Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2007
Publication Date: 4/22/2008
Citation: Davis, J.P., Dean, L.L., Faircloth, W.H., Sanders, T.H. 2008. Physical and Chemical Characterizations of Normal and High-Oleic Oils from Nine Commercial Cultivars of Peanut. Journal of the American Oil Chemists' Society. 85 (3) 235-243. Interpretive Summary: Viscosity is an important physical parameter central to the quality and hence value of vegetable oils. Depending on the application, either high or low viscosities can be desirable. Accordingly, this study surveyed oil viscosity (and density) as a function of temperature (5 to 100°C) for nine common cultivars of peanut to determine viscosity variation (if any). Significant differences (p<0.001) were observed in viscosity among cultivars, with differences being most prevalent at lower temperatures. Excellent correlations were seen among oil density and viscosity at all temperatures, specifically viscosity increased linearly (R squared > 0.95) with decreasing oil density. Viscosity and density data were strongly related to the fatty acid profiles of the various cultivars, meaning this information can be used to breed and/or process oils with specific viscosities and/or densities, ultimately improving the marketability of peanuts and other oilseeds.
Technical Abstract: Density and viscosity data as a function of temperature (5 to 100°C) were collected for oils (normal and high-oleic) from 9 cultivars of peanut. Density decreased linearly (R squared, greater than or equal to 0.99) with increasing temperature for all oils, whereas viscosity (dynamic or kinematic) decreased exponentially with increasing temperature. At any particular temperature, dynamic viscosity increased linearly (R squared, greater than or equal to 0.95) with decreasing oil density. Slopes of the linear fits (with units of kinematic viscosity) for dynamic viscosity vs. density plots increased in an exponential fashion as the measurement temperature decreased. High-oleic oils had both the lowest densities and highest viscosities, with viscosity differences being most apparent at cooler temperatures. Increasing contents of oleic acid, decreasing contents of linoleic acid, and decreasing contents of palmitic acid were each associated with decreased density and increased viscosity among the oils. Two of the 3 high-oleic oils had the significantly (p < 0.05) highest content of total tocopherols, while the other high-oleic oil was statistically grouped with the oils having the 2nd highest total tocopherol content. This suggests a link between increased total tocopherols and high-oleic peanut oils; however, no obvious linear correlations were observed in tocopherol content and oil physical properties (density or viscosity).