The Dos and Don’ts of Keeping Leftovers Safe

W ay back in April I inadvertently sparked some controversy here on Stonesoup. It all started when I suggested that some roast butternut pumpkin would keep in the fridge for ‘a few weeks.’

One reader commented “No way would any food be safe to eat after a few weeks in the fridge. Yuck!”

Which sparked much debate and some disparaging remarks about my food safety knowledge. (For the record, I have a degree in Food Science, majoring in microbiology. So yes I know my Listeria from my E.coli.)

The thing I found most interesting was the observation that different people have different comfort levels around how long leftovers should keep.

I think the most important factor should be whether you feel comfortable eating something or not. Not whether it fits some generic ‘guidelines.’

After all, you know how it’s been stored, how well it was cooked in the first place, whether your fridge is cold enough. You can see if there’s any mould growth or if it looks and smells funny.

That being said, there are some actions you can take to make sure your leftovers are as safe as possible. So I’ve pulled together a quick ‘Dos and Don’ts’ list to help you adopt food safety best practices in your kitchen…

The Dos

DO put leftovers away ASAP
Bacteria love warm environments. The sooner you refrigerate or freeze your leftovers, the sooner bacteria growth will be slowed and the longer your leftovers will last. Simple.

Do cover food well
Food exposed to the air in your fridge or freezer will dry out surprisingly quickly. This doesn’t tend to be a food safety issue but it does make leftovers less appealing.

I always cover with cling wrap or transfer leftovers into containers with airtight lids. I love the glass ones from Pyrex with the blue coloured plastic lids. For freezing, best to use proper ‘freezer’ bags or zip lock bags to prevent freezer burn.

DO trust your instincts
If something smells funny, or doesn’t look the right colour or has mould or other nasties growing on it, it’s best to trust your senses and throw it out.

DO share the love
It’s important to be realistic about how many leftovers you can cope with. Better to send guests home with a little takeaway package than forcing yourself to eat the same leftovers for days.

DO properly reheat food again before eating
Just as low temperature is important to minimising bacterial growth, high temperatures are the best way to ‘kill off’ any sneaky fellas that have managed to grow.

The Don’ts

DON’T eat anything that feels unsafe
I still follow my Mum’s rule, ‘if in doubt, throw it out.’ If you feel that something is unsafe, there’s no point stressing yourself out and risking your health.

DON’T throw away perfectly good food
Just because food has passed some arbitrary guideline of being in the fridge for ‘X’ days, you don’t need to toss it automatically. If you know it’s been handled carefully and refrigerated promptly and it looks and smells fine, then in all likelihood it will be safe.

DON’T leave things sitting around at room temperature for long periods of time
I know we mentioned the ‘opposite’ of this in the ‘Dos’. But low temperatures are really one of the most important parts of keeping food safe so I wanted to stress it again.

DON’T feel like you always have to ‘obey’ best before dates
This applies more to packaged food than leftovers, but since we’re talking safety and waste, I thought I’d throw it in. If you’d like to learn more, check out my Insiders Guide to Use-by Dates.

hughs sweet potato gratin-2

Hugh’s Sweet Potato Gratin

Takes about 60 minutes.

Adapted from Hugh Fearnley-Whittingstall in River Cottage Veg Everyday.

Most people associate gratins with loads of cheese. As some French friends of mine pointed out recently, traditional French potato gratin is just made with potatoes and cream.

When I first mentioned this to my Irishman, he wasn’t very keen to try it. It’s definitely one of those more unusual dishes that tastes much much better than you can imagine. The salty peanut butter does a great job of contrasting the rich sweet potato.

enough for 4
1 cup double cream (or heavy whipping cream)
1 clove garlic, finely sliced
1 small red chilli, finely sliced, optional
1kg (2lb) sweet potato, scrubbed
150g (5oz) crunchy peanut butter

1. Preheat your oven to 180C (350F).

2. Mix cream, garlic and chilli, if using, in a large bowl. Season. Finely slice sweet potato into rounds.

3. Toss sweet potato slices in the cream mixture. Layer half the sweet potato over the base of an oven proof dish. Scatter over the peanut butter and finish with the remaining sweet potato.

4. Cover with foil and bake for 30 minutes.

5. Remove the foil and bake for another 20-30 minutes or until the sweet potato is tender and browned on top. Allow to cool a little before serving.

vegan / dairy-free – replace cream with coconut milk.

nut-free – replace the peanut butter with a few handfuls of chopped bacon or pancetta.

more Asian vibe – combine the peanut butter with a few tablespoons Thai red curry paste. And serve with lime wedges.

less Asian vibe
– skip the chilli and possibly the peanut butter too.

Video version of the recipe.

With love,
Jules x

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Gemma P November 21, 2012 at 6:36 am

Thank you for posting this! Oh so often friends of mine throw out perfectly good food because they’re scared of leftovers or exceeding use-by dates. The wastage drives me nuts! I’ve always been very firmly of the belief that you should use common sense and your eyes and nose rather than arbitrary rules to decide whether or not to keep something.

jules November 26, 2012 at 3:26 pm

Great Gemma!

Catie November 21, 2012 at 7:11 am

I love that music you have in the background–what is it?

jules November 26, 2012 at 3:27 pm

Sorry Catie!
I can’t remember… some sort of random jazz.. not very helpful!

Niki November 21, 2012 at 7:11 am

My colleague and I have VASTLY different ideas about throwing food out. She doesn’t do leftovers (they get binned), and if she has taken something out the freezer in the morning and doesn’t cook it that night, she bins it. I hate to think of how much food she wastes! I loathe throwing anything out (that’s the Scot in me) and have eaten some leftovers that were probably on the dodgy side, but thanks to a pretty cast iron stomach have rarely suffered any ill consequences! I think it comes down to common sense, trusting your nose and being a little adventurous occasionally!

jules November 26, 2012 at 3:25 pm

Thanks for sharing Niki!

Trevor Huxham November 21, 2012 at 8:02 am

I’m new to cooking and I have a question: should you let freshly-cooked (i.e., still very warm) food cool for a bit before placing it in the fridge? For example, today I boiled and mashed some sweet potatoes in preparation for Thanksgiving on Thursday, but before putting them in the fridge I let them cool off in their tupperware container for about 1/2 hour or so. I just feel uneasy about sticking a lid on warm food, seeing all that condensation build up, and putting it straight into the fridge. Thanks for any clarification!

jules November 26, 2012 at 3:24 pm

Great question Trevor!
I would do the same thing.. leave it for 1/2 hour so you’re not going to get heaps of condensation and then pop it in the fridge.

sherdie November 21, 2012 at 8:33 am

I completely agree with you, Jules. My thinking is that if you know the methods to control bacterial growth then it’s a matter of logic and judgement. Although, like you, my microbiology studies probably help with that judgement! I have no problem eating leftovers that are more than 4 days old, but I wouldn’t eat chicken that had sat out at room temperature on the bench for a day. It’s an individual thing, and of course people should do what they are comfortable with, but I see more and more unwarranted fear of bacteria around.

jules November 26, 2012 at 3:23 pm

Hi Sherdie
I’m with you on not eating chicken that has been sitting around at room temperature for a day!

Susan November 21, 2012 at 8:51 am

Hear Hear

Thanks for this article, as it re-affirms food safety practices that I’ve used for ages… In 50 years of life, I’ve had food poisoning once (really bad, from a restaurant seafood dish kept warm under heat lamps) but never from my own cooking, food storage and re-heating.

More power to you,

jules November 26, 2012 at 3:22 pm

Great Susan!

queenzelda November 21, 2012 at 10:10 am

It’s been said above but it’s so nice to see a rational approach to food safety.

The number of people I know who won’t touch things past a best before date but fail to defrost in the fridge or store food correctly both by refrigerating/freezing quickly or in the right locations in the fridge.

jules November 26, 2012 at 3:21 pm

Good point QueenZelda!

Heidi H. November 21, 2012 at 10:40 am

Thanks for good tips! I always worried whenever I took some leftover from fridge. And whenever I throw it away I felt some feeling of guilty because there are so many hungry people in the world. But with help of your tips, I will be able to reduce wastes.

jules November 26, 2012 at 3:20 pm

You’re welcome Heidi!

Judith November 21, 2012 at 11:16 am

A friend of mine was raised in a family with a father who was neurotic about food safety. Her stomach is so delicate she can’t eat at restaurants. I was raised by a mother who washed dodgy lamb chops and have an incredibly tough stomach. Be good to your children and let their bodies develop defences against food poisoning.

jules November 26, 2012 at 3:20 pm

Great comparison Judith!

Susie T (Australia) November 21, 2012 at 11:38 am

Thank goodness Jules, for your common sense in this matter. Food companies want us to throw away food products at the ‘best before’ date, so that we (as the dutiful consumer) simply have to purchase more. They love it that we are so gullible, as their profit margins soar…. quite simply, we are being ‘conned’. Follow the steps Jules mentioned about storing food properly and you’ll not only save money & time, but you will decrease the amount of wasted food – a very precious commodity. Thanks Jules xx

jules November 26, 2012 at 3:19 pm

Thanks Susie!
Not all food companies are wanting to con customers into buying more. It’s more about making sure that everyone who buys there product get the best tasting example.
Having short best before dates can actually cost companies money because it means they aren’t able to sell the product after the ‘best before’ date. So it works both ways.

Rebecca November 21, 2012 at 11:56 am

Thanks for the tips. My only concern is that some food borne illness can arise from microbes that are odourless and invisible (i.e. won’t smell funny or look mouldy). Thoughts?

jules November 26, 2012 at 3:17 pm

Hi Rebecca

Yes there are food bourne illness that you can’t detect.

And this is always a risk but if you make sure you cook the food properly and cool quickly, and reheat thoroughly your risk of having a problem with them is greatly decreased.

Most food poisoning comes from food that has either been handled improperly or from cross contamination between cooked food and raw so I think it’s best to focus on these areas.

Emily November 21, 2012 at 12:23 pm

It’s amazing how much personal comfort factors into it!

My grandmother grew up during the Depression, and my husband grew up on a farm in Kenya, so they are both comfortable with storing food for much longer than I am. My mother has an auto-immune disease, so she’s much more careful because she never knows what’s going to make her sick. I fall somewhere in the middle, I think. :)

jules November 26, 2012 at 3:12 pm

You’re right Emily!
thanks for sharing your families story

Eleanor Blair November 21, 2012 at 9:38 pm

You don’t mention the fact that some foods are prone to bacteria which produce a toxin which is not destroyed through reheating. Leftover rice for instance is something you need to take particular care with, as if it’s been left too long at room temperature it can look, taste and smell fine, but still cause food poisoning even if thoroughly heated!

Also those of us who are immuno-compromised in some way do need to take a little more care. (I’m expecting – and do find myself now throwing things out which I would previously have been happy to eat).

jules November 26, 2012 at 3:11 pm

Thanks Eleanor
Good points. But if the leftover rice has been properly cooled and put away the bacteria won’t produce the toxin.
I agree pregnant ladies should definitely be more conservative!

Lorna November 22, 2012 at 3:51 am

I’m sure you know this but sweet potatoes, peanuts and chillies are a classic West African combination and millions of West Africans can’t be wrong. I’ll be giving this a go…

jules November 26, 2012 at 3:07 pm

No I didn’t know that it’s a classic West African combo… thanks for sharing!

beverley November 22, 2012 at 7:29 am

I smell it and if it smells okay then i eat it and if i am still not sure i try it on the cat. Cats are not like dogs they won’t eat what is bad.

jules November 26, 2012 at 3:07 pm

LOVE it Beverley!

Melissa Loh November 22, 2012 at 11:06 am

Thanks for posting this. My husband and I often squabble about whether leftovers are safe to eat, with him having a lower comfort level. That said, his stomach is a little more sensitive than mine (we can eat the exact same meal and he would have tummy trouble, while I get away scott-free), so as your mother said, when in doubt…

jules November 26, 2012 at 3:06 pm

Great example Melissa!
Thanks for sharing

Manic Mama November 23, 2012 at 11:08 am

I think it also depends on where you live. We live in Queensland, and the idea of anything lasting, even in the fridge, for a couple of weeks just wouldn’t happen here.

We have found that even when they’re in the fridge, items don’t last as long as they do in colder areas. The difference is really noticeable in summer, because the fridges have to work so much harder to keep food cold. We have a winter setting for the fridge, and a summer setting for this very reason.

The other strategy we use to work around it is to fast-cool items – we put them into the freezer for an hour or two before transferring into the fridge, often in a wide shallow dish for even faster cooling. That way the item is warm for a much shorter period of time, lessening the window of opportunity for bacteria etc to do their thing. The food doesn’t start freezing in this short time, but is transferred into a deeper container & put into the fridge when cold. I’d rather have an extra dish to wash than food poisoning.

I think the key is awareness – of your environment, of your food item, of your individual health-needs as well as your personal comfort-level.

jules November 26, 2012 at 3:00 pm

Good point about environment… So much of shelf life is temperature dependent so if your fridge isn’t as cool as it should be because you’re living somewhere warm, you’re right it won’t last as long.
Although I’ve spent a bit of time in QLD and I really didn’t notice a massive difference in the keeping life of my leftovers..

Danielle November 25, 2012 at 9:45 am

Hi, I just stumbled upon your blog for this sweet potato gratin recipe and read your do’s and don’t’s in the kitchen when it comes to food hygiene and safety. I just completed my Food Hygiene certificate in Scotland, and I teach Home Economics, and while I agree with most of your points, I think it’s worth mentioning that leftovers must be fully cooled before going into the fridge or freezer, and this is usually achieved within a 90 minute time frame. To increase the cooling process, food can be decanted into multiple smaller containers or cooled with a fan, but should never be put into a fridge or freezer when warm as this can promote the growth of bacteria, as well as increase the temperature in your fridge or freezer, which puts other foods at risk. As cooks in our kitchens, we can go to many measures to make sure our food is risk free, but sometimes we can purchase food with food poisoning bacteria or food borne illnesses already in them, which are odourless and tasteless, and are completely different than spoilage bacteria, which simply spoils the food to make it inedible. Trevor and Eleanor bring up really good points as well.

‘Best before’ dates are a guideline to follow, but food is okay beyond those dates if it smells okay and looks okay. It’s incredible to think that some things we do in our kitchen, that one would think would be common sense in preventing the growth of bacteria, can actually promote growth instead.

jules November 26, 2012 at 3:05 pm

Hi Danielle
Thanks for your sharing your thoughts!
Really interesting that you were taught the opposite to me… We were told that with modern refrigeration putting warm food into the fridge isn’t a problem because the fridge should be able to cope. But I guess if you’re worried about the power of your fridge, cooling first to room temperature will be prudent.
I can’t understand why cooling in the fridge will increase the risk of bacterial growth though? I get that if the fridge temp increases is will be a problem for the other food in the fridge. Would love to know more about your theory there :)

Danielle December 1, 2012 at 7:19 pm

When I was taking my course, it seems that even within Britain, there are variations regarding temperatures at which food is safe and lengths of cooling time, etc. Recommended fridge temperatures in Scotland are 1′C to 4′C, while in England it’s up to 7′C I believe? Health and Safety is extremely rigid here, and at times, it seems over the top, (I’m used to North American ways being from Canada). Regarding the change in fridge temperature, this is uncommon and would only really be affected if you were to put something straight from oven/stove top to the fridge, which would create condensation, and could raise the recommended maximum fridge temperature to above 4′C, putting it in the ‘danger zone.’ By creating condensation, you’re giving bacteria moisture and warmth, two things they love!

Anne November 28, 2012 at 6:01 am

Thank you for some good commonsense answers and advice! May I ask a silly question though? I have been told that raw onions absorb unhealthy bacteria very quickly and should never be stored once cut. I have used a cut onion after 2 days when stored in a plastic bag and kept in the fridge. I always cook my onions but is this true or an old wives tale please? Thank you!

jules December 4, 2012 at 5:40 pm

Interesting question Anne!
I thought onions were meant to have antibacterial properties because of the high content of sulphur compounds… so sounds like the old wives have been at it again :)
The only reason I tend not to store cut onions is that their odour spreads to everything in the fridge.

tVM December 4, 2012 at 10:48 am

Jules, Mrs. tVM made the sweet potato au gratin this evening. WOW! I’ll be passing this one on. Don’t know about the calories involved, but the melding of tastes was extraordinary.

jules December 4, 2012 at 5:25 pm

So glad you liked it!

Alex December 5, 2012 at 8:39 am

This is my first time on the blog and I have to point out a few things.
First of all, thoroughly heating food will not prevent you from getting sick. If bacteria has been through its life cycle, when they died off they released a toxin which will remain no matter how much heating you do, and you’ll still get sick.
Another thing…working in food service we have a 4 hour rule if it’s not being heated above 165 F or below 37 F, so that’s what I abide by.
Great blog, thanks for sharing.

Valeria December 17, 2012 at 5:30 am

Oh my! This just looks delicious! What a lovely combination. Thinking of trying it over xmas…

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