Role of β-carotene and inhibitory factors on iron and zinc bioaccessibility in processed roller milled pearl millet fractions

Abstract Pearl millet is one of the potential dietary sources considered for dietary diversification, to address malnutrition due to iron and zinc deficiency. To decrease the effect of inhibitory factors and improve the bioaccessibility, a combination of strategies involving germination, hydrothermal treatment and milling were adopted. This processing separates the native and germinated-hydrothermally treated grain into coarse and fine fractions. It was observed that the inhibitory factors, polyphenol oxidase, and phytase activity were higher in coarse fractions. The decrease in the phytic acid, total polyphenol, and galloyl content was prominent (48–49%) in the coarse fraction when compared to the fine fraction. The coarse fraction recorded higher β-carotene content along with higher bioaccessible iron (0.378–0.678 mg/100 g) and zinc (1.353–2.118 mg/100 g) content. The bioaccessible iron content in the fine fraction (0.154–0.368 mg/100 g) enhanced while bioaccessible zinc content was slightly reduced (0.687–0.597 mg/100 g). Although the inhibitors were higher in the coarse fraction the bioaccessible iron was also higher which may be attributed to the higher β-carotene content. It was observed that iron bioaccessibility was more related to galloyls, soluble fibre, and β-carotene while zinc bioaccessibility mostly dependent on the phytic acid content.