Comparison Of The Digestibility Of Abalone (Haliotis Discus Hannai) After Different Processing Treatments And The Activity Of Product

Different food processing methods have varying influences on protein digestion of the products in vivo.In the present study,the effect of five processing and preservation methods including raw,boiling,canning,drying and frozen on the digestibility of abalone?Haliotis discus hannai?muscular proteins were investigated.The research is mainly focused on the impact on the quality in the process of circulation of frozen abalone products.Therefore,for the investigation of frozen abalone muscular protein digestion properties in vitro,different freezing temperatures?-20°C,-30°C,-80°C?and time?3,6,12 months?of frozen abalone were used in this study.Simulated gastric fluid?SGF?as well as simulated intestinal fluid?SIF?was applied to explore the digestibilities of abalone muscular proteins with various processing methods.The digestive products were seperated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis?SDS-PAGE?.Scanning electronic microscopy?SEM?was used to observe the differences in the fiber of the five products.The results showed that the digestibility of proteins in canned abalone was the highest among the five processing methods.Proteins from dried abalone were most resistant to digestion both in SGF and SIF.The five processing methods revealed different fiber structures under SEM.The muscle fiber proteins in the muscle of fresh abalone are dense and have a physiologically network distribution.There was a partial condensation among the myofibrils in the boiled abalone,and the dried abalone muscle fibers shrank evenly and arranged in a more orderly and dense manner.The canned abalone muscle fiber was loose and formed certain flocculation structure and space.For frozen abalone,the muscles of the sarcomere clearance is bigger than fresh abalone,with the extension of freezing time,gap becomes small.On the whole,lower freezing temperature and prolonged freezing time resulted in smaller space of muscle tissues during freezing processes.Furthermore,the angiotensin I-converting enzyme?ACE?inhibitory activity of the digestive productsexhibitedthefollowingorder:canned?464.2?g/mL?<dri ed?665.4?g/mL?<frozen?668.8?g/mL-773.2?g/mL?<boiled?775.7?g/mL?<raw?803.9?g/mL?.For different frozen abalone,ACE inhibitory activity of end-products had no obvious difference.As a result of food safety and palatability,boiled abalone has become a common consumption form.To reveal the ACE inhibitory mechanism of the digestive products of abalone,the boiled abalone muscle was subjected to simulated gastrointestinal digestion and ultrafiltration.In this study,we found that oral administration of abalone hydrolysate?UF1?decreased systolic blood pressure significantly?p<0.01?in a spontaneous hypertensive rat model?SHRs?.Furthermore,an angiotensin I-converting enzyme?ACE?inhibitory peptide was purified by sequential gel filtration chromatography and RP-HPLC.The sequence of ACE inhibitory peptide was determined to be Ile-Ile-Met-Ile-Arg-Phe?MW:773.41 u?with IC₅₀0 value of 909?mol/L.The results of Lineweaver-Burk plots suggested that the peptide was a non-competitive inhibitor against ACE.Mechanistically,the Discovery Studio 2017 and Autodock Tools analysis software were used to predict the interaction and binding sites between the hexapeptide and ACE enzyme.The results revealed that the binding energy of IIMIRF and ACE was-7.23 kJ/mol.The ACE inhibitory activity of IIMIRF was mainly attributed to hydrogen bonds formed between IIMIRF and Glu143,Ser355,Asn70,Gly404,His410 or Ala356,and the Van der Waals interaction and Pi-Sigma interaction between IIMIRF and Glu384 or His387,respectively.The results of MTT assay showed that the hexapeptide had little influence on the viability of Caco-2 cells.Even if the concentration of peptide reached up to 10 mmol/L,more than 90%of the cells survived.