Food Manager Prep / FAT TOM: the six conditions bacteria need to grow
FAT TOM: the six conditions bacteria need to grow
Updated October 2026 · Based on the FDA Food Code 2022 (the edition the exams follow) and the new 2026 edition
FAT TOM is the memory aid for the six conditions foodborne bacteria need to grow. Take one away and growth slows or stops. That is the logic behind every holding temperature, cooling limit and pH rule on the food manager exam.
FAT TOM is a teaching label, not a defined term in the FDA Food Code. The rules below are the Food Code rules it summarizes.
F is for Food
Bacteria need nutrients, and protein-rich or cooked starchy foods supply them. The Food Code groups these foods as TCS food (time/temperature control for safety): raw or heat-treated animal food, heat-treated plant food, raw seed sprouts, cut melons, cut leafy greens, cut tomatoes, and garlic-in-oil mixtures.
Kitchen example: cooked rice left in the pot after lunch service is TCS food. Uncooked dry rice in the bag is not.
A is for Acidity
Most pathogens grow poorly in acidic food. The Food Code uses pH to decide whether a food needs temperature control:
| Heat-treated and packaged (Table A) | Not TCS if pH 4.6 or less, or water activity 0.92 or less |
|---|---|
| Not heat-treated, or not packaged (Table B) | Not TCS if pH below 4.2, or water activity below 0.88 |
| Anything in between | Needs a product assessment (PA) |
Kitchen example: adding vinegar to make a sauce shelf-stable is not a home-made shortcut. Using additives or vinegar to preserve food or make it non-TCS requires a variance from the regulatory authority (3-502.11).
T is for Temperature
Pathogens grow fastest between 41F and 135F, the temperature danger zone. Cold holding is 41F or less, hot holding 135F or above.
Kitchen example: a sheet pan of cut tomatoes left on the prep line at 55F for the afternoon is out of control, even though the tomatoes look fine.
T is for Time
Growth takes time, so the Food Code caps it: cool 135F to 70F in 2 hours and to 41F within 6 hours, reheat to 165F within 2 hours, discard date-marked food after 7 days, and, with written procedures, use time alone as the control for up to 4 hours (or 6 hours if the food starts at 41F and stays at or below 70F).
Kitchen example: sandwiches set out at 11 a.m. under a 4-hour time control procedure are marked 3 p.m. and thrown away at 3 p.m. if unsold.
O is for Oxygen
Some bacteria need oxygen, others grow without it. The Food Code is strict about removing oxygen: reduced oxygen packaging (vacuum packing, for example) needs a variance unless it meets the conditions of 3-502.12, and a HACCP plan when done without a variance (8-201.13). Garlic-in-oil mixtures are also on the TCS list: the oil keeps air away from the garlic.
Kitchen example: a cook who wants to vacuum-pack portions of cooked meat for the week needs approved procedures first, not just a vacuum sealer.
M is for Moisture
Bacteria need available water, measured as water activity (aw) on a scale from 0 to 1. Under the Food Code tables, a heat-treated packaged food is not TCS at aw 0.92 or less; other foods need aw below 0.88.
Kitchen example: dry pasta sits on a shelf; the same pasta, cooked, must be held hot or cooled within the time limits.
Exam note: course books may simplify these tables into a single cut-off. The values above are the ones written in the Food Code.
How FAT TOM shows up on the exam
- "Which food is TCS?" Look for cooked plant food, cut melons, cut leafy greens, cut tomatoes, sprouts, garlic-in-oil.
- "Which condition can the operator control most easily?" Time and temperature.
- "Why is this food safe at room temperature?" Low pH or low water activity.
- Scenario questions: a food sat out, a batch cooled slowly, a sauce was vacuum-packed. Identify which letter failed, then the Food Code limit.
Keep the numbers handy with the temperature chart and test yourself with the practice test.