Extração e caracterização do óleo das sementes do fruto da graviola (Annona muricata L.)

Abstract

The seeds of graviola (Annona muricata L.) fruits present considerable oil content and they are discarded directly after the process of the fruit processing, wasting their potential use as an energy source, pharmaceutical and bioinsecticide. The aim of the present work was to extract and characterize the seed’s oil of the graviola fruit to evaluate the efficiency of the mechanical extraction using a hydraulic piston press, from the extraction using the Soxhlet method using methanol and ethanol as solvents and to analyze the Physicochemical properties of the oil samples obtained by these methods. The seeds were exposed to the sun to dry for 30 days. For the analysis of moisture content, three fruits were purchased in the local market and their seeds were removed and put to dry in a drying scale. Under these conditions, the average moisture content of the seeds in natura was 27.87 ± 0.45%. The mechanical extraction process involved the use of 100 g of crushed seeds submitted for 90 minutes at pressures of 509, 610.8, 712.6 and 814.4 kgf/cm2 which extracted 4.28 ± 0.32%, 7.16 ± 0.61%, 10.92 ± 0.87 and 13.44 ± 1.18% oil respectively. The extraction by Soxhlet used Buchi extractor, model B-811, with methanol as solvent having efficiency of 18.12 ± 0.96% and 22.43 ± 1.77% for 4h and 6h of extraction respectively. With ethanol use the process efficiency was 25.35 ± 0.63% for 4h of extraction and 27.25 ± 0.23% for 6h. The physical-chemical characterization of the samples of cold extracted oil (P), methanol (SM) and ethanol (SE) showed: acidity index (mg KOH /g) of 4,10 ± 0,58 (P), 6.49 ± 0.08 (SM) and 6.49 ± 0.4 (SE); Iodine content (g I2 / 100 g oil) of 87.67 ± 0.71 (P), 82.19 ± 1.61 (SM) and 59.56 ± 3.22 (SE); Saponification index of 159.6 ± 0.58 (P), 162.27 ± 3.51 (SM) and 199.2 ± 3.00 (SE); Peroxide index (meq O2 / kg) of 8.66 ± 0.44 (P), 9.87 ± 0.01 (SM) and 9.82 ± 4.5 (SE); Density (g/cm3) at 20 °C of 0.9117 (P), 0.9262 (SM) and 0.9469 (SE), viscosity (mm2/ s) at 25 °C of 41.02±0,07 (P), 105.04±1,54 (SM) and 94.90±1,57 (SE); And refractive index of 1.468104 (P), 1.469098 (SM) and 1.461503 (SE). Eleven fatty acids were identified in the sample P, 9 in SM and 5 in SE. The presence of acetogenins in the 3 oil samples was observed using nuclear magnetic resonance.