稳定态轻碾米的蒸煮行为和食用品质调控

Lightly milled rice (LMR) has attracted attention due to its high nutritional value and yield. However, fast rancidity, ambiguous cooking behavior (gelatinization and texture formation process) and uncontrollable eating quality are three major problems that constrain the development of LMR. The rancidity problem has been solved by using superheated steam treatment in our previous works, and a stable LMR (SS-LMR) has been obtained. In this project, SS-LMR will be used as the research object. And the aim of this project is to further solve the remaining two problems of SS-LMR (ambiguous cooking behavior and uncontrollable eating quality). The gelatinization process of SS-LMR will be clarified by studying the starch phase transitions (long-range structure, short-range structure, etc.), the hydration behavior of kernel (moisture distribution, bound water, etc.) and the cooking kinetic established for SS-LMR. The texture formation process of SS-LMR will be clarified by studying the microstructure change (porosity, mean pore size, etc.), leaching behavior (total solid loss, particle size distribution, etc.), texture change (surface and overall texture) and the relationship among them. The effect of degree of milling on the cooking behavior of SS-LMR and related mechanism will be further explored after clarifying the cooking behavior (gelatinization and texture formation process) of SS-LMR. The above results will provide a theoretical basis for using degree of milling to control the eating quality of LMR.

轻碾米（LMR）因具有较高的营养和产率而受到关注，但轻碾米易酸败、蒸煮行为（蒸煮糊化和质构形成过程）不明确、食用品质不可控，是制约其发展的三大问题。前期通过过热蒸汽稳定技术已解决LMR酸败问题并获得稳定态轻碾米（SS-LMR）。本项目拟以SS-LMR为对象，进一步解决SS-LMR蒸煮行为不明确和食用品质不可控的问题。从淀粉相变行为（长程结构、短程结构等）和颗粒水化行为（水分分布、结合水等）两方面进行研究，建立适合SS-LMR的蒸煮动力学模型，阐明SS-LMR的蒸煮糊化过程；从物理结构变化（孔隙率、平均孔径等）、成分析出行为（总固形物、粒径分布等）和质构（表面和整体质构）三方面进行研究，构建三者关系模型，阐明SS-LMR的质构形成过程；在明确SS-LMR的蒸煮行为（蒸煮糊化和质构形成过程）后，进一步探究加工精度对SS-LMR蒸煮行为的影响及机理，为利用加工精度调控LMR食用品质提供理论基础。

适度加工有利于粮食增产和营养成分保留，是我国大力推行的粮食加工策略。轻碾米作为一种大米适度加工产品而颇受学界关注，但存在易酸败和食用品质不可控两大问题。前期采用实验型过热蒸汽技术解决了轻碾米酸败问题，并制备了稳定态轻碾米。本项目进一步研发中试型过热蒸汽技术，改良过热蒸汽发生装置和作业方式，剖析稳定态轻碾米的蒸煮行为，研究加工精度对蒸煮行为的影响及机理，明确稳定态轻碾米的适宜加工精度范围。结果表明：稳定态轻碾米的蒸煮行为可以通过加工精度调控，包括水分吸收速率、水分迁移速率、水分流动性、热学性质、长程结构、短程结构和质地。当稳定态轻碾米加工精度在3%~6%时，其蒸煮行为最佳，与精白米接近。以此为蓝本，本项目还进一步研究了加工精度对其他米制品理化性质的影响及机理，得出了即食类米制品（如方便米饭）和冷冻凝胶类米制品的适宜加工精度范围分别为6%~9%和0%~3%。研究成果可为米制品适度加工和储藏提供一套可靠技术方案。此外，本研究还发现，低水分过热蒸汽处理有潜力成为一种淀粉物理改性的新手段，与传统热液处理（处理时间16 h）相比，热效率更高，处理时间更短（处理时间1 h）。