Mechanisms Of The Tissue Hardness Change Caused By Polysaccharide Characteristics In Potatoes And Lotus Rhizomes

The present study was design to investigate the effects of acetic acid immersion(AAI)pretreatment on the tissue hardness of cooked potatoes and the different varieties on the hardness of cooked.The effectiveness of pretreatments and varieties on the hardness of cooked samples were investigated by analyzing the related physicochemical properties of the starch and related physical properties of the cell wall polysaccharides,i.e.the content of the polysaccharide in the different binding states of the cell wall and the monosaccharide composition information.The main finding the current work are as follows:(1)Acetic acid immersion pretreatment increased the content of chelator soluble fraction(CSF)in the potato cell wall polysaccharides and reprieved the starch leakage in the soaking process.Furthemore acid immersion pretreatment also cause a small increase in the molecular weight of polysaccharide the in the hemicellulose fraction(HF)component.The pectin polysaccharides in the AAI group were more stable in the HF and residue fraction(RF)fractions,and the hemicellulose content of the HF group and the RF group was significantly increased in the AAI group.Acetic acid immersion pretreatment reduced the relative crystallinity of starch in potato and increased the amylose content.(2)The result showed that the cell wall polysaccharide content of 18 different varieties of lotus rhizomes,it is apparent that the CSF component has a significant positive correlation(R2 = 0.9)with the hardness of lotus rhizomes after cooking.But with the CSF contents increased,the speed of hardness of cooked tissues slowing changed.Through quadratic regression model analysis,we can calculated that CSF components not only have positive promoting effects,but also have a certain negative promoting effect,and the ratio of CSF and WSF has a significant positive correlation with the hardness after cooking of lotus rhizomes.The results showed that the higher content of CSF in the cell wall of the tissue would be beneficial to the stability of the cell wall structure.(3)The data of the monosaccharide content and sugar ratio showed that the combination of appropriate amount of hemicellulose and cellulose compound with water soluble fraction(WSF)and CSF components would have a beneficial effect on the fresh and cooked tissues to maintain a higher hardness value.And even,the polysaccharide in the CSF group compound with other polysaccharides were not dependent on the account of chain or branches but the length of main chain which containing the branched chain,while the data showed that the hardness of lotus root is closely related to the length of the main chain which containing the branched chain.(4)The starch content of different varieties of lotus rhizomes with the hardness of lotus rhizomes after cooking showed a downward tendency parabola,and the proper amount of starch improved the stability of the tissue after heat treatment.However,the ratio of amylose / amylopectin and the difference between the hardness of fresh and cooked lotus rhizomes showed a trend of rising first,then decreasing and rising again.By comprehensive analysis we found that common factors that affect the hardness of different verities of lotus rhizomes and acetic acid pretreatment on potatoes are the content of WSF,CSF and Na2CO3 soluble fraction(NSF)in cell wall polysaccharides,the composition of polysaccharides,amylose/amylopectin ratio and amylopectin starch.