ABSTRACT
Microbiological and chemical changes were evaluated in freshwater prawn stored under refrigeration at 0ºC and 5ºC during 10 days, with special emphasis on indole production as chemical spoilage indicator. The total psychrotrophic and indole positive microflora were mainly mesophilic, with indole positive microorganisms being less than 10(per cent) of the total microflora after 10 days storage under refrigeration. Bacteria from "Enterobacteriaceae" and "Vibrionaceae" families prevailed among the isolated indole positive strains. The use of the Most Probable Number-MPN method, using tryptone broth as culture medium, was the most reliable approach for the quantitative evaluation of the indole positive microflora. The stored samples showed increases in pH, L-tryptophan and total volatile bases (TBV), which were more intensive at 5ºC. The psychrotrophic counts and TVB values of samples stored at 0ºC werw lower than the recommended limits (1.0E+7 CFU/g and 30 mg N/100g, respectively), even after 10 days storage. However, in samples stored at 5ºC, these values were reached after 10 and 5 days, respectively. The presence of indole in levels above the limit recommended by FDA/USA (25(micro)g/100g) was confirmed in only one sample, suggesting that this substance, alone wouldn't be a good indicator of freshwater prawn quality stored under refrigeration