Characterization of domestic onion wastes and bulb (Allium cepa L.): fatty acids and metal contents.

Abstract

Different parts of onion bulb that constitute to waste were characterized for their nutritive value using standard methods. Proximate analysis of the samples revealed that protein (8.76%) and ash (11.46%) was highest in top-bottom part, carbohydrate (66.12%) in outer scale, fat (15.71%) and fiber (26.84%) was highest in outer scale part while highest amount of moisture (9.21%) was reported in top-bottom part. X-ray spectrometry revealed that the outer scale had the highest level of calcium (3.05%) followed by the onion bulb (2.98%) and least in the top-bottom part (2.08%). Gas chromatographic analysis of the extracted oil revealed that the oil from the outer scale part has the highest percentage of linoleic acid, 52.87%. The iodine value of the bulb oil, top-bottom oil and the outer scale oil were 143.35, 142.08 and 189.52 respectively. The properties of different parts of onion that go to waste revealed that they could be dietary sources of nutritive elements and essential fatty acids.