Resumo

ORDONEZ-SANTOS, Luis Eduardo; OSPINA PORTILLA, María Alejandra  e  RODRIGUEZ RODRIGUEZ, Diana Ximena. Thermal degradation kinetics of vitamin C in guava fruits (Psidium guajava L.). Rev. Lasallista Investig. [online]. 2013, vol.10, n.2, pp.44-51. ISSN 1794-4449.

Abstract Introduction. Vitamin C is an essential micro nutrient in human nutrition because it is associated to the synthesis of different molecules that are important for human health and to its antioxidant effect which reduces the risk of having several types of cancer, according to many epidemiological studies. Its final concentration is considered as an indicator of nutritional quality during the food processing and storage. Objective. Evaluate the thermal degradation kinetics of vitamin C in guava fruits, within a temperature range between 75-95 °C. Materials and methods. 0,53 cm thick x 6.10 cm diameter guava slices were subjected to thermal treatments (75, 85 and 95 °C during 10, 20, 30 and 40 minutes) in a jacketed kettle at atmospheric pressure. The vitamin C concentration in the samples before and after the thermal treatment were determined by the use of the 2,6 - dichlorophenol-indophenol method. Results. After the thermal treatments (75-95 °C), the vitamin C concentration in the guava fruits was reduced in percentages between 56,70-60 %, and its degradation speed and activation energy were k = 0,80-1,45 min^-1 (R² > 0,90), and E_a = 7,57 Kcal/ mol, respectively. Conclusion. The concentration of vitamin C measured in the guava fruits after the thermal treatments had a reduction as temperature increased and the time of the process and the kinetic parameters of this antioxidant were adjusted to first order kinetics and to the Arrhenius equation.

Palavras-chave : ascorbic acid; bioactive; CIE_Lab; soluble solids; pH.

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