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.

Effects of drying temperature of red popcorn grains on the morphology, technological, and digestibility properties of starch.

Popcorn consumption is becoming increasingly attractive, and the effects of post-harvest operations are essential for the improvement of industrial processes. In this context, the objective of this study was to evaluate the effects of drying temperature on the morphology, technological, and digestibility properties from the isolated starch from red popcorn grains. Red popcorn grains were dried in oven-drying (30 °C) and fixed-bed dryer at 40, 70, and 100 °C. The morphology properties of grains and starch, the technological and digestibility properties of the starch, were evaluated. The drying temperature of 100 °C reduces the extraction yield by 13.14%, changes the internal structure of the popcorn grains and the native morphology of the starch granules, increases the pasting temperature and the gelatinization enthalpy, and reduces digestibility compared to drying temperature of 40 °C, which is more indicated due to reduced drying time.

Effects of drying temperature and genotype on morphology and technological, thermal, and pasting properties of corn starch.

The objective of this study was to evaluate the effects of drying temperature (30, 50, 70, and 90 °C) and genotype (yellow floury corn, white floury corn, and yellow flint corn) on the morphology and technological and thermal properties of corn starch. The white and yellow genotypes with floury endosperm (soft) had spherical starch granules, while the granules of the yellow flint genotype were polyhedral. White floury corn showed higher extraction yield, higher resistance during granules' swelling before the physical collapse, as it was not affected by the increase in drying temperature, and at 90 °C it presented higher breakdown and energy necessary for gelatinization. There were peak viscosity and gelatinization enthalpy reduction on starch from yellow floury corn and yellow flint corn according to the increase in drying temperature. Drying temperatures below 50 °C are indicated for all genotypes studied. White floury corn is indicated due to the higher extraction yield presented. Yellow floury corn is indicated for application in chilled and frozen products due to lower starch retrogradation. The yellow flint corn is indicated for application as a thickening agent due to higher gel hardness.