Study On The Change Of Volatile Components And The Method Of Deodorization In The Enzymatic Hydrolysis Of Crassostrea Hongkongensis

Oyster(Crassostrea hongkongensis)is important economic shellfish cultured in Guangdong and Guangxi coastal areas,with wide distribution and large output.Crassostrea hongkongensis are delicious and nutritious.In recent years,nutritious functional foods developed with oysters have emerged in an endless stream.Enzymatic hydrolysis is one of the important ways to develop oyster foods.However,after enzymatic hydrolysis,unpleasant smell becomes more heavy.which seriously affects the acceptance of oyster products by consumers.Therefore,the removal of unpleasant smell of oyster hydrolysate has become one of the hotspots of scholars at home and abroad in recent years.In this study,the volatile component analysis was used as the entry point.The odor components of different edible parts of fresh Crassostrea hongkongensis and the odor changes before and after enzymatic hydrolysis of Crassostrea hongkongensis were studied.The fat oxidation of enzymatic hydrolysis was monitored and analyzed.On the basis of the influence of odor change,the deodorization method of adding tea polyphenols and enzymatic hydrolysis was carried out by vacuum enzymatic desorption and pretreatment,and the dislocation effect was evaluated by two kinds of dislocation methods,in order to increase the value of oysters.Use to provide a theoretical basis.The main research contents and results are as follows:(1)SPME-GC-MS was used to separate and identify the volatile components of oyster mantle,hepatopancreas and corpus callosum,and semi-quantitatively quantified by internal standard method.The main odor substances were further screened by OAV analysis.The results showed that 43 volatile components were detected in fresh oysters,including 23 aldehyde compounds,6 acid compounds,4 ketone compounds,4 alcohol compounds,2 alkanes,2 amines,and 1 ester.Species,one species of thioether and one species of furan.There are 11 kinds of ACs in fresh oysters,9 of which contribute to the pleasant odor of oysters,(E,Z)-2,6-nonadienal(cucumber)and(E)-2-octenal(cucumber),(E)-2-nonenal(musk),dodecanal(fat),1-octene-3-ol(mushroom),(E,E)-2,4-Hoodadienal,n-octanal,(Z,Z)-3,6-nonadienal,(E)-2-nonenal.There are two kinds of compounds that cause oyster odor,which are(E,E)-2,4-nonadienal(astringency)and dimethyl sulfide(smelly odor).There are 10 kinds of astringent ingredients(unpleasant smells)in fresh oysters,including 2 kinds of ACs,which are(E,E)-2,4-decadiene and dimethyl sulfide in the mantle..There are 8 kinds of astringent ingredients having an OAV value of less than 1.Modification of oyster taste.They are(E,E)-2,4-heptadienal(bryophyte and fishy odor),trimethylamine(fishy odor),hexanal(Oxidized fat),heptaldehyde(Oxidized fat),furfural(Oxidized fat),(Z)-4-heptenal(fishy odor)and diethanolamine(unpleasant pungent odor),isovaleric acid.(2)By measuring the TD value of enzymatic hydrolysate and TBARS in the enzymatic hydrolysis process,the fat oxidation of oyster during enzymatic hydrolysis was monitored.The fatty acid composition before and after enzymatic hydrolysis was determined by gas chromatography,and the odor evaluation before and after enzymatic hydrolysis of oyster was carried out.And the detection of volatile components,the results showed that lipids were oxidized during the enzymatic hydrolysis of oysters,among which unsaturated fatty acids were mainly oxidized.Among monounsaturated fatty acids,erucic acid was reduced by 100%,arachidonic acid by 12.93%,oleic acid.Reduced by 2.17%;among the polyunsaturated fatty acids,the docosadienoic acid decreased by 24.19%,the arachidonic acid(ARA)decreased by 16.31%,the linolenic acid decreased by 17.55%,the linoleic acid decreased by 12.52%,and the arachidonic acid decreased.12.56% and so on.These fatty acids are important precursors of aromatic substances.The degradation threshold of fatty aldehydes in the degradation products has a great influence on the odor of oyster hydrolysate.Some low-grade fatty aldehydes have a negative effect on the odor of oysters,resulting in enhanced astringency and scent of oysters after enzymatic hydrolysis.Cucumber,green and meaty are weakened.(3)Deodorization of oyster hydrolysate by vacuum dehydration and tea polyphenol desorption.The results showed that the enzymatic group had a odor score of 4.9(very heavy),a odor score of 2.6(general)after vacuum desorption,and a tea polyphenol component value of 0.5(almost no astringency).In the enzymatic hydrolysis group and the vacuum desorption group,fat oxidation occurred in the enzymatic hydrolysis process,while the fat oxidation of the tea polyphenol group was inhibited.38,24,and 22 volatile compounds were detected in the enzymatic hydrolysate,vacuum dehydrogenase,and tea polyphenol dehydrogenase.There are 11 kinds of ACs compounds in the enzymatic hydrolysate:(Z)-4-heptenal,n-octanal,(E)-2-octenal,furfural,(E,Z)-2,6-Xantadienal,furfural,(E)-2-nonenal,(E,E)-2,4-nonadienal,(Z,Z)-3,6-nonadienal,twelve Aldehyde,1-octene-3-ol.There are 9 kinds of ACs compounds decomposed by vacuum,namely:(E)-2-octenal,furfural,(E,Z)-2,6-nonadienal,furfural,(E,E)-2,4-decadienal,(E)-2-nonenal,(Z,Z)-3,6-nonadienal,undecaned,dodecanal.There is only one ACs compound in the enzymatic hydrolysate of tea polyphenols,which is dodecanal.