freezing cooked rice at home and food safety

January 18, 2023 12:45 PM

When I make a batch of brown rice in my Instant Pot, I put a couple of cups in the fridge and the rest in the freezer. What are good, easy practices to avoid food poisoning?

I've been cooking and freezing (and refrigerating) rice for years with no problems, and I'm not too worried about any of my practices, including occasionally eating rice that's been in the fridge for a week. But if there are some easy steps I can take to keep the rice on the safer side, that'd be good to know.

Unfortunately, even authoritative sources vary wildly in what they recommend and how cautious they are (NHS says no more than a day in the fridge, other sources say 4-6 days).

I freeze my rice in plastic deli container tubs.

I'd rather not get additional plates or vessels dirty, so, for example, I'd prefer not to spread rice on a sheet pan to put in the freezer (not that that would fit in my freezer anyway).

So:

Should I let it cool in the Instant Pot for a while, or put the super-hot rice straight into the plastic tubs?

Should I put the tubs into the fridge first and then into the freezer, or straight into the freezer?

Is there a danger from the plastics if I put very hot rice into the plastic tubs?

I'm looking for specific step-by-step best practices, like "1. let your rice cool for 20 minutes in the pot; 2. transfer it to your plastic tubs; 3. place the tubs straight into the freezer" or whatever the actual recommendations are.

I would especially appreciate citations to sources that are
* authoritative (.gov, .edu, other well-researched and evidence-based organizations)
* realistic (e.g. not recommending throwing it out after a day)
* home kitchen oriented (not restaurant oriented, not aimed at people cooking a lot for others)

Thank you!

posted by kristi to Food & Drink (7 answers total)

Bacterial growth happens mostly between between 8C and 60C (46F and 140F). Your aim is to get the hot food below that minimum temperature as quickly as possible, or to keep it above the maximum, to prevent that growth.

The only reason you don't just throw the hot food directly into the refrigerator or freezer is because those appliances aren't really designed to cool hot food, and you risk defrosting other food or pushing it into the 'danger zone'. Once the food is at, say, body temperature or below, it should be fine to move it to the refrigerator/freezer. Or if you have an empty shelf away from other food, it can go in while it's a little hotter.

Spreading it out to increase the surface area improves convection, cooling it faster. A shallow tray over a cake cooling rack is ideal. Or use a fan to help cool it. Or put it on a conductive surface (a stone counter-top or a metal surface, which will help to conduct heat away. I usually put food in left-over plastic tubs from takeaways, as they're pretty shallow. Another option is to put your pot into a sink of cold water. Anything that cools the food quicker is good.

Food-grade plastics will not generally react with hot foods. They'll sometimes take on colour from tomatoes or turmeric, but that's about all.

How long rice will keep in the refrigerator depends a lot on how much bacterial growth happens during cooling. In theory at least, the quicker you get it cooled, the longer it should last. But I never keep rice more than 48 hours, tops. It's just too good a growth medium for pathogens.

(Apologies for the lack of citations, but most of this stuff is widely-known).
posted by pipeski at 1:28 PM on January 18, 2023

If your tubs are shallow, that's going to be best.

I am super paranoid about rice safety, after having the worst food poisoning of my life from rice. I don't keep it in the fridge just because the quality is so much better microwaving from frozen. I eat what I'm going to eat, leaving the pot on the counter while we eat, and then scoop from that into freezer bags and flatten them out. You want a thin layer if at all possible so it cools faster. I then stack these flattened baggies in the freezer.

To reheat, I put the frozen blob in the microwave with about 2 Tbsp water and microwave covered on high for a minute. Then it's defrosted enough to break up. Then another 2 or so minutes on high. It comes out almost as good as fresh.

I mostly use brown rice. YMMV but I've done it with other kinds and it works fine.
posted by fiercecupcake at 2:02 PM on January 18, 2023

Your rice will cool faster if you take the liner out of the Instant Pot and set it on a trivet, the insulated walls make a big difference.

I would not worry overmuch about how you cool a 16 fl oz deli container. Problems (takes too long to cool, heat from container defrosts other things in freezer) are much more likely to come from foodservice-scale amounts. If you want to get scientific, you can shove a food thermometer in there after two hours to make sure it's within the safety zone.
posted by momus_window at 3:23 PM on January 18, 2023

One of the problems with rice is that the Bacillis cereus spores usually found in uncooked rice can survive ordinary stovetop boiling temperatures, and that appears to be the reason the NHS is so strict in its recommendations about refrigerating cooked rice.

But since you are cooking your rice in an Instapot, which for brown rice typically is done at high pressure for 20 minutes (implying a temperature of ~250°F), you will have sterilized your cooked rice completely and can rely on the more liberal guidelines.

But only if your deli containers are new and unopened before you use them, and you use a sterilized spoon to put the rice in them. Because sterilizing used plastic food containers is essentially impossible.

I use stainless or glass containers with stainless lids, which have been either steamed or dry sterilized in my countertop convection oven at ~450°F, and I don’t worry about cooked rice that's been in the fridge for 2 weeks or a bit more.
posted by jamjam at 4:23 PM on January 18, 2023

My mom would cook a big pot of rice. Let it cool a bit, stir it, and then fill about 8 sandwich bags with cooked brown rice. She flattened them out, got the air out and stacked them into her freezer. Each bag was exactly the right amount for her dinner. She reheated the rice in a ceramic bowl.
posted by Oyéah at 4:23 PM on January 18, 2023

I buy korean/asian containers that are made for storing rice. I get mine from the asian market (H Mart) for about $1.50 each but you can get similar ones on Amazon here:
https://www.amazon.com/KEEPBOB-saving-container-microwave-freezer/dp/B071GBMF7D?th=1
These containers are made for this purpose. They seal well and have steam holes that automatically let steam out when reheating. They are BPA-free, microwave and dishwasher safe.

I would suggest not using ziplock bags because they're not really made to get so hot (unless you're getting the kind that you can sousvide with). If you're really worried about the plastic, I've seen similar glass containers that have a steam vent. Not sure how they do in the freezer.

As far as the process of freezing, here's what I usually do and seems to be common practice for many of my asian friends. I cook about 4- 5 cups in my rice cooker. Whatever I don't plan to eat that day, I put into these containers and put straight into the freezer. No cooling. When it's time to eat the rice, I microwave the whole container unopened (important) for about 3-4 minutes. The rice turns out like freshly cooked rice. This is perfect for me since I'm usually the only one eating rice in my household.

I don't have any references, but FWIW, I am an asian chemist/microbiologist and I'm good with this routine:)
posted by jraz at 1:08 PM on January 19, 2023

Thanks to everyone who answered.

I marked momus_window's as best because that gave me a specific action I could take that fits with my workflow (taking the liner out of the pot) and reassured me that cooling a 16 oz deli container was not likely to cause problems.

Thanks, all!
posted by kristi at 4:48 PM on January 20, 2023