溶出固形物对软米硬度和黏弹性的影响

以粳米和糯米为对照,研究了溶出固形物对软米硬度和黏弹性的影响。分析发现软米溶出固形物质量分数为11.85%,显著高于粳米和糯米(P<0.05),与弹性显著正相关(P<0.05)；与粳米和糯米相比,软米中的固形物直支链淀粉比最低,利于形成连续凝胶网结构。此外,软米溶出淀粉侧链中聚合度为6~12的短链A链比例最高,赋予其较好的黏弹性。质构和流变分析结果表明:除溶出固形物后,软米的硬度显著增加,黏硬比和弹性显著降低。扫描电子显微镜结果表明:除溶出固形物后米粒表面粗糙、凹凸不平,有明显的孔洞；软米表面所形成的渔网状孔洞状结构能够对饭粒起到支撑作用,使得整个饭粒弹性更好。溶出固形物含量、组成、分子结构及其在米饭表面分布的差异是软米较低硬度和较好黏弹性优势产生的主要原因。

Effect of Dissolved Solids on Hardness and Viscoelasticity of Soft Rice

The effects of dissolved solids on the hardness and viscoelasticity of soft rice were studied in comparison with that in japonica rice and glutinous rice. The mass fraction of dissolved solids of the soft rice was 11.85%, which was significantly higher than that of japonica rice and glutinous rice, and was positively correlated with rice elasticity (P<0.05). Compared with those in japonica rice and glutinous rice, the amylose-amylopectin ratio in dissolved solids of soft rice was the lowest, which was conducive to the formation of continuous gel network structure. In addition, the proportion of short chains with a range of 6-12 in dissolved starch of soft rice was the highest among all varieties tested, giving soft rice better viscoelasticity. The results of texture and rheological analysis showed that the hardness increased, while the viscosity-hardness ratio and elasticity decreased of soft rice after removing the dissolved solids. The results of scanning electron microscope found that rice surface was rough, uneven and pertusate after removing dissolved solids. The fishnet-shaped hole of soft rice could support the rice grains, causing better elastic quality. In conclusion, the differences in the content, composition, molecular structure and distribution of dissolved solids on rice surface might be the main reasons for the low hardness and good viscoelasticity of soft rice.