Estudo dos efeitos da aplicação de tratamentos micro-ondas sobre a estrutura de grãos-de-bico (Cicer arietinum L.)

Abstract

Chickpeas are one of the most cultivated legumes in the world, ranking third in global production, and are used in various types of food products. Thus, evaluating and understanding the microstructural changes in cereal grains and legume seeds during operations such as milling, dehulling, or storage is crucial to understanding the final quality of these products. In light of this, the aim of this study was to investigate the physical, morphological, and structural changes in chickpeas subjected to different exposure times to microwaves, with varying initial water content and different intermittence times (OFF time). Pre-hydrated grains were exposed to electromagnetic waves, based on the premise that water molecules (dipoles) absorb energy and change state. When the water vaporizes, internal pressure increases, potentially forming pores, fissures, and cavities. The effects of thermal treatment were evaluated through the physical characterization of the grains and microscopic images. In general, for the factors of exposure time and water content, the grains exhibited the same behavior. That is, when compared to the pre-hydrated grains, the treated grains presented smaller dimensions, lower volume, and surface area, resulting in a reduction in density and bulk volume. The treatments made the grains more fragile than the native grains, reducing their resistance to rupture. The images revealed a modification in porosity, the formation of pores, fissures, and cavities, as well as the detachment of the seed coat from the cotyledons. Depending on the treatment applied, the grains were dried and roasted, with changes in color and final water content. Finally, it was found that these pre-treatments of the grains can facilitate the dehulling, grinding, or milling processes while improving preservation and developing new flavors and aromas. However, further studies are needed to assess the impact on other parameters, understand the mechanisms behind the formation of fissures and cavities at macro and microstructural levels, evaluate the interaction between the studied factors, and establish an energy balance for these treatments in grain processing.