MCQ Detailed View

Yogurt is a fermented dairy product made by the action of specific beneficial bacteria on milk. The primary bacteria responsible for yogurt production is Lactobacillus, specifically species like Lactobacillus bulgaricus and Lactobacillus acidophilus, often working together with Streptococcus thermophilus. These bacteria are known as lactic acid bacteria because they convert lactose (milk sugar) into lactic acid during fermentation.

The process works as follows:

1. 
   

   Fresh milk is heated and cooled to an optimal temperature (around 40–45°C).

   
   


2. 
   

   A starter culture containing Lactobacillus bacteria is added.

   
   


3. 
   

   These bacteria feed on lactose, producing lactic acid, which lowers the pH of milk.

   
   


4. 
   

   The acidic environment causes milk proteins (casein) to coagulate, giving yogurt its thick texture and tangy flavor.

   
   


5. 
   

   The acidity also helps inhibit the growth of harmful microorganisms, making yogurt safe and long-lasting.

   
   

The other options listed are incorrect:

• 
  

  Escherichia Coli (E. coli): While some harmless strains exist in the gut, E. coli is not used for making yogurt and some strains can cause foodborne illness.

  
  


• 
  

  Staphylococcus aureus: A type of bacteria that can cause infections and food poisoning, not beneficial in yogurt production.

  
  


• 
  

  All of these: Incorrect, as only Lactobacillus is involved in yogurt fermentation.

  
  

Yogurt bacteria are probiotics, meaning they promote healthy gut flora, aid digestion, and strengthen the immune system. This is why yogurt is considered a nutritious food in many cultures.

Thus, the bacteria that help make yogurt are Lactobacillus, which drive the fermentation process and give yogurt its characteristic taste and texture.