R. J. Bryant

Rapid gas chromatographic technique for quantifying 2-acetyl-1-pyrroline and hexanal in rice (Oryza sativa, L.).

ABSTRACT The aroma of rice plays a role in its consumer acceptability. The popcorn-like smell of aromatic rice stemming primarily from its 2- acetyl-1-pyrroline (2-AP) content is considered desirable by many consumers. Conversely, hexanal has been correlated with off odors in rice that develop from lipid oxidation. A rapid method for 2-AP and hexanal quantification suitable for use in breeding programs, large-scale research efforts, and quality assurance programs is needed. While developing such a method, sample preparation (degree of milling, particle size), solvent extraction time and temperature, and gas chromatographic parameters were studied. Particle size had no influence on 2-AP or hexanal recovered. One extraction solubilized ≈80% of the 2-AP and 56% of the hexanal present in milled rice. The optimum extraction method was assessed to require 0.3 g of ground brown or milled rice in methylene chloride held at 85°C for 2.5 hr. The complete gas chromatographic run requires ≈25 min, and 50 samples can ...

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

ABSTRACT Elevated 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 cultivars 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...

Impact of production practices on physicochemical properties of rice grain quality

BACKGROUND Rice growers are interested in new technologies that can reduce input costs while maintaining high field yields and grain quality. The bed-and-furrow (BF) water management system benefits farmers through decreased water usage, labor, and fuel as compared to standard flood management. Fertilizer inputs can be reduced by producing rice in rotation with soybeans, a nitrogen-fixing crop, and with the use of slow-release fertilizers that reduce nitrogen volatilization and run-off. However, the influence of these cultural management practices on rice physicochemical properties is unknown. Our objective was to evaluate the influence of nitrogen fertilizer source, water management system, and crop rotation on rice grain quality. RESULTS Grain protein concentration was lower in a continuous rice production system than in a rice-soybean rotation. Neither amylose content nor gelatinization temperature was altered by fertilizer source, crop rotation, or water management. BF water management decreased peak and breakdown viscosities relative to a flooded system. Peak and final paste viscosities were decreased by all fertilizer sources, whereas, crop rotation had no influence on the Rapid Visco Analyser profile. CONCLUSION Sustainable production systems that decrease water use and utilize crop rotations and slow-release fertilizers have no major impact on rice physicochemical properties.

Effect of Cultural Management Practices on Grain Quality of Two Rice Cultivars

ABSTRACT To reduce fuel and labor costs and increase profits, farmers are trying new ways of growing rice (Oryza sativa L.). This includes changing crop rotations, tillage systems, and fertilization levels. There is little information on how these changes affect the cooking quality of rice. We therefore looked at the parameters associated with cooking and processing quality (apparent amylose, gelatinization temperature, lipid and protein contents, and pasting properties) of two U.S. long grains (Cybonnet and Wells) that were grown using two different tillage systems, standard rate and high rates of fertilization, and different crop rotations (continuous rice R-R, rice after soybeans R-SB, and rice after corn R-C). No differences in quality traits were observed among any of the tillage systems. Rice grown in continuous rice rotation had the lowest protein content of brown and milled rice (8.6 and 8.1%, respectively) as compared to the highest levels observed in the rice-soybean rotation (9.3 and 8.6%, resp...

Evaluation of a M-202 × Oryza nivara advanced backcross mapping population for seedling vigor, yield components and quality

AbstractOryza nivara, the ancestral species of cultivated rice (O. sativa), has been the source of novel alleles for resistance to biotic and abiotic stress lost during domestication. Interspecific advanced backcross (ABC) populations permit the introgression of desirable alleles from the wild species into O. sativa and allow traits to be mapped to chromosomal regions by QTL mapping. An ABC population was developed by crossing M-202, a California medium grain, temperate japonica cultivar with O. nivara (IRGC100195). The population has 177 BC2F2:5 progeny lines and was evaluated for 17 traits including seedling vigor under cool temperature (mesocotyl, coleoptile, shoot and root lengths), agronomic (days to heading, plant height, culm angle, panicle type), yield components (panicles per plant, panicle length, florets and seeds per panicle, 100-seed weight) and quality [kernel length and width, apparent amylose content (AAC), alkali spreading value (ASV)]. Most exciting was that the O. nivara parent improved seedling vigor by increasing both the coleoptile and shoot lengths. Wild donor alleles increased the panicles per plant and seed weight, but M-202 alleles improved fertility. For one locus, the O. nivara alleles accounted for increased kernel length even though this parent had smaller seeds than M-202. The AAC mapped to the WAXY locus and ASV to the ALK locus, with most progeny being similar to M-202 for these quality traits. Select progeny lines could be useful for improving seedling vigor. This interspecific population is the first in the background of a U.S. temperate japonica rice cultivar.

The effect of induced yellowing on the physicochemical properties of specialty rice

BACKGROUND Postharvest yellowing (PHY) of rice kernels can be a major problem in the rice industry. This is especially true with high-valued specialty rice, because profit loss will be greater. The objective of this work was to determine whether a significant change occurs in the physicochemical properties (apparent amylose and protein concentrations, viscosity profile and gelatinisation temperature) as a result of induced PHY. RESULTS In this study, four specialty rices (Basmati, Jasmine, Arborio and Sushi) were yellowed using a laboratory method. PHY increased apparent amylose concentration. It also significantly increased onset and peak gelatinisation temperatures. However, peak, breakdown and setback Rapid ViscoAnalyzer viscosities were decreased by PHY. Trough viscosity for Basmati and Jasmine decreased, whereas it increased for Arborio. Moisture and protein concentrations were unchanged by the yellowing process. Attempts to rehydrate the kernels after induced PHY caused them to fracture, thus making them unsuitable for their intended purpose. CONCLUSION This study indicates that rice that has been subjected to PHY shows a reduction not only in appearance but also in cooking and processing quality, decreasing its value. However, the changes differed for each rice type, with Jasmine being affected the least.

Physicochemical and Sensory Analysis of U.S. Rice Varieties Developed for the Basmati and Jasmine Markets

There is a steady demand for imported basmati and jasmine rice in the United States. Rice varieties that can be domestically produced and compete with these imports have been developed from basmati, jasmine, and other aromatic germplasm sources. This study evaluated differences among eight U.S. aromatic varieties and imported basmati and jasmine samples. Basmati market types (Aromatic se2, Sierra, Dellmati, and Dellrose) and jasmine market types (JES, Jasmine 85, Jazzman, and Charleston Gold) grown in Arkansas and Texas were evaluated for descriptive flavors, apparent amylose, protein, and lipid contents, pasting profile, alkali spreading value, volatiles, grain color, grain dimensions, and agronomic traits. Seven natural flavor attributes and six volatiles differentiated the varieties within the jasmine and basmati classes along with several physicochemical traits, such as pasting profiles, grain dimensions, and grain color. U.S. varieties developed for either the basmati or jasmine market all had a flav...