Study On Quality Deterioration Of Wet-processing Konjac Powder During Storage

The drastic decrease of quality for wet-processing konjac powder,which included reducing viscosity and yellowing appearance,occurred during storage.Thus,a large number of researches were carried out in this study to provide theoretic and technological bases for further improving processing and storage technology of konjac powder.Firstly,main factors induced quality decrease were investigated on the basis of single factor experiment of pH for acidic ethanol,moisture content,storage temperature,inactivating enzyme,presence of oxygen and sunlight intensity on quality.The second step was to look for the reasons that induced quality decrease for wet-processing konjac powder through monitoring the physical and chemical indexes of konjac power during storage.Thirdly,storage experiments that based on practical plant conditions were practiced under actual storage conditions to obtain decreasing rules of quality.The main results were as follows:1.The pH range of sol for konjac powder treated by different process engineering and storged under different condiction was between 5.0 and 6.0.Except for the sample stored in the sunlight,no significant changes occured for the others.The decreasing viscosity and brightness were observed with a prolonged storage period.More details were as follows:the unremarkab difference and a decreasing brightness were found with the decrease of pH value for konjac powder processed by acidic ethanol with different pH values.No evidence was found that?-mannanase could affect the viscosity and whiteness of wet-processing konjac powde.The decrease of viscosity and whiteness were promoted by presence of oxygen,more water content,higher storage temperature and higher sunlight intensity.2.The changes of average molecular weight,free reducing sugar content,free amino acid content and total phenol content of konjac powder were determined during storage,It was concluded that higher sunlight intensity would lead to the degradation of KGM molecules that induced the decrease of average molecular weight and viscosity.The decreasing reducing sugar and amino acid content and increasing phenolic content were promoted by higher value of water content,pH,storage temperature,light intensity and aerobic environment,which indicated more intense Maillard reaction occured during storage.While the increase of these substances in the sample during the storage intensified the Maillard reaction.Thus,it was deduced that photodegradation and Maillard reaction may be two important reasons for the deterioration of quality of konjac powder during storage.3.On base of investigating the quality change of wet-process konjac powder under actual storage conditions,the simulated equations between quality index?including mainly viscosity and brightness?and storage time under normal and vacuum conditions were summarized.The equations were showed as follows:q=3×10^-6t²-0.002t+1.002 and q=10^-6 t ²-0.001 t+1.017.The decreasing rules of quality of konjac powder were invetigated further.And it was found that the decline rate of quality in the early stage was higher than that in the later stage during storage,which may be related to the higher substrate content in the samples for Maillard reaction in the early stage.4.It was appropriate to control the pH of sol around 5.0for konjac powder.Inactivating enzymewas not helpful to improve the quality of wet-processing konjac powder.it was found that vacuum packing,lower temperature environment and darkness were effective measures during storage and transport of wet-processingkonjac powder.