Question

Cultures used in industrial production of yogurt are:

• A. Lactococcus lactis subsp. lactis
• B. Streptococcus thermophilus
• C. Leuconostoc mesenteroides subsp. cremoris
• D. Lactobacillus delbrueckii subsp. bulgaricus

Hint:

For optimal yogurt production, the combination of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus is essential for ensuring proper fermentation, texture, and flavor. These two cultures are the standard in the industry.

Answer 1

The Correct Option is B, D

Yogurt production is a complex fermentation process that requires specific bacterial cultures to convert lactose (the sugar in milk) into lactic acid. The lactic acid fermentation process results in the sour taste and thickened texture characteristic of yogurt. The bacteria used in industrial yogurt production play a vital role in ensuring the desired texture, flavor, and nutritional value of the final product. The two most critical bacterial strains used in the industrial production of yogurt are:
1. Streptococcus thermophilus (Option B)
- Role in yogurt production: Streptococcus thermophilus is a thermophilic bacterium, meaning it thrives at elevated temperatures. It is one of the most important bacteria used in the fermentation of milk to produce yogurt. It helps in the initial fermentation of milk, converting lactose into lactic acid, which lowers the pH of the milk and causes it to thicken. This bacterium is highly active in the early stages of yogurt fermentation.
- Benefits in yogurt making: It contributes to the characteristic tangy flavor of yogurt and works synergistically with Lactobacillus delbrueckii subsp. bulgaricus to enhance texture and flavor. It also produces some of the essential compounds that promote the growth of other bacteria in yogurt.
2. Lactobacillus delbrueckii subsp. bulgaricus (Option D)
- Role in yogurt production: Lactobacillus delbrueckii subsp. bulgaricus is a crucial bacterium in yogurt production. It works in tandem with Streptococcus thermophilus to ferment lactose into lactic acid. While Streptococcus thermophilus acts in the initial stages of fermentation, Lactobacillus delbrueckii subsp. bulgaricus takes over in the later stages of fermentation. It contributes to the flavor and texture by continuing to ferment lactic acid.
- Benefits in yogurt making: This bacterium enhances the flavor profile of yogurt, making it more aromatic and flavorful. It also produces bioactive compounds, such as bacteriocins, which can have probiotic benefits.
3. Other Bacteria:
- Lactococcus lactis subsp. lactis (Option A): While Lactococcus lactis is commonly used in cheese production, it is not a primary culture for yogurt. It does not have the same effect as Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in the yogurt-making process.
- Leuconostoc mesenteroides subsp. cremoris (Option C): This bacterium is primarily used in the production of fermented dairy products like cheese but is not commonly used in yogurt production. It is more involved in the fermentation of milk for products like cream and cheese, where it contributes to the development of specific textures and flavors.
Therefore, the correct answers are (B) Streptococcus thermophilus and (D) Lactobacillus delbrueckii subsp. bulgaricus, as these two bacteria are the most commonly used in the industrial production of yogurt.