So, what happens when you go to your freezer to pick out your favorite tub, only to find mold growing on it? Is the ice cream still safe to eat and how can you tell if it’s gone bad?
Ice cream can get moldy when stored above 32°F (0°C) for even short periods, so keeping it at 0°F (-18°C) in an air-tight container is recommended to prevent mold growth and spoilage. Stored ice cream in an airtight container will also help to prevent cross-contamination, slowing fungal growth.
In this article, we will be answering these questions and more, so, for all you need to know about mold on ice cream, keep reading!
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Can ice cream get moldy?
Ice cream can grow mold just like any other dairy product can. The high moisture content, minerals, proteins, and fats are exactly what mold uses for nutrition and hydration, so if there is ever an opportunity for mold to grow in a tub of your favorite ice cream, it will happily take it.
The difference between ice cream and other dairy products is that it is of course kept in the freezer, this extends its shelf-life considerably, but even so, it does still have a use-by date and will begin to become rancid after this point in time has passed.
Whilst mold grows most successfully in warm and moist environments, there may have been points where the ice cream was left out of the freezer for some time to soften up, this can be all that’s needed for mold spores to find their way into your strawberry gelato and begin to breed.
Once you put the ice cream back in the freezer, many mold spores in the tub will go into a state of almost hibernation, but some strains may still be able to breed and live in very cold temperatures. The ideal temperature range for mold to grow is between 60-80
degrees Fahrenheit, but many strains of mold can still successfully live and breed at temperatures as low as 32 degrees (0 Celsius).
Bacteria is another issue with freezing and re-freezing ice cream, as again, when the bacteria becomes too cold, it simply slows to a state of hibernation, so as soon as the ice cream comes back out of the freezer to begin softening, the bacteria awaken and start to breed, spoiling your ice cream and potentially causing illness in anyone who eats it.
What does ice cream mold look like?
It can be incredibly difficult to determine whether or not ice cream has become moldy by sight alone.
You may have seen mold growing on food before, such as on bread or on fruits that have been left in the bowl too long. In these cases, you can see green or blue, to even black and brown patches of powdery growth which indicates mold.
This is not the case with ice cream, as often the mold growth will be very small and hard to detect.
The easiest way to determine if your ice cream has begun to turn bad is to look for signs in its texture, taste, and smell. Mold will begin to grow in ice cream more quickly once the product has become rancid, so check for signs of rancidity, such as discoloration, a sour smell, and a foul taste, should you notice any of these, your ice cream has turned rancid and may be growing mold and bacteria.
If left for long periods out of the freezer, there is a chance that you may begin to see small clusters of blue, green, brown, or black dots on the surface of the ice cream, this is a certain indication of mold growth, but this would take the ice cream being at room temperature for several hours to even a day or two before the mold was to become noticeable to the naked eye.
If you’d like to see what mold growing on ice cream looks like, here is a fantastic time-lapse of just that happening. You’ll notice it takes three full days before you start to see the fungi forming, but remember that it will have been forming for a considerable time before you can see it.
What strains grow on ice cream?
Penicillium and Mucor genera are two of the most common strains found growing within dairy products and ice cream in general.
Penicillium strains are very common and can be found in soil, decaying plant matter, grains, and rotting fruits. When its spores are airborne, they can easily find their way into the milk the ice cream is manufactured from during the bottling, storage, or shipping stages of ice cream production.
Mucor genera is similar to penicillium, in that it is often found within soil, within decaying organic material, and also within animal dung. Cross continuation of cow dung into the milk that ice cream is made from is one possibility for mold growth within the ice cream, and although pasteurization will kill most strains of mold and bacteria, some may survive the intense heat the milk is subjected to.
How long does it take for Ice cream to mold?
How quickly mold begins to grow on your ice cream depends on a few factors, which include, temperature, moisture, storage conditions, and contamination. Under near-perfect conditions, (as seen in the video above), mold will be able to grow on ice cream kept at room temperature within 2-3 days.
Of course, most people don’t store their ice cream at room temperature, so let’s have a deep dive into these factors.
Temperature
Mold grows at its most rapid rate in temperature ranges between 77° Fahrenheit (25° Celcius) and 86° Fahrenheit (30° Celsius). A freezer would never get near these temperatures unless it were broken, however, some mold strains have adapted to grow at lower temperatures, and so storing at even a few degrees higher than recommended can increase the rate at which it can begin to grow, so it is important to check the thermostat of your freezer to make sure it is being stored at the correct temperature to slow potential growth.
A popular method of letting ice cream soften before serving is to remove it from the freezer and leave it at room temperature for a while to soften up. This increase in temperature will speed up the rate at which fungi can grow, so if using this method, you should serve out the ice cream to be eaten and place the rest back into the freezer. Do not allow the whole container to soften and then re-freeze as this could increase the chances of bacteria and mold growth.
Moisture
Mold needs moisture to grow, and while ice cream has a very high water content, it cannot be used as a source of hydration if it is frozen. This is another reason to never let your ice cream thaw and then refreeze, as when the ice cream melts, the water becomes available as a source of hydration, and mold and bacteria can use it to hydrate.
Storage conditions
It’s important to store your ice cream under the correct conditions to slow down the rate at which mold can grow. Storing your ice cream in an air-tight container will prevent spores and bacteria from settling on the ice cream and setting up colonies.
You should also check the “use-by” date of the product, as after this date, spoilage is more likely to begin and mold growth will become more likely.
Where you store your ice cream can also have an impact on the speed at which it spoils and can become moldy. Storing at the front of the freezer drawer or cabinet is one of the warmest parts of the unit, as it is exposed to the most frequent temperature fluctuations when the door is opened and closed. String your ice cream towards the back will prevent this.
Contamination
Cross-contamination can occur when dirty utensils such as spoons are used to serve ice cream. If mold spores or bacteria are present on a spoon that is used to serve ice cream, they will be pushed deep into the tub and will begin to form a colony. Ensuring all utensils are cleaned properly before use will limit the exposure of bacteria and mold spores, slowing their growth.
If you find other items in your freezer that have turned moldy, the spores could have infected other items too. This is another reason for always keeping ice cream in an air-tight container.
Can the fungi be dangerous?
Yes, both penicillium and Mucor strains can produce mycotoxins which if ingested can cause health complaints such as:
- Nausea
- Breathlessness
- Vomiting
- Diarrhea
These symptoms and other allergic reactions are more common in people with suppressed immune systems and allergic asthma, however, even otherwise healthy individuals can suffer from them as well.
Bacteria can also breed and multiply at the same temperatures that mold begins to spread, so food poisoning is also a very real possibility from eating ice cream that has become rancid and gone bad.
Can it still be eaten?
Ice cream mold is potentially dangerous, and so should be discarded as soon as it is discovered, as any mycotoxins present in the product could cause health complaints. The enzymes molds secrete negatively impact both the taste and texture of the product and as mold typically grows on rancid ice cream and dairy products, so there would be very little to enjoy from eating moldy ice cream.
Can you scrape off the bad parts and eat the rest?
No, scraping the top layer of soft-serve ice or any other type of ice cream may remove the visible mold growth, however, mold “threads”, which are root-like structures called hyphae can be buried deep down into the remaining ice cream, so you would only be removing a small proportion of mold.
The remaining ice cream is still likely to contain mycotoxins if they were released, and will be rancid and inedible, so scraping the top layer off with not resolve the issue. The whole tub should be discarded and a new one purchased.
What happens if you accidentally eat moldy ice cream?
The good news is that in the majority of cases if you were to accidentally eat a small amount of moldy or rancid ice cream, it is unlikely that you would suffer from any major symptoms unless you have a suppressed immune system or are allergic to the strain that was growing.
Due to the high likelihood of the ice cream being rancid, you would likely be unable to eat much of it before noticing it had turned bad.
If you were to eat moldy ice cream and begin to experience new symptoms such as vomiting, gastrointestinal discomfort, or any other symptom, it is advised that you seek the advice of a medical professional.
How to tell if ice cream has gone bad
Along with any obvious signs of ice cream going bad such as visible mold growth, there are a few other signals you can look out for.
Ice crystal formation is a clear signal that freezer burn has taken place. This is when differences in temperatures (usually from being taken in and out of the freezer), result in moisture from the air becoming trapped in the container and freezing as ice.
Smell is a little more tricky, as due to the cold temperature of ice cream, its smell is not always particularly strong. However, when the ice cream has begun to become rancid, it will often have a sour and unpleasant smell instead of the smell of the flavoring.
The product will also begin to change color, for example, vanilla ice cream which usually has a light yellow color will have parts (usually around the edges) that are a darker yellow than usual. This is again a symptom of freezer burn, and whilst this will not necessarily make the ice cream inedible, will certainly affect its texture and taste.
Finally, the texture of the ice cream will be affected if it has suffered from freezer burn or has become rancid.
Fresh ice cream has a soft texture, whereas if it has gone bad, will have a lumpy consistency, may have chunks of ice within it, and can also become chewy.
How to store ice cream to prevent mold
Storing your ice cream properly in the first place is without a doubt the best preventative measure you can take against mold and bacteria growth spoiling your favorite dessert. Unopened ice creams will last longer generally than an opened container, with opened tubs lasting 2-4 months in the freezer and opened tubs lasting roughly six weeks.
With that in mind, here are some of the techniques you can use to increase the shelf-life of ice cream and to stop mold from growing.
Store ice cream at the back of the freezer
Storing your ice cream tub at the front of the freezer subjects it to momentary fluctuations in temperature. Even if only for a short period, these fluctuations can decrease the overall shelf life of your ice cream and lead it to spoil faster.
Instead, store the container as far towards the back of the freezer as possible, here the temperature will remain near constant, and mold and bacteria growth will be far less likely.
Store leftover ice cream in an airtight container
Mold spores are airborne, and if they get an opportunity to land in a new environment and set up a colony, they certainly will. So, keep the container of your ice cream as airtight as possible.
If the product you bought came in a cardboard tube, put any leftovers in an airtight container and if possible, remove as much air as possible.
The added benefit of this is that the ice cream will not be able to pick up any unwanted flavors found within your freezer in this kind of container. Unopened ice cream tubs will of course not pick up additional flavors from other food items within the freezer, but they should be checked to ensure the seal is fully intact to guarantee it stays fresh.
Cover the ice cream with parchment paper
High moisture levels can not only make ice cream a better environment for mold and bacteria to live in but can also increase the risk of ice crystal formation.
Ice crystals can spoil the soft texture of ice cream and make it less pleasant than when you first purchased it.
After you have put the leftover ice cream in an airtight container, cover it with a piece of parchment paper. The paper will help to absorb any excess moisture, reducing ice crystal formation and making a less hospitable environment for mold and bacteria.
Check the seals (gaskets) on your freezer door
Seals (called gaskets), on freezer doors can sometimes be damaged over time, and are a major cause of spoiled foods.
When a seal breaks on a freezer door, warm air is allowed to enter the unit, making the motor work harder to try to maintain the temperature within. Temperature fluctuations over time can spoil foods and allow bacteria and mold growth to occur, and it also allows cold air out, so during winter months, will add to your heating bill.
Check for signs of wear and tear on the seals of your freezer and replace any that look damaged to maintain the shelf life of not only your ice cream but your entire freezer.
Do not refreeze thawed ice cream
Once the ice cream has reached the temperature where it starts to thaw, molds and bacteria can begin to grow at a rapid rate. It is not wise to re-freeze ice cream once it has melted, as bacteria can be trapped within the product in a state of hibernation, only to cause symptoms in those who eat the ice cream at a later date.
The more times the lid of the ice cream is opened, the more chances bacteria and mold spores have to settle on the ice cream, so keeping the number of times a lid is taken off the ice cream to a minimum will help to preserve it. Once the ice cream has been allowed to soften, it should be eaten straight away and not refrozen.
If you prefer to let your ice cream sit out for just a while before you enjoy it, consider portioning it out so that the whole tub does not need to be softened each time.
Don’t use wet ice cream scoops
You may have seen ice cream parlors using ice cream scoops that are left in water after each use. Keeping the scoops wet does help the ice cream fall off the scoop more easily, but it also passes a lot of additional moisture (in the form of water droplets) back into the ice cream container.
Ice cream parlors can do this, as they are likely to use up several tubs of ice cream each day, and will not be refreezing the majority of their stock, so ice crystal formation and mold growth are not issues for them.
At home, however, it is more likely that you will take a few scoops of ice cream from the tub and put it back in the freezer. Additional moisture from water droplets falling off your ice cream scoop not only encourages bacteria and mold growth but also makes ice crystal formations almost a certainty.
Conclusion
Despite being kept at very cold temperatures, ice cream can grow mold under the correct circumstances. The mold that grows on or within ice cream is often not visible to the naked eye, so signs of rancidity such as a sour smell and taste along with discoloration are visual cues to look out for. And finally, storing your ice cream correctly in the freezer and exposing it to as little air as possible is the best way to prevent mold and bacteria growth.
Over to you
I hope this article has given you some good tips on how to tell if your ice cream has gone moldy before you sit down to eat it, but now I’d like to turn things over to you. Have you ever had any experiences with moldy ice cream, or have you got any storage tips that help you keep yours fresh for longer? Or do you have any questions about anything in this article? If so, please leave a comment below and I’ll get back to you ASAP.
