Changes Of Lipid During Processing Of Dry-cured Duck And The Effect On Lfavor Quality

Dry-cured duck is one of traditional dry-cured meat products of China, the unique flavorand the condensation of traditional culture make it win a high reputation abroad, and it is alsothe important constituent of Chinese diet culture heritage. But so far the traditional processinghold back the step of dry-cured duck industrialization development. The main reason is lockof science research on dry-cured duck, it is difficult to improve and optimize the processingfor lack of scientific theory.This paper mainly studied lipolysis and lipid oxidation propertiesand its effect on flavor quality during processing of dry-cured duck, then the effect ofair-drying temperature on lipid oxidation and integrated quality of dry-cured duck wereresearched. The aim is to provided some theoretical basis for the study on flavor formationmechanism and the control of quality and standardization of production processing ofdry-cured duck. The main contents are organized as the following:Lipolysis and lipid oxidation properties of intramuscular and subcutaneous lipid indry-cured duck were studied, and the correlation among indices were built. The resultsshowed that glyceride content in subcutaneous lipid of dry-cured duck was more than95%, itslipolysis was weak. The lipolysis of intramuscular was relatively strong,64.71%ofphospholipids was hydrolyzed and FFA significantly increased during processing. POV andTBA increased significantly during entire processing, carbonyl value and conjugated dienesvalues of intramuscular lipid changed greatly during air-drying processing. Subcutaneouslipid oxidation degree was low, so lipolysis and lipid oxidation of intramuscular were themain changes during processing of dry-cured duck. Palmitic acid(C16:0), steartic acid(C18:0),oleic acid(C18:1) and linoleic acid(C18:2) in intramuscular and subcutaneous lipid accountedfor96.50%and95.60%of total FFA respectively, were the main FFA of dry-cured duck.Intramuscular phospholipid showed highly significant negative correlation with main FFA(p<0.01), which was the major source of FFA. TBARS and POV showed significantlypositive with main FFA (p<0.05), the accumulation of FFA could promote lipid oxidation.By tracking changes of volatile compounds during processing of dry-cured duck,combined with sensory evaluation, the correlation between lipid oxidation and flavor qualitywere built. The results showed that during processing of dry-cured duck lipid oxidation was inappropriate range without rancidity flavor production, and sensory flavor quality continuouslyimproved. Aldehydes increased significantly and reached51.96%in the final product, hexanal,heptanal, octanal and nonanal were the dominant of aldehydes. Aldehydes and acidscorrelated well with POV and TBARS and sensory evaluation indices, were important forpromotion of flavor quality of dry-cured duck, especially aldehydes and lipid oxidation (POVand TBARS) were significantly positive correlation (r=0.905and0.936). The futher analysisshowed that hexanal, heptanal, octanal and nonanal were the important component for flavorof dry-cured duck, lipid oxidation had a significant effect on the accumulation of aldehydesand on smell and colour quality of dry-cured duck.By analyzing the differences in physicochemical indices, TBARS, sensory quality andvolatile flavor compounds between high-temperature and low-temperature air-drying ripened dry-cured duck, the effect of air-drying temperature on the quality characteristics and lipidoxidation were studied. The results showed that high-temperature air-drying significantly(p<0.05) accelerated the decline of moisture, Aw and accumulation of salt, and also showsignificant effects in a*values (p<0.05), but not in texture. TBARS values ofhigh-temperature air-drying group were extremely higher than that in low-temperatureair-drying ripened group (p<0.01), temperature showed extremely significant effects on lipidoxidation. Aldehydes in the final products of high-temperature and low-temperature air-dryingripened dry-cured duck were higher than that in raw material,54.85%and67.1%respectively.Hexanal were mush higher than other aldehydes, accounting for65.59%and67.66%of thetotal aldehyde respectively. High-temperature air-drying ripening produced more acids andketones, which might be corrected with lipid peroxidation and rancid flavor.