Effects of Particle Size, Applied Pressure and Pressing Time on the Yield of Oil Expressed from Almond Seed
An investigation of the effects of particle size, applied pressure and pressing time on the yield of oil expressed from almond seeds was undertaken. The oil was expressed mechanically using a mini laboratory oil press. The fixed processing parameters were: moisture content of 17% wet basis, heating temperature of 65 - 70oC and heating time of 15 min. The pressing pressures used were 60.6 kPa, 101.3 kPa and 116.6 kPa. Pressing times used were 2, 4, 8 and 12 min, and particle size of Ö < 0.5 mm (fine sample) and Ö > 0.5 mm (coarse sample) were used. The result shows that oil yield increased with increase in applied pressure and pressing time, however result obtained from fine and coarse sample sizes are similar. Pressing time and applied pressure had significant (p < 0.05) difference on oil yield; particle size had no significant (p > 0.05) difference on oil yield. Regression and correlation analysis gave a reasonable experimental prediction between oil yield and applied pressure with correlation coefficient r = 0.952 and also with pressing time with r = 0.7342. Higher oil yields were obtained from samples with fine particles size (Ö < 0.5 mm) and coarse particles size (Ö > 0.5 mm) samples pressed at 116.6 kPa pressure for 12 min. Maximum oil yields of 48.44%
and 48.40% were obtained from coarse and fine samples respectively. The results obtained can be used in the design of a suitable process and machine for the expression of oil from almond seed.
Keywords: Almond oil, almond seed, applied pressure, particle size, pressing time.