What are the life processes of microorganisms in yogurt?

The life processes of microorganisms in yogurt involve several crucial stages that transform milk into the delicious and nutritious fermented dairy product. Here are the key processes carried out by microorganisms, primarily lactic acid bacteria (LAB), during yogurt production:

1. Fermentation:

LAB in yogurt, such as Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, ferment the lactose (milk sugar) into lactic acid. This process gives yogurt its characteristic tangy flavor and acidity.

2. Acidification:

As LAB produce lactic acid, the pH of the milk decreases, causing the proteins in milk (mainly casein) to coagulate and form a gel-like structure. This coagulation process gives yogurt its thick and creamy consistency.

3. Aroma and Flavor Development:

During fermentation, LAB also produce aromatic compounds such as acetaldehyde and diacetyl. These compounds contribute to the distinctive flavor and aroma of yogurt. The production of aroma compounds varies among different LAB strains, influencing the sensory characteristics of yogurt.

4. Nutrient Enhancement:

Yogurt fermentation enhances the nutritional profile of milk. LAB can synthesize certain vitamins, such as vitamin B12 and riboflavin, increasing the nutritional value of yogurt. Additionally, the fermentation process makes some minerals, such as calcium and phosphorus, more bioavailable, improving their absorption by the body.

5. Probiotic Effects:

Yogurt often contains live and active probiotic bacteria. Probiotics are beneficial microorganisms that, when consumed in adequate amounts, can provide health benefits, including improved digestion, enhanced immune function, and potential reduction in certain health conditions.

6. Preservation:

The presence of lactic acid and the resulting low pH in yogurt inhibits the growth of harmful microorganisms, acting as a natural preservative. This extends the shelf life of yogurt and helps maintain its safety and quality.

These life processes demonstrate the remarkable capabilities of microorganisms in converting milk into yogurt, transforming its physical, chemical, and organoleptic properties while also imparting numerous health-promoting benefits.