Study On The Changes Of Volatile Compounds Of Sachima During Shelf Life And Improvements Of Quality

Sachima is a kind of Chinese-style pastry, which originates from China’s Manchu ethnicgroup. It now has become more and more popular due to its deliciousness and convenience.Sachima contains a lot of lipid. Lipid oxidation and auto-oxidation is one of the major causesof deterioration, which directly results in the development of a stale or rancid flavour. Also,the volatile flavor components of Sachima easily lose during the storage. Therefore,prevention of lipid oxidation has become one of the biggest technical challenges facing theSachima maker. The present study deals with the changes and improvements of the qualitiesof Sachima during the shelf life.Firstly，the volatile flavor components from Sachima were studied, and they wereextracted and determined by solid phase microextraction-gas chromatography-massspectrometry(SPME-GC-MS). The results showed that the conditions of solid phasemicroextraction were as follows:75μm CAR/PDMS fiber, equilibrium time was30min,extraction temperature was60℃and extraction timewas45min. At this condition37components were separated and indentified. Among these flavor components, the majorvolatile components were aldehydes, ketones, esters and heterocyclic compounds. Accordingto “ROAV” method,2-methyl propanal,3-methyl butanal,2-methyl butanal,2,4-decadienal,dimethyltrisulfide, dimethyldisulfide,2,3-butanedione, nonanal and hexanal were determinedas the key odor compounds of Sachima.The changes of the qualities of Sachima during the shelf life were studied. The storageexperiment of Sachima indicated that moisture of Sachima during the storage time decreasedfrom7.84%to6.88%, and water activity decreased from0.628to0.512. The lipid oxidationoccurred during the storage, peroxide values increased from0.029g/100g to0.096g/100g, andthen decreased, while, acidity values increased continuously during the storage. The key odorcompounds2,4-decadienal, dimethyltrisulfide and dimethyldisulfide couldn’t be indentifiedafter1month of storage; the relative percentage of2-methyl propanal,3-methyl butanal, etcdecreased significantly during the storage, while, the relative percentage of hexanal increased.Maillard reaction process was optimized with antioxidant properties. Based on the resultsof single factor test, the optimized reaction conditions were as follows: amino acid kind:defatted peanut meal (DPM) hydrolysate; sugars: glucose syrup; amino acid addition4%(w/w), reaction time temperature was60℃, reaction time was60min. The method ofSPME was chosed to extract the volatile compounds of the Maillard reaction products. Through the analysis of GC/MS,46main volatile compounds were obtained,6key odorcompounds of Sachima were indentified in Maillard reaction products as follows:2-methylpropanal,3-methyl butanal,2-methyl butanal, dimethyldisulfide,2,3-butanedione andhexanal.The Maillard reaction products (MRPs) were prepared at the optimized reactionconditions. The effects of MRPs on Sachima quality characteristics and flavour wereinvestigated. Addition of MRPs affected lipid oxidation during Sachima storage. MRPs hadan inhibitory action on lipid oxidation and extended the induction period. Sachima treatedwith MRPs showed good effect on the flavour of Sachima compared to control.