淀粉凝胶冷藏过程中水分分布、流变性、热焓值和晶体结构的变化

Changes in water distribution, rheology, thermal enthalpy and crystal structure during starch gel freezing

以20%的籼米淀粉(IRS)、糯米淀粉(GRS)在100℃下糊化30 min,待其降至室温后放置在4℃中贮藏,于0 h、3 h、6 h、12 h、1 d、3 d、5 d、7 d、14 d和21 d取样测定水分分布和物化性质。结果表明,籼米淀粉胶(IRSG)在贮藏0~3 d之间,结合水(A21)变化不大,半结合水(A22)快速下降,从第5天开始,出现了自由流动水(A23),A23缓慢上升;糯米淀粉胶(GRSG)在0~21 d期间,A21缓慢上升,A22快速下降。籼米和糯米淀粉凝胶的储能模量(G′)和损耗模量(G″)都随贮藏时间的延长而增大,IRSG的G′和G″在老化的0~6h内增幅平缓,第12小时至第3天迅速增加,5~14 d平缓增长,21 d又迅速增加。GRSG的G′和G″的增速一直保持平稳。IRSG和GRSG冷藏过程中老化焓(ΔH)和结晶度随着贮藏时间的延长而平缓增加,并且IRSG的最终ΔH和结晶度比GRSG大。

In this experiment,20%Indica rice starch(IRS)and glutinous rice starch(GRS)were gelatinized at 100℃for 30 min.When the samples were cooled to room temperature,which were further stored at 4℃for 0 h,3 h,6 h,12 h,1 d,3 d,5 d,7 d,14 d and 21 d to detect the water distribution and physicochemical properties.The bound water(A21)of Indica rice starch gel(IRSG)changed little during storage period of 0-3 days,and the semi-bound water(A22)decreased rapidly.On the 5 th day,free flowing water(A23)appeared,and A23 increased slowly.During the storage of glutinous rice starch gel(GRSG)for 0-21 d,A21 slowly increased,while A22 decreased rapidly.The storage(G′)and loss(G″)moduli of IRSG and GRSG increased with the prolongation of storage time.The G′and G″of IRSG increased slowly for aging 0-6 h,increased rapidly from the 12 th hour to the 3 rd day,increased slowly from the 5 to the 14 day,and then increased rapidly on the 21 th day.The increased G′and G″in GRSG remained stable.The aging enthalpy(ΔH)and crystallinity of IRSG and GRSG increased slowly with the prolongation of storage time,and the finalΔH and crystallinity of IRSG were larger than GRSG.