Thermal Degradation of Antioxidant Micronutrients in Citrus Juice:  Kinetics and Newly Formed Compounds

Abstract

The thermal degradation kinetics of vitamin C, two carotenoids (beta-carotene and beta-cryptoxanthin), and hesperidin, as a function of temperature, were determined for Citrus juice [Citrus sinensis (L.) Osbeck and Citrus clementina Hort. ex Tan]. The influence of dissolved oxygen on the rate of ascorbic acid degradation was also assessed. Analysis of kinetic data suggested a first-order reaction for the degradation of vitamin C and carotenoids. The kinetics parameters Dtheta, z, and Ea have been calculated. Following the Arrhenius relationship, the activation energy of ascorbic acid was 35.9 kJ mol-1 and agreed with the range of literature reported value. The results on vitamin C and carotenoids from citrus juice made it possible to validate the predicting model. Thermal degradation of carotenoids revealed differences in stability among the main provitamin A carotenoids and between these and other carotenoids belonging to the xanthophyll family. The activation energies for the two provitamin A carotenoids were 110 and 156 kJ mol-1 for beta-carotene and beta-cryptoxanthin, respectively. On the other hand, no degradation of hesperidin was observed during thermal treatment. Finally, the vitamin C in citrus juice was not as heat sensitive as expected and the main provitamin A carotenoids present in citrus juice displayed a relative heat stability. The high-performance liquid chromatography-diode array detection-mass spectrometry analysis of degradation products showed that the isomerization of the epoxide function in position 5,6 into a furanoxide function in position 5,8 was a common reaction for several xanthophylls. These findings will help determine optimal processing conditions for minimizing the degradation of important quality factors such as vitamin C and carotenoid in citrus juice.

Thermal degradation kinetics of ascorbic acid, thiamine and riboflavin in rosehip (Rosa canina L) nectar

“…The activation energy for AA degradation was found as 55.30 kJ/mol. This value is higher than the values of 47.5 kJ/mole for rosehip pulp (Karhan et al 2004) heated under anaerobic circumstances (70-95 ºC), 15.7 kJ/mol for raspberry pulp (Summen & Erge 2014) heated at 60-90 ºC, and lower than the value of 115.5 kJ/mole for orange juice (Johnson et al, 1995) but in good agreement with the activation energies (35.9-94.0 kJ/mol) for ascorbic acid degradation (Dhuique-Mayer et al, 2007;Lima et al, 2010).…”

Identification of roselle varieties through simple discriminating physicochemical characteristics using multivariate analysis

“…Ascorbic acid was assessed by HPLC according to Dhuique-Mayer et al (2007). A 10 g sample was weighed and homogenized with 40 mL of metaphosphoric acid solution at 45 g L -1 .…”

Thermal and mechanical properties of polyurethanes modified with L-ascorbic acid

“…Pharmaceutical supplements and products containing AA are often subjected to thermal treatment during preparation, processing, and storage [25][26][27][28][29]. In case of using AA as a polyurethane chain modifier, it would be also subjected to thermal treatment such as polyurethane synthesis and curing (both carried out at 80°C).…”

“…When 5 % v/w moisture was present in a solid ascorbic acid sample, the discoloration was observed, from white to dark brown [31]. Studies on decomposition kinetics of vitamin C in various food products under different storage and processing conditions revealed that decomposition of AA follows with first-order kinetics [25][26][27][28][29]. Jingyan et al also proposed the explanation of three indicated degradation stages of solid ascorbic acid.…”