Study On The Processing Technology Of Dry-Cured Mackerel And The Relationship Between Lipid Hydrolysis And Oxidation And Flavor

As a traditional processed aquatic food in my country,dry-cured mackerel has suitable salty aroma and unique flavor,which is deeply loved by consumers.In this paper,response surface methodology was used to optimize the dry-curing process of mackerel,the lipid hydrolysis and oxidation during the processing of dry-cured mackerel were studied,and the formation mechanism of characteristic flavor compounds was preliminarily discussed.The main conclusions were as follows:1.A single factor experiment was used to study the effects of salt addition,air-drying temperature and air-drying time on the acid value,peroxide value,TBARs and sensory evaluation of dry-cured mackerel,and the response surface model was used to optimize the process conditions.Single factor results showed that when the amount of salt added,airdrying temperature,and air-drying time were 4%,16℃,and 5d,the lipids of dry-cured mackerel products were moderately hydrolyzed and oxidized,the sensory score was higher,and the overall quality was the best;In the response surface test,the order of factors affecting the sensory quality of dry-cured mackerel was: air-drying temperature(B)> air-drying time(C)> salt addition(A),refer to the optimal processing technology factors obtained from response surface analysis,and combined with actual production,the final production process was determined as follows: salt addition amount 4.5%,air-drying temperature 15.5℃,airdrying time 5.5d.2.Under the optimal process conditions,changes of the salt content,moisture content,p H,water activity,acid value,peroxide value,TBARs,endogenous lipase activity,free fatty acid content,volatile flavor compounds of dry-cured mackerel products during processing were studied.During the processing,the salt content continued to increase while the water content continued to decrease,and the water activity presented a significant downward trend;The acid value,peroxide value and TBARs all showed a significant upward trend during processing;The activities of neutral lipase,acid lipase,and phospholipase first increased and then decreased during processing,while lipoxygenase also showed a trend of first increase and then decrease;The total amount of free fatty acids increased continuously during the processing process,increasing by 307.29%,the precursor fatty acids C18:1N9,C18:2N6,C20:3N3 and C22:6N3 of the key flavor compounds of dry-cured mackerel all increased during the processing;Five major categories of 38 volatile flavor components were detected in the dry-cured mackerel at the processing stage,including 12 aldehydes,10 alcohols,6ketones,3 esters and 7 other substances,there were 15 key volatile flavor substances(OAV>1)in dry-cured mackerel,of which 12 were derived from fatty acid oxidation,which were hexanal,heptanal,octanal,nonanal,sunflower aldehyde,and cis-4-decylal,1-octene-3-ol,1-hexanol,1-heptanol,2-octanol,6-methyl-5-hepten-2-one and 2,3-octanedione.3.The UPLC-Orbitrap mass spectrometry system was used to analyze the lipidomics of mackerel samples at different processing stages.The results showed that PC,PE,TG,DG,LPC,and PI were the main lipid subclasses in dry-cured mackerel,after curing and air-drying,the content of these lipid classes decreased significantly;30 lipid species(VIP>2)were selected for analysis,of which 27 lipid species showed a downward trend during processing,the VIP value of PE(19:0/22:6)was 10.0,which was the lipid specie with the most significant difference during processing,among the 27 lipid species,15 lipid species contained oleic acid(C18:1)in the fatty acid composition,2 lipid species contained linoleic acid(C18:2),and 6 lipid species contained DHA.(C22:6),indicating that the key flavor precursor fatty acids of the three dry-cured mackerel might be generated by the degradation of these 23 lipid species.