Thai food leftovers: storing curries and rice, the 2-hour rule, reheating

Thai leftovers keep safely if you get three things right: refrigerate them fast, within 2 hours or within 1 hour when it is above 32°C; keep them at 5°C or below and finish them within a few days; and reheat until hot through, to 74°C, with curries and soups brought to a boil. Two dishes need extra care: coconut-milk curries and steamed rice.

Thailand is hot most of the year, and many kitchens are above 32°C on an afternoon. The rule Western guides give for “a picnic in the sun” is an everyday rule here.

The 2-hour rule, and 1 hour in the heat

The US FDA says to refrigerate or freeze perishable cooked food within 2 hours of cooking or buying it, and within 1 hour if it is above 90°F (about 32°C) outside. WHO uses the same 2 hours.

Germs grow fastest between cold and hot. WHO advises keeping cooked food hotter than 60°C or colder than 5°C; food that sits in between for a long time is the risky food.

Room temperature	Cooked food can sit out for
Up to 32°C	No more than 2 hours
Above 32°C	No more than 1 hour

The clock counts everything from when the food is cooked or bought, including the ride home and the time it sits on the table while you eat.

Coconut curries spoil fast

A former head of Thailand’s Department of Health warned people to be careful with foods and desserts made with coconut milk because they spoil easily. Green curry, panang, massaman, tom kha and coconut desserts deserve faster handling than other dishes.

How to handle them:

• Do not leave the pot on a switched-off stove. A big pot cools very slowly and stays in the risky range for a long time.
• Split it into shallow containers. The FDA advises dividing large amounts into shallow containers so they cool quickly in the fridge.
• Use clean containers with lids, as the Department of Health advises.
• Bring it to a boil when reheating. The Department of Health says to heat refrigerated food until it boils before eating and not to reheat it over and over. Take out only what you will eat.

Rice and Bacillus cereus

Uncooked rice often carries Bacillus cereus. It forms spores that resist heat and survive cooking. If cooked rice cools slowly and sits between 5°C and 60°C for a long time, the spores germinate, grow and make a toxin that causes vomiting.

What people often do not know:

• Reheating does not help. It does not kill the spores or destroy toxin that has already formed.
• You cannot tell. Rice with the toxin looks, smells and tastes like normal rice.

The health department of Western Australia advises cooling rice as fast as possible: spread it into shallow containers no more than 10 cm deep, kept apart rather than stacked, then refrigerate below 5°C. Rice held on a rice cooker’s keep-warm setting stays above 60°C and is not the same problem. The problem is a pot that is switched off and left to cool by itself.

Reheat to 74°C

The FDA says to reheat leftovers to 165°F, about 74°C, measured with a food thermometer, and to bring sauces, soups and gravies to a boil. WHO says to bring soups and stews to a boil so they reach 70°C, and to reheat cooked food thoroughly.

Without a thermometer: boil curries and soups hard, heat stir-fries and fried rice until steam rises from the whole plate, and stir partway when using a microwave, because microwaves heat unevenly.

How many days in the fridge

Source	Fridge temperature	Leftovers keep
Thai Department of Health	5°C or below	3 to 5 days; boil before eating
FDA and USDA (via Texas A&M)	40°F (about 4°C) or below	3 to 4 days
Freezer (USDA-based)	0°F (about -18°C)	About 3 to 4 months for quality

The figures differ slightly. To be safe, use 3 days for coconut curries and rice, and write the date on the lid.

Example: a Saturday dinner at home

Say you make a 3-litre pot of green curry and a pot of rice. Dinner ends at 20:00 and the kitchen is 33°C.

1. The room is above 32°C, so the 1-hour rule applies. The food has been on the table since 19:00, so the time is already up at 20:00. Put it away as soon as dinner ends.
2. Split the 3 litres into 3 shallow boxes of about 1 litre each. Spread the rice in a shallow tray no more than 10 cm deep. Everything is in the fridge by 20:15.
3. Three days from Saturday means finish it by Tuesday. Write “Sat” on the lids.
4. On Sunday, take out one box only and bring it to a boil. The other two stay cold.
5. If the curry or rice had sat out until Sunday morning without refrigeration, throw it away. Reheating would not make it safe.

Time and temperature decide whether food is safe, not smell.

Common mistakes

• Leaving the curry pot on the stove overnight and boiling it in the morning. Boiling kills some germs, but some toxins, such as that of Bacillus cereus, survive heat.
• Putting the whole pot in the fridge. The centre of a deep pot cools slowly. Split it into shallow boxes first.
• Reheating the whole box at every meal and putting the rest back. Reheating again and again is exactly what the Department of Health says to avoid.
• Trusting your nose. Rice with toxin smells normal.
• Forgetting the trip home. Takeaway that spends an hour in a hot car has used up most of its time.

Pregnant women, young children, older people and anyone with weak immunity should be stricter than usual. If vomiting or diarrhoea will not stop, or you have a fever or signs of dehydration, see a doctor. For eating out, see Thai street food safety.

Sources

• Safe Food Handling — U.S. Food and Drug Administration
• Safe cooling of cooked rice — HealthyWA, Government of Western Australia
• WHO Five Keys to Safer Food poster text — SafeConsume
• Storing leftovers safely — Dinner Tonight, Texas A&M AgriLife Extension
• Department of Health on coconut-milk foods spoiling easily (Thai) — MGR Online
• Department of Health on fridge storage at 5°C for 3 to 5 days (Thai) — MGR Online