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Screening of Antioxidative Lactic Acid Bacteria and Its Application in Aquatic Product Processing and Preservation

Author: HongSongHu
Tutor: WuZuFang
School: Ningbo University
Course: Aquatic Products Processing and Storage Engineering
Keywords: lactic acid bacteria antioxidative activity fermented eel surimi
CLC: S983
Type: Master's thesis
Year: 2009
Downloads: 123
Quote: 0
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Abstract


36 strains were obtained by isolating from some samples,such as pickle and picking eel,etc.20 of them was confirmed as lactic acid bacteria by morphological examination, cataloes test and producing qualitative test of lactic acid formation. At alst, 25 strains were determined by addition of other 5 strains stored in laboratory. Two excellent strains named H15 and H17 were re-screened using inhibition ability of lipid peroxidation and scavenging capacity of superoxide anion radicals as an indicator, Vitamin C as a positive control. Finally, the strains of H15 and H17 were classified L.plantarum and L.pentosus after sequence analysis of 16S rDNA and rhamnose fermentation test.Antioxidative mechanisms including superoxide dismutase activity, glutathione peroxidase activity, reducing activity and metal ion chelating ability for Fe2+ of H15 and H17 were studied. It demonstrated that the superoxide dismutase activity of intact cell and cell- free extracts of H15 were 2.12U/mL and 2.68U/mL,while it’s 7.37U/mL and 5.92U/mL respectively of H17.The glutathione peroxidase activity of H15 and H17 were7.37U/mL and 5.92U/mL,respectively.Both of two strains had reducing activity,and the OD value of intact cell and cell- free extracts of H15 were 0.12 and 0.148 under 700nm,while H17 were 0.073 and 0.113,respectively.The metal ion chelating ability for Fe2+ was not found in two strains.The condition of preparation for lactobacillus starter was studied for processing application. Effects of temperature, culture time and protecting agent of lactic acid bacteria were also investigated. The optimum preparation conditions were obtained as follows: culture temperature was 30℃, harvesting time was 12h, the protectiog agent was 5% cane sugar with 5% monosodium glutamate.The two strains of lactic acid bacteria H15 and H17 were used as culture starter in the fermented eel surimi can processing. It showed that those strains have distinct effect to improve the flavor and resist the growth of harmful bacterium.The harmful bacterium after fermentation was reduced as the inoculums size increases.The harmful bacterium was 1.2×104cfu/g when the inoculums size was 0.15%, and it met the health standards.The optimum fermentation conditions of fermented eel surimi can were obtained as follows:mixed culture fermentation as the ratio of H15 and H17 was 1:1,seed size 0.07%( weight of intact cell),incubated at 30℃for about 3d. Finally, the peroxide value (POV) of eel surimi can was studied under the optimum fermentation condition.The results showed that the fermentation agent using H15 and H17 can resis the oxidation of lipid of fermented eel surimi during fermentation and storing time.The POV of eel surimi that not fermented was 0.12g/100g,while the fermented eel surimi was just 0.05g/100g after fermentation.The POV of eel surimi that not permented increased rapidly at an early stage,while permented eel surimi remained stable,and its POV after two weeks storage was also higher.It was promising to apply antioxidative activity of lactic acid bacteria to aquatic product processing and storing.

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CLC: > Agricultural Sciences > Aquaculture, fisheries > Product water transport,preservation,storage,processing,packaging > Fish preservation technology
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