Characterization of seed oils from different varieties of watermelon [Citrullus lanatus (Thunb.)] from Pakistan

Abstract

This paper reports the physicochemical characteristics of the seed oils from different varieties of watermelon (Citrullus lanatus) cultivated in Pakistan, namely Sugar Baby, Q-F-12, D-W-H-21 and Red Circle-1885. The oil and crude protein contents from watermelon seeds, within the range of 28.25 to 35.65% and 20.50 to 35.00%, respectively, varied significantly (p < 0.05) among the varieties tested. The levels of moisture, ash, and crude fiber in the seeds tested were found to be 2.16-3.24%, 1.95-3.42% and 4.29-6.60%, respectively. The physicohemical characteristics of the extracted oils were: free fatty acid contents (1.17-2.10% as oleic acid), iodine value (97.10-116.32 g of I2 100g^-1 of oil), saponification index (190.20-205.57 mg KOH g^-1 of oil), unsaponifiable matter (0.54-0.82%) and color (1.12-4.30 R + 12.20-33.40 Y). The oils revealed a reasonable oxidative parameter range as depicted by the determinations of specific extinction at 232 and 270 nm (2.90-4.40 and 2.05- 3.09, respectively), p-anisidine value (5.60-7.70) and peroxide value (2.90-5.06 meqO₂ kg^-1 of oil). Linoleic acid was the major fatty acid found in all the seed oils with contributions of 45.30-51.80% of the total fatty acids (FA). Other fatty acids detected were known to be oleic acid (20.2- 23.5%), palmitic acid (15.1-16.9%) and stearic acid (11.5- 14.4%). The contents of α- and δ-tocopherol in the oils accounted for 120.6-195.6 and 9.1-58.3 mg kg^-1, respectively. The physicochemical attributes of the watermelon seed oils showed a wider variation among the varieties tested. The results of the present study indicate that the seeds of the tested watermelon varieties from Pakistan are a potential source of high-linoleic oil and thus can be explored for commercial use and value addition.