If you're the type with enough self-restraint to allow cheese to stay in the fridge for a while, you might be alarmed by the fact that it's turned pink. Not to worry. It's probably due to a harmless, and ancient, additive.
Pink cheese isn't appetizing. In many cases, this is a good thing. It keeps people from eating cheese that has developed an ecosystem in the form of mould. Other times, it's just an embarrassing mismatch in food manufacturing. While science can extend a cheese's shelf-life, it won't make money for that cheese's manufacturers unless someone is willing to buy it even after it has been sitting on a shelf a long time. People generally are put off by foodstuff that's turned a funny colour, nor do they like being reminded that their cheese has additives -- even if those additives have been a traditional part of the cheese-making process for quite some time.
The substance that turns cheese pink, at least when it comes to cheddar and other orange varieties, is a seed called annatto, a spice that's been used in cheeses for about five hundred years. Farmers found that adding a little annatto to their pale cheeses turned them a rich gold colour. This wasn't just an aesthetic preference. Orange cheeses used to only turn up in the summer months, when cows could eat a good diet of fresh plants rich in beta carotene. Adding annatto was a farmer's slippery way of passing off winter cheese as summer cheese.
Those farmers didn't have to contend with display cases blasting the cheese with fluorescent light twenty-four hours a day. New technology created a problem for a very old science. The light bleaches out the yellow component in annatto, leaving only the darker reddish component, and giving the cheese a creepy pink colour.
Food scientists have since discovered that a lot of factors affect this pinking. Acidic cheese tends to lose colour more asymmetrically. The yellow colour components bleaches faster than the red, leading to more pinking, while neutral cheese fades evenly. Full-fat pinks more than reduced-fat.
Mostly, though, the problem is oxygen. Even in shrink-wrapped packages, the cheeses pink up around seams and bubbles. So when you see your cheese slices packaged tight, it's not just because individual slices of cheese make such great snacks. It's partly because the more air the cheese gets, the pinker it gets.
[Source: Getting the Pink Out]