Wheat and lupin protein interaction at baking: Modifying extractability from lupin-wheat bread

Mixing of lupin flour to wheat in bread making provides a number of health benefits and has major effects on bread properties including protein extractability. The study investigated wheat and lupin protein interaction as influenced by baking process and modification of protein extractability, which is important for the final quality of bread. MALDI-TOF mass spectrometry and 2 dimensional gel electrophoresis followed by MS/MS peptide sequencing were used to study bread protein matrix and wheat and lupin flour proteins. The results demonstrated that many of the wheat and lupin proteins including high molecular weight glutenins remained unchanged in baking as per their elctrophoretic behavior. However, some of the proteins of wheat and lupin became unextractable from the bread, indicating lupin-wheat protein interaction during baking. For the lupin proteins, most of the α-conglutins could be readily extracted from the lupin-wheat bread even at low salt and non-reducing/non-denaturing extraction conditions. In contrast, most of the β-conglutins lost extractability suggesting that they were cross-linked to the wheat gluten network and trapped into the bread matrix. The higher thermal stability of α-conglutins compared to β-conglutins is speculated to account for this difference