Castello cheeses remarkable popularity both in Denmark and abroad.” Castello was acquired by Arla Foods, who expanded Castello into cheese markets in North America. Castello blue cheeses were developed in the 1960s. The curds are dipped into salt water, drained, and put into molds. The cheese is punctured with tiny holes and then brought into the ripening room, where it stays for about 15 days. It is then washed, cut, packed, and put in a "cooling room" for about a week at a temperature close to freezing. The washed rind hosts various molds that add to the cheese's mildly spicy flavor. It
Blue cheese enzyme, rennet, plays in removing the hairy layer in the casein micelle. Rennet is an enzyme that cleaves the κ-casein off the casein micelle, thus removing the strain that occurs when the hairy layer entangles. The casein micelles are then able to aggregate together when they collide with each other, forming the curds that can then be made into blue cheese. "Penicillium roqueforti" and "Penicillium glaucum" are both molds that require the presence of oxygen to grow. Therefore, initial fermentation of the cheese is done by lactic acid bacteria. The lactic acid bacteria, however, are killed by the low pH