Phytic Acid in Brown Rice Can Be Reduced by Increasing Soaking Temperature.

Ayaka Fukushima,Ayaka Aiseki,Tatsuki Akabane,Gun Uchino,Ishara Perera,Naoki Hirotsu

doi:10.3390/foods10010023

Abstract

Phytic acid (PA) is a storage form of phosphorus in seeds. Phytase enzyme is activated at germination and hydrolyses PA into myo-inositol and inorganic phosphate. PA inhibits the absorption of minerals in the human intestine by chelation. Its degradation, therefore, is a key factor to improve mineral bioavailability in rice. Germinated brown rice (GBR) is favoured because it improves the availability of nutrients, and thus have a positive effect on health. In this study, we show the effects of soaking temperature on phytase activity and PA content in GBR. Rice phytase showed thermostability and its activity peaked at 50 °C. After 36 h of soaking, phytase activity was significantly increased at 50 °C and PA content was significantly decreased, compared to that at 30 °C. Zinc (Zn) analysis revealed that there was no significant difference in Zn content among different temperature treatments. Calculated total daily absorbed Zn (TAZ) was significantly higher in GBR compared with non-soaked seeds. Moreover, brown rice grains germinated at 50 °C showed a higher TAZ value than that at 30 °C. Seed germination and seed water soaking at high temperatures reduce PA content in brown rice showing a potentially effective way to improve mineral bioavailability in brown rice.

Highlights

The world population is steadily increasing and is estimated to reach approximately 10.9 billion by 2100 [1]
We investigated the effect of different temperatures at soaking on Phytic acid (PA) content and phytase activity
For short-time analysis of PA content and phytase activity, ca. 50 grains were soaked at 30 ◦C and 50 ◦C and collected every 12 h up to 48 h and stored at −80 ◦C for analysis

Summary

Introduction

The world population is steadily increasing and is estimated to reach approximately 10.9 billion by 2100 [1]. To support this rise in population, there is a need to increase the demand for food supply and production. Brown rice contains phytochemical compounds, including dietary fibre, phenolic acids, flavonoids, tocopherols, minerals, vitamins, amino acid, and γ-oryzanol [3]. These nutritive ingredients help reduce blood pressure, prevent cancer [4,5] and heart disease [6], and have antioxidative effects [7]. The consumption of brown rice, instead of white rice, is increasingly becoming the focus of healthy diet recommendations, especially in Asian countries [8]

Methods

Results

Conclusion