Impact of synbiotic formulation on lactic acid bacteria viability and quality attributes of yogurt during cold storage

Abstract

This study evaluated the impact of synbiotic formulation on lactic acid bacteria (LAB) viability and quality attributes of yogurt during cold storage. Yogurt was manufactured with traditional starter cultures ( Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus ) with or without Lactobacillus acidophilus and enriched or not with freeze-dried banana powder, yielding three formulations: (i) conventional, (ii) probiotic and (iii) synbiotic. After fermentation at 41.5 °C to pH 4.7 ± 0.2, samples were stored at 4 °C and analysed on days 1, 7, 14 and 21 for LAB counts, physicochemical parameters (pH, titratable acidity, protein, moisture, ash, serum separation), total phenolic content, viscosity and sensory properties. The synbiotic formulation supported LAB viability throughout storage, while the probiotic formulation exhibited the highest LAB counts at the end of the storage period. However, the addition of banana powder also intensified post-acidification due to enhanced microbial metabolism, leading to lower pH and higher titratable acidity. From a structural perspective, interactions between banana-derived components and the casein network modified the gel microstructure, resulting in increased syneresis and reduced viscosity. These physicochemical changes were reflected in sensory properties, with the synbiotic yogurt showing slightly lower scores despite its functional benefits. In contrast, probiotic yogurt received the highest sensory scores in the trained panel evaluation. Overall, the findings demonstrate that banana-based prebiotic enrichment can support LAB viability and functional properties of yogurt but also induces structure-related changes that influence texture and stability. These results suggest that optimisation of ingredient interactions is important for balancing functionality and product quality in synbiotic dairy systems.