Effect of extraction methods on the stability of benniseed oil from Nigeria

Abstract

The effect of extraction methods on the stability of benniseed oil was investigated. The samples of the benniseed oil were extracted by three methods namely: solvent, mechanical press and vegetable oil expeller. The indicators of stability used were free fatty acids (FFA) and peroxide values (PV). The free fatty acid (FFA) expressed as percentage oleic acid were 2.42mg KOH/g, 3.06mg KOH/g and 6.02mg KOH/g for the oil expeller, mechanical press and solvent freshly extracted oil samples respectively. The corresponding peroxide values were 1.47mg eq/g, 2.14mg eq/g and 2.89mg eq/g. The FFA for the oils after 4 mon storage were 2.46mg KOH/g, 3.22mg KOH/g and 8.30mgKOH/g, while the PV were 2.09mg The eq/g, 3.44mg eq/g, 6.50mg eq/g for expeller, mechanical press and solvent extraction respectively. After 8 mon corresponding PV were 3.51mg eq/g, 6.65mg eq/g, and 9.13mg eq/g for expeller, mechanical press and solvent extraction methods respectively. After the storage of the oil samples for a period of 12 mon, the FFA values were 2.68mg KOH/g, 3.99mg KOH/g and 12.14mg KOH/g for the oil expeller, mechanical press and solvent extraction respectively. The peroxide values were 3.94mg eq/g, 7.68mg eq/g and 10.12mg eq/g. The result of the investigation has shown that benniseed oil, despite its inherent anti-oxidative properties, can undergo some degree of auto-oxidation, which is dependent on the extraction method. The expelled oil was more stable on storage while solvent extracted oil was the least stable. The FFA values were 2.55mg KOH/g, 3.52mg KOH/g, and 11.02mg KOH/g.

Keywords: Sesamum indicum, benniseed oil, storage stability; auto-oxidation, physicochemical properties

Nigerian Food Journal Vol. 23 2005: 121-127