Effect of zinc sulfate fortification in germinated brown rice on seed zinc concentration, bioavailability, and seed germination

Rice is the staple food for more than half of the world's population and, hence, the main source of a vital micronutrient, zinc (Zn). Unfortunately, the bioavailability of Zn from rice is very low not only due to low content but also due to the presence of some antinutrients such as phytic acid. We investigated the effect of germination and Zn fortification treatment on Zn bioavailability of brown rice from three widely grown cultivars using the Caco-2 cell model to find a suitable fortification level for producing germinated brown rice. The results of this study showed that Zn content in brown rice increased significantly (p < 0.05) as the external Zn concentrations increased from 25 to 250 mg/L. In contrast, no significant influence (p > 0.05) on germination percentage of rice was observed when the Zn supply was lower than 150 mg/L. Zn fortification during the germination process has a significant impact on the Zn content and finally Zn bioavailability. These findings may result from the lower molar ratio of phytic acid to Zn and higher Zn content in Zn fortified germinated brown rice, leading to more bioavailable Zn. Likewise, a significant difference (p < 0.05) was found among cultivars with respect to the capacity for Zn accumulation and Zn bioavailability; these results might be attributed to the difference in the molar ratio of phytic acid to Zn and the concentration of Zn among the cultivars evaluated. Based on global intake of Zn among the world population, we recommend germinated brown rice fortified with 100 mg/L ZnSO(4) as a suitable concentration to use in the germination process, which contains high Zn concentration and Zn bioavailability. In the current study, the cultivar Bing91185 fortified with Zn through the germination process contained a high amount as well as bioavailable Zn, which was identified as the most promising cultivar for further evaluation to determine its efficiency as an improved source of Zn for target populations.