Effects of added fruit polyphenols and pectin on the properties of finished breads revealed by HPLC/LC-MS and Size-Exclusion HPLC

The positive roles of fruit polyphenols (PPs) and dietary fibres (DFs) in promoting human health and well-being are now well recognised. This study investigates the effects of added fruit PPs and pectin on the composition and extractability of PPs and proteins from finished breads, and complements our recently published papers that focus on the rheological and physicochemical properties of breads containing added PPs and pectin. Breads were prepared in the absence or presence of a high methoxyl (HM) apple pectin and kiwifruit, blackcurrant or apple PP extract, and subjected to texture measurements (crumb firmness), informal sensory evaluations and chemical analyses. An epicatechin standard was also used in place of the fruit PP extract to estimate the extractability and recovery of PPs from bread. Results show that adding a PP extract and pectin to bread modified bread firmness, specific volume, recovery of added PPs, amount of free thiol groups of bread proteins, and also the extractability of PPs and proteins from bread. The recovery of added PPs was the lowest for the APE + HM pectin bread which had the highest bread firmness. High performance liquid chromatography (HPLC)-mass spectrometry (MS) PP profiling revealed that baking caused oxidation of some added PPs such as quercetin and myricetin. Size-Exclusion HPLC analysis showed that adding a combination of PP extract and HM pectin decreased the S–H group concentration and increased the percentage of the Unextractable High Molecular Weight (UHMW) proteins, compared to the control bread. The added pectin and PPs, and possibly the oxidation products of the added PPs, affected the interactions between water and bread components (such as gluten proteins) during dough development and bread baking, causing differences in bread cross-linking microstructure and textural properties, which ultimately influenced the extractability and/or stability of added PPs.