Premilling pearling for producing wheat fractions with distinct digestibility and fermentability

Abstract

Background and objectives Wheat bran contains 16%–18% protein which has a nutritionally balanced amino acid composition but is not fully digestible by human enzymes. The objective of the study was to examine the impact of different levels of pearling wheat prior to milling on protein digestibility in the resultant bran fractions and pearlings and to study their fermentability. Findings Breaking down bran cell wall material, the main constituent of which is the dietary fiber arabinoxylan (AX), by pearling increases the in vitro protein digestibility of the resulting material. Pearling fractions enriched in pericarp tissue and hence in insoluble AX with a high arabinose to xylose ratio (A/X) are poorly fermented in vitro with fecal inoculum. In contrast, fermentation of fractions enriched in aleurone tissue produces more short‐chain fatty acids than unmodified wheat bran. This is mainly attributed to the lower A/X of aleurone AX and to pearling‐induced cell wall structure degradation, which makes the dietary fiber better accessible to fecal bacteria. Conclusions Pearling of wheat prior to milling leads to bran and pearling fractions with distinct digestibility and fermentability characteristics. Significance and novelty The present work is a step toward understanding and exploitation of the nutritional potential of wheat fractions offered by pearling prior to milling.