| Popis: |
The present study aimed to evaluate the efficiency of pressurized liquid extraction (PLE) in obtaining steviol glycosides, natural sweeteners, from Stevia rebaudiana leaves. The extractions were conducted in an experimental apparatus operated in semicontinuous mode with fixed temperature, pressure and time at 120 ºC, 100 bar and 60 min, respectively, evaluating the effects of solvent to sample ratio (30 to 90 mL/g), concentration of ethanol in the extractor solvent (100 and 70 % v/v) for leaves with and without pretreatment. The results obtained were compared with the ultrasound-assisted extraction (UAE) conducted at 50 ºC, 60 min and solvent to sample ratio of 10 mL/g. Under pressurized conditions, the results showed greater extraction of sweeteners when pretreated leaves were used, reaching a yield of 70.94 ± 0.83%, which was higher than that obtained with the leaf without pretreatment (59.85 ± 1.14%). Increasing the solvent to sample ratio from 30 mL/g to 90 mL/g did not promote greater extraction in sweeteners from pretreated leaves (75.05 ± 1.89%), demonstrating that an excess of solvent in the medium does not result in higher yields. In parallel, little solvent (10 mL/g) did not contribute to obtaining sweeteners via UAE, promoting a yield of 46.78 ± 0.31%. The contents of sweeteners and mass obtained by PLE were about ~ 65% and ~ 55 % higher when compared to those obtained from UAE, respectively. The best results for sweeteners extraction (76.97 ± 2.70%) were obtained using pretreated leaves, at 30 mL/g and with 70% ethanol. |
