TABLE 2.
The effect of different blanching method on the color, proximate composition and gross energy, mineral, vitamin, total polyphenol content (TPC), and antioxidant activity of sweet potato leaf powder
| Treatment | Control group | Cut group | Uncut group |
|---|---|---|---|
| Color | |||
| L* | 43.25 ± 0.45a | 41.14 ± 0.34b | 40.83 ± 0.63b |
| a* | −10.20 ± 0.13a | −8.66 ± 0.12b | −8.33 ± 0.16b |
| b* | 17.50 ± 0.18a | 15.42 ± 0.21b | 14.83 ± 0.24c |
| ΔE* | 52.50 ± 0.41b | 54.16 ± 0.30a | 54.38 ± 0.59a |
| Proximate composition and gross energy (g/100 g DW) | |||
| Moisture a | 6.22 ± 0.00b | 6.66 ± 0.00a | 5.74 ± 0.04c |
| Crude protein | 30.05 ± 0.15a | 29.55 ± 0.15a | 29.85 ± 0.25a |
| Crude fat | 4.12 ± 0.01a | 3.96 ± 0.01c | 4.04 ± 0.02b |
| Carbohydrate | 14.30 ± 0.00b | 9.20 ± 0.00c | 17.50 ± 0.00a |
| Crude fiber | 35.00 ± 0.00b | 40.40 ± 0.00a | 32.80 ± 0.00c |
| Soluble fiber | 7.26 ± 0.10c | 9.69 ± 0.10a | 8.78 ± 0.01b |
| Insoluble fiber | 27.68 ± 0.16b | 30.73 ± 0.16a | 24.05 ± 0.09c |
| Ash | 10.41 ± 0.01a | 10.08 ± 0.01c | 10.18 ± 0.01b |
| Gross energy b | 1,184.00 ± 0.00b | 1,131.00 ± 0.00c | 1,214.00 ± 0.00a |
| Mineral (mg/100 g DW) | |||
| Na | 47.36 ± 0.01c | 101.35 ± 0.01a | 90.11 ± 2.89b |
| P | 384.10 ± 3.00a | 387.40 ± 3.00a | 378.00 ± 2.80a |
| Ca | 916.30 ± 4.90b | 994.95 ± 4.90a | 911.70 ± 5.70b |
| K | 4,803.50 ± 20.50a | 2,851.50 ± 20.50b | 2,543.50 ± 10.50c |
| Mg | 258.40 ± 0.70a | 194.15 ± 0.70c | 215.75 ± 8.05b |
| Fe | 12.54 ± 0.10a | 10.08 ± 0.10b | 8.33 ± 0.39c |
| Zn | 2.65 ± 0.01a | 1.71 ± 0.01c | 2.06 ± 0.07b |
| Cu | 1.19 ± 0.00a | 1.05 ± 0.00b | 1.20 ± 0.02a |
| Mn | 16.95 ± 0.04a | 8.98 ± 0.04c | 10.59 ± 0.36b |
| Se c | 5.37 ± 0.15b | 5.16 ± 0.15b | 6.52 ± 0.30a |
| Pb d | N.D. (<0.04) | N.D. (<0.04) | N.D. (<0.04) |
| As | 0.16 ± 0.01b | 0.23 ± 0.01a | 0.21 ± 0.00a |
| Hg d | N.D. ( <0.010) | N.D. (<0.010) | N.D. (<0.010) |
| Vitamin (mg/100 g DW) | |||
| Vitamin C | 77.69 ± 0.96a | 75.64 ± 0.96a | 70.32 ± 0.08b |
| Vitamin B1 d | N.D. (<0.12) | N.D. (<0.12) | N.D. (<0.12) |
| Vitamin B2 | 1.02 ± 0.01b | 1.03 ± 0.01b | 1.11 ± 0.00a |
| Vitamin B3 | 0.55 ± 0.00a | 0.56 ± 0.00a | 0.57 ± 0.02a |
| β‐carotene | 82.10 ± 1.60c | 126.50 ± 1.60a | 121.5 ± 5.00b |
| Vitamin E | 8.00 ± 0.16c | 14.70 ± 0.16b | 18.90 ± 0.30a |
| Folic acid c | 56.43 ± 0.66a | 54.03 ± 0.66a | 56.36 ± 0.82a |
| TPC (g CAE/100 g DW) | 6.42 ± 0.05A | 2.90 ± 0.10B | 4.91 ± 0.20C |
| Antioxidant activity (g TE/100 g DW) | 14.76 ± 0.09a | 6.10 ± 0.08c | 11.66 ± 0.09b |
Data are means ± SD (n ≥ 2). Values within rows with different letters are significantly different (p < .05).
a
Moisture content was expressed in g/100 g DW.
b
Gross energy was expressed in kJ/100 g DW.
c
Se content and Folic acid content were expressed in μg/100 g DW.
d
N.D. means the content of minerals and vitamin B1 were not detected in sweet potato leaves powder.