Table 3. Quantification of almond skin polyphenols from raw almonds and comparison of extraction and blanching methods (n = 3).
| Peak, polyphenols (μg/g) | Methanol steeping 24 h | Assisted solvent extraction | |||
|---|---|---|---|---|---|
|
|
|
||||
| Liquid N2 | Hot water | Liquid N2 | Hot water | ||
| (1) | (+)-catechin | 157.93 | 331.22 (66)a | 345.22 | 366.26 (63) |
| (2) | −)-epicatechin | 94.88 | 232.01 (74) | 145.90 | 266.08 (69) |
| (3) | procatechuic acid | 12.88 | 41.52 (65) | 39.34 | 61.92 (49) |
| (4) | p-hydroxybenzoic acid | 3.97 | 9.37 (76) | 8.38 | 12.30 (58) |
| (5) | quercetin-3-O-rutinoside | 12.64 | 16.59 (80) | 10.30 | 16.22 (80) |
| (6) | naringenin-7-O-glucoside | 30.40 | 49.31 (72) | 36.94 | 58.84 (62) |
| (7) | quercetin-3-O-galactoside | 9.91 | 13.64 (73) | 8.80 | 13.69 (74) |
| (8) | bkaempferol-3-O-galactoside | 7.24 | 19.90 (65) | 14.16 | 21.69 (60) |
| (9) | kaempferol-3-O-rutinoside | 151.92 | 232.52 (83) | 130.30 | 219.64 (84) |
| (10) | cdihydrokaempferol | 71.84 | 97.89 (85) | 53.31 | 97.06 (86) |
| (11) | isorhamnetin-3-O-rutinoside | 538.23 | 741.36 (77) | 416.82 | 717.63 (79) |
| (12) | isorhamnetin-3-O-glucoside | 149.27 | 145.39 (75) | 88.83 | 147.03 (76) |
| (13) | kaempferol-3-O-glucoside | 26.74 | 37.39 (73) | 28.98 | 37.71 (73) |
| (14) | eriodictyol | 4.53 | 4.60 (70) | 3.01 | 4.35 (75) |
| (15) | quercetin | 1.73 | 1.04 (78) | 0.01 | 1.25 (65) |
| (16) | naringenin | 97.04 | 97.36 (76) | 65.71 | 94.70 (78) |
| (17) | kaempferol | 3.72 | 4.86 (65) | 3.66 | 4.36 (64) |
| (18) | isorhamnetin | 13.31 | 32.00 (53) | 13.10 | 13.72 (75) |
| Sum of polyphenols | 1388.17 | 2107.96 (75) | 1412.76 | 2154.47 (73) | |
a
Percentage of component recovered in the residual blanch water.
b
Kaempferol-3-O-glactoside concentration was determined on the basis of kaempferol-3-O-glucoside equivalents.
c
Dihydrokaempferol concentration was determined on the basis of eriodictyol equivalents.