Risk ranking — Canned foods and botulinum toxin: Arrange the following canned foods in descending order of toxin risk/potency based on typical acidity and composition (highest risk first).

Introduction / Context:
Clostridium botulinum grows and forms toxin most readily in low-acid, anaerobic, moist foods. Acid level (pH) and substrate characteristics influence risk and thus define thermal processing requirements for canned foods.

Given Data / Assumptions:

• Commodity pH and solids vary: corn and peas are typically low-acid; string beans are borderline low-acid; spinach tends to be slightly more acidic among these vegetables.
• Higher pH (more neutral) generally increases botulinum risk.
• All items are assumed to be improperly processed hypothetically for ranking purposes.

Concept / Approach:
Arrange items from lowest acidity (greatest risk) to higher acidity (lesser risk). Sweet corn and peas are classic high-risk low-acid canned vegetables. String beans follow, while spinach is comparatively less risky due to slightly lower pH and matrix differences.

Step-by-Step Solution:
Assess typical pH ranges: corn and peas near neutral > string beans > spinach. Rank accordingly: Corn first, followed by Peas, then String beans, and finally Spinach. Select the option that matches this descending order.

Verification / Alternative check:
Thermal process schedules (12D concepts) for low-acid vegetables commonly cite corn and peas among those requiring stringent retorting, supporting their higher risk ranking.

Why Other Options Are Wrong:

• Other sequences misplace the relatively higher-risk low-acid vegetables (corn/peas) lower in the ranking or elevate spinach incorrectly.

Common Pitfalls:
Assuming ‘‘green’’ vegetables are always riskier; actual risk tracks pH and process adequacy, not color.

Final Answer:
Corn > Peas > String beans > Spinach