Influência dos tratamentos banho de ultrassom e secagem com descanso no rendimento e composição do óleo essencial de Alfavaca (Ocimum gratissimum L.)

Abstract

Medicinal, spicy, and aromatic plants comprise several species that may present therapeutic actions, preservatives in food, and flavorings due to the presence of active compounds. Alfavaca (Ocimum gratissimum L.) is a widely used plant and has industrial interest due to the concentration of essential oil. This raw material can be stored for extended periods, and generally, the drying treatment is applied, which, if properly used can provide safe storage and quality preservation. To promote the reduction of drying time and enhance quality preservation, ultrasound bath treatment can be adopted before drying treatment, as well as resting insertion during drying. Ultrasound bath treatment leads to disruption of histological structures of plant tissues which brings benefits to the increase of the drying rate and minimization of volatile loss. During rest-periods, the goal is to use the thermal load contained in the product to promote the vaporization and migration of water molecules from the innermost parts to the outermost parts, which may increase the drying rate. Thus, in this study, the objective was to optimize the drying process by minimizing drying time and maximizing the essential oil yield of Ocimum gratissimum L. Sand a Central Composite Rotational Design (CCRD) effects of the following factors duration of the ultrasound bath, drying air temperature, rest insertion time, and duration of rest which led to the organization of 17 treatments. The mathematical model that best described drying kinetics was Midilli. Within the experimental region evaluated, the optimum point was for the drying time of 72.87 min (1.21 h) and essential oil yield equal to 1.22%. This situation occurred for bath duration equal to 13 min, drying air temperature of 54 ºC, rest-period insertion time of 36.5 min, and rest-period duration of 21.5 min. The main substances found were Eugenol (54.7 – 80.1%), β-Ocimene (8.1 – 20.8%), Germacrene D (2.2 – 6.5%), and E-Cariofilene (1.6 – 4.5%).