Physico-chemical characteristics of citrus seeds and seed oils from Pakistan

The physico-chemical characteristics of the seeds and seed oils of four citrus species, Mitha (Citrus limetta), Grapefruit (Citrus paradisi), Mussami (Citrus sinensis), and Kinnow (Citrus reticulata) were investigated. The hexane-extracted oil content of citrus seeds ranged from 27.0 to 36.5%. The protein, fiber and ash contents were found to be 3.9-9.6%, 5.0-8.5%, and 4.6-5.6%, respectively. The extracted oils exhibited an iodine value of 99.9-110.0; refractive index (40 degrees C), 1.4639-1.4670; density (24 degrees C), 0.920-0.941 mg/mL; saponification value, 180.9-198.9; unsaponifiable matter, 0.3-0.5%; acid value (mg KOH/g of oil), 0.5-2.2 and color (1-in. cell) 1.4-3.0R + 15.0-30.0Y. The oils revealed a good oxidative stability as indicated by the determinations of specific extinctions at 232 and 270 nm (2.3-4.4 and 0.6-0.9, respectively), p-anisidine value (2.2-3.2) and peroxide value (1.6-2.4 mequiv/kg of oil). The citrus seed oils mainly consisted of linoleic acid (36.1-39.8%). Other prominent fatty acids were palmitic acid (25.8-32.2%), oleic acid (21.9-24.1%), linolenic acid (3.4-4.4%), and stearic acid (2.8-4.4%). The contents of tocopherols (alpha, gamma, and delta) in the oil were 26.4-557.8, 27.7-84.1, and 9.1-20.0 mg/kg, respectively. The results of the present study demonstrated that the seeds of citrus species investigated are a potential source of valuable oil which might be utilized for edible and other industrial applications.