Changes in K value and microorganisms of tilapia fillet during storage at high-pressure, normal temperature.

This study determined the effect of high-pressure, normal temperature (25 degrees C) storage on tilapia fillets. After pressurization, the fillets were stored at normal condition (1 atm [1 atm = 101.29 kPa] and 25 degrees C) for 12 h to evaluate the changes of microbes and K value. The fillets stored at 2,000 atm for 12 h still kept the K value, a freshness index that represents putrefaction with the value beyond 60%, still below 40%, and the K value of the meat without pressurization was up to 92%. Total plate counts of the fillets stored at below 1,000 atm for 12 h were maintained at the value of 4.7 log CFU/g of meat, which was similar to the initial level. However, the counts were obviously decreased to about 2.0 log CFU/g of meat for the fillets stored at above 2,000 atm. The same effect was obtained for psychrophilic bacteria. Enzymes and microbes reactivated apparently after 12 h of normal condition storage of mild pressurized fillets. The study demonstrates that high-pressure storage can inhibit the putrefaction of tilapia meat but no longer after that.