Bioaccessibility of ferulic acid in hulless barley varieties at stages of simulated in vitro digestion

Abstract

Background and Objectives: Ferulic acid has antioxidant, anti-inflammatory, and antimicrobial activity. Ferulic acid in barley is present in esterified form in the bran layer, however, only the free form is bioaccessible in the upper gastrointestinal tract. The objectives of this study were to investigate the bioaccessibility of ferulic acid at four stages of simulated gastrointestinal digestion of two barley varieties to determine when ferulic acid is released and investigate factors which may affect the release of ferulic acid including digestive enzymes and pH. Findings: The release of ferulic acid was strongly influenced by digestive enzymes and minimally by pH. The presence of enzymes reduced free ferulic acid but increased the amount of esterified ferulic acid. The major release of esterified ferulic acid occurred during the final hour of small intestinal digestion. The amount of bioaccessible ferulic acid remained constant throughout digestion. The bran thickness, measured by microCT imaging, significantly differed between the varieties. Conclusion: During digestion, ferulic acid changed structurally, as observed by the changes in the amount of free and esterified ferulic acid at four digestion timepoints. The release of ferulic acid was strongly influenced by exposure to digestive enzymes and minimally by pH, although the mechanism of the presence of enzymes on ferulic acid release is unclear. The bioaccessibility of ferulic acid may be determined by the bran layer thickness and further investigation is required. Significance and Novelty: This is the first study to investigate the bioaccessibility of ferulic acid in barley at various stages of digestion and to measure the bran thickness of barley using microCT imaging with preliminary findings indicating enhanced ferulic acid bioaccessibility in grains with a thinner bran layer.