Effects of Guarana Aqua Extracts on Fermentation Kinetics and Quality Properties of Set-Type Yogurts

Abstract

The combination of bioactive phytochemicals with yogurt in the form of plant extracts or essential oils stimulates the scientific community’s interest and consumers’ preferences. Extracts from guarana are considered bioactive agents and have important health protective properties. In this study, concentrations of guarana aqua extracts 0%, 0.5%, 1%, 2%, 3%, and 4% w/w were added to milk and yogurt fermentation kinetics, acidity, color, water-holding capacity, hardness, and microstructure and were evaluated. The presence of guarana aqua extract reduced the time needed for the completion of yogurt fermentation compared to the control samples. A drop in ${\text{L}}^{\ast }$ and an increase in ${\text{a}}^{\ast }$ parameters were also observed with increased guarana aqua extract concentrations. The lowest concentration of guarana aqua extract decreased titratable acidity, hardness, and syneresis. While different casein networks were observed in microscopy, yogurt without and yogurt with 3% w/w guarana extract had the same acidity and hardness. Finally, this research indicates the suitability of guarana extracts in the production of functional set-type yogurt and increases the knowledge on the effects of plant extracts on milk fermentation and yogurt quality characteristics.