History

"Boeren Leidse kaas" is by origin a by-product of butterproduction.
In the past milkfat was precious for it's nutritional value. It was retailed as butter. Because of limited preservation butter had to be produced in the direct environment of the cities where it was sold. This is the explanation for the production of butter on farm-houses in the west-side of Holland.
When the cream was seperated from the milk, the leftover, so called skim-milk, was fed to the calves, since this was of limited value.
An other alternative was the production of low-fat cheese. It is assumed that low-fat cheese was used for provision on ships to the east. Because it's low-fat one can preserve this cheese better than full-cream cheese, especially at high temperature.

Cheeses produced in the region of the City of Leiden (Netherlands) were known for it's remarkeble and fine taste, here Cumin-seed was added and so this was called Leidsche Kaas. These cheeses obtained a red skin, so when brought to market traders could recognize it as low-fat and added with cumin-seeds made in the region of Leiden. The red coating was and still is a trade mark.

"Boeren Leidse kaas" is no longer considered a by-product of butterproduction, now we consider butter as by-product in the production of Boeren-Leidsekaas.

Why is it a red colour?
In the past cheese obtained a coating from colostrum (first milk given after a cow gave birth). Colostrum containes microbes proofed against bacteries (like human colostrum). Annatto (made out of the seeds of the Orleaan-plant) can be added to cheese for the purpose of colouring it slightly.
In the region of Leiden farmers added Annatto to the colostrum before coating their cheeses. This resulted in a deep red skin.
Nowadays the coating we use is ready-made.