132. The principle microorganism for yogurt is:
A. Streptococcus thermophilus
B. Lactobacillus acidophilus
C. Streptococcus lactis
D. Leuconostoc citrovorum

Correct Answer:

A. Streptococcus thermophilus

Detailed Explanation:

The production of yogurt involves a fermentation process in which bacteria convert milk sugars (lactose) into lactic acid. The principle microorganisms responsible for yogurt fermentation are Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. These bacteria work symbiotically to ferment milk and give yogurt its characteristic texture, flavor, and consistency.

• Streptococcus thermophilus: This bacterium is a key player in yogurt production. It is responsible for initial acid production, which helps in the coagulation of milk proteins. This acidification process leads to the thickening of milk, giving yogurt its creamy consistency. Streptococcus thermophilus also produces various enzymes that contribute to the development of yogurt’s flavor.

• Lactobacillus delbrueckii subsp. bulgaricus: Alongside Streptococcus thermophilus, this bacterium helps complete the fermentation process by producing additional lactic acid and contributing to the flavor profile of yogurt.

Other Options:

• Lactobacillus acidophilus: While it is beneficial for gut health and is found in some dairy products, it is not typically the primary microorganism used in yogurt production.

• Streptococcus lactis: Although it is a related species, it is not the primary organism used for yogurt fermentation.

• Leuconostoc citrovorum: This bacterium is involved in some fermentations, but it is not the main microorganism used in yogurt production.

Conclusion:

The principle microorganism responsible for yogurt fermentation is Streptococcus thermophilus. It plays a crucial role in the fermentation process, contributing to the texture and flavor of the yogurt.

Correct answer: A. Streptococcus thermophilus.