Which sign indicates bacterial contamination after processing?

• A. Green ring
• B. Bone taint
• C. Gray centers
• D. Yellowing

Answer: (A)

Post-processing bacterial contamination shows up in discoloration patterns caused by microbial activity. A green ring is a classic sign because it reflects bacteria growing after processing and producing pigments or other compounds that alter the color around the product. This direct link to post-heat-treatment microbial growth makes it the best indicator of contamination after processing. Other signs point to non-microbial issues: bone taint comes from physical contamination with bone fragments and associated off-flavors, gray centers suggest internal pigment changes or oxidation not driven by microbes, and yellowing is usually due to aging or lipid oxidation rather than bacterial growth.