Table 8.

Phenolic compounds and antioxidant activity of biscuits enriched by increasing levels of almond skins. Control = biscuits without almond skins; AS10 and AS20 = biscuits prepared by adding 10 g and 20 g almond skin powder per 100 g of wheat flour, respectively.

	Control	AS10	AS20
AA (DPPH) (µmol TE/g)	1.89 ± 0.16 c	6.11 ± 0.61 b	9.76 ± 0.74 a
Single phenolic compounds (µg/g)
Vanillic acid	1.43 ± 0.02 c	2.77 ± 0.18 b	4.53 ± 0.10 a
Syringic acid	2.69 ± 0.02 c	6.04 ± 0.45 b	9.71 ± 0.30 a
p-Coumaric acid	0.36 ± 0.01 c	0.79 ± 0.12 b	1.14 ± 0.08 a
Ferulic acid	63.72 ± 0.52 a	55.21 ± 1.47 b	55.96 ± 1.50 b
Sinapic acid	5.33 ± 0.04 a	4.30 ± 0.15 b	4.25 ± 0.20 b
p-Hydroxybenzoic acid	0.44 ± 0.02 c	5.49 ± 0.19 b	12.96 ± 0.44 a
Protocatechuic acid	0.00 ± 0.00 c	3.55 ± 0.06 b	12.67 ± 0.31 a
(+)-Catechin	0.00 ± 0.00 c	11.17 ± 0.06 b	19.52 ± 1.06 a
(-)-Epicatechin	0.00 ± 0.00 c	8.54 ± 0.02 b	11.45 ± 0.21 a
Total sum	73.97 ± 0.54 c	97.84 ± 2.55 b	132.18 ± 1.63 a

AA = antioxidant activity; TE = Trolox equivalents; DPPH = 2,2-diphenyl-1-picrylhydrazyl radical. Different letters in row indicate significant differences (p < 0.05).