2.11. Quality control
In-house control materials (black rice flour, soybean flour, and
ginger powder) were used for quality control of all analysed data
and Tang (natural fresh orange powder) was used as control
material for vitamin C analysis. Black rice flour and ginger power
were used as in-house control materials for daily control
samples of antioxidant content and activity and soybean flour
as a control material for macro-nutrient and mineral analysis.
Precision of the analysis was evaluated and monitored by a