Abstract

Influence of various extraction techniques (solvent-solvent, cold maceration and soxhlet extraction) on the mineral content and antioxidant capacity of ginger oil was investigated. The minerals determined were magnesium, manganese, zinc, iron, calcium, potassium, sodium and phosphorus. Flavonoid and phenolic contents were determined alongside the antioxidant capacity of the oils which was assayed using DPPH radical scavenging activity and total reducing power. Extracted oil showed strong characteristic pungent gingerly odor and was liquids at room temperature. Highest oil yield was obtained by soxhlet extraction technique (8.04± 0.04%); followed by cold maceration technique (5.30±0.03%) and the lowest by solvent-solvent extraction technique (4.83±0.08%). The results of the mineral analysis showed that oil obtained by soxhlet extraction technique had the highest concentration of all minerals determined, except manganese (3.80±0.01 mg/100g) which was highest in the oil obtained by cold maceration. The oil obtained by solvent-solvent extraction showed lowest concentration of all minerals determined, except calcium (1.08±0.10mg/100g) and zinc (0.63±0.11mg/100g) which were lowest in oil obtained by cold maceration. However, the concentration of phosphorus was highest in all the oils when compared with other minerals. Oil obtained by soxhlet extraction showed the highest concentration of flavonoids (118.00±1.00mgQE/g) and phenolics (217.33±1.53 mgGAE/g) as well as the highest average DPPH radical scavenging capacity (55.56±0.04%) and average total reducing power (0.88±0.002) while the least concentration of flavonoids (44.45±2.97 mgQE/g), phenolics (112.43±1.42 mgGAE/g), average DPPH radical scavenging capability (19.73±0.01%) and average total reducing power (0.55±0.030) were obtained for the oil obtained by solvent-solvent extraction technique. The results showed that heat and reflux condition involved in the soxhlet extraction technique enhanced the extraction of minerals and phytochemicals from ginger rhizome and also enhanced the antioxidant capacity of ginger rhizome oil.