Vacuum or oxygen-impermeable packaging — Bacon spoilage: Unopened sliced bacon, packed in film with low oxygen permeability, is most often spoiled by which microbes?

Introduction / Context:
In vacuum-packed or oxygen-resistant films, the microbial ecology shifts toward organisms that tolerate or prefer low oxygen. Understanding the dominant spoilers guides shelf-life prediction and hurdle design in ready-to-eat meats like sliced bacon.

Given Data / Assumptions:

• Product: sliced bacon, unopened.
• Packaging: relatively oxygen-impermeable.
• Storage: chilled conditions typical of retail distribution.

Concept / Approach:
Lactic acid bacteria (LAB), particularly Lactobacillus species (now reclassified into several genera, but commonly referred to as lactobacilli), tend to dominate under vacuum/low-O2 conditions. They cause souring, slime formation, and off-odors without overt gas swelling. Micrococci favor higher oxygen and are more relevant to curing reactions, while molds require oxygen and are suppressed in tight packaging.

Step-by-Step Solution:
Relate packaging atmosphere to microbial selection: low O2 → LAB succeed. Match typical spoilage signs: acidification, mild slime, ‘‘sour’’ aromas. Select ‘‘Lactobacilli’’ as the most common spoiler.

Verification / Alternative check:
Studies of vacuum-packed meats consistently report LAB as primary spoilers, impacting sensory quality before safety concerns arise.

Why Other Options Are Wrong:

• Micrococci: more active in oxygenated curing and color stability roles than in anaerobic spoilage.
• Fecal streptococci: not typical dominant spoilers of vacuum-packed bacon.
• Molds: require oxygen; growth is limited by the low O2 barrier.

Common Pitfalls:
Assuming gas-producing coliforms dominate; in tight, cold packs, LAB outcompete many aerobes.

Final Answer:
Lactobacilli