Patrick Oconnell
Cheese is a beloved food, but it can be hard to tell when it's gone bad. Cheese is a perishable food and a living thing, constantly maturing and changing texture. It's important to distinguish between voluntary and involuntary mould. Blue cheese and flowery-rind cheeses are impregnated with Penicillium, a type of controlled mould. However, mould other than Penicillium on soft cheese should be discarded. In addition to mould, there are three main attributes to determine if cheese has gone bad: smell, appearance, and taste. A spoiled cheese may smell like ammonia, rancid milk, or vinegar. It may also taste terrible, like wine. While colour changes may not mean the cheese is unsafe to eat, its flavour and texture will be sub-optimal.
| Characteristics | Values |
|---|---|
| Smell | An "off" smell can indicate that cheese has gone bad. This could be the scent of spoiled milk, ammonia, or even of a refrigerator or freezer. |
| Appearance | Any significant colour change can indicate that cheese has spoiled. The presence of certain types of mould can also be a sign of spoilage, especially on soft cheeses. |
| Texture | Changes in texture can indicate that cheese has gone bad. Hard cheeses can become brittle and prone to cracking due to changes in moisture content. Soft cheeses can become mushy. |
| Taste | A sour or unpleasant taste can indicate that cheese has gone bad. |
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What You'll Learn
Cheese smell alone may not indicate spoilage
While smell can be a good indicator of whether cheese has gone bad, it is not always reliable on its own. Cheese is an ever-changing ingredient that will continue to mature after purchase, and different cheeses age and spoil differently. Therefore, it can be tricky to determine if cheese has gone bad, especially if it is already mouldy or has a strong odour.
The smell of cheese can indicate spoilage when there is an "off" smell, which could be of spoiled milk, ammonia, or even of a refrigerator. This is due to the growth of bacteria or the breakdown of proteins and fats in the cheese. However, some cheeses can be pungent and have an "off" smell even when fresh, so smell alone may not be a reliable indicator of spoilage for these varieties.
In addition to smell, it is important to consider other factors such as appearance, texture, and taste. Mould, for example, is well-known to appear on cheese, but it is important to distinguish between voluntary and involuntary mould. Most blue cheeses and flowery-rind cheeses are impregnated with Penicillium, a type of controlled mould. If other types of mould develop on soft cheeses, it is recommended to discard the entire product.
Texture can also be an indicator of spoilage. Hard cheeses like Cheddar can start to crack due to changes in moisture content and the growth of unwanted bacteria. On the other hand, soft cheeses with higher moisture content, such as Brie, are more prone to spoilage caused by bacteria that produce butyric acid, resulting in an unpleasant smell and taste.
Therefore, while smell can be indicative of cheese spoilage, it is important to consider other factors such as appearance, texture, and taste to make a comprehensive determination. Each cheese is unique, and a combination of these indicators will provide a more accurate assessment of whether the cheese has gone bad.
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Ammonia and other chemicals can cause a pungent smell
Cheese is a wonderful food, but it can be hard to tell when it has gone bad. This is because cheese is an ever-changing ingredient that continues to mature after purchase. As such, it's important to use your senses, especially sight, smell, and taste, to determine whether your cheese has spoiled.
Ammonia is one of the most common chemicals found in spoiled cheese. Produced by bacteria breaking down protein, it has a strong, pungent smell similar to cleaning products or urine. Excessive amounts of ammonia indicate spoilage, though small amounts are normal in aged or washed-rind cheeses. Butyric acid (or butanoic acid) is another chemical that can be present in spoiled cheese. This short-chain fatty acid is produced when bacteria break down fats in the cheese, resulting in a pungent, rancid smell and an unpleasant taste.
Other compounds can also cause pungent smells in cheese. For example, the earthy aroma in some soft cheeses like Brie de Meaux is caused by a compound called geosmin, produced by the bacteria used in the ripening process. Additionally, mold can develop in cheese, and while some types of controlled mold are normal, the presence of other molds can indicate spoilage.
It's important to note that the smell of cheese can be indicative of spoilage, but it's not always a reliable indicator. Some cheeses are naturally pungent and "off"-smelling, so it's essential to consider other factors such as appearance and texture. Significant colour changes and unusual texture variations, such as cracking in hard cheeses, can indicate that cheese has gone bad.
To summarize, ammonia and other chemicals like butyric acid and geosmin can cause a pungent smell in cheese, but spoilage should be determined using multiple factors, including appearance and texture changes. Remember to consume cheese quickly, handle it properly with clean utensils, and store it in a cool, dry place to prevent spoilage.
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Mould can be good or bad
Mould is well-known to appear on cheese, and it is essential to distinguish between voluntary and involuntary mould. Blue cheeses and flowery-rind cheeses are often impregnated with Penicillium, a type of controlled mould. It is normal to find mould in blue cheese and on the rinds of Camembert and Brie. However, if you spot mould on a soft cheese that is not supposed to be there, it is recommended to discard the entire cheese.
Involuntary mould can indicate that the cheese has gone bad. Mould develops more easily in a damp environment, which is why softer cheeses with higher moisture content have a shorter shelf life than harder cheeses. The moisture in soft cheeses provides an ideal environment for harmful bacteria to thrive, leading to spoilage.
Additionally, the smell of cheese can be a good indicator of whether it has gone bad. Spoiled cheese may emit an unpleasant odour due to bacterial growth or the breakdown of proteins and fats. Ammonia, butyric acid, and geosmin are chemicals that can be present in off cheese, contributing to a pungent or rancid smell. Any significant change in the smell of cheese from its normal odour suggests spoilage.
Other indicators of cheese going bad include changes in appearance and texture. Colour alterations may indicate that something has changed in the milk, and hard cheeses like Cheddar may start to crack due to changes in moisture content and bacterial growth.
Therefore, while mould can be desirable and beneficial in certain types of cheese, such as blue cheese and Camembert, it can also signify spoilage in other varieties, especially soft cheeses. It is crucial to consider the type of cheese, its storage conditions, and any changes in smell, appearance, and texture to determine whether the mould is intentional or a sign of the cheese going bad.
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Colour and texture changes may indicate spoilage
Cheese is a perishable food, and it can be difficult to determine whether it has gone bad, especially as it often has a strong smell and unique texture to begin with. However, any significant colour change in cheese can be a sign that it has spoiled. While this may not necessarily mean that the cheese is unsafe to eat, its flavour and texture will likely be affected.
Texture can also be a good indicator of spoilage. It is important to note that some changes in texture may be normal for certain types of cheese. For example, maturing cheese will change in texture. However, any sudden or unusual changes in texture can indicate spoilage. Hard cheeses like cheddar can start to crack when they spoil due to changes in moisture content and the growth of bacteria. As hard cheeses age, they lose moisture, which can cause them to become brittle and prone to cracking.
To prevent cracking, store your cheese in a cool place with good air circulation. It is also important to note that soft cheeses tend to go bad more rapidly than hard cheeses, as they are more susceptible to bacteria. Therefore, soft cheeses should be consumed within two weeks of buying, whereas hard cheeses can be kept for six to eight weeks.
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Soft cheeses spoil faster than hard cheeses
Soft cheeses tend to spoil faster than hard cheeses due to their higher moisture content, which provides an environment where bacteria can more easily flourish. This means soft cheeses are more perishable and typically last only one to two weeks after opening when stored in the refrigerator. On the other hand, hard cheeses, such as Cheddar, Parmesan, and Gouda, are low-moisture foods, which makes it difficult for bacteria to grow and thrive. This gives hard cheeses a longer shelf life, with unopened blocks lasting up to six months in the fridge and opened hard cheeses lasting about three to four weeks.
It's important to note that the time it takes for cheese to spoil depends on several factors beyond moisture content, including storage practices, temperature, and preservatives. For example, harder, drier cheeses such as Parmesan and salted butter can be stored at warmer temperatures without refrigeration. Clothbound cheddars can also be stored for longer periods due to the cloth binding, which slows the drying-out process. Waxed rind cheeses may be more susceptible to temperature fluctuations but can still have a long shelf life if stored properly.
To extend the shelf life of cheese, it should be stored in a breathable material like parchment paper or cheesecloth and kept in the refrigerator at a temperature below 40°F (4°C). Additionally, when cutting cheese, it's important to use clean utensils and wash your hands thoroughly to avoid introducing bacteria that can cause the cheese to spoil more quickly.
Signs of spoilage in cheese include mould, dryness, a yeasty or ammonia smell, a slimy surface, dark spots, cracks, and changes in texture or colour. Ammonia is one of the most common chemicals found in spoiled cheese, produced by bacteria breaking down protein and giving off a pungent smell similar to cleaning products or urine. Butyric acid is another chemical produced by bacterial breakdown, resulting in a pungent, rancid smell and an unpleasant taste. A change in the smell of the cheese from its normal odour can often indicate that it has gone bad and should be avoided. However, it's important to note that some cheeses have a strong odour even when fresh, so it's helpful to smell the cheese when you first purchase it to establish a baseline.
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Frequently asked questions
There are three main attributes to look for when determining if cheese has gone bad: smell, appearance, and taste. Any significant change in the smell of the cheese from its normal odour can be a sign that the cheese has gone off.
Bad cheese can develop a range of unpleasant odours, from rancid milk to ammonia, or even of a refrigerator or freezer.
This depends on the type of cheese. It's a good idea to smell your cheese when you first purchase it so that you can notice when something is off.
It depends on the type of cheese and mould. Most blue cheeses and flowery-rind cheeses are impregnated with Penicillium, a type of controlled mould. If you spot mould that shouldn't be there, especially on a soft cheese, throw the whole cheese away.
This depends on the type of cheese and how it is stored. Hard cheeses can last up to a month in the fridge after opening, while soft cheeses should be consumed within two weeks of buying.
