Food microbiology — Concentrates of fruit and vegetable juices most commonly encourage the growth of which microorganisms?

Introduction / Context:
Fruit and vegetable juice concentrates combine low pH and high sugar. These intrinsic factors select for specific spoilage organisms and fermenters that tolerate acid and osmotic stress, a key topic in food preservation and hazard analysis.

Given Data / Assumptions:

• Juice concentrates typically have pH < 4 and high soluble solids (°Brix).
• Osmotolerant yeasts and acid-tolerant lactic acid bacteria survive such conditions.
• Molds can grow on surfaces but are less dominant in properly stored, low-oxygen concentrates.

Concept / Approach:
Yeasts (e.g., Zygosaccharomyces) and acid/sugar-tolerant Leuconostoc/Lactobacillus species are the most plausible spoilers of concentrates. Filamentous fungi like Aspergillus prefer lower water activity surfaces or require oxygen; general saprophytic bacteria are inhibited by low pH and high sugar.

Step-by-Step Solution:

Verification / Alternative check:
Food microbiology texts identify osmophilic yeasts and LAB as principal spoilers of high-Brix products when hygiene or storage is inadequate.

Why Other Options Are Wrong:

• Aspergillus spp.: possible surface molds, but less dominant in sealed concentrates.
• Saprophytic bacteria: generally inhibited by acidity and osmotic pressure.
• None: contradicts documented spoilage cases.

Common Pitfalls:
Overemphasizing molds for all fruit products; concentrates favor yeasts and tolerant LAB internally.

Final Answer:
favour the growth of yeast and of acid and sugar tolerant Leuconostoc and Lactobacillus species