Recovered lipids from prickly pear [Opuntia ficus-indica (L.) Mill] peel: a good source of polyunsaturated fatty acids, natural antioxidant vitamins and sterols

Compositions and concentrations of fatty acids, lipid classes, sterols, fat-soluble vitamins and β-carotene were determined in extracted lipids from prickly pear [Opuntia ficus-indica (L.) Mill] peel. Total lipids (TL) recovered were found to be 36.8 g kg−1 (on dry weight basis). The level of neutral lipids was the highest, followed by glycolipids and phospholipids, respectively. Among the TL, linoleic acid was the dominating fatty acid, while oleic and palmitic acids were estimated to be in relatively equal amounts. Compared with the neutral lipids, the polar fractions were generally characterised by higher percentages of saturated fatty acids and lower percentages of unsaturated fatty acids in all subclasses. Concerning trienes, γ-linolenic acid was present at 8.60% of TL, while α-linolenic acid was present at 0.69%. Recovered lipids were characterised by a high percentage of unsaponifiables (12.8% TL) and found to be a rich source of vitamin E and sterols. Free sterols accounted for ca. 29% of the total unsaponifiables, wherein β-sitosterol and campesterol were the major sterols. In terms of vitamin E, α-tocopherol constitutes about 80.0% of total vitamin E present, the rest being β-, γ- and δ-tocopherols in decreasing order. Moreover, lipids under investigation were characterised by a high levels of β-carotene and vitamin K1. The information obtained in the present investigation is useful for characterising lipid of prickly pear peel and further chemical and nutritional investigations of prickly pear peel. The results are also important for industrial utilisation of the major by-product of the fruit.