Reheating spinach - Is it safe? Everything you need to know

Spinach is one of those leafy greens that kids love to hate, but at some point in our journey to adulthood we realize that it’s surprisingly delicious.

In grocery stores, it’s not hard to find different ways to buy spinach, from fresh to frozen, in little ready-made salad packets or in huge bags or tubs that deceptively look like they’ll feed an army of ravenous vegans.

A few years ago, an interesting myth began to circulate about the safety of spinach, more specifically reheated cooked spinach.

Which, of course, begs the question: Can spinach be reheated?

Yes, you can reheat spinach. Spinach is best when heated slowly over low heat. Regardless of the appliance you use to reheat the spinach, make sure it is heated slowly and not overheated in a high-powered microwave or on the oven rack.

If you have leftover spinach, you can freeze or refrigerate it to reheat for another meal. However, this can lead to controversial dinnertime conversation, so before doing so, it’s a good idea to learn the facts behind the warnings about reheating spinach.

The myth of reheating spinach

There is a belief that became very popular after receiving some attention on the internet in the Netherlands and later in the UK, according to which the nitrates in spinach become toxic if overheated.

When heated, nitrates begin to break down and turn into nitrites, which in turn can be turned into nitrosamines. Nitrites can affect oxygen consumption and nitrosamines are a known carcinogen.

Let’s address nitrates first.

Nitrates are a single nitrogen atom with 3 attached oxygen atoms. When we eat natural nitrates, the digestive process breaks them down, removing 1 oxygen atom and creating a nitrite.

Nitrites, by themselves, are almost harmless and can actually be very good at preventing botulism, which is why they are often added to cured meats. 

When nitrates are exposed to high heat or to bacteria in your gut, they break down further. If they lose one more molecule of oxygen with the bacteria in your gut, it turns into Nitric Oxide, which is very good for your body as it helps send important signals that help regulate blood pressure.

However, high heat can completely alter the chemical compound, making it carcinogenic. This is where the myth began.

Let’s talk more about nitrosamines before jumping to dramatic conclusions. Nitrosamines are commonly found in cosmetics, preservatives, tobacco products, cured meats, and pesticides.

If reheating spinach makes you feel threatened, you’ll also need to stop putting on makeup (and washing), find a new way to prevent unintended sexual consequences, stop smoking and eating sausages and bacon, and of course, eating and using only organic products.

If this seems a bit extreme to you, here is another fun fact about nitrosamines.  If you have a diet rich in antioxidants, which come from foods like green leafy vegetables, they will help prevent nitrates from being converted to nitrosamines.

Eating the spinach first can protect you from the possible harm of reheating it later. 

Lastly, only very high heat converts the natural nitrates to nitrosamines, so avoid burning the spinach to a crisp, and you shouldn’t have a problem.

Simple Steps to Reheat Cooked Spinach

Knowing what you now know about nitrates and spinach, it’s a good idea to steam the spinach first, rather than fry it until crisp.

From now on, you’ll need to refrigerate leftovers as soon as they cool, and make sure they’re stored in an airtight container to prevent bacteria growth.

To be brutally honest, cooking most foods once will degrade their nutritional content. Reheating them again will further reduce that nutrition.

The other side of the coin is that some nutrition is better than no nutrition, and wasted food—which includes throwing it away or overeating it, since that’s just as much waste—isn’t good for anyone.

When you’re ready to eat what’s left of your leafy greens, you can choose from a few different appliances to heat them up.

How to use the microwave to heat spinach

If possible, turn the power to medium before reheating the spinach.  Make sure to place them in a microwave-safe dish, preferably glass or ceramic -never plastic- and with a lid.

If the dish doesn’t have a lid, use a microwaveable splatter guard, especially if the spinach already has butter or other ingredients.

The spinach is quite delicate, so it won’t take long to heat up.

For best results, spread the spinach as far as space will allow to help it heat evenly . Use only short 30-second bursts, stirring the spinach in between. Don’t overheat them, but stop as soon as they’re steaming.

Heat the previously cooked spinach on the fire

Again, to preserve the nutritional content and safety of spinach, you should reheat it over low to medium heat in a pot or skillet on the stove.

It’s a good idea to stir frequently to make sure they don’t stick to the bottom of the pan.  Once the container is heated, the spinach heating process will only take a few minutes.

It’s important to keep an eye on the spinach so you don’t overheat it.

Reheat foods with spinach

Spinach on its own is a treat for your taste buds, but there are so many ways to spice up this green vegetable that we thought it would be smart to talk about how to reheat a few different dishes that include spinach.

How to Reheat Spinach Artichoke Dip

Heating up yesterday’s spinach and artichoke dip is a very similar process to baking it in the first place. If you use the oven, lower temperatures for a longer period of time are going to achieve a more complete heat than if you try the fast and furious technique.

Try 350F for 15 - 20 minutes, checking from time to time until it seems like the perfect temperature for your liking. 

If you prefer to use the microwave, it will help to use smaller portions. A large plate will not heat evenly in the microwave, so try serving individually or be prepared to stir to distribute the heat. It is best to work in 30 second intervals until you get the right temperature.

reheat spinach soup

The best way to reheat spinach soup is on the stove over low to medium heat and stirring constantly, especially if it is a cream of spinach soup.

If you don’t have a stove handy, or the patience to wait and stir, you can use the microwave, but watch out for splatters. Use a splatter guard and heat only in 30-second bursts, stirring each time.

If you leave the soup out too long at a time, it’s likely to bubble up and make a mess in the microwave.

How to reheat spinach pie

Spinach Pie, also known as Spanikopita, is a phenomenal Greek dish made from puff pastry that wraps spinach and feta. Served hot it melts in your mouth.

To reheat it without damaging its delicate puff pastry and melt-in-your-mouth quality, you should use your oven or a toaster oven.

Depending on whether you’re reheating a full-size pie or a single serving by hand, you’ll want to slowly toast it at 350 degrees for 10-20 minutes, checking often for over-browning.

If you decide to use the microwave, you should prepare for a slightly soggy crust. To avoid this as much as possible, place a paper towel on the microwave-safe plate before heating it.

Reheat Spinach Quiche

When it comes to a spinach quiche, the quiche part is the hardest to reheat well. If you’re not careful, you can end up with a gummy, gummy cake.

But if done right, it can taste just as delicious as the first time it was served.

If you are heating a frozen spinach quiche, you can pop it directly into a preheated 350F oven . However, you will need to cover it with aluminum foil to ensure it doesn’t dry out.

Bake for about 30 minutes , checking at 25 to check heat levels and leaving just longer, uncovered, if necessary.

As with any type of pie, it’s good to let it rest for about 10 minutes before serving, as otherwise it’s hard to serve and more likely to fall apart.

If you have a spinach quiche in the fridge, it will heat up faster. If your oven is hot to 350F, it should only take 15-20 minutes for the quiche to heat up again.

If you have a toaster oven, you can use the same temperatures and times as above. In both cases, the quiche will heat more evenly if you place it in the oven or toaster in individual portions, separated from each other.

Microwaving isn’t the best way to reheat spinach quiche, but if it’s your only option, it’s possible.  In general, you should only microwave things for as long as absolutely necessary.

However, when it comes to a quiche, there is a secondary option that you can consider. For nutritional content, stop doing it as soon as it’s the right temperature.

However, if texture is important to you, there is a trick that you might find useful.

Heat the quiche 30 seconds longer than you think it needs to, then let it rest for at least 5 minutes. The extra time will cause it to get a little hotter, and as it cools it will release steam, releasing some of the moisture that could lead to a soggy crust.

It’s not perfect or foolproof, but it’s a technique that works for some.

The best ways to preserve spinach

Cooked spinach is interestingly much easier to store than fresh. Once cooked and cooled, you just have to transfer the spinach to an airtight container and place it in the fridge.

Cooked spinach can last up to 5 days if stored properly in the fridge. 

Fresh spinach can be frustrating to store. If there’s any moisture on the leaves, they wither and rot, giving off a foul odor and encouraging all their neighboring leaves to follow suit.

To prevent this from happening and to keep your spinach as fresh as possible for as long as possible, line the container with a paper towel before placing it in your fridge. This will help absorb any moisture that may be lurking.

It is also much better to store spinach in a container than in a bag, because if it is crushed the leaves will also wilt and rot. 

Can spinach be frozen, and how?

Spinach can be frozen without a problem and can be a great option if you have more spinach than you can eat in a few days.

Freezing your leafy greens will protect the nutritional content better than leaving them in the fridge, and your spinach will last 6 months to a year in the freezer. 

Once thawed, the leaves will no longer be crisp and fresh, so it’s not an ideal way to store salad greens. However, if you plan to cook the spinach in the future, cleaning, blanching, and freezing it is a perfect solution for fresh spinach all year long.

If you’re actually working with spinach straight from the garden, you should wash the leaves several times to make sure you get all the dirt off. If it’s fresh spinach from the supermarket, you can skip this step if the package says the spinach is pre-washed.

Blanching simply means to steam the spinach for a very short period of time, usually 2 minutes, and then immediately place it in an ice bath to stop the cooking process. You want to kill all the harmful bacteria, but you don’t want to cook the spinach. 

Once the spinach is blanched, it is essential to remove all the water before freezing it. Frozen water damages the structure of the spinach, so it will be mushy when thawed if you don’t dry it well first. You can use a salad spinner and/or dry them carefully with a towel or kitchen paper. 

Using a freezer-safe Ziploc bag is probably the easiest way to freeze spinach, but you can also use a Tupperware container.

The trick is to pack the sheets as much as possible to reduce the space that air can get between them. If you use a bag, you can squeeze out even more air as you seal it. If you do it right, your spinach will stay fresh for a year.

Related questions

Is creamed spinach keto?

Spinach itself is a keto favorite because it packs a wide variety of nutrients, including protein, in a very low-calorie, low-carb serving.

When you add cream to the mix, it changes the story a bit, but it’s still possible to be keto.

Look for full-fat dairy products, and be sure to check the carbohydrate and sugar content of Parmesan, cream cheese, sour cream, or any other ingredients you add.

How many spinach is too much?

Some extremists have claimed that because spinach is a source of oxalic acid, which binds calcium and other nutrients so your body can’t process it, it’s actually toxic and can be deadly.

To reach fatality level, you would have to eat about 5 pounds of spinach a day. Considering how light spinach is, this is highly unlikely.

In fact, with all the incredible nutritional value that spinach contains, it would be best to eat a cup of fresh spinach each day.

Can spinach cause diarrhea or gas?

As a vegetable, spinach is not known to cause any digestive upset, such as diarrhea, gas, bloating, or constipation.

However, it is one of the green leafy vegetables most likely to be infected by E. coli bacteria and norovirus.

Both contaminants can cause food poisoning and therefore diarrhea or vomiting. The easy solution is to simply make sure you wash your spinach well before eating it, especially if you eat it raw.