Double emulsion with improved stability for Lactobacillus acidophilus encapsulation in a liquid formulation

Nowadays, probiotics cover a fundamental role in the sector of functional food. Despite the several benefits on human health related to the probiotic consumption, their delivery is still a challenge due to their high sensitivity to environmental stresses. Encapsulation can improve their vitality and stability, allowing survival during storage and consumption. Double emulsions are selected as potential encapsulating systems due to their unique multi-compartmentalizing structure. The objective of this work was to stabilize Lactobacillus acidophilus in a double emulsion to have directly a liquid formulation. The double emulsion was produced using a rotor-stator emulsifier and the selected emulsion compounds have been chosen to be suitable for food applications. A feasibility study on operating conditions was carried out to identify the best production conditions. The loaded emulsions were characterized in terms of morphology, microorganism vitality, encapsulation efficiency, stability over time, and survival to in vitro digestion. As main results, the operating conditions allowed the desired size of about 5 μm, they did not affect the microbial vitality allowing an encapsulation efficiency of 95–99%. Moreover, the physical and microbial stability were ensured over a period of 45 days of storage at 4 °C. In particular, the sunflower oil as carrier agent guaranteed a survival rate of 85% after one month. Finally, the encapsulated strain was able to survive during digestion in comparison with the non-encapsulated one, ensuring a microbial survival of about 62%. Double emulsions emerge as a promising encapsulation system for obtaining a liquid formulation with enhanced long-term stability for food applications.