Stability of vitamin C in broccoli at different storage conditions

Abstract

In this study, the retention of vitamin C in fresh broccoli stored at different temperatures (i.e. chiller, room, cooking, and roasting or baking; 5-120°C) was investigated. The thermal stability of vitamin C in broccoli was analysed at 5, 20, 45, 60, 70, 80, 110, and 120°C. The vitamin C content was measured by the indophenol titration method. Vitamin C was affected negatively at all stored temperatures. The degradation of vitamin C was modelled by first-order reaction kinetics and the reaction rate constants were observed as 9.03×10-8 and 5.65×10-3 s-1 when stored at 5°C and 120°C, respectively. The activation energy was estimated as 74.2 kJ/mol within the temperature range used in this study. The lowest decay of vitamin C was observed during the chilling condition. The data on retention of vitamin C in broccoli could be used to determine their stability, when stored as raw, and when heated at different temperatures.

Stability of vitamin C in broccoli based on the chemical reaction kinetics, micro-region state diagram, and empirical correlations

“…Figure 3 shows typical graphs of vitamin C degradation and plots of first-order kinetics of freeze-dried samples at −80°C (Figure 3a and b) and 60°C (Figure 3c and d). The initial increase of vitamin C in Figure 3c could be due to the release of bound vitamin C. As reported earlier by Al-Habsi et al, [29] degradation of vitamin C was followed as a first-order reaction. Table 1 shows the rate constant of vitamin C degradation as a function of moisture content and storage temperatures.…”

“…The kinetics data for fresh broccoli samples stored at 20°C, 45°C, 60°C, 70°C, 80°C, 110, and 120°C from Al-Habsi et al [29] were used in the current study. In their experiments, samples (around 200 g) were placed in glass beakers placed in air-tight aluminum cells and stored at different temperatures 5°C, 20°C, 45°C, 60°C, 70°C, 80°C, 110°C, and 120°C.…”

“…However, 2 g sample was used to determine the vitamin C analysis for the freeze-dried powder. The vitamin C concentration was measured by titration method as described in Al-Habsi et al [29] according to the AOAC method. [30] The vitamin C concentration is expressed as mg/100 g broccoli.…”

“…The degradation of vitamin C is commonly modeled by the first-order reaction kinetics and it is expressed as [29] ln…”

“…The rate constant was determined from the slope of a linear plot ln (C/C o ) versus t by excluding the initial lag period to reach isothermal temperature. [29] Activation energy of first-order kinetics was estimated using the Arrhenius equation as…”