Thermal Degradation of Carotenoids from Jambu Leaves (Acmella oleracea) during Convective Drying

Abstract

Jambu (Acmella oleracea) is a vegetable used in human food. Drying is an alternative to increase the shelf life of the product. High temperatures can induce the degradation of carotenoids and reduce the health benefits of these compounds. This study investigated the effect of the Jambu leaves’ drying temperature on the carotenoid composition. It was performed previously by screening 16 plants from different localities based on the total carotenoid content. The process of drying by convection was carried out at temperatures of 35, 40, 50, and 60 °C in an air circulation oven, at an air velocity of 1.4 m/s−1 and a processing time of ~20 h. The drying data were fitted to six mathematical models and the quantification of the carotenoid retention was determined by HPLC-DAD. The study demonstrates that the carotenoid content among the samples collected from the 16 producers varied by 72% (lower—175 ± 16 μg/g, higher—618 ± 46 μg/g). Among the models, the Page model was found to be the most suitable model to explain the variation of the experimental data. The drying process at 40 °C reduces the Jambu leaves’ carotenoid content significantly (p < 0.05) (All-trans-β-carotene—86 ± 2 μg/g, All-trans-lutein—141 ± 0.2 μg/g) but does not alter the carotenoid profile. The occurrence of similar reduction behavior was observed for the different carotenoids at all the temperatures studied. The drying process at 35 °C was the condition that ensured the highest retention of carotenoids, and also a product classified as a very high source of carotenoids (total carotenoids—748 ± 27 μg/g, vitamin A—17 ± 1 μg RAE/g). Thus, this study concludes that a temperature of 35 °C for 14 h (air velocity—1.4 m/s−1) is the best drying condition for Jambu leaves using a low-cost dryer and as a possibility for the preservation and marketing of this Amazonian raw material.