Peanut skins-fortified peanut butters: Effect of processing on the phenolics content, fibre content and antioxidant activity

•We fortify peanut butters (PBs) with ground peanut skins to increase the level of bioactives.•We examine changes in the levels of phenolics and fibre contents as well as antioxidant capacity in PBs.•We identify the proanthocyanidins in the peanut skins responsible for the increase in PB phenolics.•Addition of 5% peanut skins to PBs can permit a “good source of fibre” claim to be made on the label.•Better by-product utilisation can improve an existing product and allow diversification of a brand. Incorporation of ground peanut skins (PS) into peanut butter at 1.25%, 2.5%, 3.75%, and 5.0% (w/w) resulted in a marked concentration-dependent increase in both the total phenolics content (TPC) and antioxidant activity. Using dry-blanched PS to illustrate, the TPC increased by 86%, 357%, 533%, and 714%, respectively, compared to the peanut butter control devoid of PS; the total proanthocyanidins content (TPACs) rose by 633%, 1933%, 3500%, and 5033%, respectively. NP-HPLC detection confirmed that the increase in the phenolics content was attributed to the endogenous proanthocyanidins of the PS, which were characterised as dimers to nonamers by NP-HPLC/ESI-MS. FRAP values increased correspondingly by 62%, 387%, 747%, and 829%, while H-ORACFL values grew by 53%, 247%, 382%, and 415%, respectively. The dietary fibre content of dry-blanched PS was ∼55%, with 89–93% being insoluble fibre. Data revealed that PS addition enhances the antioxidant capacity of the peanut butter, permits a “good source of fibre” claim, and offers diversification in the market’s product line.