Yogurt manufacture — starter composition used in commercial practice Modern yogurt is produced using which starter culture combination to achieve rapid acidification and characteristic flavor?

Introduction / Context:
Yogurt relies on a symbiotic starter pairing that coordinates acid production, flavor compound formation (for example, acetaldehyde), and texture development. Identifying the correct starter pair is a foundational competency in dairy processing.

Given Data / Assumptions:

• Product: yogurt (thermophilic fermentation).
• Goal: rapid acidification to pH targets and desired flavor.
• Starters must be compatible and mutually stimulating.

Concept / Approach:
Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus form a protocooperative pair: S. thermophilus initiates rapid acidification and provides formate and CO2, while L. bulgaricus contributes strong proteolysis and flavor notes. Together they achieve efficient fermentation profiles and consistent sensorial attributes.

Step-by-Step Solution:
Recognize yogurt as a thermophilic product.Identify the symbiotic pair L. bulgaricus + S. thermophilus.Select the mixed culture option.

Verification / Alternative check:
Codified dairy standards and industrial practice specify the two-organism yogurt starter system.

Why Other Options Are Wrong:
Single-organism options fail to produce the classic yogurt profile; S. cremoris and Lactococcus/Leuconostoc pairs are mesophilic buttermilk or cultured cream starters, not yogurt.

Common Pitfalls:
Confusing Bulgarian sour milk with modern yogurt; both involve thermophiles but yogurt specifically uses the defined two-strain symbiosis.

Final Answer:
A mixed culture of Lactobacillus bulgaricus and Streptococcus thermophilus.