Author : Poonsap Virulhakul

Summary : The effects of additives (sodium metabisulfite SMB; sodium tripolyphosphate, STPP and citric acid, CA) on bacteriological, biochemical and sensory changes in frozen shrimps (Metapenaeus ensis, De Haan) stored at -12°C and -18°C for 8 months were studied. Storage temperature and additives did not affect the changes on mesophilic and psychrophilic bacterial counts with storage time. However, the differences, in quantity of bacterial composition on all samples were observed. Biochemical analyses showed that pH of samples had tendency to increase at -18°C, but not much at -12°C, due to interaction of various biochemical changes. The increases in TVN of STPP- and CA-treated samples stored at -18°C were faster than those stored at -12°C while the same on the control and SMB-treated samples. Both AA-N and TBA increased up to a maximum of 4 months of storage, whereas Hx up to 6 months and then declined after these periods as results of transformation into other products. Cathepsin D activity decreased while histamine increased with storage time. In both storage temperatures, the rate of change in AA-N, Hx, cathepsin D activity, histamine and TBA was lamost the same.