高温对水稻淀粉及品质的影响

Effects of High Temperature on Starch and Quality of Rice

高温通过影响淀粉合成关键酶的活性,在外观上使淀粉表面变得粗糙、松散,从而增加了垩白;在淀粉结构上促使其含量及链长分布发生变化,从而进一步改变淀粉的糊化特性及热学性质。支链淀粉中长链含量的提高,使淀粉结晶度增高,从而使糊化温度、热焓值和消减值提高;短链会促进淀粉颗粒膨胀能力和体积,使大米在蒸煮过程中粘度提升。不同时期高温处理对淀粉颗粒大小形成的影响有所不同,灌浆期高温提高了大颗粒淀粉的含量,花期高温提高了小颗粒淀粉的含量。此外,温度对直链淀粉含量的影响因品种而异。一般来讲,随着温度的升高,稻米直链淀粉含量逐渐降低。

High temperature increases chalkiness by affecting the activity of key enzymes in starch synthesis,making starch surface rough and loose in appearance.The gelatinization and thermal properties of starch were further changed by the change of starch content and chain length distribution in the structure layer.With the increase of the content of long chain in amylopectin,the crystallinity of amylopectin increased,and the gelatinization temperature,enthalpy value and subduction value increased.The short chain will promote the expansion capacity and volume of starch particles,so that the viscosity of rice cooking process.The effect of high temperature treatment on starch grain size was different in different stages,high temperature increased the content of large starch grain at filling stage,and high temperature increased the content of small starch grain at flowering stage.In addition,the effect of temperature on amylose content varies with varieties.General,the amylose content of rice gradually decreases with the increase of temperature.