Changes In Degradation Of Fatty Acid,and Flavor Component During The Processing Of Shanghai Fried Fish

This thesis studied the whole process of processing Shanghai fried fish,from fresh fish,pickled,fried one minute,two minutes,three minutes,four minutes,five minutes,impregnated and finished frie fish in 8 process stages,Fat content and changes in lipid degradation,fat oxidation and flavor components of fried fish.Simultaneously,the fatty acid degradation of fried fish products and the flavor components of fried fish were studied under different oil temperatures(140 °C,150 °C,160 °C,170 °C,180 °C,190 °C)which affected the fatty acid composition of fried fish.The results showed that the crude fat content of the fried fish in the process of fried fish was significantly increased by 77.34%(P<0.05).The thiobarbituric acid(TBA)is on the rise and the degree of oxidation of fatty acids is increasing.Oleic acid(C18:1),linoleic acid(C18:2),palmitic acid(C16:0)and stearic acid(C18:0)are the main fatty acids in fish,and the total saturated fatty acids in the preparation of fried fish The decline trend,polyunsaturated fatty acids showed an upward trend,the percentage of unsaturated fatty acids in the finished fried fish increased from the original 72.44% to79.24%,and the flavor of fried fish has a certain improvement effect.A total of 95 volatile flavor substances were detected during processing.Aldehydes,alcohols and hydrocarbons were important volatile flavors in fried fish.The characteristic flavors were hexanal,furfural,anti-anti-2,4-anthracene.Dienyl,2,4-nonadienal and1-octene-3-ol.Among them,hexanal and 1-octene-3-ol have the characteristics of earthy taste and fishy smell.With the preparation process of fried fish,the content and relative odor activity value decrease,which reduces the earthy taste and fishy smell ofthe finished fried fish.Flavor,furfural,trans,trans-2,4-nonadienal,2,4-nonadienal with fatty aroma,with the progress of the preparation process of fried fish,its content is increasing,relative odor activity The value is greater than one is a higher value,which contributes a lot to the flavor of the fired fish,and improves the fat aroma of the fried fish product.The total content of free amino acids in the process of fried fish increased,from the initial 391.52mg/100 g to 472.8mg/100 g.The free amino acids with higher content are glycine,alanine,serine,lysine,histidine and proline,among which serine,glycine,alanine and proline contribute sweetness to the flavor of fried fish,histidine And lysine provides bitterness to the flavor of fried fish.As the preparation stage of the fried fish progressed,the total TAV value of the free amino acids with sweetness and umami taste increased,and the total TAV value of the bitter taste free amino acid increased slowly.Among them,glutamic acid and histidine have TAV values greater than one,and the TAV values of glutamic acid and histidine are increased compared with the TAV values of fresh grass glutamic acid and histidine,respectively.The fresh flavor of the finished fish,histidine provides a bitter taste for the finished fried fish.The contents of ATP and ADP decreased during the preparation of fried fish,while the contents of IMP,AMP,HX and HXR increased.The higher free nucleotide were IMP,AMP and HXR,among them,IMP and AMP have a freshening effect on the flavor of fried fish,and there is also a significant umami-stimulating effect when coexisting with glutamic acid.The TAV value of IMP in each stage of fried fish processing is greater than one,and the TAV value of AMP is less than one,so IMP contributes a lot to the flavor of fried fish,as a characteristic taste nucleotide,it has a large freshening effect on fried fish.Thefatty acid composition of fried fish products under different oil temperatures:oleic acid(C18: 1),linoleic acid(C18:2),palmitic acid(C16: 0)and stearic acid(C18:0)are the main fatty acids of fish pieces.With the increase of oil temperature,SFA increased first,then decreased,and finally increased.PUFA decreased first,then increased and then decreased.The percentage of unsaturated fatty acids in the finishedsmoked fish reached a maximum of 79.24% at an oil temperature of 180 °C,high percentage of unsaturated fatty acids,which enhances the taste of fried fish.The key volatile substances in the preparation of fried fish at different oil temperatures are aldehydes,alcohols and hydrocarbons,of which the relative percentage of aldehydes is the highest.The key flavor substances of fried fish at different oil temperatures are hexanal,furfural,trans,trans-2,4-nonadienal,2,4-nonadienal,trans,trans-2,4-nonadienal,1-octene-3-ol and xylene,wherein the hexanal and 1-octene-3-ol having a soily taste decrease as the oil temperature increases,and the relative odor activity value decreases.Fried to reduce the soil and fishy smell of the fish.On the contrary,the anti--2,4-nonadienal,2,4-nonadienal,anti-,trans-2,4-nonadienal,as the oil temperature increases,its percentage and relative odor activityvalueincreases,It provides aroma and fatty aroma for smoked fish,and contributes the most to the flavor of fried fish.During the preparation of fried fish under different oil temperatures,the total free amino acid content increased with the increase of oil temperature,and the free amino acid content reached 489.12 mg/100 g at 190 ?.The free amino acids with higher content are threonine,glycine,alanine,lysine,histidine and proline,among which threonine,glycine,alanine and proline contribute sweet flavor to fried fish.Flavor,histidine and lysine provide bitterness to the flavor of fried fish.As the temperature increases,the TAV value of each free amino acid increases slowly.Among them,aspartic acid,glutamic acid and histidine have TAV valuesgreater than one.Aspartic acid and glutamic acid provide fresh fried fish products.It has a fragrant taste,while histidine provides a bitter taste for fried fish products.Under different oil temperature conditions,the ATP content decreased with the increase of temperature,and the contents of IMP,AMP and HXR increased,which was due to the high temperature promoting the degradation of ATP.The higher content of taste nucleotides are IMP,AMP and HXR,among which IMP and AMP have a freshening effect on the flavor of fried fish,and HXR has a certain bitter taste.During the preparation of fried fish at different oil temperatures,the content of AMP and IMP is higher and has a freshening effect on friedfish,the TAV value of IMP is greater than one under different oil temperature conditions,and the TAV value of AMP is less than one,so IMP has a greater contribution to the flavor of fried fish at different oil temperatures,and has a greater effect on the flavor of fried fish products.