This study evaluated the effect of thermal treatment on the total carotenoid concentration, the carotenoid profile (lutein, zeaxanthin, β-cryptoxanthin and β-carotene), total phenolic compound content, ascorbic acid content and antioxidant capacity of Murcott Tangerine juice. Using a tubular heat exchanger eleven treatments were evaluated based on a full 2² factorial design with three replicates at the central point, four axial points and a region of observation from 88 to 100 ºC and from 16 to 44 s. The total carotenoid content decreased significantly in almost all treatments when compared with the results obtained for the fresh juice. The carotenoid levels (lutein, zeaxanthin and β-cryptoxanthin) were not significantly reduced by most of the treatments studied, and the β-carotene content was not significantly changed by any treatment. For the carotenoid contents, the analysis of variance showed no significant interactions between the variables of temperature and time. The levels of ascorbic acid and total phenolic compounds decreased in six of the conditions evaluated, while in four treatments an increase in the total phenolic compounds was observed, probably due to evaporation of water from the juice. The greatest reduction and the greatest increase of, respectively, ascorbic acid and total phenolic compounds were observed for the binomial of 100 ºC/30 s. The ascorbic acid content was significantly influenced by the temperature, and its degradation process can be described using a quadratic model. All the treatments applied reduced the antioxidant capacity of the juice, but the reduction was higher for the binomial 100 ºC/30 s. The nutritional characteristics of the juice were little affected by the changes observed, and the heat treatments carried out at 94 ºC for 16 to 44 s allowed for the smallest changes and/or the highest retentions of the determined compounds.
Citrus; Murcott tangerine; Juice; Thermal treatment; Antioxidant capacity
