OPTIMIZATION OF GINGEROLS EXTRACTION KINETICS TOTAL OF GINGER USING POWER ULTRASOUND AS PRE-TREATMENT

Zingiber officinale Roscoe (Zingiberaceae) is a rhizome that has been widely used in the food and pharmaceutical industry due to its characteristic pungent flavor and nutraceutical properties. These characteristics are due to the presence of gingerols, among them are 6-gingerol, 8-gingerol, and 10-gingerol. The 6-gingerol compound represents the total gingerols because it has a higher proportion when compared to the others. Therefore, this work aimed to study the optimization of the kinetics of total gingerol extraction using power ultrasound as pretreatment. In the preparation of the raw material, the rhizome fresh went through the process of visual inspection, cutting, drying at 40°C, grinding in a rotor mill, and sieving with a 2mm granulometry. The extraction was performed with 80 g of dry ginger and 2000 ml of 95% ethyl alcohol (1:25 (w/v)) at 40°C for 48h with 32 different times. Two studies were carried out, the control with conventional extraction and the pre-treated with the application of power ultrasound for 60 minutes. The power ultrasound is of the UP400S probe type (model H22L2D, Hielscher Ultrasonics GmbH, Germany), with a nominal power of 200 Watts and a continuous system of dispersion of the ultrasonic waves in the axial direction by the probe tip. After extraction, the extract was filtered with filter paper and the solvent evaporated under vacuum in a rotary evaporator at 40ºC. The determination of the total gingerol content was performed by a spectrophotometer (Biospectro, SP22, São Paulo) at 280 nm. The reagent 6-gingerol was used to construct the standard curve, obtaining a coefficient of determination >0.99. The two treatments showed differences (p<0.05) in extraction kinetics ranging from 4.880 to 59.042 and from 2.614 to 71.266 mg of gingerols/g of dry ginger, for the conventional treatment and the pre-treated with ultrasound, respectively. The increase in extraction with ultrasonic pretreatment is due to the phenomena of cavitation and sponge effect, causing changes in the matrix, such as cell rupture, increasing the contact surface between the raw material and the solvent. The highest levels of total gingerols were observed from 18 to 30 hours during conventional extraction, with no significant difference (p<0.05) in this period. As for the extraction with ultrasound pretreatment, the highest levels of total gingerols were observed in the period from 16 to 30 hours, with no significant difference (p<0.05) in this period. Therefore, the shortest time for higher levels of total gingerols was 18 and 16 hours for the conventional and pre-treated processes, respectively. Long extraction periods from 30 hours promoted the degradation of total gingerols in both processes, due to high temperature, light exposure and the presence of oxygen. With this, it is concluded that the pre-treatment with ultrasound application in the extraction of total gingerols promotes greater extraction in less time, resulting in the optimization of the process.