Effects of drying methods on properties of watermelon (Citrullus lanatus) seed oil.

Abstract

An experiment to investigate the effect that different drying methods would have on the quality and quantity of oil from water melon (Citrilus lanatus) seeds was conducted. The water melon seeds were removed from the pod and washed. The sample was weighed and divided into two equal parts; one part was subjected to sun drying while the other part was subjected to oven drying (at a temperature of 30oC). Drying by sun as expected was gradual as compared to the oven drying method which was faster and more rapid. The dried seeds (sun-dried or oven-dried) were de-husked, dry-milled into fine crumbs using hand milling machine. The powdered product from the mill was then subjected to oil extraction using hexane as solvent. Results show that there was no significant difference in the quantity of oil obtained from either of the samples. The sun-dried sample yielded 56% of oil/100g of seeds, compared to the oven-dried samples which yielded 57% of oil/100g of seeds. However, it was observed that Free Fatty Acid (FFA) and Acid values were higher in oven-dried sample relative to the sun-dried sample; whereas other chemical properties were not affected. Free Fatty Acid value for the oven-dried sample was 6.4% and 2.4% for the sun-dried sample. This is an important variable in considering the quality of oil because the lower the FFA, the better the quality of the oil. Analysis also revealed that the properties of oil extracted from both samples fall within that of non-drying oil. Crude protein in the seed was 26 % which compared favourably with high protein seeds and nuts like cowpea (22.7%) soybeans (35%). This implies that the oil samples are edible to humans. The high protein content of the seed coupled with a fairly high concentration distribution of the Amino acids makes the seed suitable for fortification of foods while the oils can serve as a good supplement in animal feed formulation. Oil from the sun-dried sample will however be preferable because of its low acid value though the extracted oil from the two samples still needs to be refined. Meanwhile, the oil samples may not be used as alkyl resin for manufacturing of paints or bar soap due to their low saponification values. Large quantity of potassium hydroxide will certainly be required to prepare soap from these oils. Keywords: Sun-dried, Oven-dried, Watermelon, Seeds AJFAND Vol. 8 (4) 2008: pp. 493-501