Effect of Microwave Treatment on Adzuki Beans (Vigna angularis L.) under Dry State—Analyzing Microstructure, Water Absorption, and Antioxidant Properties

Abstract

In this study, a microwave was used on adzuki beans (Arari and Geomguseul) without water, in order to investigate their changes in microstructure, water absorption, and antioxidative properties. As the microwave treatment time increased (2450 MHz, 0 to 60 s), the lightness, redness, and yellowness were reduced, and moisture content significantly decreased in both varieties. The microstructure space between the seed coat, cotyledon, and pores within the cotyledon were observed, due to the loss of moisture. Regardless of microwave treatment, the water absorption behavior of the adzuki beans was sigmoidal. However, the water absorption kinetics of Arari increased after microwave treatment, whereas with microwave-treated Geomguseul, the water absorption rate decreased, compared to the control, except for the sample treated for 30 s. During soaking, the water absorption and softening rates in the microwave-treated adzuki bean were twice as fast as the untreated beans. Antioxidant activity, total phenolic compounds, and total flavonoid compounds were greatly improved by microwave treatment. These results indicate that microwave treatment affects the color, hydration, and bioactive compounds, and it can be used as a pretreatment method before processing adzuki beans.

Proposition of empirical equations to describe the kinetics of water absorption by film-coated maize seeds during germination

“…For Bi < 0.1, a lumped model may be preferred, and the limitations associated with the use of such models are considered acceptable. Thus, more specifically, although the kinetics of water absorption by seeds during germination can be described by diffusion models (Josiah et al, 1994;Meyer, et al, 2007), it is predominantly described in the literature by empirical models (Kashiri et al, 2010;Da Silva et al, 2018;Kuna-Broniowska et al, 2020;Oyedeji et al, 2021;Oh et al, 2022).…”

“…Water absorption by plant materials, such as seeds, is influenced by process parameters (temperature, pressure) and also by the physical and chemical properties of the materials. These parameters mentioned have been investigated by Silva et al (2012), Da Silva et al (2018), Oyedeji et al (2021), andOh et al (2022), among others. The results found by these authors clearly show the role of temperature in relation to the time of the water absorption process.…”