Stability of vitamin C in fresh and freeze-dried capsicum stored at different temperatures

The objective of this study was to determine vitamin C stability in fresh and freeze-dried capsicum during storage at different temperatures. Fresh capsicum stored at 20 °C showed an initial decrease in vitamin C with a minimum peak after 2 days and then increased to a maximum peak after 13 days followed by a gradual decay. In general a gradual decrease of vitamin C was observed in the cases of fresh (i.e. stored at 5, −20, −40 °C) and freeze-dried capsicum stored at all temperatures (i.e. 60 to −40 °C). The degradation kinetics of vitamin C was modeled by zero and first order reaction and rate constants were estimated. The rate constant increased with the increase in storage temperature, while it was decreased with the decrease of moisture content. At storage temperature 5 °C, first order rate constants were observed as 7.1 × 10⁻², 7.7 × 10⁻², and 4.3 × 10⁻³ day⁻¹ in the cases of samples containing moisture contents 94, 15 and 5 g/100 g sample, respectively.