穗型与胚乳成分对稻米黏弹性的影响

Effect of Panicle Type and Endosperm Composition on Viscoelasticity of Cooked Rice

北方直立穂型水稻是超级稻的重要株型之一,但这类水稻的适口性一般并不理想。为明确该类水稻的适口性差异所在及其可能的原因,本研究选取70份直立穗型和非直立穗型水稻材料,利用质构仪和快速黏度分析(rapid viscosity analysis,RVA)仪分别对米饭粒和米淀粉进行黏弹性检测,同时分析稻米蛋白质量分数(proteincontent,PC)、表观直链淀粉质量分数(apparent amylose content,AAC)以及支链淀粉精细结构(Fa、Fb_(1+2)和Fb_3)的差异。结果表明:1)根据测试性状按Ward法可以将试材分为3类,直立穗型不能构成独立的一类,但直立穗型品种占比较大类的硬度大、黏性小、拉丝长度短、咀嚼性大,RVA的崩解值小、回冷值大,表现出不良适口性,其胚乳性状表现为AAC、PC、Fb_3质量分数高,而Fa/Fb_3低;2)总体上,黏弹性与AAC、Fb_3质量分数、Fa/Fb_3存在密切的相关关系,但类间相关关系有差异;与RVA特性相比,质构特性与胚乳性状的相关关系更紧密;3)质构测试结果的主要参数与RVA结果存在密切的相关关系。综上可见,穗型与黏弹性可能没有直接联系,部分直立穗型品种可能由于胚乳淀粉组成不佳导致米饭硬度大、黏性小的不良适口性;与RVA相比,质构测试对适口性评价更加简洁直接。

Northern erect panicle type rice is one of the important super-rice strains.However,the palatability of this kind of rice is generally unsatisfactory.In this study,70 samples of erect panicle type and non-erect panicle type rice were chosen to identify the variability in the palatability of erect panicle type rice and to analyze the possible causes.Textural analyzer and rapid viscosity analysis(RVA)were used to detect the viscoelasticity of cooked rice and rice starch,respectively;meanwhile,the differences in rice protein and apparent amylose contents and amylopectin fine structures(Fa,Fb1+2 and Fb3)were analyzed.The results showed that:1)all samples were classified by the Ward method into three categories,and erect panicle type rice could not classified into one of these categories;moreover,the categories with high proportions of erect panicle type rice possessed low adhesiveness and stringiness,high hardness and chewiness,small breakdown and high setback value,which revealed poor palatability,and endosperm composition presented high apparent amylose content(AAC),protein content(PC)and Fb3 content as well as low Fa/Fb3 ratio;2)generally,viscoelasticity had a close correlation with AAC,Fb3 content and Fa/Fb3 ratio,but the correlation among these categories was different.Compared with RVA characteristics,texture properties had greater correlation with endosperm composition;3)the major texture parameters were closely related with the RVA results.All the above results indicate that there may be no direct correlation between panicle type and viscoelasticity.Some erect panicle type rice cultivars have poor palatability such as high hardness and low viscosity which may be related to endosperm starch composition.Compared with RVA characteristics,texture analyzer is a more direct and simpler method to evaluate rice palatability.