Toasted yerba mate: Impact of drying methods on bioactive compounds, antioxidant capacity, and mate tea consumer acceptance

Abstract

This work investigates the consumer's acceptance of hot and iced mate tea, bioactive compounds content and antioxidant capacity of toasted yerba mate leaves dried from various processes, aiming at presenting drying alternatives to the traditional, and mostly used, methods. Therefore, five drying methods were tested, traditional rotary dryer, conveyor dryer and three alternatives including microwave oven, over dryer at 40, 60, 80℃ and freeze-drying, which was followed by toasting. Overall, the microwave oven and freeze dryer were highly efficient and can be considered as drying alternatives with high values of total phenolic compounds (78.72 mg GAE g−1), antioxidant capacity by DPPH/ABTS (376.6 TEAC µmol g−1/1062.04 TEAC µmol g−1), caffeine (13.25 mg g−1) and caffeoylquinic acids (69 mg g−1). Using a reworked python script, the preference map of teas dried in microwave oven and freeze-drying resulted in similar sensory acceptance for hot tea, produced using traditional drying methods, with a slight decrease for the iced tea. Novelty impact statement The tea industry can adopt microwave and freeze drying as alternative methods for drying mate leaves, this is followed by toast in order to obtain the commercial tea. These methodologies present smaller equipment sizes and removes the dangerous traditional process known as “zapeco”. The microwave and freeze drying have a small decrease in sensory acceptance compared to traditional methods used in agri-food industry but with high content of total phenolic compounds, caffeoylquinic acids and high antioxidant activities; also, in the case of microwaves, this method has the advantage of reducing the drying time.