Effects of chemical composition and baking on in vitro digestibility of proteins in breads made from selected gluten-containing and gluten-free flours

Breads prepared from cereal grains are a dietary staple, providing a significant proportion of daily energy, but not necessarily of dietary protein. However, good digestibility of proteins in bread is important to avoid potential immunogenic effects of undigested peptides, including for those gluten-intolerant. Four gluten-containing (white wheat, wholemeal wheat, spelt and rye) and four gluten-free (chick pea, lupin, buckwheat, amaranth) flours were used to make yeast-leavened breads standardized for protein. In vitro gastro-intestinal digestion of pre-mixes, doughs and breads baked for 20 and 35 min was conducted followed by correlation analysis between fitted parameters of digestion profiles, chemical composition (protein, non-fibre carbohydrates, fibre, ash and total polyphenolics) and amino acid profiles. The results indicated that digestibility generally increased during proofing and decreased during baking. Relatively higher protein digestibility was correlated with ratio of non-fibre carbohydrate to protein and lower digestibility with increasing contents of fibre and total polyphenolics in pre-mixes.