| Summary: | 碩士 === 國立海洋大學 === 食品科學系 === 89 === The stability of meat color has long been concerned by meat industry and consumers, and is largely depended on the states of myoglobin. It was found that lactic acid bacteria (LAB) could keep blue-fin tuna bright red color from browning. It was hypothesized that the myoglobin (Mb) or oxy-Mb of tuna was nitrosylated with the nitric oxide (NO), which was produced by NO synthase in LAB broth. In order to investigate the mechanism of keeping red color by LAB, production of NO synthase by LAB, determination of the maxima absorbances for Mb, oxy-Mb and NOMb, conversion of Mb or oxy-Mb into nitrosomyoglobin (NOMb) during immersion of tuna meat in LAB broth were performed. Comparing 3 strains of LAB, Lactobacillus fermentum CCRC 11698, 12190, and 10360, the NO synthase activity increased with the incubation and reached highest levels after 8 h incubation. However, the highest NO synthase activity was obtained in Lactobacillus fermentum CCRC10360 after 8 h incubation at 37oC. According to the absorbance scanning against wavelength, the Mb, oxyMb, metMb and NOMb had maximum absorbance at 418 (Mb), 544 and 582 (oxyMb), 410 (metMb) and 548 & 579 nm (NOMb), respectively. For investigating the converting ability of NO synthase produced by LAB, pure Mb was added in the LAB broth. It was found that the conversion of Mb to NOMb increased with the cultivation and reached highest level after 8-12 h incubation. Similar phenomenon was observed in the addition of tuna meat in LAB broths. These results suggested that the keeping red color of tuna meat from browning in LAB broth is dus to the nitrosylation of Mb or oxyMb by NO synthase in broth.
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