Document the observation
Describe swelling, haze, gas, off-odors, visible growth or another observed change. Record when it first appeared, storage conditions, package type and whether the issue follows a particular product, ingredient or production date.
Collect comparisons
Affected product alone may not explain the pattern. Keep unopened units from the same lot and unaffected comparison lots available. Identify all units without combining or opening them unnecessarily.
Choose the next analytical question
Counts, enrichment and isolate identification provide different information. A useful investigation may move from a broad finding to a specific organism question. The scope is designed around the food or product rather than a universal spoilage panel.
Separate finding from cause
Recovering an organism can support an investigation, but it does not by itself establish where contamination occurred. Pair laboratory findings with production, sanitation and storage records.
Related testing & guidance
Technical & service references
Vanguard microbiology service menuFDA: Bacteriological Analytical ManualUSP: General Chapter <61>Source review: November 8, 2026. The agreed method and project scope govern the testing.