Sterilization Process Of Slightly Acidic Electrolyzed Water In The Purification Of Japanese Scallop

The Japanese scallop is one of the most important cultured shellfish in China; however, being filter feeder, it is easy to gather harmful microorganisms, so procedures of purification and sterilization are necessitated before it is ready for the market. For its qualities of minor irritation, non-residue and bactericidal broad-spectrum, slightly acidic brine electrolysis is widely applied to fields of medical instrument disinfection, cleaning of fruit and vegetable and so on; nevertheless, related researches on the sterilization of Japanese scallop is have yet to be made. This experiment has used self-made equipment for preparation of slightly acidic brine electrolysis, and has discussed the influence of various factors over the physical parameters of slightly acidic brine electrolysis during its preparation; based on this, the paper has inquired into the influence of the prepared slightly acidic brine electrolysis on Japanese scallop’s survival rate and germicidal efficacy, and at the same time, it has carried out studies on its germicidal efficacy via vibrio parahaemolyticus infection of scallops; then it has studied the changes of microflora of the Japanese scallop before and after the treatment of slightly acidic brine electrolysis; finally, methods of single element experiment and orthogonal experiment have been implemented to explore the influence of different treatments on the coliform and total number of bacteria of living specimens of Japanese scallop and the optimum parameters of the sterilization process have been achieved. The main research contents and results are as follows:The electrolyzed water is made by adopting different parameters to inspect differences of pH, ORP and available chlorine in physicochemical properties of electrolyzed water. Its results are as follows.(1) With the increasing dilution ratio of electrolyte when preparing, pH of prepared electrolyzed water turns to acidity from alkalinity, its ORP increases gradually and the available chlorine declines gradually in proportion.(2) The separation distance between polar plates has little influence on p H of prepared slightly acidic electrolyzed water, ORP increases first and declines later with the separation distance change between polar plates, and the avail chlorine shall decline when the separation distance between polar plates is more than 20 cm.(3) pH of slightly acidic electrolyzed water shall be higher and closer to the neural electrolyzed water for longer electrolyzing time. ORP declines gradually because zwitterion tends to be balanced at the moment. The concentration of available chlorine increases gradually with the increasing ratio of chlorine ion in water.(4) pH of prepared slightly acidic electrolyzed water shall be lower for more dosage of hydrochloric acid. ORP shows an gradually increasing tendency within certain limit(p<0.05). The available chlorine shall increase gradually due to increasing amount of chlorine ion in water.The influences on survival rate of Japanese scallop imposed by the slightly acidic electrolyzed water are inspected. Meanwhile, the germicidal effect on vibrio parahaemolyticus is verified. Its results are as follows.(1) The survival rates of all untreated groups decreased gradually as the increasing time of holding culture, but are higher than 90% during 8 hours of storage.. The survival rates for Contamination Group and Control Group decline rapidly at 10 hours later. The survival rates for Control Group and Contamination Group are 72% and 70% respectively at the end of experiment(12 hours). When ending various groups of experiments which are processed with slightly acidic electrolyzed water, the survival rates at 1 minute, 2 minutes and 4 minutes are 80%, and the survival rate for Treatment Group at 8 minutes is 82%.(2) Slightly acidic electrolyzed water on Japanese scallop has a certain effect of sterilization.(3) Comparing with > 1100Mpn/g of Contamination Group, the vibrio parahaemolyticus in scallops of groups processed for 30 seconds declines to 150 Mpn/g. Meanwhile, its amount shall be less for longer processing time. The vibrio parahaemolyticus in scallops of group with longest processing time of 240 seconds is only 28Mpn/g.The Japanese scallops are divided into 4 groups by applying the conventional biochemical identification method, namely, the microflora before processing with slightly acidic electrolyzed water, microflora after processing with slightly acidic electrolyzed water, Japanese scallop microflora before processing at 24 hours later and microflora after processing with slightly acidic electrolyzed water at 24 hours later. The microorganism proportions are calculated, and the dominant bacteria are analyzed.(1) As for the recently caught Japanese scallops, their dominant bacteria consist of pseudomonas(31.25%) and vibrio(25%). Bacteria of these two species account for more than half of initial microflora. The rest part consists of alcaligenes(18.75%), neisseria(12.5%), erysipelothrix(6.25%) and chromobacter(6.25%).(2) After processing with slightly acidic electrolyzed water, 13 species of bacteria are detected. The main dominant bacteria are changed to vibrio(25%), klebsiella(16.67%), corynebacterium(16.67%) andenterobacter(16.67%) from pseudomonas. Bacteria of these four species account for 75% of bacterial species processed with electrolyzed water. The proportion of other 9 species is only 25%.(3) After 24 hours, the dominant bacteria in Japanese scallops not processed with electrolyzed water include pseudomonas(35%), vibrio(25%) and aeromonas(20%). As bacteria of photobacterium(5%), chromobacterium(5%), plesiomonas(5%) and moraxella(5%) only account for a quarter of total microflora, these four species are non-dominant bacteria. After 24 hours, the dominant bacterium in Japanese scallops processed with electrolyzed water is pseudomonas(44.44%). The aeromonas(16.67%), vibrio(16.67%), plesiomonas(11.11%), chromobacterium(5.56%) and moraxella(5.56%) are non-dominant bacteria.The single-factor experiment and orthogonal experimental method are applied to test influences on total bacterial number and coliform bacteria of live Japanese scallops imposed by different processing methods. Then, the best processing method for microorganism reduction is determined through the orthogonal experiment. Its results are as follows.(1) The single-factor experiment shows that the available chlorine concentration, processing time and ORP of slightly acidic electrolyzed water have different influences on reducing the total bacterial number and coliform bacteria in Japanese scallops.(2) The orthogonal experiment confirms that the processing time is the main factor influencing the reduction of total bacterial number and coliform bacteria. In this test, the processing method for maximum reduction of total bacterial and coliformnumber is the available chlorine concentration of 40mg/L, processing time of 16 minutes and ORP of 900 mV.