Effects Of Bacteriostasis Preservation And Processing Methods On The Immunological Activity Of Major Allergen Tropomyosin In Shrimp

Shrimp aquatic products are rich in protein,minerals,vitamin A and unsaturated fatty acids such as eicosapentaenoic acid(EPA)and docosahexaenoic acid(DHA),providing high quality protein for human body.Due to the rich nutrients of shrimp and shrimp aquatic products,the consumption of shrimp increases year by year,but the followed allergic problems attract public attention.With the increase of consumption,the safety problems caused by shrimp have also attracted people’s attention.Tropomyosin(TM)is a myofibrillar protein with two identical subunits,molecular weight of about 36 kDa.It has thermal stability and accounts for 6% of total shrimp protein.TM can cause IgE allergic reactions in human body and has been proved to be the main allergen of shrimp.Due to the high cross-reactivity and homology of tropomyosin,TM has become the main research object of shrimp allergens.Preservation and processing are indispensable steps of shrimp products from fishing to table.Studies indicated that the quality and nutrients will be affected in food preservation and processing,and the conformation of allergens in food will also be changed,leading to the loss of immune activity.In order to research the immunological activity changes of shrimp major allergens during preservation and processing.The enriched TM was treated with biopreservatives of chitosan and tea polyphenol.The shrimp meat was treated with bacteriostatic method of acidic electrolytic water,and traditional processing method of cooking and fermentation.The changes of TM content and immunological activity in different preservation and processing methods were evaluated by SDS-PAGE,Western-blotting and competitive ELISA.The effects of different preservation and processing methods on the immunological activity of allergen TM were discussed,which provided a scientific theoretical basis for tracing the risk of allergens in shrimp aquatic products and developing hypoallergenic shrimp products in the future.The main research contents and results are as follows:1.The allergen TM of Litopenaeus Vannamei was enriched and purified,and the different concentrations of chitosan and tea polyphenols were mixed and reacted.The content and immunological activity of TM were analyzed before and after freshkeeping treatment.The results of SDS-PAGE and Western-blotting showed that there was no change in the protein bands and specific reaction bands of TM in chitosan and tea polyphenols processed samples.It indicated that the two biopreservative treatments had no effect on TM content.The results of competitive ELISA showed that the inhibition rates of chitosan and tea polyphenols treated samples were more than 80%,and there was no significant difference compared with the control group(P > 0.05).These results suggested that the two preservatives did not destroy the immunological activity of TM.2.Through the treatment of acidic electrolytic water and thermal-processing on shrimp meat,it was found that acidic electrolytic water treatment had no significant effect on the content of TM,while the immunological activity of TM decreased slightly.The immunological activity of shrimp samples soaked in acidic electrolytic water for 10 minutes decreased by 14%.The protein bands and specificity reaction bands of TM were decreased after the treatment of acidic electrolytic water after boiling or steaming treatments.The immunological activity of TM decreased by 12.9% and 15.7% respectively in shrimp samples cooked in acidic electrolytic water for 10 minutes and steamed for 10 minutes.It indicated that the allergen TM in shrimp samples was destroyed and the immunological activity was slightly decreased after acidic electrolyzed water treatment and combined with boiling and steaming cooking treatments.3.The crayfish was treated with fermentation.During the natural fermentation of shrimp paste at 37 °C,the content and immunological activity of TM gradually decreased,and the immunological activity of TM decreased by 69% after 18 days of fermentation.The fermentation conditions were optimized by add enzymes of papain,alkaline protease and neutral protease.It was found that the TM allergen in shrimp paste could be reduced by about 70% within 30 minutes.The sensory scores of shrimp paste fermented by natural fermentation and enzymatic fermentation were more than 3 points,and the shrimp paste products had good color and odor.However,the natural fermented shrimp paste had a strong smell and stratification.The enzymatic fermented shrimp paste was superior to the natural fermented paste in taste and tissue state.The results indicated that fermentation processing could significantly reduce the immunological activity of TM in shrimp products.In conclusion,the single biological preservative does not reduce the immunological activity of shrimp main allergen TM.However,acidic electrolytic water or combined with thermal processing treatments reduce the immunological activity of TM slightly.The fermentation processing methods have significant effects on reducing the immunological activity of allergen TM.The immunological activity of TM decreases similarly in natural and exogenous enzymatic fermentation treatments,but faster in exogenous enzymatic fermentation.Proteins in shrimp paste products are rapidly decomposed under both endogenous enzymes and exogenous protease,while the natural fermentation process only exists endogenous enzymes action.This study provides a theoretical basis for the future traceability of shrimp products and the development of hypoallergenic products.