Impact of environmental factors on rice starch structure: A review

Abstract

Among cereal grains, rice is the world's leading source of caloric energy in the human diet. About 90% of a milled rice kernel is starch (dry weight basis), thus justifying the need to understand the impacts of factors affecting starch composition and behavior when processed. This review presents past and current perspectives regarding the effects of growing environment on the macro, micro, and nano level structures of rice starch. The environmental elements considered in this work are: air temperature, atmospheric carbon dioxide, light, water, and soil nutrients. All these elements are essential for plant development and reproduction. The effect of air temperature is the most widely explored aspect of the environment in relation to rice production and grain quality. This could be attributed in part to the recently purported and highly publicized global warming phenomenon. Amylose content has remained a major predictor of rice starch quality but emerging instrumental techniques have facilitated more thorough research addressing the fine structure of amylopectin, which constitutes ∼70% of the starch present in a milled rice kernel. Kernel chalkiness appears to be the most common visual manifestation of environment-related stress. Typically, there are genotype by environment interactions; this may result in inconsistent temporal and spatial findings. However, such interactions may prove useful in identifying particular genotypes that are adaptable and stable across growing locations.