Kamil Perry
Occasionally, cheese can develop a pinkish hue, known as 'pinking'. This phenomenon is considered a defect by the cheese industry, and it is particularly common in aged Cheddars, Swiss alpine cheese, and some Italian cheeses, such as Parmigiano Reggiano and Fontina Val d’Aosta. Despite extensive research, the exact cause of pinking remains a mystery, although it has been linked to the presence of certain microbes and chemical changes in the cheese.
| Characteristics | Values |
|---|---|
| Type of cheese | Cheddar, Swiss, Italian |
| Cause | Unknown, but may be due to a change in annatto, or the Maillard reaction of cheese components |
| Microbe | Deinococcus-Thermus, Thermaceae, Thermus, Thermus thermophilus |
| Bacteria | Propionic acid bacteria |
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What You'll Learn
- Pinking is a defect that affects the cheese industry worldwide
- The phenomenon has been noted since 1933 but its basis remains unknown
- Pinking is caused by the presence of the microbe Thermus thermophilus
- The defect can manifest in a number of ways, depending on the cheese type
- Pinking is of no danger to the consumer
Pinking is a defect that affects the cheese industry worldwide
The defect can manifest in different ways, depending on the type of cheese. It may appear as patches or cover the entire surface of the cheese block, or it may occur as a uniform pink border below the external surfaces, giving the cheese a pink ring appearance. It can also be distributed sporadically within the cheese block.
The cause of pinking has not been conclusively determined, although several hypotheses have been proposed. One theory suggests that it is due to a direct chemical change of cheese constituents, such as a change in annatto (the natural colour used in cheeses) to other coloured chemicals such as carotenoids, which may be influenced by sunlight. Another hypothesis involves the Maillard reaction of cheese components.
Research has also implicated the presence of certain microbes in the development of pinking. It has been found that cheese with pinking contains an extra microbe from the phylum Deinococcus-Thermus, specifically the genus Thermus and family Thermaceae. These microbes are known as thermophiles, as they thrive in environments with temperatures above 65°C. Additionally, there appears to be an interplay between Thermus thermophilus and propionic acid bacteria, with higher levels of both resulting in increased carotenoid production and pinking.
Pinking is considered a defect by the cheesemaking industry, and if detected before shipment, affected cheese wheels are discarded or repurposed, resulting in financial losses for cheesemakers. However, it is important to note that this discard is purely for aesthetic reasons, and pinking poses no danger to consumers.
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The phenomenon has been noted since 1933 but its basis remains unknown
The phenomenon of cheese turning pink, or 'pinking', has been noted since 1933 but its basis remains unknown. It particularly impacts a range of ripened cheeses, including Swiss, Cheddar, and Italian-type cheeses. It can manifest in a number of ways, depending on the cheese type: at the surface of the cheese block (in patches or over the entire surface), as a uniform pink border occurring below the external surfaces of the cheese block, conferring a pink ring appearance, or distributed sporadically within the cheese block.
Pinking is considered a defect by the cheesemaking industry, and if caught before shipment, it will mean discarding or repurposing the entire cheese wheel, resulting in a financial loss for cheesemakers. However, it should be noted that this discard is for aesthetic reasons only, and pinking is of no danger to the consumer.
Several hypotheses have been put forward to explain the cause of pinking. One theory suggests a direct chemical change of cheese constituents, such as a change in annatto (the natural colour used in cheeses) to other coloured chemicals such as carotenoids due to sunlight. Another theory proposes that pinking may be caused by the Maillard reaction of cheese components.
Research has also identified the presence of certain microbes in pinking cheese that are not found in non-pinking cheese. Specifically, pinking cheese has been found to contain microbes from the phylum Deinococcus-Thermus, family Thermaceae, and genus Thermus. These microbes are known as thermophiles, as they prefer to grow in environments where the temperature is greater than 65 °C. Additionally, it has been observed that cheese made with Thermus thermophilus addition showed increased carotenoid production and pinking, suggesting a potential interplay between microbes and the pinking phenomenon.
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Pinking is caused by the presence of the microbe Thermus thermophilus
Some cheeses, particularly aged Cheddars, Swiss alpine cheese, and some Italian cheeses, can develop a pinkish hue, known as 'pinking'. This phenomenon has been observed since 1933, but its cause has never been conclusively explained. One hypothesis is that pinking is caused by a direct chemical change of cheese constituents, such as a change in annatto (the natural colour used in cheeses) to other coloured chemicals such as carotenoids due to sunlight. Another hypothesis is that pinking is caused by the Maillard reaction of cheese components.
Recent research has provided some insight into the potential microbial causes of pinking. It has been found that pinking cheese contains an extra microbe from the phylum Deinococcus-Thermus, family Thermaceae, and genus Thermus. This phylum of microbes are known as thermophiles, as they are able to grow in environments where the temperature is greater than 65 °C.
Further genetic examination has identified specific strains of the Thermus microbe present in pinking cheese and not within control samples. Specifically, three out of four cheeses that exhibited pinking contained *Thermus thermophilus* with lactic acid starter cultures and varying levels of propionic acid bacteria. The cheese made with *Thermus thermophilus* showed increased carotenoid production and pinking, while the cheese made without *Thermus thermophilus* lacked any form of pinking.
Therefore, it can be concluded that pinking is caused by the presence of the microbe *Thermus thermophilus*, which interacts with propionic acid bacteria to produce carotenoids, resulting in the pinkish hue observed in some cheeses.
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The defect can manifest in a number of ways, depending on the cheese type
The cause of this 'pinking' has never been conclusively explained, although many hypotheses have been put forward. One theory is that it is caused by a direct chemical change of cheese constituents, such as a change in annatto (the natural colour used in cheeses) to other coloured chemicals such as carotenoids due to sunlight. Another theory is that it is caused by the Maillard reaction of cheese components.
Investigators have also used genetic techniques to examine the microbes present in pinking cheese. They found that pinking cheese contained an extra microbe from the phylum Deinococcus-Thermus, family and genus Thermaceae and Thermus respectively. This phylum of microbes are known as thermophiles, as they are able to grow in environments where the temperature is greater than 65 °C. The cheese which had the highest levels of propionic acid bacteria also showed the most pinking, suggesting interplay between the two microbes.
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Pinking is of no danger to the consumer
Occasionally, you may come across cheese with a pinkish hue, or 'pinking', often just under the rind. This phenomenon is a defect in the cheese, which, if caught before shipment, will result in the entire cheese wheel being discarded or repurposed, causing a financial loss for cheesemakers. However, it is important to note that this discard is purely for aesthetic reasons, and pinking is of no danger to the consumer.
Pinking is most often found in aged cheddars, but it can also affect Swiss alpine cheese and some Italian cheeses, such as Parmigiano Reggiano and Fontina Val d’Aosta. It can manifest in different ways, depending on the cheese type. For example, it may appear as patches on the surface of the cheese block, a uniform pink border below the external surfaces, or be distributed sporadically within the cheese block.
The cause of pinking has never been conclusively explained, although several hypotheses have been proposed. One theory suggests that it is due to a direct chemical change of cheese constituents, such as a change in annatto (the natural colour used in cheeses) to other coloured chemicals like carotenoids, which are produced by the microbe Thermus thermophilus. Another hypothesis involves the Maillard reaction of cheese components.
Investigators have used genetic techniques to examine the microbes present in pinking cheese compared to non-pinking control samples. They found that pinking cheese contained an extra microbe from the phylum Deinococcus-Thermus, family Thermaceae, and genus Thermus. This phylum of microbes, known as thermophiles, prefer to grow in environments where the temperature is greater than 65 °C. The specific strains present in pinking cheese, but not in control samples, were also identified.
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Frequently asked questions
There is no specific type of cheese that is pink. However, some cheeses can turn pink due to a defect in the cheesemaking process.
The pink colour, known as 'pinking', is caused by an extra microbe from the phylum Deinococcus-Thermus. This microbe is known as Thermus thermophilus, and it increases carotenoid production, resulting in the pink hue.
Yes, pink cheese is safe to consume. The pinking is considered a defect by the cheesemaking industry for aesthetic reasons only, and it does not pose any danger to consumers.
Aged cheddars are the most commonly affected, but Swiss alpine cheese and some Italian cheeses, such as Parmigiano Reggiano and Fontina Val d'Aosta, can also turn pink.
The presence of Thermus thermophilus can result in increased carotenoid production and pinking in the cheese. The level of pinking is also influenced by the amount of propionic acid bacteria present, with higher levels of this bacteria leading to more pronounced pinking.
