Polyphenols and antioxidant properties of almond skins: influence of industrial processing.
Almond (Prunus dulcis[Mill.] D.A. Webb) skins have been proposed as a source of bioactive polyphenols. In this article, the phenolic composition and antioxidant activity of almond skins obtained from different processes (blanching [freeze-drying], blanching + drying, and roasting) were studied. A total of 31 phenolic compounds corresponding to flavan-3-ols (33% to 56% of the total of phenolic compounds identified), flavonol glycosides (9% to 36%), hydroxybenzoic acids and aldehydes (6% to 26%), flavonol aglycones (1.7% to 18%), flavanone glycosides (3% to 7.7%), flavanone aglycones (0.69% to 5.4%), hydroxycinnamic acids (0.65% to 2.6%), and dihydroflavonol aglycones (0% to 2.8%) were determined in the skins from 3 different varieties of almonds. The total contents of phenolic compounds identified were significantly (P < 0.05) higher (around 2-fold) in the roasted samples than in the blanched almonds (freeze-dried). Industrial drying (oven drying) of the blanched almond skins produced an increase (< 2-fold) in the contents of phenolic compounds, although the results were only statistically significant (P < 0.05) for some samples. The antioxidant activity (ORAC values) was higher for the roasted samples (0.803 to 1.08 mmol Trolox/g), followed by the samples subjected to blanching + drying (0.398 to 0.575 mmol Trolox/g) and then the blanched (freeze-dried) samples (0.331 to 0.451 mmol Trolox/g). Roasting is the most suitable type of industrial processing of almonds to obtain almond skin extracts with the greatest antioxidant capacity.
Garrido
I
I
Inst. de Fermentaciones Industriales (CSIC), Juan de la Cierva 3, 28006 Madrid, Spain.
Monagas
M
M
Gómez-Cordovés
C
C
Bartolomé
B
B
D000975:Antioxidants / Q000032:analysis*; D005419:Flavonoids / Q000032:analysis*; D005511:Food Handling / Q000379:methods*; D005525:Food-Processing Industry / Q000379:methods* / Q000592:standards; D010636:Phenols / Q000032:analysis*; D059808:Polyphenols; D027861:Prunus / Q000737:chemistry*; D012639:Seeds / Q000737:chemistry; D013045:Species Specificity
D000975:Antioxidants; D005419:Flavonoids; D010636:Phenols; D059808:Polyphenols