The Evaluation of Moisturizing Effect of Metasilicate Extracted from Rice Hull

Abstract

In recent years, the Sustainable Development Goals (SDGs) adopted at the United Nations Summit (2015) set the goal of achieving sustainable management and efficient use of natural resources, and this has become a mainstream issue worldwide [1]. In Japan, effective utilization of rice hulls, one of the agricultural by-products generated during rice production, has become an issue. In this study, the utilization of metasilicate which is produced during the extraction of silicic acid present in rice hulls was focused. Metasilicate is mainly a free component of hot springs and is reported to have a moisturizing effect [2] [3]. To examine the use of rice hulls as a moisturizing component, the elution characteristics of metasilicate present in rice hulls were first evaluated. As a result, 546 mg/kg of metasilicate was eluted from the rice hull in tap water at a water temperature of 40 °C. This value was much higher than 50 mg/kg of metasilicate, which is defined as a mineral spring. Next, the moisturizing effect of metasilicate extracted from rice hulls was evaluated by taking a warm bath in the water in which the hulls were immersed. As a result, the ratio of change of the moisture content of the skin remained higher than the value before the experiment even 30 minutes after the warm bath. In the paired t-test at a significance level of 5%, there was no significant difference in the rate of change of the moisture content of the skin 5 and 30 minutes after the warm bath, suggesting that the rice hull may have a moisturizing effect.