Microwave treatment regulates the free volume of rice starch

Abstract

The aim of this work was to investigate the role of microwave parameters and moisture content on the free volume (FV) changes of rice starch by positron annihilation lifetime spectroscopy analysis (PALS) and to explore the potential relationship between the changes of FV and physicochemical properties of rice starch. Microwave heating and water molecules lead to the increasing of FV of starch. However, this result is largely influenced by the plasticization of water molecule. The anti-plasticization caused by water evaporation resulting in a decrease in the size and concentration of FV during microwave heating. Significant decrease (p < 0.05) in the thickness of amorphous region of microwave-heated rice starch was found by small angle X-ray scattering (SAXS), and the glass transition temperature ( Tg ) and gelatinization temperature significantly increase (p < 0.05) after microwave heating. According to correlation analysis, the power intensity and heating time were correlated negatively with the lifetime of o-Ps. In addition, the changes of amorphous region and Tg of rice starch were strongly related to FV changes. These results provided a theoretical basis for further research on the directional regulation of FV and improvement the quality of starch-based food by using microwave treatment.

Characterisation and emulsifying properties of microwave pretreated camelina seed mucilage

“…(2017) and Yan et al . (2019). Having a higher T g for food powders is important for maintaining stability during storage (Ramakrishnan et al ., 2018).…”

“…MW pretreatment caused an increase in the T g values of the mucilage samples and this increase was more significant when the MW pretreatment time was 7.5 min. The reason of this phenomena could be related to the transition of cytoplasmic bulk water to bound water as stated by Zhao et al (2017) and Yan et al (2019). Having a higher T g for food powders is important for maintaining stability during storage (Ramakrishnan et al, 2018).…”

Microwave reheating increases the resistant starch content in cooked rice with high water contents

“…An early study showed that microwave heating (60 min) had no significant effect on the digestibility of waxy and non-waxy rice starches (with 20% water content), but changed their viscosity [17]. Also for rice starch, it was reported that microwave treatment made the amorphous lamellae more compact [18] and resulted in the double helices of amylopectin becoming more optimally or densely packed and thus more ordered crystalline lamellae [19]. The effect of microwave on the amorphous and double-helical structures of starch granules was considered to be mainly related to the rapid heating effect of microwave [19].…”