Probiotic viability in yoghurt: A review of influential factors

Probiotic yoghurt is a popular functional food product around the world. Delivering an appropriate number of viable probiotic bacteria is critical in determining the health-improving properties of yoghurt. The viability of probiotics in yoghurt can be affected by food components (e.g., sugars, proteins, fat, vitamins, minerals, flavouring agents, antioxidants, and amino acids), processing-related factors (e.g., heat treatments, homogenisation, and fermentation temperature) and also microbiological factors (e.g., type of strains and inoculum level). Approaches including appropriate selection of acid- and bile-resistant strains, using oxygen-impermeable containers, two-step fermentation, stress adaptation, prebiotic addition and microencapsulation have been purported to be effective. Considering the importance of keeping the viability of probiotic bacteria, the major factors from production to the gastrointestinal tract have been investigated in this review with the emphasis on viability improvement. It is concluded that viability could increase with appropriate ingredients, suitable bacteria and standard production procedures.