Study On Starch Aging Of Fresh-keeping Taro At Room Temperature

Man-tou, a traditional Chinese food. The two critical reasons for Man-tou deterioration are mold and staling, which delay the industrial production of Man-tou, frozen preservation method commonly adopted at present to help Man-tou preservation, but high energy consumption and with terrible taste. By using hot online package technology, secondary contamination by microbes can be avoided and starch retrogradation can be markedly delayed, with Man-tou shelf-life under room temperature extended from a few to at least 90 days without any additives. The study takes hot online packaged Man-tou as the material, to investigate physico-chemical changes and quality changes of Man-tou by vacuum degree (VD), water content and composition, thermodynamic and crystalline characteristics. The research shows the results as follows:(1) The experiments studied the effect of water addition (WA) on VD, water migration and mobility, thermodynamic and crystalline characteristics of thermal-vacuum packaged Man-tou.With the WA increased from 40% to 44% during dough making, negative correlation coefficients were observed between WA and VD of the package during first 21 hours, leveled off at 6 h, the initial deep-bound water (DBW) content of Man-tou was also found to be opposite to WA, the retrogradation enthalpy and the relative crystallinity became pronounced. During room temperature storage (0-91 d), the VD of three samples' package have similar tendency, i.e., raised firstly and then declined, MC in different zone of Man-tou:crust>intermediate zone>center zone, moisture migration from the crust and intermediate zone to center zone, the DBW decreased first and then leveled off. Over time, the thermodynamic parameters and the relative crystallinity became pronounced but slightly.(2) The effect of curing time on the texture characteristics, organoleptic properties, thermodynamic and crystalline characteristics of thermal-vacuum packaged Man-tou during room temperature storage.Curing time (30 min,60 min,90 min) had a significant effect on taste, Man-tou steamed for 60 min with the highest sensory grade, the quality of steamed bread are declined if the curing time is too long or too short. Texture profile analysis showed that curing time had a great influence on buns'hardness, viscosity and chewiness. The retrogradation enthalpy and the relative crystallinity all decreased with curing time increasing, the Man-tou with lower curing time were easily aging during room temperature storage. Curing time had no significant effect on the pH of buns, during room temperature storage, pH value maintain constant and with a little acid. The retrogradation enthalpy and the relative crystallinity became pronounced with the store time extended, but slightly.Research shows that hot online packaging effectively inhibited the retrogradation of Man-tou. Provide the theoretical basis for industrial production of traditional Chinese staple food, it is a beneficial exploration to development of stacle food industrialization.