Effects of Far-Infrared Radiation Drying on Starch Digestibility and the Content of Bioactive Compounds in Differently Pigmented Rice Varieties

Abstract

Far infrared radiation (FIR) was applied to six rice varieties with different coloring of the pericarp (purple, red or non-pigment). Changes were determined in amylose content, in gelatinization parameters, in the content of bioactive compounds, in antioxidant activity and in the in vitro digestibility of pigmented rice as affected by FIR. The highest contents of amylose, total phenolic (TPC), total flavonoid (TFC) and total anthocyanins (TAC) were found in the purple and red varieties. Overall, FIR increased TPC, TFC and TAC, including antioxidant capacity. Quercetin and apigenin contents were increased while rutin and myricetin decreased significantly (p < 0.05) in all FIR-dried samples. Dephinidin, cyanidin-3-glucosides and pelargonidin increased after FIR treatment. Mostly, FIR-treated samples were found to have greater gelatinization enthalpy, compared with unheated rice samples. FIR-dried rice showed lower starch digestibility (25–40%) than unheated rice. This research suggested that the specific genotype of rice had the greatest influence on amylose content in pigmented rice, while FIR drying had no further effect. Our results suggest that FIR could enhance the content of the bioactive compounds capable of inhibiting α-amylase, thereby lowering starch digestibility. Hence, FIR may be considered as an appropriate drying method for pigmented rice regarding health benefits.

Artificial aging of rice using a sterilization box equipped with infrared heating and ultraviolet‐C radiation

“…The cooking, color, texture gelatinization, microstructure, and pasting properties of stored brown rice were all improved by IR heating method with excellent drying as well as heating efficiencies (Ding et al, 2018). Ratseewo et al (2022) reported both positive as well negative impacts of far‐IR (FIR) treatment of normal rice and pigmented rice. Increase in total phenolic, anthocyanin, and flavonoid contents as well as antioxidant activity, were reported as positive impacts of FIR treatment.…”

Changes in the Physical Properties and Volatile Odor Characteristics of Shiitake Mushrooms (Lentinula edodes) in Far Infrared Radiation Drying

“…Therefore, it is important to identify a suitable method to extend the shelf life, preserve the quality, and minimize nutrient loss during the preservation of shiitake mushrooms. Far infrared radiation drying utilizes the resonance between the radiation frequency and the inherent frequency of the moisture in materials to heat materials [11], and it has been widely used for drying biomaterials [12,13]. The far infrared radiation source releases energy that directly penetrates into the material, effectively heating both the surface and interior for ensuring consistent internal heating and swift dehydration.…”