Effects of Nighttime Air Temperature During Kernel Development of Field‐Grown Rice on Physicochemical and Functional Properties

Abstract

Cereal Chem. 89(3):168-175Elevated nighttime air temperatures (NTATs) occurring during critical grain-filling stages affected rice physicochemical properties, which impacted functional quality. Six cultivars were grown at multiple field locations from northern to southern Arkansas during 2007 to 2010. Nighttime temperatures were recorded throughout production at each of the locations, and 95th percentiles of NTATs were calculated for each cultivar's reproductive (R) stages. Amylose content and crude protein content decreased linearly, whereas total lipid content increased linearly, with increasing NTATs occurring during the grain-filling stages (R6-R8). Effects of NTAT on proximate composition influenced functional properties. Peak viscosities increased linearly as NTAT increased, whereas setback viscosities decreased. Setback viscosities were linearly correlated to NTATs for medium-grain cultivars, but correlations were quadratic for the long-grain cultivars. Gelatinization temperatures increased linearly with increasing NTAT. The R stages in which correlations were strongest varied by cultivar and by property, hypothesized to result from differences in kernel development patterns among cultivars. These findings have significant implications for rice production scientists and processors, in that understanding the effects of NTAT on physicochemical and functional properties may help explain and reduce quality variation.Recent studies in both controlled-temperature and field-scale environments have established that elevated nighttime air temperatures (NTATs) occurring during critical grain-filling stages affect rice kernel development, resulting in reduced yield, increased kernel chalkiness, and reduced milling quality (Peng et al 2004; Cooper et al 2006, 2008; Ambardekar et al 2011; Lanning et al 2011). Other studies have shown that the chemical makeup of starch is affected by elevated NTAT, as evidenced by decreased amylose content (AC) and changes in ratios of long-to shortchain amylopectin (Counce et al 2005; Cooper et al 2008). Several hypotheses have been presented to explain the effects of NTAT stress, including reduced substrate supply to the endosperm, initiating slow starch granule growth and irregular granular organization (Fitzgerald and Resurreccion 2009) and disruption of enzymatic activity responsible for starch formation (Counce et al 2005).Although the underlying mechanisms that tie the effects of NTAT to the structural and functional changes of starch are not clearly established, these findings are critical to rice end-use applications, because functional properties of milled rice, which directly impact cooking and sensory quality, are primarily determined by starch physicochemical properties.AC of a given rice strain is determined by the expression of two alleles of a polymorphic waxy gene, Wx a and Wx b , which regulate amylose synthesis by controlling the activities of grain-bound starch synthase (GBSS) enzymes (Counce et al 2005). Suzuki et al (2003) reported that mutations to Wx a and Wx b a...

Effects of Preharvest Nighttime Air Temperatures on Whiteness of Head Rice

“…This observation is illustrated in Figure 4, in which head rice samples of Cypress collected in 2010 from two growing locations (Keiser and Rohwer) were analyzed for whiteness with and without chalky kernels. This effect may also impact the starch structure in these nonchalky portions, albeit to a lesser degree than that associated with chalk Lanning et al 2012). More importantly, overall whiteness of the sample grown at Rohwer, where NT 95 (R8) was 32°C, was significantly greater than that of the sample grown at Keiser, where NT 95 (R8) was only 27°C, even when chalky kernels were excluded from the sample, confirming the trends shown in Figure 1.…”

“…Cultivars varied in their susceptibility to this response, such that in general, the susceptibility of a cultivar to changes in whiteness resulting from NTAT corresponded to that observed for milling quality and functional properties (Lanning et al , 2012. Whiteness generally increased, whereas yellowness decreased, with increasing chalkiness.…”

“…Early studies showed strong correlations of yield decrease with NTATs above 24°C (70°F) during the grain-filling stages (Downey and Wells 1975), as well as reduced kernel dimensions and induced morphological damage in kernels, including loosely packed starch in the endosperm, manifested as chalk (Tashiro and Wardlaw 1991). Chalk and lipid contents were shown to increase with increasing NTAT, whereas amylose and protein contents were shown to decrease (Lanning et al , 2012. Fitzgerald and Resurreccion (2009) also demonstrated that warm temperatures during the grain-filling stages induced chalkiness and suggested that elevated temperatures reduced the substrate supply from vegetative tissues, thereby inhibiting the expression of genes that control enzymes associated with starch synthesis.…”

Effect of different doses of nitrogen on protein profiling, pasting and quality attributes of rice from different cultivars

“…Light coloured milled rice grains were found to have lower protein content (r = −0.591, p ≤ 0.005). L* value was correlated to packing of granules by Lanning et al (2012). This indicated that the N dose affected the packing of granules in grain.…”

Influence of Early and Delayed Transplantation of Paddy on Physicochemical, Pasting, Cooking, Textural, and Protein Characteristics of Milled Rice

“…An increase in proportion of proteins relative to starch with elevated temperatures without any effect on the total amount of protein was also reported (Fitzgerald and Resurreccion 2009). Lanning et al ( , 2012 demonstrated that higher NTAT resulted in increased accumulation of lipids and decreased accumulation of proteins and starch. Lanning et al ( , 2012 demonstrated that higher NTAT resulted in increased accumulation of lipids and decreased accumulation of proteins and starch.…”