Study On Flavor Compositon Of Aloididae Aloidi Hydrolysate And Flavor Improvement By Photocatalysis

Aloididae aloidi is a low-value shellfish,which is rich in the coast of China,and can be an ideal raw material for preparing seafood flavoring because of its high amino acid content.However,some off-odor and bitter substances produced in enzymatic hydrolysis process affects quality of product in large degree,which seriously affected the application of its enzymatic hydrolysate.In this paper,the composition of the flavor substances in Aloididae aloidi hydrolysate was analyzed,and the changs of flavor in the process of enzymatic hydrolysis were also studied.Besides,chitosan-TiO₂ was prepared and explored application in the improvement of the flavor of the Aloididae aloidi hydrolysate.The purpose of this study is to provide some reference for application of photocatalytic technology in aquatic seasoning base materials.The main conclusions are as follows:1.Aloididae aloidi hydrolysate was prepared by protamex,papain,bromelain,alkaline and neutral protease.Solid phase micro extraction-mass spectrometry?SPME-GC-MS?,electronic nose?E-nose?and electronic tongue?E-tongue?were used to analyse flavor substances of different hydrolysate.In each group,protamex hydrolysate has high hydrolysis degree?28.02%?,and bromelain has high soluble peptide content?6.75 mg/mL?.Different enzyme hydrolysate showed great differences and can be distinguished by E-nose and E-tongue.The response value of umami and richness in alkaline proteasase hydrolysate was higher than other groups.GC-MS showed that the content of heptanal and 1-octene-3 alcohol in the protamex group was higher than others,and the higher content of benzaldehyde in the alkaline protease group can form aroma for hydrolysate.After enzymatic hydrolysis,the contents of sweet amino acids in bromelain and alkaline proteases were higher than others.However,the content of arginine in protamex group was higher than that in control group,which provides some bitterness.2.Protamex was selected to prepare the hydrolysate.E-nose,E-tongue and GC-MS combined with soluble peptide and free amino acid analysis were used to analyze the flavor changes of Aloididae aloidi during enzymolysis.The degree of hydrolysis increased with the prolongation of enzymolysis time,and reached the maximum at 8 hours.The content of soluble peptide of hydrolysate increased firstly and then decreased in the later process.The E-nose and the E-tongue could clearly distinguish the odor and taste difference of hydrolysates at different enzymolysis time.The content of nitrogen oxides,alkanes and alcohols increased with the prolongation of enzymolysis time,and the hydrolysate presented strong bitterness and astringency during the whole enzymolysis.The total amount of free amino acids in the hydrolysate increased gradually,and some sweet,fresh and bitter amino acids increased in varying degrees during the process of enzymatic hydrolysis.3.Chitosan-TiO₂ photocatalytic composite was prepared with anatase TiO₂?P25?and edible chitosan.X-ray diffraction?XRD?,FT-IR,UV-vis and SEM was used to characterize the structure of the composites.The photocatalytic degradation performance of the composites was studied by constructing a simulation system.The results of FT-IR,UV-vis,XRD and SEM showed that the combination of titanium dioxide and chitosan was stable.The results of photocatalytic simulation system showed that the composite had great photocatalytic degradation.0.4%addition of chitosan-TiO₂ showed the higher degradation efficiency and the degradation degree of heptanal,?E?-2-heptenal,octenal,?E?-2-octenal and 1-octen-3-ol reached 83.82%,96.33%,81.73%,93.36%and 75.79%,respectively.4.The photocatalytic composite was used for improving the flavor of hydrolysate to compare with tea polyphenols and fermentation.E-nose,E-tongue,GC-MS and free amino acid analysis were used to analyze effect of different treatments on the flavor of enzymatic hydrolysate.Tea polyphenols and fermentation can effectively reduce aldehydes in enzymatic hydrolysate,and alcohol and ester content in yeast group increased significantly.The treatment of photocatalytic-fermentation can also effectively reduced the content of hexanal,pentanal and heptanal.E-tongue result showed that the response of bitterness in hydrolysate treated by photocatalysis and yeast were decreased significantly,while the acid response value was increased in yeast treated groups.Both fermentation and photocatalytic treatment could increase the content of free amino acids in the hydrolysate,and the effect was more obvious in group of photocatalytic-fermentation.