ARS | Publication request: Roast effects on the hydrophilic and lipophilic antioxidant capacities of peanut flours, blanched peanut seed and peanut skins

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 19, 2009
Publication Date: June 24, 2009
Citation: Davis, J.P., Dean, L.L., Price, K.M., Sanders, T.H. 2009. Roast effects on the hydrophilic and lipophilic antioxidant capacities of peanut flours, blanched peanut seed and peanut skins. Food Chemistry. 119 (2) 539-547.

Interpretive Summary: Hydrophilic and lipophilic antioxidant capacities of peanut flours, peanut seed and peanut skins were characterized as a function of different roast intensities relevant to the food industry. Darker roasts were consistently associated with higher hydrophilic and lipophilic antioxidant capacities for both peanut flours and peanut seed. These increased antioxidant capacities were attributed to the increased concentration of Maillard browning compounds and/or the release of previous bound phenolic compounds within these roasted materials upon roasting. Peanut skins, which are currently a waste product of industrial peanut processing, had remarkably high hydrophilic and lipophilic antioxidant capacities across all roast conditions tested, emphasizing the potential for using this low value material as a natural antioxidant. Finally, this work provides a valuable insight into Vitamin E degradation in oils from peanut seed roasted to different intensities. Specifically, mild roasts most severely induced Vitamin E degradation in agreement with earlier findings; however, in some cases, oil from darker roasted peanut seed actually had greater retention of key tocopherols than that of raw or mildly roasted seed, presumably due to the increased concentration of oil soluble Maillard reaction products with additional antioxidant properties.

Technical Abstract: Hydrophilic and lipophilic oxygen radical antioxidant capacity (H&L-ORAC) of peanut flours, blanched peanut seed, and peanut skins were characterized across a range of roast intensities. H-ORAC ranged from 5910-7990, 3040-3700 and 152,290-209,710 'moles Trolox/100g for the flours, seed, and skins, respectively. H-ORAC increased linearly with darker seed color after roasting at 166 ºC from 0-77 min, whereas skin H-ORAC peaked after roasting for 7 min. Linear correlations with H-ORAC and total phenolic content were observed. Additionally, completely defatted peanut seed were solubilized (5% w/w) in water and H-ORAC measured. For these samples, H-ORAC decreased with roast intensity which correlated with soluble protein. L-ORAC ranged from 620-1120, 150-730 and 2,150-6,320 'moles Trolox/100g for peanut flours, seed, and skins, respectively. L-ORAC increased linearly with both darker seed color and skin color across the 77 min range. L-ORACs of roasted peanuts and ingredients are discussed in terms of tocopherol contents and Maillard reaction products.