| Treatment | Soaking time (minutes) | ||
| 1 | 3 | 5 | |
| Control | 4.76a | 2.38cd | 3.37b |
| 9:1 H2SO4 | 0.40g-j | 0.00h-j | 0.60f-j |
| 7:3 H2SO4 | 0.80e-g | 0.20g-j | 0.40g-j |
| 1:1 H2SO4 | 0.40g-j | 0.80e-g | 0.00h-j |
| 4:6 H2SO4 | 2.98bc | 0.40g-j | 1.99c-e |
| 3:7 H2SO4 | 1.59d-f | 0.40g-j | 0.40g-j |
| 2:8 H2SO4 | 0.80e-g | 0.20g-j | 0.99e-g |
| 1:9 H2SO4 | 1.19e-g | 0.40g-j | 0.00h-j |
| SE (±) 0.38 | |||