Effect of gamma irradiation and cooking on the physico-chemical properties, nutrients, and anti-nutrients compositions of egusi melon (Citrullus vulgaris) seeds

The effect of gamma irradiation and cooking on the physico-chemical and functional properties of "egusi" melon as well as its impact on quality attributes of the oil were investigated. The seeds of "egusi" melon were divided into five portions. One part was cooked, one irradiated at 5KGy, another was irradiated at 10KGy, and one part was cooked and irradiated at 10KGy as a double treatment method. The last part was left as is (raw) for reference. Irradiation was done using Cobalt-60 as gamma radiation source. Proximate compositions, mineral contents, amino acid contents, oil quality attributes, as well as anti-nutritional factors were determined for all samples using standard methods. Results revealed that gamma irradiation caused a decrease in values of moisture from the raw sample (5.80) with cooked, 10KGy and 5KGy irradiated samples of "egusi" melon showing reduced moisture contents of 4.27, 4.27 and 4.14% respectively. Protein decreased from 32.20% in raw "egusi" melon seeds to 29.77% and 29.47% in the 10KGy and 5KGy irradiated samples respectively. Mineral content of "egusi" melon seeds were affected by irradiation at 10 and 5kGy where the values of potassium increased from 14.93 in the raw to 20.88 in the 10KGy irradiated and 22.83 in the 5KGy irradiated samples. For the quality attributes of "egusi" melon oil, gamma irradiation caused significant decrease (P=0.05) in iodine value and significant increase in acid and peroxide values. The treatments had profound effects on the Amino Acid Contents of "egusi" melon. Cooking increased the level of amino acids except for glutamic acid which decreased from 14.26 to 13.63 when cooked. Irradiation also had this effect, increasing in all but glutamic acid (14.26 to 13.83) but the combined treatment (cooking and Irradiation) showed an increase in glutamic acid content. Lysine, Histidine, Valine, and Leucine decreased when subjected to the combined treatment. The study showed that irradiation only caused little changes in the nutrient composition of "egusi" melon at low dosage highlighting its potential as a preservation and disinfection treatment for "egusi" melon.