Effects of soaking, germination and fermentation on phytic acid, total and in vitro soluble zinc in brown rice

Jianfen Liang; Bei-Zhong Han; M J Robert Nout; Robert J Hamer

doi:10.1016/j.foodchem.2008.02.064

Effects of soaking, germination and fermentation on phytic acid, total and in vitro soluble zinc in brown rice

Food Chem. 2008 Oct 15;110(4):821-8. doi: 10.1016/j.foodchem.2008.02.064. Epub 2008 Feb 29.

Authors

Jianfen Liang¹, Bei-Zhong Han², M J Robert Nout³, Robert J Hamer³

Affiliations

¹ College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, PR China; Department of Agrotechnology and Food Sciences, Wageningen University, Wageningen, The Netherlands. Electronic address: liangjf@cau.edu.cn.
² College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, PR China.
³ Department of Agrotechnology and Food Sciences, Wageningen University, Wageningen, The Netherlands.

PMID: 26047266
DOI: 10.1016/j.foodchem.2008.02.064

Abstract

Rice is an important staple food in Asian countries. In rural areas it is also a major source of micronutrients. Unfortunately, the bioavailability of minerals, e.g. zinc from rice, is low because it is present as an insoluble complex with food components such as phytic acid. We investigated the effects of soaking, germination and fermentation with an aim to reduce the content of phytic acid, while maintaining sufficient levels of zinc, in the expectation of increasing its bioavailability. Fermentation treatments were most effective in decreasing phytic acid (56-96% removal), followed by soaking at 10°C after preheating (42-59%). Steeping of intact kernels for 24h at 25°C had the least effect on phytic acid removal (<20%). With increased germination periods at 30°C, phytic acid removal progressed from 4% to 60%. Most wet processing procedures, except soaking after wet preheating, caused a loss of dry mass and zinc (1-20%). In vitro solubility, as a percentage of total zinc in soaked rice, was significantly higher than in untreated brown rice while, in steeped brown rice, it was lower (p<0.05). Fermentation and germination did not have significant effects on the solubility of zinc. The expected improvement due to lower phytic acid levels was not confirmed by increasing levels of in vitro soluble zinc. This may result from zinc complexation to other food components.

Keywords: Fermentation; Germination; In vitro solubility; Phytic acid; Soaking; Zinc.