Effects of Olive Oil Varieties and Emulsifiers on Oxidative Stability, Microstructure, and Functional Properties of Oil-in-Water Emulsions

Tan, Jia Shyen (2025) Effects of Olive Oil Varieties and Emulsifiers on Oxidative Stability, Microstructure, and Functional Properties of Oil-in-Water Emulsions. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Mayonnaise is an oil-in-water emulsion system where oil serves as the dispersed phase and water as the continuous phase. The replacement of conventional vegetable oil (soybean oil) with olive oil that is rich in monounsaturated fatty acid and polyphenol contents may enhance oxidative stability, emulsion stability, and functional properties in mayonnaise production. This study investigated the effects of commercial olive oil varieties (pure, extra light, and pomace) combined with emulsifiers (egg yolk and soy lecithin) on emulsion properties at storage temperatures of 4 ℃ and 28 ℃. Soybean oil was utilized as the control sample. The objectives were i) to determine the effect of commercial olive oil type and emulsifier on emulsion stability ii) to evaluate the droplet size distribution of oil-in-water emulsion, and iii) to analyze chemical, physicochemical and microbial properties of oil-in-water emulsions. This study focused on analyzing emulsion stability, pH, water activity, moisture content, color, total phenolic content (TPC), total flavonoid content (TFC), peroxide value, droplet size distribution, and microstructure. The pomace olive oil variant showed significantly higher TPC (104.49 mg GAE/mL at 4 ℃; 104.76 mg GAE/mL at 28 ℃) and TFC (61.41 mg CAE/mL at 4 ℃; 59.45 mg CAE/mL), along with the lowest peroxide value (3.00 meq/kg fat at 4 ℃) among all tested olive oil varieties indicate enhanced functional properties and oxidative stability. Emulsions stored at 4 ℃ have a more uniform droplet size (19.13 μm) and a span value of (1.66) compared to other storage conditions. Microbial safety was confirmed through negligible colony count. This study suggested the potential of using pomace olive oil and soy lecithin to enhance the functional properties and oxidative stability of mayonnaise formulations. Keywords: Olive oil; emulsion stability; soy lecithin; total phenolic and flavonoid contents.