| dc.description.abstract | In the rice storage, changes in the grains physic-chemical properties occur due to a
process called ageing, which is fundamental to the culinary quality of this cereal. This work was
conducted aiming to determine the most favorable atmosphere and temperature conditions for the
ageing process in the rice storage, reducing the time for this cereal to present satisfactory cooking,
without compromising the technological and sensory characteristics of the grains. Different
varieties of rice (BR-IRGA 410, IRGA 416 and IRGA 417), the chemical composition of the
grains and, by sensorial analysis, the consumers acceptance and preference were simultaneously
assessed. The intensity of rice ageing process was periodically verified by the analysis of the
following characteristics; cooking, elongation, texture, viscosity, enzyme activity, coloration and
the grains chemical composition after being polished. The storage in longer periods (up to 180
days) and higher temperatures (up to 35 °C) evidenced more pronounced changes in the
parameters evaluated by the cooking properties (lower water absorption, pH levels and solid
content in the cooking water); cooking test (greater volume yield, cooking time and more loose
grains); elongation (higher values of proportional change, elongation ratio and actual elongation);
texture (lower hardness and adhesiveness, besides higher springiness and cohesiveness);
viscoamylographic properties (more organized starch granules during the storage, noticed mainly
by its lower breakdown, higher viscosity and setback). Meanwhile these storage conditions,
combined with controlled atmospheres, demonstrated that the changes resulted from the ageing
process were accelerated in the presence of O2 and retarded in the presence of CO2, that was
observed through the cooking properties (lower water absorption and pH levels), color (increase
in the chromaticity coordinates a* and b*, besides the reduction in the luminosity, whiteness,
transparency and milling degree) and enzymatic activity (great falling number) in the samples
stored in the presence of O2. Although the most favorable storage conditions for the rice ageing
process were obtained in higher temperatures and atmospheric concentrations of O2, the storage at
35 °C combined to lower atmospheric concentrations of O2 is recommended to retard or inhibit
metabolic processes, preventing undesired color changes and enzymatic activity in the grains. The
varieties showed distinct behavior in the analytical parameters tested, but all of them presented
better culinary characteristics in storage conditions that were favorable to the rice ageing process.
The chemical composition of the grains suffered small alterations in the storage, most
significantly in the ashes, phenolic compounds, amylose and resistant starch. In the sensory
analysis, conducted after 60 and 180 days of storage, a greater consumers acceptance and
preference was observed for the rice that presented more ageing characteristics. | |
