Effect of Emulsifier Addition on the Thermomechanical Properties of a High Oleic Palm Oil Based Oleogel

Abstract

Oils naturally high in saturated fatty acids (mono- and polyunsaturated), are often liquid at room temperature. Emulsifiers have been used to create solid oil matrices, or oleogels, at room temperature to broaden the applications for these oils. This study assessed and compared the effects of mono- and diglycerides on the mechanical and thermal properties of high-oleic palm oil (HOPO) oleogels. HOPO was mixed with emulsifier in eight concentrations (3%, 5%, 7% and 10% w/w), four each for mono- and diglycerides respectively. Thermomechanical properties were assessed by differential scanning calorimetry (DSC), using a temperature regime with a cooling rate of 10˚C/min to -60˚C and a heating rate of 10˚C/min to 80˚C. The oils and emulsifiers were melted at 80°C and then placed in a series of cooling water baths designed to create identical cooling rates for multiple crystallization temperatures. A puncture test using a texture analyzer was used to assess texture of the resulting oleogels. The results showed that the use of mono- and diglycerides significantly changed the thermal and mechanical properties of HOPO. The addition of saturated monoglycerides promoted an early (high temperature) nucleation stage that did not previously occur in HOPO. The onset crystallization temperature increased with the addition of diglycerides, promoting early crystallization of the high melting fraction of HOPO. The hardness of the oleogel increased with the addition of emulsifier. The effect of temperature on hardness was significantly greater in the diglyceride oleogel than in the monoglyceride oleogel. This study shows that the addition of emulsifiers to create stable oleogels increases the industrial usefulness of HOPO. This work also creates the possibility of further study and characterization of HOPO oleogels, especially concerning crystalline structures.