Effect of High-Pressure Homogenization and Heat Treatment on the Emulsification Properties of Oat Protein Concentrate

Abstract: This master thesis project was performed in collaboration with an agricultural cooperative Lantmännen Oats AB, who has developed a dry protein powder concentrate PrOatein™. The powder consists of oat proteins, dextrins, lipids and β-glucans. The aim of the thesis was to investigate the powder’s functionality in a liquid emulsion and see if it can be improved by pre-treating it with thermal heating and high-pressure homogenization (HPH) under different pH conditions. The emulsification properties of the protein concentrate were first evaluated in the means of the protein’s solubility and its efficacy of producing small oil droplets in different pre-treatment conditions. The effect of high-pressure treatment nor heating in slightly alkaline conditions (pH 7.5) was statistically proved. However, the solubility was highest, when the sample was heated to 85 ºC and high-pressured with 600 bars. In slightly acidic conditions (pH 4.5) the effect of high-pressure treatment was significantly proved. Under acidic conditions, the increased temperature during heat treatment and increased pressure during homogenisation decreased the solubility. The light scattering analysis showed that the particle size in pH 7.5 was smaller at all pre-treatment conditions compared to pH 4.5 The smallest particle size was achieved by treating the sample with pH 7.5 with 85 ºC and 800 bars. The effect of HPH and heat treatment on particle size was also significantly proved. The stability analysis showed that heat and high-pressure treatment can delay the sedimentation, which is the dominating instability mechanisms in emulsions consisting of 5 % w/v PrOatein™ powder and 3 % v/v oil. The emulsion sedimented, when the oil content was increased to 10 %, suggesting that the optimal ratio of oil and PrOatein™ in a liquid emulsion should be 1:1.