Thermally processed lignin reduces the apparent hydrolysis rate of pancreatic α-amylase in starchy foods

Abstract Lignin, despite being the second most abundant constituent of plant cell walls, is thought to be chemically inert during gastrointestinal digestion and therefore attracts little attention for its role in the human diet. This study explores the heat modifications of lignin to derive species capable of slowing starch digestion in vitro. We applied various advanced biochemical (e.g. enzymic digestion, solubility) and physio-chemical (e.g. scanning electron microscopy, Fourier-Transform-Infrared Spectroscopy, 13C-NMR) analysis to characterize the structure-function of lignin induced by heat treatment. It was found that lignin thermally processed above 300 °C reduced the apparent hydrolysis rate of pancreatic a-amylase, which is ascribed mainly to the insoluble lignin with a modified particle surface morphology. A further kinetic study showed that lignin species derived by thermal processing slowed in vitro digestion rates of potato starch and pasta. The findings highlight the potential for utilizing thermally processed lignin in slowing digestion of starchy foods.