Evaluation of Processing Factors in Screw Expeller and Comparison With Other Extraction Methods of Ethiopian Shea (Vitlleria Paradoxa) Butter

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Addis Ababa University


Shea butter is a versatile plant fat extracted from kernels of Shea nuts, seeds of Shea trees (Vitellaria paradoxa). Shea butter has long been used in Gambella, Ethiopia and other part of Sub-Saharan region, Africa. It has been used for food, medicinal, and cosmetics applications. In the manufacture of chocolate Shea butter used as cocoa butter equivalent or replacer also as ingredient in cosmetics. The nutritional composition, physicochemical property and fatty acid profiles of Shea butter depend on pretreatment and extraction method. Thus, the objective of this work was to evaluate the effect of processing factors in screw expeller; and different extraction methods (screw expeller, solvent, combined and manual pressing) on nutritional composition, physicochemical properties and fatty acid profiles of Shea butter (Vitellaria paradoxa) subspecies nilotica from Phugnido district Gambella, Ethiopia. The combined effects of conditioning time (CT), kernel moisture content (MC) and pressing temperature (PT) in screw expeller were investigated by a 33 full factorial design combined with response surface methodology, selecting the butter yield, fines content in butter (foot), minerals and butter quality (refractive index, acidity, peroxide value) as the response variables. The model enabled to identify the optimum operating settings for maximize butter yield, under which it predicted 42.1 g/100 g d.w yield and 83.13 % extraction efficiency. Conformation run was conducted to affirm the predicted values and the resulted butter was used for quality comparison with other extraction methods. In the comparison among extraction methods, specific gravity (0.8881 – 0.9046), viscosity (25.63 – 55.10), refractive index (1.4666 – 1.4676), melting point (35.33 – 36.33 oC), acid value (1.5 – 2.6 mg KOH/g), peroxide value (3.7 – 49.4 mEq/kg), iodine value (53.03 – 57.74 g I2/100 g), saponification value (194.40 – 206.74 mg KOH/g), unsaponifiable matter (3.27 – 3.75 %) and oxidative stability index (2.3 – 12.27 hr) show significant variation (P < 0.05). Moreover, color values lightness (60.48 – 65.78), greenness (-5.64 – -3.30) and yellowness (17.71 – 19.62) show significant difference (P < 0.05). In contrast, fatty acid profiles palmatic acid (3.5 – 2.6 %), steric acid (40.5 – 36.3 %), oleic acid (55.0 – 54.3 %), linoleic acid (1.2 – 1.3 %) and linolenic acid (0.5 – 0.3 %) did not show significant (P < 0.05) difference except steric acid in manually pressed butter. Hence, quality parameters which showed the highest variation like acid value, peroxide values and oil stability index need to be controlled for consistent butter quality. Generally, Shea butter from screw expeller was superior in quality. Whereas, combined method was favorable from yield and butter quality perspective. Keywords: Conditioning time; Fatty acids profile; Nilotica; Characterization; Screw expeller; Shea butter; Pressing temperature; Vitellaria paradoxa.



Conditioning time, Fatty acids profile, Nilotica, Characterization, Screw expeller, Shea butter, Pressing temperature, Vitellaria paradoxa