Research On Anaerobic Fermentation Processing Technology Of Dead Tilapia

In this experiment, dead tilapia was fermented under different conditions (including fish to water ratio, ambient temperature, rotting fish fluid).And microorganism colonies, nutritions, enzyme activity in different liquid fermentations were measured. Nutrient in fermented liquid and fermentation speed basis to determine the best processing mode.1.Variation of dead Tilapia in the different fish to water ratios and different ambient temperatureDead fish was diluted with water in containers at three fish to water ratios (1:0.5, 1:1 and 1:2). These containers were respectively processed at outside temperature, room temperature and low tempreture indoor. The present work showed that liquid fermentation temperature was 1-2℃higher than that of external environment. After fermentation, the solution of dead fish was acidic, pH was 7.0-5.5, and the pH value decreased with the zymotic time. Environmental temperature had a great effect on analytical rate, Fermentation proceeding accomplished after 14 days at high outside temperature, 21 days at room temperature, and 28-35 days at low temperature.In outside and indoor fermentation solution, both showed increased content of gross nitrogen respectively by the 14th and 21th day, and this proceeding would last to 28th day at low tempreture. The former higher than the latter at the earlier stage, in the later period, there was no obvious difference. The content presented a relationship with the qualitative ratios of fish/water (1:0.5>1:1>1:2). The content changing patterns of gross phosphorus, nitrogen, phosphates, nitrates, and ammonia nitrogen showed the same.In fermented solution, there were many bacteria and mycete, a few yeast, few actinomycetes. The concentration of bacteria reached its peak of 10¹⁰-10¹² cfu/ml on the 14th fermentation day under outside and indoor environments at room temperature, on the 28th day at low temperature. The concentrations of mycete, yeast were respectively 10⁸-10⁹ cfu/ml, 10⁷-10⁸ cfu/ml, and actinomycetes was the least, the concentration was 10⁶-10⁷ cfu/ml. The number of four kinds of colony increased at first, then decreased, and stabilizated at last. The number presented a relationship with the qualitative ratios of fish/water (1:0.5> 1:1>1:2). The urease and protease activity reached the highest on the 7th fermentation day under outside conditions, on the 14th day indoor, on the 21th day at low temperature, then decreased in the later periods. The catalase activity was high in the early fermentation days under outside and indoor conditions, the highest on the 14th fermentation day at low temperature, then gradually decreased.2. Variation of dead Tilapia in different rotting fish fluid at different ambient temperatureAccording to ratio of fish/ water 1:1, the addition amount of rotting fish liquid were respectky 0.5ml, 1ml, 2ml, while 1ml rotten fish fluid, 2% dead fish lactobacillus and yeast as another group. All those materials were added to the containers which were placed outdoor, indoor and at low temperature condition respectively. The results showed as follow: the zymotic temperature was 1-3℃higher than ambient temperature. After fermentation, the pH of dead fish was 7.0-5.0, and the pH value decreased with zymotic time. The pH of composite group which added lactic acid bacteria was low. The environmental temperature played a great effect on the decomposition rate. The fermentation completed during 14 days in high temperature outdoor, and the composite group was the most thorough.Nutrient increased with zymotic time extended, and stabilized at last. the orders from high to low as follow: group of rotting fish liquid and complex bacteria in prior time, 2ml rotting fish liquid, 1ml rotting fish liquid and 0.5ml rotting fish liquid. In the later stage, group 1ml and 2ml was almost the same, and the combined group was higher than others.The bacteria levels were 1010-1012 cfu/ml, which would reach to 1012 cfu/ml in the previous 3 to 7 days outdoor and indoor, 14 to 21 days at low temperature, the orders from high to low as follow: group of adding rotting fish liquid and complex bacteria in prior time, 2ml rotting fish liquid, 1ml rotting fish liquid and 0.5ml rotting fish liquid. Mycete levels were 10⁹-10¹⁰ cfu/ml, yeast levels were 10⁶-10⁸cfu/ml, and actinomycetes levels were 10⁶-10⁸ cfu/ml. The trend of major class bacteria was low-high-low, and stabilized at last.The activity of urease, protease was high in the first 7 days outdoor and indoor, then became lower, and was high in the 21st day at low temperature. The orders were the same, but showed no difference at the later stage. It was higher in high temperature outdoor and normal temperature indoor than the low group. The activity of Catalase was relatively higher at the early stage in outdoor and indoor, followed by a slow decline, and at low temperature, it increased to the14th day, then declined.As comprehensive comparison, it would be the best group with the molar ratio of fish and water 1:1, 1ml rotting fish liquid and 2% of the combined bacteria to ferment for 14 days in outdoor.