Effect Of High Pressure Processing On Quality And Safety Of High Value Shellfish

China is the biggest aquaculture country in the world and there are abundant resources of shellfish, the total yield of shellfish was up to13.80 million tons in 2013. Shellfish is delicious and rich in nutrition, it was known as the delicacies in table for a long time. The main consumption style of shellfish in china is cook-eaten while in many European countries, more and more people tend to raw-eaten for the purpose of the pursuit of freshness. But the properties of shellfish made them became a main source of food-borne disease. Although the microorganisms in shellfish could be inactivated by heat-processing(He P), they are poor in taste and quality after processing. This study explored a new physical technology based on high pressure processing(HPP) as a treatment technique for oyster(Crassostrea gigas) and abalone(Haliotis discus hannai Ino). Microbial inactivation and changes of spoilage organisms in oyster and abalone during 4℃ storage were studied and the optimum conditions of HPP for extending the microbiological shelf-life were investigated. Quality changes in storage period of oyster and abalone by HPP were researched and the total volatile basic nitrogen(TVB-N), p H value, Thiobarbituric acid(TBA), color value, muscle tissue and taste weredetected at the same time. The mainly research results are as follows:1. Microbial inactivation and changes of spoilage organisms in oyster and abalone during 4℃ storage were studied and the optimum conditions of HPP for extending the shelf-life were investigated. The results showed that no microbe in oyster and abalone could be detected when the pressure conditions reached to 500 MPa for 10 min and 400 MPa for 10 min. The shelf-life of raw-eaten oyster could be extended to 15 ds at 4℃ when HPP conditions reached to 300 MPa for 15min、400MPa for 10 min or 500 MPa for 5min. The microbiological shelf-life of raw-eaten abalone could be extended to 20 ds and 25 ds at 4 ℃ when HPP conditions reached to 400 MPa for 10 min and 500 MPa for 10 min. Dominant spoilage bacteria in oyster and abalone could be change by HPP. Pseudomonas spp. and Shewanella spp. are the dominant spoilage bacteria in untreated oyster while it changed to Shewanella spp.and Staphylococcus spp. in HPP treated oyster. Enterobacteriaceae and Lactobacillus spp.are the dominant spoilage bacteria in untreated abalone while it changed to Lactobacillus spp. and Staphylococcus spp. in HPP treated abalone. The results indicated that the optimum HPP conditions in microbiological shelf-life of oyster and abalone are 300 MPa for 15 min and 400 MPa for 10 min, respectively.2.The effect of HPP on quality changes during storage at 4℃ of oyster were researched based on the condition of extend the microbiological shelf-life. The results showed that the change of TVB-N values by HPP was inhibited effectively. TVB-N levels for HPP at 300 MPa for 15 min did not reached 10mg/100 g after 20 d storage. HPP have significantly(p<0.05) higher p H in oyster and hardness and springiness increased after HPP compared to untreated oyster. HPP have significantly(p<0.05) higher whiteness and lower redness in oyster while yellowness and total color changed slightly during storage. There difference in taste between Hep and untreated oyster are larger than HPP oyster. The results indicated that the quality of HPP oyster at 300 MPa for 15 min keeps well in 20 d storage.3.The changes of different HPP conditions on total TVB-N, p H value, TBA, muscle tissue and hardness of abalone during chilled storage were investigated. Quality changes of abalone by HPP were compared with He P. The results showed that the change of TVB-N values by HPP was inhibited effectively. TVB-N levels for HPP during storage period did not reached 35mg/100 g. HPP have significantly(p<0.05) higher p H in abalone, but it is lower than untreated abalone after 30 ds storage; The TBA values of abalone increased slower after HPP compared with untreated and He P abalone. Abalone muscle fibers condensed under HPP according to thetissue slice. The hardness of abalone increased firstly and then decreased. The results indicated that the quality of abalone keeps well in 30 ds storage after HPP at 400 MPa for 10 min and the quality be improved at the same time.