Study On The Formation Law Of Volatile Compounds Like Oxygenated ?,? Unsaturated Aldehydes During Lipid Oxidation

The oxidation of edible oils is a key factor for the metamorphism of food which happens during the food processing,storage and transporting.It always causes the nutritional losses and shortens the shelf life.Besides,it will also produce toxic compounds.The oxygenated ?,?-unsaturated aldehydes formed during the lipid oxidation are considered to be potential causal agents of degenerative diseases,such as cancer,atherosclerosis and Alzheimer's,could be a threat to human health.In this research,with a novel HS-SPME-GC/MS method we developed for the analysis of volatile compounds in oils,the forming of volatile aldehydes in 4 different vegetable oils during heating at 150,180 and 210 ? were studied.And the fatty acids and oxidative indexes of those oils were also determined.In order to further explore the formation regularity of lipid oxidation products,the PCA analysis was used.The main contents and results are as follows:1.Optimization of the SPME conditions for the GC-MS analysis.The best parameters were obtained as follows: SPME Fiber: Assembly 50/30?m DVB/CAR/PDM,Equilibrium Time: 15 min,Extract at 50 ?for 60 min,Resolved Temperature: 230 ?,Resolved Time: 15 min.2.Development and validation of the qualitative and quantitative method for the analysis of volatile aldehydes.6 alkanals,11 alkenals and 4 alkadienals were successfully identified by searching the NIST 2008 and referring to retention index O??UAs and alkylated furans are identified by comparing with standards.This method was validated to be accurate.3.The formation of normal aldehydes,O??UAs and alkylated furans in oils during heating processing was studied.4 different vegetable oils were heated under different temperature,and their volatile aldehydes,fatty acids and oxidative indexes were determined.8 kinds of aldehydes generated more rapidly under higher temperature during the oil oxidation.On the contrary,the formation of other several compounds with lower molecular weight decreased with higher temperature.This may be due to the high volatilization of the compounds under higher temperature.PCA analysis was applied on the variations of aldehydes and fatty acids and thescore plot showed that octanal,nonanal,2-nonenal,2-decenal and 2-undecenal are closely related with oleic acid,hexanal,heptanal,2-propenal,2-hexenal,2-heptenal,2-octenal,ONE,and 2,4-decadienal are closely related with linoleic acid,and 2-butenal,2-pentenal,2-ethyl furan,benzaldehyde,HHE and 2,4-heptadienal are closely related with linolenic acid.It is possible that those compounds are formed from the degradation of their related fatty acid respectively.Due to the different fatty acid composition,the 4 vegetable oils have varied characteristics of the oxidation index.The PCA was applied to study the relationship between fatty acids and oxidation index.It showed that the iodine value was highly related with the unsaturated fatty acid which has the highest concentration in oil.But the anisidine value was found to be negative related with the unsaturated fatty acids.