A method for manufacturing superior set yogurt under reduced oxygen conditions

Area of Science:

• Food Microbiology
• Dairy Science
• Fermentation Technology

Background:

• Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus are key yogurt starter cultures.
• These bacteria are facultatively anaerobic, capable of growth in oxygenated environments.
• Dissolved oxygen (DO) levels in yogurt mixes can influence fermentation dynamics.

Purpose of the Study:

• To investigate the effect of dissolved oxygen (DO) on the acid production of yogurt starter cultures.
• To determine if reducing DO concentration impacts the growth phase and fermentation efficiency.
• To evaluate the influence of DO reduction and temperature on the final yogurt quality.

Main Methods:

• Yogurt fermentation was conducted with and without prior dissolved oxygen (DO) reduction treatment.
• DO concentration was reduced using nitrogen gas dispersion in the yogurt mix.
• Fermentation temperatures were maintained at 43°C and 37°C.

Main Results:

• Yogurt starters Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus actively produced acid only after DO levels decreased to 0 mg/kg.
• Pre-fermentation DO reduction treatment accelerated the exponential growth phase of the starter culture LB81.
• Combining DO reduction with a lower incubation temperature (37°C) produced superior yogurt with smooth texture and strong curd.

Conclusions:

• Dissolved oxygen retards acid production in yogurt fermentation.
• Optimizing DO levels and temperature enhances starter culture performance and yogurt quality.
• DO reduction is a viable strategy for improving yogurt fermentation efficiency and product characteristics.