Viability of probiotic strains Lactobacillus acidophilus NCFM® and Bifidobacterium lactis HN019 and their impact on sensory and rheological properties of milk and dark chocolates during storage for 180 days

• The effects of incorporating probiotics in milk and dark chocolate were studied.
• Viability of probiotics in chocolates lasted for 180 (probiotic D), i.e. 90 days (probiotic B).
• A longer availability of probiotics was achieved than in case of milk carriers.
• Sensory properties of chocolates were not significantly changed during storage.
• Probiotics had a greater impact on the yield value than the viscosity of chocolates.

The popularity of chocolate as food around the world combined with high level of health-related awareness of the contemporary consumer, imposed the idea of enriching composition of different kinds of chocolate with probiotic bacterial strains. In this study, two strains of probiotic bacteria, Lactobacillus acidophilus NCFM® and Bifidobacterium lactis HN019, were incorporated in milk and dark chocolate. Final products were kept at two temperatures (4 °C and 20 °C) at which viability of added strains was monitored with the aim of determining the recommended storage temperature. In order to determine the effects of probiotics an examination of their sensory and rheological properties was carried out immediately after production (0–30 days) and during storage of 90 and 180 days. Based on the obtained results it can be seen that the probiotic strain L. acidophilus NCFM® exerted higher viability compared to strain B. lactis HN019 in both kinds of chocolates, while a greater number of cells of both strains was determined at 4 °C. The increase in yield stress of chocolates with probiotics with larger granulation was observed, while the apparent and plastic viscosity did not experience major changes. Despite the occasionally noticed sandiness, sensory properties of chocolates were not significantly changed during storage.