Study On The Eating Safety And Process Control Of Uncooked Crayfish (Procambarus Clarkii)

Crayfish(Procambarus clarkii)deeply loved by the majority of consumers because of its delicious meat and rich nutrition.However,as a kind of freshwater shrimp with high content of moisture and protein,crayfish is prone to spoilage after death,which will cause excessive microorganism and the accumulation of harmful substances.Therefore,eating dead crayfish is easy to be poisoned.On the other hand,there are key factors causing rhabdomyolysis in meat and viscera of crayfish,so that improper consumption of crayfish can cause rhabdomyolysis.In recent years,the frequent occurrence of food safety incidents caused by eating crayfish has severely damaged consumers’ confidence in crayfish and hindered the booming development of the crayfish industry.Therefore,this paper mainly studied the differences in microbial safety and the effects on the integrity of biologically active muscle cells between live and dead shrimp of uncooked crayfish,and carried out research on the preservation and pretreatment process control to improve the food safety quality of fresh crayfish.Firstly,aiming at the food safety problem that eating spoiled crayfish is prone to be poisoned,the differences in microbial safety of uncooked crayfish were clarified through the determination of physical and chemical indicators and high-throughput sequencing(HTS)analysis.It was found that the relevant microbial indicators of live crayfish did not exceed the safe limit.However,the relative abundance of biofilms-forming bacteria and potential pathogenic bacteria in live crayfish was high,especially the relative abundance of Acinetobacter and Citrobacter in gills,intestines,and glands(GIG).Therefore,the main microbial safety risk in live crayfish was the accumulation of biofilms-forming bacteria and potential pathogenic bacteria.The total volatile base nitrogen(TVB-N)value and cadaverine content in GIG of the dying crayfish were 25.55 mg/100 g and 19.24 mg/kg,respectively,both higher than the safe limits.The microbial diversity of crayfish after death was fatal decreased,indicating that crayfish was more prone to spoilage.Meanwhile,dominant spoilage bacteria such as Shewanella,Pseudomonas,Aeromonas increased rapidly in the dead crayfish,so the dead crayfish could not be used for processing.Secondly,in view of the food safety problem that improper consumption of crayfish is easy to cause rhabdomyolysis,a reaction model of crayfish extract and physiologically active muscle cells was established to elucidate the difference in the impact of uncooked crayfish on the integrity of physiologically active muscle cells.It was found that the water-soluble extract of crayfish was the most destructive.The total antioxidant capacity(T-AOC),total superoxide dismutase(T-SOD),glutathione peroxidase(GSH-Px),catalase(CAT)and creatine kinase(CK)of physiologically active muscle cells rapidly decreased to 1.81 U/mg protein,21.8U/mg protein,42.7 U/mg protein,0.87 U/mg protein and 24.8 U/mg protein,respectively.Malondialdehyde(MDA)content of physiologically active muscle cells increased rapidly to1.73 nmol/mg protein.There were significant differences in the destructive effects between the water-soluble extract of high vitality crayfish and those of crayfish stored at 25°C for 2 h after death,and between the water-soluble extract of high vitality crayfish and those of crayfish refrigerated for 8 d after death.After the death of crayfish,the destructive effects of water-soluble extract of GIG decreased,while the destructive effects of water-soluble extract of muscle increased.Therefore,both live and dead crayfish posed a safety risk of damaging the integrity of physiologically active muscle cells.Then,given that dead crayfish could not be used for processing and there were microbial safety risks in live crayfish,chitosan and chlorine dioxide were used to reduce the relative abundance of biofilms-forming bacteria and potential pathogenic bacteria in live crayfish.It was found that 100 mg/L chlorine dioxide treatment killed the most microorganisms in crayfish.When the viability of crayfish treated with 100 mg/L chlorine dioxide decreased to upon-death stage,the total viable counts in meat,shell,GIG were 3.85 lg(CFU/g),3.82 lg(CFU/g)and 4.81 lg(CFU/g),respectively,which was much lower than that of untreated crayfish.The highest microbial diversity was found in crayfish treated with 100 mg/L chlorine dioxide,and the microbial composition was the closest to that of fresh crayfish.100mg/L chlorine dioxide treatment killed the most biofilms-forming bacteria and potential pathogenic bacteria in crayfish.After 100 mg/L chlorine dioxide treatment,the relative abundance of biofilms-forming bacteria and potential pathogenic bacteria decreased by 11.1%and 10.9%,respectively.Therefore,100 mg/L chlorine dioxide provided the best microbial control of fresh crayfish.Finally,given that there was safety risk of damaging the integrity of physiologically active muscle cells in live crayfish,boiling,frying,and microwaving treatments were used to reduce the damaging effect of live crayfish.It was found that boiling,frying and microwave treatment could reduce the damage to the integrity of physiologically active muscle cells to a certain extent,and the longer the heat treatment time,the weaker the damage effect of crayfish.After frying,crayfish had minimal damage.After fried for 45 s,T-AOC,T-SOD,GSH-Px,CAT,CK of physiologically active muscle cells increased significantly to 93.2%,96.2%,88.4%,96.0% and 95.6% of the control group,respectively.The content of MDA decreased significantly to 1.26 times of the control group.The damage effect of crayfish did not change significantly after frying for more than 45 s.Therefore,it is recommended that the frying time of crayfish should be at least 45 s when cooking.