Mechanical expression of oil from melon seeds

Abstract

Investigations were conducted on the mechanical expression of oil from melon seeds ( Citrullus vulgaris ) in a laboratory press. The processing variables were particle size, moisture content, heating temperature and heating time. Physical properties such as colour, specific gravity, refractive index and viscosity were determined. Coarsely ground samples gave consistently lower yields of oil than finely ground samples. The oil yield was affected by the seed moisture content, heating temperature and heating time. The oil yield was however, mostly dependent on the amount of moisture reduction achieved during heating. Highest oil yields of about 41% were obtained, at an expression pressure of 25 MPa, when samples conditioned to initial moisture contents of 9 and 12% (wet basis) were heated to achieve a moisture content reduction of about 5%. This yield corresponds to an expression efficiency of about 80% when compared to melon oil content of 51%. Further reduction in moisture content did not increase oil yield from the samples. Melon oil was found to have a pale yellow colour, refractive index of 1.468, specific gravity of 0.918 and viscosity of 50.1 × 10 −3 kg m −1 s −1 . These properties were not affected by processing conditions.