Answer 1. We usually measure residual SO2 content every step. 1.1 Preserved by so 2 solution. 1.2 After 1st dried hot air oven or 1st boiled. 1.3 After soaked in syrup. 1.4 Before 2nd dry hot air oven. 1.5 After 2nd dried hot air oven. 1.6 Before pack.