Potential of Homopolysaccharide-Producing Starter Cultures in the Fermentation of Coconut Yoghurt Alternatives Enriched with Pea Protein Isolate

This study investigates the use of a homopolysaccharide (HoPS)-producing <i>Latilactobacillus sakei</i> strain for the production of protein-enriched plant-based yoghurt analogues based on coconut milk. Formulations varied in added sucrose (2.5% or 5.0% <i>w</i>/<i>w</i>), pea protein isolate (PPI; 0-5.0% <i>w</i>/<i>w</i>), and tapioca starch (0%, 1.5% <i>w</i>/<i>w</i>), and were fermented with either a HoPS-producing strain (<i>L. sakei</i> 1.411), or a non-exopolysaccharide (EPS)-producing control strain (<i>L. sakei</i> 1.2037) with very similar acidification kinetics. Microbial growth and pH were monitored, HoPS content was determined via HPLC, and both firmness and syneresis were assessed during 5 days of storage at 4 °C. EPS yields were significantly higher (<i>p</i> < 0.05) in samples with 5.0% <i>w</i>/<i>w</i> added sucrose compared to those with 2.5% <i>w</i>/<i>w</i>. Fermentation with <i>L. sakei</i> 1.411 generally resulted in firmer gels (<i>p</i> < 0.05) and reduced syneresis (<i>p</i> < 0.05) compared to <i>L. sakei</i> 1.2307 and the enhanced viscosity (sample thickness) was also observed in a sensory analysis. Samples containing starch and 5.0% <i>w</i>/<i>w</i> PPI showed the highest firmness-related values. These findings demonstrate the potential of in situ HoPS production to improve the texture and stability of protein-enriched coconut-based yoghurt analogues. It highlights the importance of matrix formulation, strain selection and process control, which all contribute to the final product quality.