| Summary: | 博士 === 國立海洋大學 === 食品科學系 === 91 === During 72 h fermentation at 37°C, rapid increase in lactic acid bacteria count (LAB), dramatic decline in pH and suppression in the growth of contaminating Pseudomonas, Staphylococcus, and Enterobacteriaceae of mackerel minces with Pediococcus pentosaceus L and S were observed (p<0.05). When the mackerel mince was processed into Chinese style sausage with 4% sucrose, no significant changes in pH, growth of LAB, Aerobic Plate Count and Pseudomonas of the fermented mackerel sausage with Ped. pentosaceus L and S were obtained (p > 0.05) during 3 wk storage at 4°C, however, the growth of Enterobacteriaceae and Staphylococcus were effectively suppressed. The residual nitrite in sample decreased during processing and fermentation, and was minimally detected after 72 h fermentation. Suppression of VBN and psychrophilic microflora, and lowering residual nitrite suggest the potential of using these two strains in the fermented fish products. To improve the functionality, quality and further expand the market of seafood, mackerel minces were fermented with lactic acid bacteria (LAB) ~Lactobacillus plantarum CCRC10069, Lactococcus lactis subsp. lactis CCRC 12315, Lactobacillus helveticus CCRC 14092, or their combination at 37oC. Rapid growth of LAB, decline in pH, suppress of main microflora, increases in whiteness, Hunter L, nonproteinous nitrogen, sensory quality and free amino acids related to taste were observed. However, VBN of samples fermented with LAB were still ≤ 25 mg/100 g after 36 h fermentation. SDS-PAGE indicated the obvious degradation of water- and salt-soluble muscle proteins after 12h fermentation. Animal test demonstrated the LAB fermented mince has the functionality on reduction of blood pressure, glucose, and total cholesterol of SHR. These results suggested that LAB fermentation could highly improve the quality and increase their nutrition value, functionality and consumer’s acceptability. This study was, therefore, continuing to adjust the protein concentration of substrate and perform the LAB fermentation, which was try to develop a new processing technique. Mackerel mince was firstly homogenized with equal volume of 5% NaCl solution and then dilute with various amounts of 2.5% NaCl solution to obtain different media with protein concentration of 90, 45, 22.5 mg/mL, respectively. Lactic acid bacteria (LAB) strains of Lb. plantarum CCRC 10069, Lactococcus lactis subsp. lactis CCRC 12315, Lb. helveticus CCRC 14092, Ped. pentosaceus L or S were inoculated to the media. During 48 h fermentation at 37oC, rapid growth of LAB, decline in pH, suppress of main microflora and increases in whiteness, Hunter L and sensory quality were observed and the VBN of all fermented samples was still below 25 mg/100g. Samples after 24 hr fermentation by mixture of Ped. pentosaceus L and S had higher antioxidative ability including chelating Fe2+ ability and scavenging DPPH free radical ability, comparing with those without starters. They also could stimulate the proliferation of both mouse macrophage J774.1 and human hybridoma HB4C5, suggesting they could increase the human and mouse immunity. After 24 and 48 h fermentation, the sensory evaluation and photographic records indicated the high acceptability of the fermented products. According to the results obtained from this study, various LAB fermented fish products such as fish butter, fish pudding or fish custard can be produced by only adjusting the protein concentration of substrates and this technique has very high commercial potential.
To clarify the roles of the LAB starters played during fermentation, two strains of Ped. pentosaceus L and S, isolated from refrigerated pork by our laboratory were selected to purify and characterize their bacteriocins. These antimicrobial substances were purified to electrophoretical homogeneity by chloroform extraction and designated as pentocins L and S with molecular mass (M) of 27 and 25 kDa, respectively. Both pentocins had broad inhibition spectra and thermal-resistance. They could inhibit the growth of tested spore - forming, G (+) and G (-) strains, and the germination of B. subtilis ATCC 10225, B. subtilis ATCC 10254 and B. cereus ATCC 11778 spores. However, the inhibition activities decreased when the glucose in medium decreased from 8.0% to 2.0%. No significant inhibition on Enterobacteriaceae and Pseudomonas was observed in sample with adjusted pH using lactic acid, which was followed the pH profile of mackerel minces during LAB fermentation. However, the inhibition capability of lactic acid against Staphylococcus was almost similar to those with Ped. pentosaceus L and S. According to this result together with the characters of these 2 bacteriocins, the inhibition of main pathogenic bacteria of mackerel minces during fermentation was considered to be mainly resulting from the action of bacteriocins and then from the pH effect.
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