Changes in Freshness Indexes and Bacterial Flora during Storage of Pressurized Mackerel

Abstract

Changes in freshness indexes, sensory evaluation and bacterial flora were examined for minced meat of mackerel (Scomber japonicus) stored at 5°C after pressurization at 2, 000atm for 60min. Control samples were stored at 5°C without pressurization. Bacterial counts were decreased by 80% after pressurization, and bacterial growth was retarded for 4 days. Changes in bacterial flora of minced meat caused by pressurization were observed. Bacillus, Moraxella, Pseudomonas I/II and Flavobacterium, which had been found before pressurization, disappeared after pressurization, while coryneforms, Staphylococcus and Micrococcus, became dominant during the storage after pressurization. After spoilage, Ps. I/II predominated in both samples. Changes in pH, VBN, TMA and amines were related to bacterial growth. There were no significant differences in the K-value or the amount of lactic acid between control and pressurized samples, but lipid oxidation was advanced in pressurized samples at the early stage of deterioration. From freshness indexes and sensory evaluation, the shelf-life of pressurized samples was judged to have been rolonged by about 4 days.