Intermittent drying of clove basil leaves: Process optimization and essential oil yield

This study investigated the effect of a drying method with intermittent ratios on the effective drying time, specific energy consumption and essential oil yield of clove basil (Ocimum gratissimum L.) leaves. The drying tests were conducted at the Postharvest Laboratory of Medicinal, Aromatic and Condiment Plants, from the Departamento de Engenharia Agricola of the Universidade Federal de Vicosa, Vicosa, MG, Brazil (20 degrees 46' 13.5 '' S; 42 degrees 52' 23.3 '' W, and altitude of 645 m) in October and November 2017. The experiment was conducted by using a 3 x 4 factorial scheme including three drying temperatures at 50, 60 and 70 degrees C, with four drying processes: continuous drying and the following three intermittent drying/tempering ratios in minutes: 10/20, 15/15 and 20/10. The design was completely randomized and with three repetitions. The application of the 10/20 intermittent ratio reduced the effective drying time and the specific energy consumption. Regarding the essential oil yield, the use of the intermittence presented different results for each temperature of drying; the highest yields were observed with continuous drying at 50 degrees C and drying with the 20/10 intermittent ratio at 60 degrees C. The results indicate that intermittent drying at 50 degrees C is not recommended to preserve essential oil yields.