Degradation kinetics of vitamin C in orange juice (Citrus sinensis) at ambient and cold shelf life

Abstract

The aim of the research was to establish the kinetics of vitamin C degradation in orange juice packaged and displayed at room and cold temperatures. Vitamin C was evaluated in juice packaged in transparent plastic bottles at 27, 16 and 8 °C for six hours; degradation rate (K), decimal reduction time (D), half-life (T0,5), Q10and activation energy (Ea) were determined. The degradation kinetics corresponds to a first order model; the reaction rate K27°C = 0,0017806; K16°C= 0,0012819 and K8°C= 0,0012763 min-1; thedecimal reduction time D27°C= 9,36, D16°C= 13,00 and D8°C= 13,06 h; the half-life T0.5 (27 °C)= 6.49, T0.5 (16 °C)= 9.01 and T0.5 (8 °C)= 9.05 h; the value of Q10= 0.833 and the Activation Energy 3,066 Kcal/mol. The fresh juice had 74,034 mg of ascorbic acid/100 g, which was reduced by 48 % in 6 h at 27 °C, 37 % at 16 °C and 33 % at 8 °C; Therefore, the display of orange juice should be avoided even at low temperatures, due to the significant loss of vitamin C.