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

ABSTRACT 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 Agrícola of the Universidade Federal de Viçosa, Viçosa, MG, Brazil (20° 46’ 13.5” S; 42° 52’ 23.3” W, and altitude of 645 m) in October and November 2017. The experiment was conducted by using a 3 × 4 factorial scheme including three drying temperatures at 50, 60 and 70 °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 °C and drying with the 20/10 intermittent ratio at 60 °C. The results indicate that intermittent drying at 50 °C is not recommended to preserve essential oil yields.

摘要
本研究探究了带间歇比例的干燥方式对丁香罗勒（Ocimum gratissimum L.）叶片有效干燥时间、比能耗及精油得率的影响。本干燥试验于2017年10月至11月在巴西米纳斯吉拉斯州维索萨市维索萨联邦大学农业工程系药用、芳香及调味作物采后实验室开展，试验地点坐标为南纬20°46′13.5″、西经42°52′23.3″，海拔645米。本试验采用3×4析因设计，设置50、60、70℃共3个干燥温度，以及4种干燥工艺：连续干燥，以及分钟级的3种间歇干燥/暂歇比例：10/20、15/15与20/10。试验设计为完全随机设计，设置3次重复。采用10/20间歇比例可缩短有效干燥时间并降低比能耗。就精油得率而言，采用间歇干燥在不同干燥温度下呈现出不同结果：50℃连续干燥与60℃下采用20/10间歇比例干燥的精油得率最高。研究结果表明，为保留精油得率，不建议采用50℃的间歇干燥工艺。