Study On The Texture Formation Mechanism Of Canned Yellow Peach Based On The Change Of Pectin And Syrup Characteristics

In this paper,Jintong No.5 yellow peaches were used as the test material,which were prepared into cans by washing,dicing,peeling/pitting pre-cooking,canning and sterilization.Changes of the texture of yellow peach during processing and storage were analysed systematically.The changes of the contents of the pectin components including water-soluble pectin(WSP),chelator-soluble pectin(CSP)and sodium carbonate-soluble Pectin(NSP),the degree of methylation(DM),the degree of acetylation(DAc),the molecular weight(MW),the neutral sugars and functional groupscanned during storage as well as the activity of pectinase(PME and PG)were researched deeply.Meanwhile,p H value,soluble solids,turbidity,viscosity,color,osmotic pressure,water-soluble pectin content of syrup of canned yellow peach during the storage were also analyzed.The correlations among texture and pectin characteristics during processing as well as texture and pectin characteristics of canned yellow peach,texture of canned yellow peach and syrup characteristics during storage were constructed respectively.The study aimed to clarify the texture formation mechanism of canned yellow peaches during processing and storage,which could provide a theoretical basis for the production of canned yellow peaches with high qualiy and improve the texture quality of canned yellow peaches,and extend the shelf life.The main conclusions of the experiment were as follows:1.Hardness,chewiness and resilence of canned yellow peaches were significantly reduced during the processing.Microstructure analysis showed that cells with ununit pore size were destoried,however,cell wall remained basically intact after precook treatment.After the heat sterilization treatment,cells with irregular shape and disappeared division were collapsed.Pectinase activity analysis showed that PG activity decreased slightly after pre-cooking and sterilization treatment.PME activity decreased significantly after pre-cooking,however PME was inactivated after heat sterilization.Resutles of pectin characteristics showed that contents of WSP and CSP were increased significantly after pre-cooking and heat sterilization treatment.DM was decreased significantly.The acetyl group was slightly reduced after heat sterilization treatment.MW of WSP increased slightly,however,MW of the CSP component increased firstly and then decreased after heat sterilization.No significant changes of NSP was observed because of strong polymerizability.The linearity of the three pectins was reduced after pre-cooking treatment.Additionally,RG-I branching degree of the WSP and CSP components was reduced during the processing,while the RG of the pectin was protected well.FT-IR measurement results showed that DM values of WSP and CSP components were significantly reduced,which is consistent with the DM measurement results.Positive correlation between enzymes and texture quality,negative correlation between texture quality and pectin characteristics were obtained by the results of correlation analysis.It was clear that changes in the structural characteristics of enzymes and pectin during processing could be main factors of texture mechanism of canned yellow peaches.2.Texture quality(hardness and chewiness)of canned yellow peaches significantly decreaed during storage.Microstructure analysis revealed the expand of pulpcells.There were no significant differences between the syrup samples from different locations.p H of syrup remained stable,and TSS was slightly reduced.Turbidity of the syrup showed an increasing trend,and the syrup samples of the lower layer showed the greatest change during the storage.L* value had no significant change,while,a* value,b* value and ?E* were increased significantly along with the storage time.Osmotic pressure,SWSP content,and syrup viscosity showed significantly increased.The good correlation between characteristics of the syrup and texture quality of canned yellow peaches was established.Water-soluble pectin content and osmotic pressure of the syrup were significantly and negatively related to the texture quality,respectively.It can be inferred that changes in characteristics of the syrup and pectin might contribute to the texture formation of canned yellow peaches.3.During storage,the activity of PG was increased maintained high activity.The residual endogenous PME with low acitiviey was activated.Meanwhile,SWSP content was increased because of the degradation of pulp's WSP caused by the osmotic pressure.Content of the CSP component decreased during the initial storage,kept stable within 10 to 70 days,and then decreased slightly.Content of NSP components decreased firstly.The acetyl group of WSP did not show significant change during storage.DM of WSP was increased significantly,and DM of CSP was decreased slightly,which were consistent with the FT-IR results.No significant difference in Mw of WSP was obsereve.Meanwhile,CSP and NSPwere significantly increased and decreased,respectivley,during storage.CSP The highest linearity was obtained in CSP,and the linearity was decreasesd significantly along with storage time.No significant differences the linearity of WSP and NSP of were obsereced during storage.Degree of RG-I branching of CSP and NSP was decreased,and their RG was significantly changed along with the storage time.Correlation analysis showed that good correlation between pectin characteristics and texture quality was obtained,PG activity and texture quality of pulp showed the negative connection,while pectin contents and texture quality showed the positive correlation The results indicated that changes of PG activity and pectin characteristics significdanlty affected the texture fromationof canned yellow peaches.