Physicochemical Characterisation, and Antioxidant Properties of the Seeds and Oils of Ginger (Zingiber Officinale) and Garlic (Allium Sativum)

Abstract

Ginger (Zingiber officinale) and garlic (Allium sativum) were characterized with respect to their proximate composition, energy value, mineral content, anti-nutrient constituents, functional and antioxidants properties. Their seed oils were also extracted and characterised with respect to their physicochemical properties and fatty acid profiles. The crude protein (CP), crude fibre(CF), ether extract (EE), ash and gross energy of ginger averaged 7.8, 6.2, 11.0, 9.0 g/100gDM and 385.6 kcal/100g respectively. The corresponding values for garlic were 27.7, 1.0, 2.5, 1.5 g/100gDM and 411.3 kcal/100g. K was the most abundant mineral followed by Mg, Na and Ca. Among the trace minerals, Mn was the most abundant and Zn, the least. A similar trend was found in garlic. The mean value for water absorption capacity (WAC) and oil absorption capacity(OAC) in ginger(410.0, 407.3%) respectively were lower than those of garlic (580.0, 630.9 %) while the foaming stability and emulsion stability(43.7 and 48.0%) were higher. Mean phytate and phytin-P content in ginger (27.1 & 7.6mg/g) were similar to those of garlic ( 23.7 & 6.7mg/g) respectively while the polyphenols (as tannic acid equivalent) and oxalate levels in ginger were generally lower than in garlic as indicated by very high CV(%) ranging from 139.3 to 118.4%. Diethylether extracted oils from ginger had acid value(%), free fatty acid(%), saponification value (mmKOH/g), peroxide value (mmKOH/g) and iodine value(Wij’s) of 4.1, 2.1, 90.9 2.31 and 17.1 respectively. The corresponding values for garlic were 2.8%, 1.4%, 92.1mmKOH/g, 5.8mmKOH/g and 10.9 Wij’s, respectively.The thin layer Gas chromatographic analysis of the seed oils revealed the presence of fatty acids varying from C2 to C18 with concentrations of individual fatty acids varying from 0.30 to 1.6%. Oleic, stearic, palmitic and lauric acids were the principal fatty acids contributing to 1.43, 1.5, 1.3 and 1.0% respectively in ginger while the corresponding values in garlic were 1.5, 1.6, 1.4 and 1.1%, respectively. Antioxidant potentials measured as total phenol g/100g, reducing power (OD700) and free radical scavenging ability(%) were higher in ginger(3.6, 1.0,14.4; respectively than in garlic (2.9,0.7,13.1).