冻融对糯米淀粉性质的影响

考察了水分含量30%（w∶w）和40%（w∶w）左右的糯米淀粉以及糯米淀粉-水1∶1.5（w∶v）悬浮液多次冷冻和解冻后的淀粉颗粒形貌、晶体和糊化特性、破损淀粉含量等一系列性质。结果表明,与原淀粉相比,反复冻融后,淀粉颗粒棱角出现损伤,且随着冻融次数的增加,表面更为粗糙和出现更多的凹洞;糯米淀粉颗粒晶型没有改变,仍为A型,经淀粉与水1∶1.5（w∶v）比例冻融处理的糯米淀粉相对结晶度由25.19%降低至21.34%,而水分含量30%和40%经冻融处理的糯米淀粉相对结晶度由25.19%分别提高至32.47%和31.65%,且多次冻融之间的相对结晶度呈下降趋势;经淀粉与水1∶1.5（w∶v）比例冻融处理的糯米淀粉在冻融前后起始糊化温度降低0.3～0.67℃,黏度（热糊黏度,保持热糊黏度,冷糊黏度等）降低30～60BU,水分含量30%和40%经冻融处理的糯米淀粉在冻融前后黏度（热糊黏度,保持热糊黏度,冷糊黏度等）降低150～300cp,但多次冻融之间的黏度无显著性差异;经反复冻融后破损淀粉含量降低。 

Effect of freezing and thawing on the properties of glutinous rice starch

The properties of samples of moisturised glutinous rice starch (30% and 40% w∶w±, respectively) and glutinous starch-water suspension (1∶1.5 w∶v) were evaluated, followed by repeatedly freezing and thawing. The study included particle morphology, crystal properties, gelatinization properties and damaged starch. It was found that after treating, the edges of the starch granules were injured and with the increasing of freezing-thawing cycles, the particle surface appeared more pit. Though the rice starch crystal type did not changed, staying as A-type, the relative degree of crystallinity reduced from 25.19% to 21.34% (starch∶water 1∶1.5 w∶v) , but the relative degree of crystallinity increased from 25.19% to 32.47% and 31.65% (30% and 40% w ∶w ± , respectively) . Also between freezing-thawing cycle, there was a downward trend of the relative degree of crystallinity.The initial gelatinization temperature decreased by 0.3～0.67℃, the paste viscosity (hot paste viscosity, keeping paste viscosity, cold paste viscosity) reduced by 30～60BU (starch∶water 1∶1.5 w∶v) , and the paste viscosity reduced by 150～300cp (30% and 40% w∶w±) . However, between freezing-thawing cycle, there was no significant difference. Moreover, after treating, the damaged starch content decreased.