Impact of air-drying temperature on nutritional properties, total phenolic content and antioxidant capacity of quinoa seeds (Chenopodium quinoa Willd.)

Abstract

Quinoa has gained an increasing interest in recent years due to its nutritional value (rich in protein, fat, dietary fibre, ash, carbohydrates and minerals). Furthermore, it is an excellent source of natural antioxidants such as vitamin E and other phytochemicals. Dehydration of quinoa between 40 and 80C was performed in order to evaluate the effect of air-drying temperature on these quality attributes. When comparing the fresh with the corresponding dehydrated quinoa samples, it was shown that the drying operation led to reductions of 10% in proteins, 12% in fat and 27% in both fibres and ashes. In fresh quinoa, potassium and copper were found to be the most and least abundant minerals, respectively. Sucrose was the predominant sugar, followed by fructose and glucose. Overall antioxidant activity was affected by drying temperatures. Thermal degradation, especially at 60, 70 and 80 ºC, resulted in a notable reduction in TPC. However, Vitamin E showed an important increase at 70 and 80 ºC. The antioxidant capacity presented similar values at 40, 50 and 80 °C due to temperature/drying time equivalent processes.