Enhancing survival of Bifidobacterium spp. in yoghurt through oxidative stress adaptation

Abstract

BACKGROUND : Bifidobacterium spp. are widely recognised probiotic bacteria with well-documented health benefits associated with their incorporation into foods. Despite these benefits, maintaining their viability in oxygen-rich environments like yoghurt poses substantial challenges. AIM : This study examined the impact of oxidative stress adaptation on the viability, fermentation characteristics and physicochemical properties of Bifidobacterium spp. during yoghurt production and shelf-life at 4°C. METHODS : Oxidative (H2O2) stress-adapted and unadapted strains of Bifidobacterium bifidum, B. breve and B. animalis subsp. animalis, 6–7 log cfu/mL, were incorporated during yoghurt fermentation. Two independent yoghurt batches were produced for each treatment combination, with two replicates analysed per batch. Viability (via plate counts and PMAxx-qPCR) and physicochemical properties were monitored over 28 days at 4°C. MAJOR FINDINGS : Stress adaptation enhanced B. bifidum survival during fermentation by 1.0 log cfu/g compared with unadapted strains (P < 0.0001), with B. breve showing similar improvement. Although adaptation initially improved survival, this advantage diminished throughout shelf-life in both species. B. animalis remained stable. The plate count method showed a decline of B. bifidum and B. breve populations, while the PMAxx-qPCR method detected a significantly higher level of viable cells (P < 0.05) in the yoghurt. SCIENTIFIC IMPLICATIONS : Oxidative stress adaptation may enhance Bifidobacterium spp. viability and the functional value of probiotic yoghurt.