Fitness Factors and Microbial Behavior in Guarana Beverages

Area of Science:

• Food Microbiology
• Microbial Ecology
• Food Science

Background:

• Limited data exists on microbial behavior within the guarana production chain.
• Previous studies identified various bacteria in guarana beverages, particularly from soda fountains.
• Understanding microbial fitness is crucial for guarana product safety.

Purpose of the Study:

• To assess the growth and fitness of bacterial isolates from guarana products and by-products.
• To evaluate the impact of environmental factors (pH, temperature, water activity) on bacterial survival.
• To determine the efficacy of guarana beverages in inhibiting microbial growth.

Main Methods:

• Seventeen bacterial isolates were tested under varying pH, temperature, and water activity conditions.
• Enzymatic activities and antimicrobial resistance of isolates were analyzed.
• Eight representative isolates were challenged in different guarana beverage matrices (powdered and ready-to-drink).

Main Results:

• Most isolates thrived between 25-42°C and pH 6-7, but growth was inhibited at extreme conditions (low/high temperatures, acidic pH, low water activity).
• Bacillus cereus showed proteolytic and lipolytic potential, with several isolates exhibiting antimicrobial resistance.
• No bacterial growth was observed in any tested guarana beverages, with significant reductions (up to 6 log CFU/mL) in reconstituted formulations.

Conclusions:

• Guarana-based products and production residues harbor diverse bacterial communities with varying environmental tolerances.
• Acidic pH and low water activity are key factors limiting bacterial proliferation in guarana.
• Both reconstituted and ready-to-drink guarana beverages effectively inhibit the growth of tested bacteria, ensuring microbiological safety.