Scientific Study

Polyphenols and antioxidant activity of skins from California almonds subjected to roasting; pasteurization; and storage were determined by LC-MS quantification; total phenols (TP); and ferric reducing antioxidant power (FRAP). Pasteurization did not significantly change TP; FRAP; or flavonoids and phenolic acids (FP). Roasted almonds had 26% less TP and 34% less FRAP than raw; but equivalent FP (n = 12). Storing almonds at 4 and 23°C for 15 mo resulted in gradual increases in FP; up to 177 and 200%; respectively (n = 13). At 4°C and 15 mo; polyphenols increased 18-fold for p-hydroxybenzoic acid; while others were 45 to 200% higher compared to baseline values. Isorhamnetin-3-O-rutinoside accounted for 48% of the increase in FP. After 15 mo; FRAP and TP increased to 200 and 190% of initial values. Accelerated aging of whole almonds increased FP content by 10% after 3 days; but TP and FRAP values were not significantly different from baseline to day 10. Thus; in almond skins; roasting decreases TP and FRAP but not FP; while storage for up to 15 mo doubles FP.