Characterization and storage stability study of alibambang seed oil (Bauhinia purpurea L.)

The seeds of alibambang (Bauhinia purpurea L.) were analyzed to determine its proximate and mineral composition. Alibambang seed was found to contain 23.36 percent crude fat, 32.62 percent crude protein, 6.60 percent crude fiber, 29.56 nitrogen free extract, and 516.80 cal/100 g gross energy on a dry matter basis. Mineral analysis of alibambang seeds contained relatively high levels of calcium (12.60 g/kg DMB) and iron (61.33 mg/kg DMB). Defatted alibambang seed showed high levels of crude protein and carbohydrates which could be possibly used as animal feed ingredient. Alibambang seed oil was extracted using petroleium ether which had a recovery of 20.82 percent. The oil was golden yellow in color with a Lovibond tintnometer reading of 23R/15Y. The treatment of the oil with activated carbon made the color lighter (1R/27Y). The physico-chemical characteristics of the freshly extracted oil were as follows: specific gravity, 0.868, refractive index, 1.4533; iodine number, 80 mg I2/100 g oil; saponification number, 153 mg/g oil; peroxide value, 5.31 meq/kg oil; free fatty acid number, 0.67 mg/g oil; and unsaponifiable matter, 1.2 g/100 g. These values are comparable with those obtained by Billena (1999). HPLC analysis of the extracted oil showed moderate amonts of - tocopherol (160.1 microgram/g) and Beta-carotene (49.3 microgram/100 g) which were responsible for its golded yellow color. GLC analysis of the fatty acid methyl esters of alibambang seed oil showed the predominance of linoleic acid (52.86 percent) and palmitic acid (21.59 percent). The stability of the oil on storage at different conditions revealed that the oil was more susceptible to oxidative rancidity which is attributed to its high content of unsaturated fatty acids. Statistical analysis showed that the rate of oxidation was faster at room temperature than at 4 deg C with or without purging with nitrogen gas. The physicochemical characteristics of the oil such as peroxide value changed markedly while iodine number specific gravity and saponification number showed only slight variations after storage for six weeks.