Physicochemical Properties of Nutmeg Oleoresin Obtained by Ultrasound-Assisted Extraction from Different Raw Material Qualities and Drying Methods

Oleoresin is one of the processed nutmeg products that become the potential agro-industrial export product for Indonesia. The main problems of oleoresin production are the quality diversities of nutmeg as the raw materials because of the improper and inadequate drying process. Ultrasound-assisted extraction (UAE) has recently proposed to shorten the extraction time, increase recovery yield, and also improve oleoresin quality. This study aims to determine the effect of the raw material qualities and drying methods on the yield and physicochemical properties of the nutmeg oleoresin obtained by UAE. Nutmeg was dried with two drying methods (smoked drying and sun-drying) and graded into two kinds of nutmeg quality (grade 1 and 2), then ground into the particle size of 60 mesh. UAE was applied on nutmeg powders with ethanol solvent (1:4 w:v) at 20 kHz frequency, 700 W power, 90% amplitude, at 50oC maximum temperature, and 45 minutes of extraction time. Maceration was carried out as the control treatment by 7 hours of extraction time at room temperature. The raw material qualities and drying methods produced oleoresin obtained by UAE with yield, and physicochemical properties (specific gravity, refractive index, and non-volatile content) were statistically different among treatments. The nutmeg oleoresin obtained by UAE from grade 1 and smoked drying has the highest yield (23.63%) and the lowest non-volatile content (35.54%). The volatile compound as identified by GCMS with 35 total compounds by representing 93.18% of the volatiles where isocoumarin (20.30%), myristic acid (16.81%), myristicin (14.76%), dehydrodiisoeugenol (11.11%) dominated