Formulation and physical stability of high total solids lentil protein-stabilised emulsions for use in plant protein-based young child formulae

The demand for high quality plant protein products is rising with increasing awareness of the environmental impact of animal-based products on the current food system. Moreover, the need for special formulations related to animal product intolerances or allergies is also driving plant protein research. The aim of this work was to evaluate the impact of increasing total solid (TS) content on the formulation and stability of lentil protein stabilised oil-in-water emulsions. The emulsions were formulated at 23, 26, 29, 32 and 35% TS (w/v) using three ingredients — lentil protein, sunflower oil, and maltodextrin, which made up 15.85, 27.43 and 56.72% (w/w) of TS, respectively. The 23% TS emulsion displayed colour space L*, a*, b* values of 78.37, 5.82 and 10.85, respectively. The increase in TS led to a decrease in brightness and increase in a* (5.82 to 7.70 at 35.0% TS) associated with increased redness intensity. Apparent viscosity of the emulsions increased with increasing TS, with values ranging from 25.6 (23% TS) to 130 mPa.s (35% TS). The particle size distribution of all the emulsions showed a bimodal distribution with two peaks at 0.36 and 17.35 µm, corresponding to oil droplets and insoluble plant material, respectively. Among the samples, no significant differences (p >0.05) in particle size distribution were observed. The extent of sedimentation ranged from 1.52 to 2.02 mm; the higher TS emulsions showed faster separation and lower colloidal stability. Thermal processing resulted in greater destabilisation at higher TS, especially in the range 29-35% TS, highlighted by greater changes in particle size, along with decreased redness and increased whiteness. These results bring a better understanding of high TS plant protein emulsions and factors affecting their stability, which will allow the development of cost-effective and sustainable processing solutions for the production of plant protein-based young child formulae.