Postharvest UV-C irradiation for fungal control and reduction of mycotoxins in brown, black, and red rice during long-term storage.

The formation of fungal colonies, mycotoxins, phenolic compounds, cooking quality and color properties were evaluated in freshly-harvested brown, black, and red rice grains and then subjected to ultraviolet radiation (UV-C) for 1 and 3 h. Assessments were made after 6 months of storage. The exposure of black and red rice at 1 h of UV-C was enough to decrease the presence of fungal colonies by 22% and 79%, respectively, without any changes in cooking and coloring properties. In brown rice, only 3 h of UV-C irradiation was able to reduce the formation of fungal colonies. The release of phenolic compounds associated with cell wall was observed only in black and red rice subjected to UV-C radiation. The levels of mycotoxins gradually decreased with the increase in the time of exposure to UV-C radiation, demonstrating UV-C irradiation to be an effective method in fungal control and reduction of mycotoxins in stored rice.

Fluidized-bed drying of black rice grains: Impact on cooking properties, in vitro starch digestibility, and bioaccessibility of phenolic compounds.

This study evaluated the influence of different fluidized-bed drying temperatures (20, 60, and 100 °C) on the cooking properties, in vitro starch digestibility, and phenolic bioaccessibility of black rice. The results indicated that the formation of fissures in the grains dried at or above 60 °C reduced the physical integrity of the grains after cooking, increasing the starch digestion and the rehydration ratio, and reduced the cooking time, the hardness and adhesiveness. Due to the higher digestibility of grains dried at higher temperatures, an increase in the bioaccessibility of ferulic acid, which was previously associated with the polysaccharides, was observed. Caffeic acid was the only phenolic compound whose levels decreased when the drying temperature increased. At high temperatures and in the gastric phase, cyanidin chalcones were formed due to the deglycosylation of cyanidin-3-O-glucoside. PRACTICAL APPLICATION: The results of this study provide information to the food industry about the effects of different fluidized-bed drying temperatures on the rice structure after cooking and that, consequently, affect the availability of bioactive compounds after digestion and the glycemic index of black rice.

Effects of drying temperature and long-term storage conditions on black rice phenolic compounds.

This study aimed to investigate the influence of drying temperatures (20, 40, 60, 80, and 100 °C) followed by 12 months-storage under normal-atmosphere (conventional), nitrogen-atmosphere, and vacuum-atmosphere on black rice phenolics. Increase in drying temperature reduced the total content of free-phenolics, free-flavonoids, and anthocyanins. An increase in bound phenolics extractability was observed at 60 and 80 °C, suggesting some extent of phenolics polymerization and complexation at these drying temperatures. The free fraction of ferulic, caffeic, p-coumaric, and gallic acids were the most thermally unstable compounds. After storage, no reductions were observed only for free caffeic and protocatechuic acids. For total flavonoids, an increase in the free fraction and reduction of the bound fraction were observed in the grains stored under conventional- and vacuum-atmosphere. A reduction of total phenolics occurred regardless of the storage condition. However, storage under nitrogen-atmosphere is the most recommendable condition for maintenance of phenolics in black rice.

Quality of black beans as a function of long-term storage and moldy development: Chemical and functional properties of flour and isolated protein.

The aim of this study was to evaluate the effects of moisture content and storage temperature on the percentage of moldy and fermented beans, mycotoxins levels, phenolic acids content, pasting properties of whole flour, as well as functional and thermal properties of protein isolates from black beans stored for 12 months. Beans stored under 14%/32 °C exhibited 16% of fermented grains, while at 17%/25 °C (42.3%) and 17%/32 °C (93.5%) of moldy plus fermented grains, named drastic conditions (DC). Mycotoxins were not present in grains from all storage conditions. Reduction of gallic, caffeic, and p-hydroxybenzoic acid contents, and increase of sinapic acid were observed in DC. Reduction of peak, final, and setback viscosities of bean flours in DC indicate the application in refrigerated and frozen products. The increase in foaming and reduction in foam degradation of the proteins highlights their use in beverages where the foam is an important factor.

Foliar Desiccators Glyphosate, Carfentrazone, and Paraquat Affect the Technological and Chemical Properties of Cowpea Grains.

The effects of the use of glyphosate (GLY), glyphosate plus carfentrazone (GLY/CAR), and paraquat (PAR) as plant desiccators on the technological and chemical properties of cowpea grains were investigated. All studied desiccants provided lower cooking time to freshly harvested cowpea. However, the coat color of PAR- and GLY/CAR-treated cowpea was reddish in comparison to the control treatment. Principal component analysis (PCA) from liquid chromatography-mass spectrometry (LC-MS) data sets showed a clear distinction among cowpea from the different treatments. Catechin-3-glucoside and epicatechin significantly contributed for discriminating GLY-treated cowpea, while citric acid was responsible for discriminating GLY/CAR-treated cowpea. Quercetin derivative and gluconic acid were responsible for discriminating control treatment. Residual glyphosate and paraquat content was higher than the maximum limits allowed by Codex Alimentarius and the European Union Commission. Improvements in the technological and chemical properties of cowpea may not be overlapped by the risks that those desiccants exhibit when exceeding the maximum limits of tolerance in food.