Is sous vide safe when the food never gets very hot?

Conventional cooking temperatures are written as single numbers because they are instantaneous targets — reach 75°C in the centre of a chicken and it is done, immediately. That hides the fact that the same safety can be bought more slowly at a lower temperature, which is the entire basis of sous vide.

Safety

Step by step

1. Understand pasteurisation as a curve, not a threshold.Bacterial reduction depends on how hot and for how long. Around 70°C the reduction is effectively instant. At 65°C it takes minutes. At 60°C it takes tens of minutes. At 55°C it takes hours. All of those points can reach the same level of safety; they just buy it differently.
2. Accept the floor at roughly 54–55°C.Below about 54°C, bacteria are not reliably being reduced at all — some are still able to multiply. Cooking below that is not slow pasteurisation, it is warming. Food cooked below this line must be treated exactly like raw food: served immediately, never held warm, never chilled and reheated.
3. Time from when the bath is at temperature, and add the come-up time.The clock starts when the water is at the set point, and the food then needs time to reach that temperature through its thickness before the pasteurisation hold even begins. A thick piece needs the come-up time plus the hold. Published sous vide tables give both — use them rather than guessing.
4. Keep everything under the water.A bag that floats has a section sitting in air, which is far cooler than the water and is a straightforward food safety failure. Weigh bags down, use a rack, and check on long cooks that the water has not evaporated below the top of the bag.
5. Do not park food in the danger zone at either end.Between roughly 8°C and 55°C, bacteria multiply. Food should pass through that band quickly going up, which it does in a preheated bath, and quickly coming down if it is being chilled — into iced water, not left on the side.
6. Treat long low cooks with particular care.A 48-hour cook at 60°C is safe because it is well above the floor and held for a very long time. A 48-hour cook at 52°C is not safe at all. When people get sous vide wrong it is nearly always by lowering the temperature for texture without checking that it is still above the pasteurisation line.
7. Chill fast and eat within a few days if you are storing.Cooked sous vide food that is being kept goes straight from the bath into an ice bath until cold right through, then into the fridge, and is eaten within about three days. The bag is not sterile and it is not a preserving process.

Tips

• Whole muscle beef and lamb carry bacteria on the surface, not through the middle, which is why a rare steak is safe and rare mince is not. Sous vide does not change that — anything minced, rolled, needled or stuffed is contaminated throughout and needs pasteurising throughout.
• Chicken cooked sous vide to 62–63°C and held is fully pasteurised and still juicy, but it will look faintly pink at the bone, which is colour rather than a safety signal.
• If your circulator loses power mid-cook, treat it as the danger zone: if the food has been below 55°C for more than about two hours, throw it away.
• Serving anyone pregnant, elderly, very young or immunocompromised is the point to stop being clever. Cook those portions conventionally to standard temperatures.

Common mistakes

• Lowering the bath temperature for a softer texture without checking the pasteurisation tables — A few degrees down can move you from a safe hold to no pasteurisation at all. The texture change is small; the safety change is not.
• Cooking sous vide in the morning and leaving it in the bath all day at serving temperature — That is fine at 60°C and above, where the food is being held safely hot. It is not fine at steak temperatures, where you are holding food in or near the danger zone for hours.

Questions people ask