Thermal stability and bioavailability of bioactive compounds after baking of bread enriched with different onion by-products

•Quercetin glycosides, dimers and trimer in onion peel decomposed during bread baking.•Onion by-products did not affect sensory properties.•Onion peel-enriched bread increased antioxidant activity of volunteers’ blood. This study investigated the effects of the addition of onion waste fractions into gluten-free (GF) bread to promote its health benefits. 5% of the control (C) GF flour blend was replaced with three waste fractions in the form of: fried onion (FO), dried onion (DO) and onion peel (OP). Antioxidant activity, content of flavonols and total polyphenols of breads increased in the following order: C