fish cakes can decrease to-18℃quicker when the size fishcakes were smaller and the water content was lower. Using liquid quick-frozen can let thefish cakes get through the maximal ice crystal production area faster when comparing tothe gas quick-frozen condition, which can help to maintain the quality of fish.Effects of freezing point regulators such as sodium chloride, sucrose, sorbitol, vitaminC and glucose were analyzed by response surface methodology. The variables ranges usedaccording to the single factor experiment were sodium chloride3%～7%(w/w), sorbitol5%～9%(w/w) and sucrose2%～3%(w/w) and the responses were optimized by anumerical method and were found to be sodium chloride5.16%(w/w), sorbitol7.15%(w/w) and sucrose2.96%(w/w). All the derived mathematical models for the responseswere found to be fit significantly to the predicted data. The results show the freezing pointof large yellow croaker decreased from-1.5to-4.2oC after adding the optimized freezingpoint regulators and the texture parameters were not significantly affected in comparison tothe control group. Comparing with atmospheric pressure or vacuum degrees treatment,using injection method to deal with the freezing-point regulators could decrease thefreezing point in a short time and benefit to the meat quality.Bactericidal efficiency of strongly acidic electrolyzed water (SAEW) and to considerSAEW used as a safe sanitizer on the inhibition of bacteria for large yellow croaker wereevaluated. More specifically, bactericidal activities on large yellow croaker treated by fourkinds of electrolyzed water (SAEW1, SAEW2, SAEW3and SAEW4) were compared.Morphological changes of Ecoli, amino acid composition and texture of large yellow croaker were evaluated during the SAEW1treatments. Suspension quantitative bactericidaltest showed that bactericidal efficiency of SAEW for Staphylococcus aureus, Escherichiacoli, Bacillus subtilis and Candida were62%,48%,28%and57%, as theoxidation-reduction potential of SAEW increased from640mv to1250mv, thebactericidal efficiency for the bacteria above-mentioned increased to100%,100%,97%and100%, respectively. The damage process of Ecoli O157: H7under the SAEW1treatment was observed. Amino acid composition and texture analysis showed there wereno significant different (P>0.05) between the treated and control groups, which indicatedthat SAEW was a safe and effective sanitizer for inactivating bacteria in large yellowcroaker.Several test items such as pH value, flavor, TVB-N, total bacterial count, juice leakageand chroma of large yellow croaker during different storage, separately at-4℃（controlgroup）,-4℃(treated group),-1.5℃and4℃were observed to determine the shelf lifeof ice temperature preservation. The result shows that the test items of the tested groupwere better than the control group and the shelf life of large yellow croaker was24dayswhen using strongly acidic electrolyzed water and storing at-4℃.Finally， freezing-point regulator machine was designed according to the data obtained fromthe previous experiments，which promote the application of ice temperature preservation inindustry.