Tuning oil release in meat analogues by modifying size and surface properties of oil droplets

Juiciness perception of meat analogues is closely related to water and oil release during preparation and consumption. Although water-release of meat analogues has been extensively studied, oil release is underexplored. It is crucial to understand which properties of meat analogues drive oil release in order to modulate it. In this study, the interactions between oil droplets and the meat analogue matrix were varied by changing the size of oil droplets and surface properties using different emulsifiers. Plant-based patties were prepared with oil-in-water emulsions stabilised by whey protein isolate (WPI), sodium dodecyl sulphate (SDS), and sunflower (SFL), soy (SL) and rapeseed (RL) lecithin, at three oil droplet diameters (3, 6 and 30 μm). Patties with non-pre-emulsified oil were used as reference. For the reference patty and patties containing WPI- and SDS-stabilised oil droplets, oil release during cooking (<1 % of the added oil) and under mechanical compression (9–22 %) was low, regardless of oil droplet size. Conversely, patties containing lecithin-stabilised emulsions (SL, SFL and RL) released up to 11 % of oil during cooking, which was most pronounced for smaller droplets, and between 27 and 42 % under compression, which was independent of droplet size. Based on the physical stability of the oil droplets and a comparison between rheological properties and predictions of the Kerner model for emulsion-filled gels, we suggest that WPI- and SDS-stabilised oil droplets were integrated into the patty matrix as active fillers, while lecithin-stabilised oil droplets were incorporated as inactive fillers. Oil droplets incorporated as active fillers were only released under sufficient mechanical stress, likely due to coalescence. When oil droplets were incorporated as inactive fillers, smaller droplets resulted in more oil release. Under compression, this effect was nullified by coalescence, resulting in similar oil release across patties. We conclude that oil release of plant-based patties can be engineered by changing the size and surface properties of oil droplets using different emulsifiers. Future studies should explore how these differences impact sensory properties such as juiciness.