Dissertation > Industrial Technology > Light industry,handicrafts > Food Industry > Aquatic products processing industry > Aquatic food processing and preservation

Study on the Combined Effects of Ozone Sterilization, Chitosan and Map on the Qualities of Sinonovaculla Constricta Lamark

Author ZhangChao
Tutor JiangYueMing
School Zhejiang Technology and Business University
Course Food Science and Engineering
Keywords razor clams ozone MAP chitosan temperature shelf-life preservation effects
CLC TS254.4
Type Master's thesis
Year 2012
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Sinonovaculla constricta Lamark, popular name is razor clam, belongs to lamellibranch classes, different teeth subclass, razor clam Branch, it is one of China’s four major shellfish, which widely distributed in coastal areas. Fresh razor clam are delicious and nutritious, while the shell is thin and breakable, as well as prone to spoil, so it is crucial to solve the problem of preservation. To extend the shelf life of razor clam and further expand its sales coverage and circulation, in this paper, studies on the razor clams on the basis of the basic conditions were investigated under different conditions, ozone treatment, modified atmosphere packaging and chitosan coating technology were used to investigate preservation effecsts of razor clams, and total number of bacteria, TVB-N, pH, sensory score and K values were measured to examine quality changes, providing a theoretical basis and technical references for fresh razor clams and other fresh shellfish. The results were as follows:1. Analysis of basic composition of razor clams:Razor clam is a typical low-fat and high-protein food, it owns great value of development and application with abundant protein, nutrient-rich amino acids in meat; Lactic acid in razor clams had little change during purification process, which would not result in making impact to the the parameters measured latter; The number of E. coli was lower than30MPN/100g in razor clams, and did not detect Salmonella, Shigclla, a. Staphylococcus, p. Vibrio and other bacteria, revealing razor clams has a good safety.2. Preservation effects of razor clams under different concentrations of OzoneStudies on the quality change of razor clams with processing of0.5mg/L and1.Omg/L O3, the processing time is l0min, stored at0℃. The results showed that ozone water could effectively reduce the number of razor clams’s TVC delayed the changes of pH, TVB-N and other physical and chemical indicators during the initial storage, and the higher the concentration, the more obvious preservation effects. However, with the rapid decomposition of ozone during latter storage, it could not inhibit the propagation of bacteria and restrain the breakdown of protein during the late period, when physical and chemical indicators of treatment groups increased rapidly, and late in the storage, the processing groups had no significant difference with control group(P>0.05).3. Preservation effects of razor clams under different packages of MAP:Studies on different gas ratios (60%CO2/30%N2/10%O2,60%CO2/40%N2)to the preservation effects of of razor storing at0℃. The results showed that the TVC of control group reached1.76×107cfu/g after4days at0℃, while the TVC in aerobic and anaerobic MAP reached1.87×107cfu/g and1.03×107cfu/g respectively after10days, exceeding the prescribed health standards; The non-oxygen MAP could extend razor clams’s shelf-life to8~9d at0℃, and the preservation effects inclouding TVC, TVB-N, K value, pH, sensory evaluation were better than the one in oxygen MAP.4. Preservation effects of razor clams under different concentrations of Chitosan coating:Studies on the preservation effects of different concentrations of chitosan solution(dissolved in1%phytic acid) to razor clams at0℃, the results showed that the treatment groups could slow down ascending trends of the pH, TVB-N and other physical and chemical indicators, as well as had a slower growth of bacteria and maintained good sensory quality during refrigeration process compared with the control group, Of which2%phytic acid solution of chitosan had the best preservation effects, extended shelf-life of3~4d. 5. Preservation effects of razor clams under the combination of ozone treatment, modified atmosphere packaging and chitosan coatingFirst, use1mg/L ozone water to reduce razor clam’s initial bacteria, then through the combination of MAP and chitosan for processing respectively, investigated the quality changes of razor clams at0℃. The results showed that the compounds could effectively inhibit bacterial growth and maintain good sensory quality during storage, delayed the K value, TVB-N and other physical and chemical indicators increased. Moreover, Based on total number of bacteria, pII, TVB-N, K values combined with a comprehensive analysis of sensory evaluation, the preservation effects of ozone sterilization combined with MAP, ozone sterilization combined with chitosan and three composite film were better than the one in a separate process, of which combined treatment of ozone sterilization, MAP and chitosan coating had the best preservation effects, the shelf-life could reached the16days around.6. Microbial changesof razor clams by combined treatment of ozone treatment, MAP and chitosan coating during storageIt confirmed that Vibrio was the main bacteria in razor clams by Gram staining and biochemical identification,1mg/L ozone could effectively reduce the number of Vibrio, verifying that a certain concentration of ozone pre-treatment had the disinfection capacity. Studies on bacterial components of razor clams during storage, the number of the main bacteria gradually decreased by combined treatments of ozone sterilization MAP and chitosan coating advantages during storage, indicating that the composite condition could effectively maintain sensory quality and extend products’shelf-life. However, due to the anaerobic packaging, oxygen content decreased in storage environment with time, resulting in the growth of anaerobic microorganisms and decomposition of protein, which caused product spoiled.

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