Soft drink spoilage (yeasts and bacteria): Which defect is a major result of marked microbial growth in carbonated soft drinks?

Introduction / Context:
Soft drinks are high-sugar, often acidic beverages that should be microbiologically stable if processed correctly. When yeasts and certain bacteria proliferate, they create characteristic defects that compromise clarity, texture, and mouthfeel. Recognizing the hallmark defect helps direct quality control.

Given Data / Assumptions:

• We focus on defects caused by yeast/bacterial growth in soft drinks (not canned low-acid foods).
• Products are typically clarified and filtered; turbidity indicates microbial proliferation.
• Some bacteria produce extracellular polymers that cause viscosity issues.

Concept / Approach:
Cloudiness arises when microbial biomass and by-products scatter light in otherwise clear beverages. Ropiness is due to exopolysaccharides produced by organisms such as certain lactic acid bacteria or Zymomonas, resulting in viscous, slimy strands. Yeasts (e.g., Saccharomyces, Candida) also cloud beverages and ferment sugars, producing CO2 and off-flavors. These are classic defects for sweet, acidic soft drinks with preservative failures or post-contamination.

Step-by-Step Solution:
List common microbial defects in soft drinks. Match yeasts/bacteria to turbidity and exopolysaccharide production. Identify “cloudiness and ropiness” as the primary combined manifestation. Select option reflecting both clarity loss and viscosity change.

Verification / Alternative check:
Quality manuals cite ropiness and turbidity as typical microbial spoilage signs in soft drinks, often with gas production and package swelling if yeasts grow.

Why Other Options Are Wrong:

• Flat sour spoilage: Pertains to canned foods by thermophilic spore-formers, not soft drinks.
• Superficial fungal spoilage / Pin-spot molding: Surface molds occur more in juices or inadequately closed containers; not the principal yeast/bacterial soft drink defect.
• Glass corrosion: Chemical/packaging issue, not a microbial growth signature.

Common Pitfalls:
Confusing carbonation loss with “flat sour”; the latter is a specific canned food defect unrelated to beverage clarity.

Final Answer:
Cloudiness and ropiness are major spoilage outcomes of yeast/bacterial growth in soft drinks.