Raman confocal microscopy investigation of dairy‐relevant model oil in water emulsions and impact of emulsifier and temperature variation

Background Emulsions are common in many food systems, including dairy food systems. Emulsifiers can have different physicochemical properties acting in different ways. Processing conditions, such as temperature and pH, can affect emulsion stability, as can storage conditions. Formulation of food emulsions to provide the required characteristics of products has some theoretical basis, but much remains empirical. Aim(s) Our aim was to use Raman confocal microscopy to determine the molecular arrangement of the chemical components of dairy food emulsions and understand how these arrangements, and therefore the stability and behaviour of the emulsions, change with component types and temperatures. Methods Raman confocal imaging was performed on multiple droplets of seven model oil‐in‐water emulsion systems using decolourised anhydrous milkfat and canola oil with two different emulsifiers at 4 and 24°C. The emulsions were visualised by creating integrated peak maps focussing on the Raman C–H bond region 2820–2940 cm −1 . Multivariate algorithm K‐means clustering was used to obtain a more detailed analysis of the Raman images, and principal components analysis was used to assess overall differences. Major findings Raman confocal microscopy successfully resolved and distinguished the chemical components of the model emulsions. The continuous, droplet and interfacial phases were clearly identified as chemically distinct. The interfacial region was sensitive to both fat and emulsifier type. Fat composition and concentration had a strong influence on component distribution. More complex interactions between the emulsion ingredients and/or component phases at the higher temperature were found. Scientific or industrial implications These results show that Raman confocal microscopy is a useful approach to the study of oil‐in‐water emulsions. We can now build on these data to establish a strong scientific basis for the targeted choice of emulsifiers and ingredients to resolve emulsion‐related issues in the development of dairy food systems, including hybrid dairy/nondairy food emulsions.