Study On The Changes In Nutrition And Flavor Of Mackerel During Drie Process

Mackerel(Pneumatophorus japonicus)is one of the most important marine commercial fishes in China.Its flesh is rich in unsaturated fatty acids(DHA,EPA and so on),protein and other nutrients,so it can prevent cardiovascular and cerebrovascular diseases,and also improve human immunity.In addition,the price of mackerel is low.However,because its muscular enzyme system is very strong and the content of histidine is high,it is easily perishable.So mackerel is often saled in the form of dried products.In the process of dried,the lipid oxidation and Maillard reaction made the nutrition composition and flavor change a lot.In this paper,we studied these changes in the trend to ensure the quality of dried mackerel products and optimize the factory production management with basic data and theoretical guidance.In this paper,4 samples during mackerel dried process were selected as the study objects,including fresh sample,cooked sample,air-dried sample and sun-dried sample.First,the nutrients and fatty acid were measured;the organic acids,flavonucleotides and free amino acids were determined by HPLC;second,SPME conditions were optimized and the types of volatile compounds were identified by MS and RI method,and the content of flavor compounds was determined by internal standard method.Third,Principal component analysis(PCA)was used to determine the characteristic flavor substances.The main research results were as follows:1.The general nutrients of the mackerel changed obviously during air-dried process:the moisture,the ash and crude fat content decreased significantly;crude protein increased significantly,and the general nutrients content of mackerel did not change significantly after sun-dried process.During dried process,saturated fatty acids(SFA)incraeased gradually;monounsaturated fatty acids(MUFA)did not change a lot after cooked and air-dried;polyunsaturated fatty acids(PUFA)decreased gradually,and DHA,EPA were the two highest contents among PUFA.2.Tartaric acid was the most important organic acid in all mackerel samples,followed by succinic acid,which gave the taste of umami and spicy,and the content of acetic acid was also high in all samples.After Cooked,malic acid and lactic acid decreased significantly.Citric acid and propionic acid were not detected.Tartaric acid,succinic acid,acetic acid,malic acid and lactic acid reached the maximum in the air-dried sample,and the five organic acids were all active substances in all samples.IMP was the most important nucleotide,and its content was positively correlated with the dried process and all of its TAV was more than 1;AMP was not detected in the fresh mackerel,but it was detected in the other three samples,and its TAV was more than 1,which gave the sample a sweet taste;GMP was negatively correlated with the process.Among the free amino acids,the TAV of glutamic acid(Glu)was more than 1,which was an important taste active substance during dried process.The bitter amino acid was the highest free amino acid in all samples.The content of histidine(His)was the highest in all the bitter amino acids,and its TAV value was also the largest.The EUC of fresh sample was the largest;and the EUC in the final product decreased significantly,but its value was still more than 1,so it had a certain effect on the flavor.3.The optimal.extraction conditions were as follows:75?m CAR/PDMS extraction fiber,5g sample,40 minutes extraction time,70 ? extraction temperature,4 minutes desorption time,0.15g sodium chloride.2,4,6-trimethylpyridine was selected as internal standard(IS),the amount of the IS was also optimized,the results were as followed:120?L IS in the fresh sample,200?L IS in the cooked sample,300?L IS in the air-dried and sun-dried samples.4.The volatile compounds under the suitable condition of SPME-GC-MS for mackerel samples were identified by RI and MS.73 volatile flavor substances were identified in four samples in total,and 41,46,53 and 48 volatiles were identified in fresh,cooked,air-dried and sun-dried mackerel respectively.The volatiles were mainly composed by alkanes and aldehydes.The cooking process resulted in a significant increase in the content of aldehydes and the identification of butanal,2-(4-methyl-3-cyclohexenyl)propanal,undecanal,dodecanal,which were not detected in the fresh sample.Among the four samples,aldehydes,ketones,alcohols,alkanes and other compounds were all the highest in the cooked sample,which gave it a charming and complex flavor.After air-dried,except the aromatic compounds,the content of the rest of the volatile flavor substances all reduced because of the evaporation.After sun-dried,the content of aldehydes,ketones,alcohols and other compounds increased,mainly because the temperature rose,and the light enhanced.5.10,14,12 and 11 kinds of flavor active substances were identified in fresh,cooked,air-dried and sun-dried samples.PCA could reflect the characteristic signals of volatile flavor in different samples.Nonanal,dodecanal,2-nonanone,2-undecanone,phenylacetaldehyde,butyraldehyde,hexanal had a greate contribution to the mackerel sample.