Cheese Gone Bad: What You Need To Know

Cheese is a staple in many households, but it's important to know when it goes bad to avoid food poisoning. Cheese can last in the fridge anywhere from two weeks to six months, depending on factors like storage practices, moisture content, and preservatives. Hard cheeses, such as cheddar and Parmesan, tend to last longer than soft cheeses like mozzarella or cream cheese due to their lower moisture content, which makes them less susceptible to bacterial growth. However, it's crucial to inspect your cheese for signs of spoilage, such as an unpleasant smell, a slimy surface, dark spots, dryness, cracks, or mold. If you spot any of these issues, it's best to discard the cheese.

To prolong the shelf life of your cheese, proper storage is essential. Avoid tightly wrapping cheese in plastic wrap, as it can suffocate the cheese and promote the growth of unwanted bacteria. Instead, use parchment paper, cheesecloth, butcher paper, or cheese storage bags, and store the cheese in the vegetable drawer of your refrigerator, maintaining a temperature below 40°F (4°C).

Mould growth

Different types of mould can cause various colour changes on the cheese, such as blue, red, or white spots. While some moulds on cheese are harmless, others can be toxic and potentially dangerous if consumed in large amounts. It is crucial to check for signs of unsafe mould growth, such as unusual colours, textures, or odours. Any cheese that appears spoiled or contaminated should be discarded.

When examining cheese for mould, it is important to note that some moulds may be desirable and safe for consumption. For example, white specks or crystallised patches on aged hard cheeses like cheddar, parmesan, and gouda are typically safe and indicate the presence of calcium lactate crystals rather than mould.

To prevent mould growth and extend the shelf life of cheese, proper storage is essential. Soft cheeses like mozzarella should be kept in their original liquid to prevent drying out. Additionally, storing cheese in a suitable container, such as a sealable Tupperware box, can help maintain freshness.

In summary, mould growth on cheese can be both desirable and undesirable, depending on the type of cheese and the presence of controlled moulds. It is important to check for signs of unsafe mould growth and practise proper storage methods to ensure the safety and longevity of your cheese.

Discolouration

One factor that can cause discolouration is oxidation. This occurs when beta-carotene, a compound found in high levels in cow's milk, breaks down. Beta-carotene is responsible for the yellow colour of most cheeses, so when it breaks down, the exposed part of the cheese will lose its yellow colour and appear much whiter.

Another cause of discolouration is browning, which can be a sign of spoilage in cheeses like Gouda and Parmesan. Browning is the result of a complex reaction between reducing sugars and amino acids from the breakdown of protein in the cheese. This reaction is more likely to occur in cheeses that contain thermophilic cultures because of their effect on lactose, which can result in a build-up of sugar. When combined with warmer temperatures and lengthy storage, this build-up of sugar can cause Maillard browning.

In addition to discolouration, other visual indicators of spoilage include mould growth and a slimy or greasy texture. While some types of mould on cheese are safe and even desirable, such as in blue cheese or Brie, others can be harmful and indicate spoilage. Harmful mould can appear in various colours, including black, red, orange, or white, and often has a fuzzy or powdery texture and an unpleasant odour. If you notice any of these signs of discolouration or other spoilage, it's best to discard the cheese to avoid potential health risks.

Changes in texture

Hard cheeses, on the other hand, tend to harden or crack when they spoil. This is due to changes in the cheese's moisture content and the growth of unwanted bacteria. As hard cheeses age, they lose moisture, becoming brittle and prone to cracking. To prevent this, store hard cheeses in a cool place with good air circulation and the right humidity conditions.

Another texture change indicative of spoilage is grittiness or graininess on the rind of soft washed rind cheeses. This is caused by deacidification, which leads to crystal formation. While a gritty rind does not always indicate spoilage, a slimy and excessively gritty rind is cause for concern.

In general, any sudden or unusual changes in the texture of cheese can be a warning sign. Trust your senses and exercise caution when determining if your cheese has spoiled.

Unpleasant odours

Off cheese is often described as rancid, sour, or putrid. It can smell like spoiled milk, ammonia, or even a refrigerator or freezer. If you notice an ammonia smell, this could be a sign that your cheese has been wrapped up too long and was unable to breathe.

Other unpleasant odours include a yeasty smell, which can indicate spoilage in feta cheese, and a vomit-like smell, caused by the presence of butyric acid, which is produced by bacteria breaking down fat in the cheese.

If your cheese smells different from when you first opened it, it's likely gone bad. Trust your senses—they are often better indicators than expiration dates when it comes to cheese.

Spoilage bacteria

Cheese is derived from milk and often involves a fermentation process, which alters the milk's composition and creates an environment conducive to bacterial growth. The type of cheese significantly impacts its susceptibility to spoilage. Soft cheeses, such as mozzarella, tend to spoil more quickly than hard cheeses. This is because they have a higher moisture content, providing an ideal environment for bacteria to thrive.

One of the key indicators of spoilage in cheese is the presence of mould. Mould growth can be both desirable and undesirable. In certain cheeses like Brie and Camembert, mould is intentionally introduced to impart specific flavours and textures. However, unintended mould growth can indicate spoilage. This mould may appear as blue, red, or white spots, and it can produce spores and toxins that are harmful to consume.

Another sign of spoilage is a change in the cheese's texture. Hard cheeses may become dry, cracked, or brittle due to changes in moisture content and bacterial growth. On the other hand, soft cheeses can become slimy due to the growth of unwanted bacteria.

Additionally, spoilage bacteria can affect the odour of cheese. An off or rancid smell can indicate the presence of spoilage bacteria. Ammonia-like odours, similar to cleaning products or urine, are often a sign of spoilage, as ammonia is produced by bacteria breaking down proteins in the cheese.

To prevent spoilage, proper storage is essential. Soft cheeses should be stored in their original packaging or submerged in liquid, while hard cheeses can be wrapped in wax paper or stored in sealed containers. Consuming cheese within a week of opening is recommended, as it reduces the risk of bacterial growth and ensures a safer and more delicious eating experience.

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