Buhei Zenitani

Spoilage of Fish and Its Preservation by Chemical Agents

Publisher Summary In consideration of the steadily increasing demand for chemical agents to preserve fish and the lack of satisfactory agents for this purpose, this chapter reviews a general survey of the problem involved. The bacterial spoilage has the most conspicuous influence upon the decrease of keeping quality, although the influences of the denaturation of protein and the rancidity of lipid are not negligible. The keeping quality of fish depends on the species of fish, fishing methods, season and fishing grounds, temperature of storage, and transportation time, as well as on various conditions affecting the physiological action of microorganisms. The invasion of bacteria into fish flesh is considered to begin at gills and kidneys and spread throughout the body by the vascular system or directly through the peritoneal lining. The most sensitive change by bacteria in fish components is that of odor. The chapter presents studies on difference in spoilage according to species. Spoilage varies with differences in constituents of the fish body, muscle structure, and bacterial load as well as with environmental factors. To measure the degree of freshness of fish, a scientific index is required. Hence, various investigations have been carried out in this field. The chapter attempt review the literature concerning fish preservation by chemical agents.

Distribution of phototrophic bacteria in Omura Bay during the summer with special reference to brownChlorobium

The distribution of phototrophic bacteria was investigated during the summers of 1969 and 1970 in Omura Bay of western Kyushu. Phototrophic sulfur- and nonsulfur-bacteria were distributed numerously in the mud and bottom water. Brown strains usually dominated in number. In water column, other than bottom water, there were usually few or no phototrophic bacteria. On occasion, however, a large number of brown bacteria were found in the middle of water column.Six strains, two each of the purple, green and brown bacterial colonies, were isolated from mud and sea water. The purple and green bacterial strains were identified as belonging to the generaChromatium andChlorobium, respectively. The brown strains could not be identified using Bergeys manual, but were found to be similar to the brownChlorobium described byPfennig. All six strains required sulfide for growth. Heterotrophic tendency was greater for the purple and green strains than for the brown strains. Their growth was enhanced by the addition of thymine. Living cells, taken from enrichment cultures of mud samples from four stations, gave absorption spectra almost identical to the spectrum of brownChlorobium. Thus it appears that during the summer brownChlorobium is the dominant phototrophic bacterial group in Omura Bay.