Pullulan as a potential enhancer of Lactobacillus and Bifidobacterium viability in synbiotic low fat yoghurt and its sensory quality

Yoghurt acts as a perfect delivery system for probiotic bacteria and some functional food ingredients, thereby enhancing their viability. Pullulan (PUL), a natural exopolysaccharide produced by yeast Aureobasidium pullulans is a low-calorie food ingredient and dietary fibre with potential prebiotic properties. The main aim of the present study was to investigate the effect of 0.5%-2.0% PUL addition on pH, sensory quality and viability of the yoghurt starter and probiotic bacteria in low-fat yoghurt during 28 days of storage. PUL addition enhanced the viability of Bifidobacterium and Lactobacillus, while it did not affect S. thermophilus count. The protective effect of PUL increased with concentration and was the highest for 1.5 and 2.0% PUL supplementation. Incorporation of PUL at 1.5% and 2.0% prolonged survival of B. animalis subsp. Lactis at a concentration above the therapeutic level ( < 10(6) cfu/mL) for the entire storage period. All the products showed a decrease in pH during the storage period. Further, the sensory analysis revealed that PUL incorporation improved thickness, smoothness, and viscosity of low-fat yoghurts, but decreased the intensity of milk taste and aroma, contributing to a decrease in overall acceptability.