| Treatment | Soaking time (minutes) | ||
| 1 | 3 | 5 | |
| Control | 3.37a | 3.28a | 2.38b |
| 9:1 H2SO4 | 0.70d-g | 0.60d-g | 0.50d-g |
| 7:3 H2SO4 | 1.39c-e | 0.60d-g | 0.40d-g |
| 1:1 H2SO4 | 0.60d-g | 1.19c-f | 0.50d-g |
| 4:6 H2SO4 | 2.38b | 1.39c-e | 1.49cd |
| 3:7 H2SO4 | 2.38b | 0.70d-g | 0.90c-g |
| 2:8 H2SO4 | 1.10c-g | 0.40d-g | 0.99c-g |
| 1:9 H2SO4 | 1.89bc | 1.19c-f | 1.19c-f |
| SE (±) 0.36 | |||