Bushra Griffith
Blue cheese is famous for its distinctive flavour and pungent smell, which are the result of a mould that is introduced during the cheesemaking process. This mould is dormant until the cheese is pierced, exposing it to oxygen and activating it. This process is done intentionally to create blue cheese, but it can also happen accidentally with other types of cheese. The mould grows from the inside out, creating the blue veins that are characteristic of blue cheese. While blue cheese can last a while in the refrigerator, it can still go bad, and it's important to know how to spot this to avoid eating spoiled cheese.
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What You'll Learn
Blue mould cultures are added to milk during the cheesemaking process
Blue cheese can be made from cow, goat, sheep, or even buffalo milk, which may be raw or pasteurized. The cheesemaker can affect the outcome of a given blue cheese in terms of how much they pierce the wheels of cheese, how the cheese is ripened, and for how long.
The mould itself is from one or more strains from the genus Penicillium. However, these are not the same strains that might become something you take as an antibiotic. The blue mould culture is already present in the cheese, to be activated later. When producing Stilton, for example, cheesemakers pierce the cheese, allowing oxygen to activate the Penicillium roqueforti that has been added to the milk.
The timing and frequency of piercing a cheese will alter its taste and appearance. When piercing a Stilton cheese, most producers would wait until the cheese is at least four weeks old. Commercial Stilton producers often pierce cheeses up to three times during the fourth and fifth weeks, which encourages a quick and heavy bluing. This allows the cheeses to be sold quickly, delivering a speedier return on the milk and increasing the volume of cheese produced in a year.
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Oxygen is introduced to the cheese through piercing
Blue cheese gets its distinctive colour and flavour from the mould that grows on it. While most other cheeses are bacteria-ripened, blue cheese is unique in that it ripens from mould activity. The mould spores are introduced into milk at the beginning of the cheesemaking process, but they remain dormant until the cheese is pierced.
The timing and frequency of piercing a cheese will impact its taste and appearance. For example, commercial Stilton producers often pierce cheeses two to three times during the fourth and fifth weeks of maturation to encourage quick and heavy bluing. This allows the cheese to be sold more quickly and increases the volume of cheese produced annually. However, some cheesemakers may choose to prioritise taste over expediency by allowing the cheese to mature longer before piercing, resulting in a more subtle blue flavour.
While blue cheese is known for its blue mould, it's important to note that not all moulds on cheese are safe. Blue cheese can still spoil, and it is recommended to check for signs of spoilage, such as sliminess, grit, an ammonia-like smell, or the presence of grey, green, pink, or white mould. Proper storage practices, such as wrapping the cheese in parchment or wax paper and storing it in the refrigerator, can help extend the shelf life of blue cheese.
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Blue mould grows and travels outwards, ripening the cheese
Blue mould, or Penicillium roqueforti, is added to milk during the cheesemaking process. However, it remains dormant until the cheese is pierced, a process that involves inserting long, thin metal needles into the cheese. When exposed to air, the mould activates and starts to grow and travel outwards, creating streaks in the cheese and maturing it from the inside out. The piercing process determines the taste and appearance of the cheese. For example, piercing a Stilton cheese earlier in its maturation process will result in a blander taste compared to piercing it at a later stage.
The growth of blue mould is encouraged by specific conditions, such as temperature and humidity. The ideal temperature for ripening blue cheese is between 8 and 10 degrees Celsius, with a relative humidity of 85-95%. The mould also requires oxygen to grow, which is why cheesemakers pierce the cheese to allow oxygen to circulate and activate the mould.
The mould breaks down the fat and protein in the cheese, contributing to the distinctive texture, flavour, and aroma associated with blue cheese. The mould changes the appearance, flavour, texture, and aroma of the cheese, enhancing its taste and making it softer and more mellow as it ages.
Cheesemakers can control the growth of blue mould through various means, such as using less salt, slower maturation, or fewer piercings. This helps produce a more balanced and rounded flavour in the cheese, ensuring that the blue flavour is not overpowering.
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Blue cheese can go bad and grow other types of mould
Blue cheese is made with the mould Penicillium roqueforti, which is added to the cheese curds. This mould is chosen because it adds flavour and texture to the cheese and is safe for human consumption. However, blue cheese can still go bad and grow other types of mould. If your blue cheese has black furry specks, this is not safe to eat. White fuzz is generally considered okay, but it is up to the consumer's taste buds. If the blue veins in the cheese have turned green, this is also not safe to eat. If the cheese smells like ammonia, it should be thrown away.
Blue cheese is made by mixing raw milk (from cattle, goats or sheep) with a starter culture, such as Streptococcus lactis, to turn the milk from liquid to solid. Then, the curds are ladled into containers to be drained and formed into a wheel of cheese. The Penicillium roqueforti inoculum is then sprinkled on top, and the curds are moulded into cheese loaves. Whey drainage continues for 10-48 hours, and salt is added to preserve the cheese. Finally, the cheese is ripened by being aged in a cool, dark and damp environment.
The process of making blue cheese has been refined over the years. In the past, cheesemakers would leave rye bread in caves for weeks to encourage the growth of mould before adding the mould to the cheese. Now, cheesemakers buy pre-grown mould spores in powder form to inoculate the milk at the beginning of the cheese-making process. This allows for more consistent cheese with specific flavour profiles.
Blue cheese is known for its distinctive texture, taste, and smell. The mould in blue cheese breaks down the cheese's proteins, making it creamy, and also breaks down the fats, giving off free fatty acids that contribute to the sharp flavour and aroma. The specific strains of Penicillium roqueforti moulds are chosen by scientists to produce the best flavours, and these moulds do not produce toxins that are harmful to humans.
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Blue cheese can be preserved through refrigeration or freezing
Blue cheese is created when mould inside the cheese is exposed to oxygen, activating and changing the texture, adding flavour, and turning the cheese blue. This process can be intentional, as in the case of Stilton, where cheesemakers pierce the cheese to allow oxygen to activate the mould. However, it can also occur accidentally during the maturation process of other cheeses.
Due to their active moulds and high moisture levels, blue cheeses have a shorter shelf life than other varieties. To extend the life of blue cheese, it should be stored in a high-humidity environment, ideally at least 80% humidity. The Cheese Grotto, a specialised storage container, is designed to maintain the necessary humidity levels and provide a constant supply of fresh air to the cheese. This helps prevent the trapping of moisture, which can lead to the growth of unwanted bacteria and the rapid degradation of the cheese.
If you're aiming to maximise the shelf life of your blue cheese, it's recommended to store it in the fridge, which will slow down fermentation. The Cheese Grotto can be placed in the refrigerator, or you can wrap the cheese in cheese paper, bee's wrap, or parchment paper and place it in a humid section of your fridge, like the vegetable drawer. Another option is to use a zipper-lock bag, but avoid vacuum-sealed bags as they can trap moisture. Additionally, avoid wrapping the cheese too tightly, as this can also trap moisture and encourage bacterial growth.
For those who prefer their blue cheese at room temperature, the Cheese Grotto can be kept on the counter. This allows the cheese to be ready to eat at any moment, eliminating the need to remove it from the fridge an hour before serving. However, storing blue cheese at room temperature will reduce its shelf life compared to refrigeration.
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Frequently asked questions
Blue mould spores are introduced into milk at the beginning of the cheesemaking process. When the cheese is pricked with needles, oxygen is introduced, and the blue mould becomes active.
Yes, blue cheese contains an edible mould. However, blue cheese can go bad like any other cheese. If it is slimy, gritty, smells like ammonia, or has grey, green, pink, or white mould, it has gone bad.
To keep blue cheese fresh for as long as possible, ensure your refrigerator temperature is not set above 40 degrees Fahrenheit. For long-term storage, blue cheese can be frozen.
Accidentally blue cheeses are completely natural and edible. Simply cut off the mouldy portions and the rest should be okay to eat.
