The Development Of The Long-term Preserved And Low Salt Semi-dry Tilapia And Its Shelf-life Prediction

In this paper, changes of the sensory quality, physicochemical properties and the microorganism of the low salt semi-dry Tilapia were analyzed during the storage; the specific spoilage organisms of the product were investigated; the effect of the single natural preservative on the spoilage bacteria was researched, the compound preservatives formulation was screened, and we developed the low salt and long-term preserved semi-dry Tilapia. The main research work is as follows:(1) C hanges of the physicochemical properties and the total microbial of the semi-dry Tilapia were investigated during the storage. Result shows that, there are significant correlations between the sensory evaluation, the total number of microorganisms and the color, TVB-N value, acid value, thiobarbituric acid, but the correlation with p H is weaker, and the correlation with peroxide value is the weakest.(2) The specific spoilage organisms in semi-dry Tilapia were investigated by 16 S r DNA clone library. Result shows that the microorganisms in semi-dry Tilapia are Staphylococcus, Lactobacillus, Lactococcus and Bacillus. And percentage of Staphylococcus, Lactic acid bacteria, and Bacillus is 46.67%, 36.67%, 12.22%, respectively.(3) The antibacterial ability of N isin, Tea polyphenols and Ethanol was tested by the filter paper inhibition zone experiment and the absorbance method. Results show that Staphylococcus, Lactic acid bacteria and Bacillus can be inhibited effectively by Ethanol of above 70% concentration,and the antibacterial ability of Ethanol on Staphylococcus and Lactic acid bacteria is better than that of N isin and Tea polyphenols. The Gram positive bacteria can be inhibited effectively by N isin, and Staphylococcus, Lactic acid bacteria and Bacillus can be inhibited very well at the concentration of 0.02%.(4) The influence of single and compound natural preservatives on the semi-dry Tilapia preservation was studied. Results show that the preservation effect of the Ethanol group is better than that of N isin and Tea polyphenols, and the differences with the two groups are significant(P<0.01). However, there is no significantdifference between Tea polyphenol group and N isin group(P>0.05). The differences between the two compound preservatives groups V,VI and the control group are very significant(P<0.01), and there are better than Tea polyphenol group and Nisin group. But there is not always significant differences with the Ethanol group. The formulation of the low salt and long-term preserved semi-dry Tilapia was determined as the mix of acid Ethanol and Tea polyphenol.(5) Results of the shelf- life prediction show that TVB-N changes according to the first order kinetics reaction model. K0=3672.765, Ea=29.026 k J/mol, and the Arrhenius equation of reaction rate constant of TVB-N and storage temperature is K =3672.765 ? e-29026 /RT, and the shelf- life prediction model of semi-dry Tilapia is:?t =ln(At)-ln?(A0)3672.765?e-29026 RT.