ARS | Publication request: Roast effects on the hydrophilic and lipophilic antioxidant capacities of almonds, cashews, hazelnuts and peanuts

Submitted to: Institute of Food Technology
Publication Type: Abstract Only
Publication Acceptance Date: June 6, 2009
Publication Date: June 10, 2009
Citation: Davis, J.P., Price, K.M., Smyth, D., Dean, L.L., Sanders, T.H. 2009. Roast effects on the hydrophilic and lipophilic antioxidant capacities of almonds, cashews, hazelnuts and peanuts. Institute of Food Technology. Abstract.

Technical Abstract: Oilseeds generally have excellent nutritional properties, which on a macro-nutritional level are attributed to favorable fatty acid, protein, and fiber profiles, among others. More recently, some oilseed antioxidant capacities have been measured as these properties are important for both nutritional and food product shelf stability considerations; however, the effect of roasting, which is the primary means of processing oilseeds, has only been minimally investigated in regards to antioxidant capacity. Accordingly, hydrophilic and lipophilic oxygen radical adsorption capacities (H&L-ORAC) were characterized for peanuts, cashews, almonds and hazelnuts dry roasted to a range of intensities (minimum of 6 roasted samples per oilseed) relevant to the food industry. Hydrophilic and lipophilic extracts were prepared according to standard procedures using a Dionex 200 Accelerated Solvent Extractor. For all raw and roasted oilseeds, H-ORAC accounted for roughly 80% of the total antioxidant capacity (sum of H-ORAC and L-ORAC). H-ORAC of almonds, cashews, blanched hazelnuts and blanched peanuts were approximately 1130-1740, 1250-2030, 750-1210, and 3440-4010 'moles Trolox equivalents 100g, respectively. Roasting significantly (P<0.05) increased H-ORAC for all oilseeds except cashew. For almonds and peanuts, good correlations (R2 >0.76) were observed in plots of H-ORAC vs. Hunter L-Value, meaning darker colors were consistently associated with increased H-ORAC. This increase is hypothesized to be associated with the release of bound phenolics and/or the increased concentration of Maillard browning reaction products upon roasting. Good correlations (R2 > 0.71) were observed in individual plots of H-ORAC vs. total phenolic content for almonds, peanuts and hazelnuts, but not cashews. Hazelnuts and peanuts were tested with and without seed coats (testae) and both H-ORAC and L-ORAC for both oilseeds were significantly (P<0.05) and dramatically increased when seed coats were present. L-ORAC roast response is discussed in terms of Maillard browning reaction products and vitamin E contents of the oilseeds.