Effects Of Electron Beam And Gamma Ray Irradiation On The Microbial Diversity And Quality Of Commercial Fresh Geoduck Clam(Panopea Abrupta)

Geoduck clam(Panopea abtupta) is one of the high-end seawater species in Asian countries, due to its nutritional benefits, high price, and delicious taste. The siphon of geoduck clam, the main edible portion, tastes delicate, tender and crisp. Although geoduck clam is considered a delicacy in Asia, live geoduck clam is a high-value food commodity in China, with retail prices up to 400-500 RMB/kg. Now geoduck clam becomes more and more popular in consumers and aquaculturists, due to its nutrition and taste. The increase in consumer demand for high-quality food products has promoted the development of new technologies.Food irradiation processing technology, including electron beam irradiation technology and gamma ray irradiation technology, has been introduced as an alternative to preserve food, considering that it does not have any negative effect on the environment and does not leave any residue on the food. Electron beam irradiation, compared with gamma ray irradiation, is with the advantage of higher-efficiency irradiation, more uniform irradiation dose, higher dose rate and so on. With the development of electron beam irradiation technology, electron beam becomes more and more popular in researchers and processers and may predominate irradiation field in the future. However, there are differences between electron beam and gamma ray on physical properties and mechanism. This study focuses on the comparison effects of electron beam and gamma ray irradiation on nutritional value, physicochemical property and microbial diversity of geoduck clam. The results are as follow:(1)The results showed that for electron beam and gamma ray irradiation, there was no significant effect was found on contents of protein, moisture, ash and fat. Irradiation treatment impacted on amino acid content, the DAA/TAA value of groups treated by electron beam irradiation were higher than groups treated by gamma ray irradiation. All samples, with irradiation treatment or not, were rich in UFA and EPA, with the contents of more than 67% and more than 13% respectively.(2)Irradiation treatment played an important role in pH stability and electron beam irradiation with dose of 2.0 kGy did better than gamma ray irradiation in maintaining pH value. Amounts of histamine, cadaverine, putrescine and total amount of biogenic amines of both irradiations patterns increased with storage days dependent and no significant difference was found in amounts of tyramine, histamine, cadaverine, putrescine, spermidine, spermine and total amount of biogenic amines between the two different types of irradiation. The volatile compounds of all samples, with irradiation treatment or not, mainly composed of aldehydes and ketones.(3) The results showed that gamma ray and electron beam irradiation could effectively decrease total viable counts and Dio were 3.2 kGy and 3.1 kGy respectively. Irradiation treatment had a significant impact on microbial community composition, the dominated microorganism strain of the control was Firmicutes, but the dominated microorganism strain of both irradiations treatments with dose of 4.0-8.0 kGy was Proteobacteria. Meanwhile, significant difference was observed between both irradiation patterns with dose of 2.0 kGy, the dominated microorganism strain of group treated by electron beam irradiation was Proteobacteria, however, group treated by gamma ray irradiation was Firmicutes, which was dominated microorganism strain of the control at phylum level. The above results were consistent with change regularity of pH value.