Study On The Digestive Enzyme Properties Of Shrimp And Shellfish And Preservation

Storage is an important process in shrimp and shellfish product.The endogenous enzymeactivity in shrimp and shellfish was higher,which was one of the factors that influence the deterioration of shrimp and shellfish.The characterization of digestive enzyme was investigated existing in mantis shrimp,sinonovacula constricta and conch,digestive enzyme was extracted from fresh seafood muscle and digestive gland,compared enzyme activity and studied its enzymology properties,analysed the quality changes under the low temperature and freezing storage.The results showed that:（1） The digestive enzyme activity of different shrimp and shellfish are different.In the same kind of seafood,activity of protease and amylase in the digestive gland were higher than that in muscle.In digestive gland of 3 kinds of shrimp and shellfish seafood,protease activity comparison:mantis shrimp>sinonovacula constricta>conch,amylase activity comparison:mantis shrimp > sinonovacula constricta > conch;In muscle of 3 kinds of shrimp and shellfish seafood,protease activity comparison:mantis shrimp > sinonovacula constricta >conch, amylase activity comparison:mantis shrimp>sinonovacula constricta>conch.（2） In the digestive gland of mantis shrimp,optimal temperature for protease was40℃,optimal pH was 6,EDTA could inhibite the enzyme activity,protease was activated by Ca²⁺ and Mn²⁺,declined by Pb²⁺,Mg²⁺,Cu²⁺,Zn²⁺,Fe²⁺;In the muscle of mantis shrimp,optimal temperature for protease was 50℃,optimal pH was 8,protease was activated by Mg²⁺,Ca²⁺ and Mn²⁺,declined by Pb²⁺,Cu²⁺,Zn²⁺,Fe²⁺;In the digestive gland of mantis shrimp,optimal temperature for amylase was 30 ℃,optimal pH was 7;EDTA could inhibite the enzyme,amylase was activated by Mn²⁺ and Ca²⁺,declined by Pb²⁺,Mg²⁺,Cu²⁺,Zn²⁺,Fe²⁺;In the muscle of mantis shrimp,optimal temperature for amylase was 30℃,optimal pH was 7,amylase was activated by Mn²⁺ at high concentration, declined by Pb²⁺,Mg²⁺,Ca²⁺,Cu²⁺,Zn²⁺,Fe²⁺.（3）In the digestive gland of sinonovacula constricta,optimal temperature for protease was50℃,optimal pH was 8,EDTA could inhibite the enzyme activity,protease was activated by Pb²⁺ and Mn²⁺,declined by Ca²⁺;Mg²⁺,Cu²⁺,Zn²⁺ and Fe²⁺ do not have an obvious effect on theenzyme activity;In the digestive gland of sinonovacula constricta,optimal temperature for amylase was 30℃,optimal pH was 7,EDTA could inhibite the enzyme,amylase was activated by Cu²⁺,Zn²⁺,Fe²⁺and Ca²⁺,declined by Pb²⁺,Mg²⁺,Mn²⁺.（4）In the digestive gland of conch,optimal temperature for protease was 50℃,optimal pH was 8,EDTA could inhibite the enzyme activity,protease was activated by Ca²⁺ and Mn²⁺,declined by Mg²⁺,Cu²⁺,Zn²⁺,Pb²⁺ and Fe²⁺;In the digestive gland of conch,optimal temperature for amylase was 30 ℃,optimal pH was 7,EDTA could inhibite the enzyme,amylase was activated by Ca²⁺ and Mn²⁺ declined by Pb²⁺,Mg²⁺,Zn²⁺ and Fe²⁺,Cu²⁺ do not have an obvious effect on the enzyme activity.（5）The quality of shrimp and shellfish at-18℃ and 0⁴℃ from fresh to death was investigated through the study on determination of TVB-N,histamine, microbial content and pH.The results showed that:During freezing storage,TVB-N and histamine were rising but not more than 15mg/100 g.The total number of colonies was increasing logarithmicly,pH value were increased;During low temperature（0⁴℃） storage:the activity of protease increased,activity of amylase decreased;The TVB-N value trend obvious over time,at the 7 day,the TVB-N value of mantis shrimp was higher than 30mg/100g; Histamine rising obviously,the total number of colonies was increasing logarithmicly, pH was decreased at first and then increased.The best storage time for mantis shrimp are 3 days,for sinonovacula constricta are 4days,for conch are 4 days.