A matter of taste

Natural History, Oct, 2003 by Stephan Reebs

Every slab of cheese is an entire community of organisms, and, as with many human communities, its character may not be appreciated by everyone. Take Stilton. Made under license by only six dairies in the English Midlands, it's one of those cheeses whose strong aroma and intense flavor some find delightful and others find repellent. But just what makes a Stilton a Stilton? Danilo Ercolini, a microbiologist at Federico II University in Naples, Italy, and his colleagues at the University of Nottingham in England aimed to find out.

Using the latest techniques of DNA analysis, the microbiologists identified the panoply of bacteria that, along with yeast and the essential Penicillium mold, give Stilton its complex taste. They also discovered that distinct regions of the cheese--the blue veins (caused by piercing the ripening curd with needles to aerate it), the creamy ivory core, and the natural crust--vary in acidity and oxygen content and harbor different kinds of bacteria. Several unexpected micro-inhabitants are worth noting: two harmless species of Staphylococcus, the usually unwelcome intestinal microorganism Enterococcus faecalis, and several species of Lactobacillus. The investigators aren't certain whether they arrive on the scene by surviving the milk pasteurization process or by being introduced through equipment or other sources.

All the interlopers can serve as starter cultures in fermented products, such as yogurt and salami, in which they control the development of flavor, color, and texture. Their roles in Stilton are unknown, but their presence or absence may help explain why different batches of the cheese made at the same dairy can have highly different characteristics. Can custom-inoculated cheeses be far behind? ("Bacterial community structure and location in Stilton cheese," Applied and Environmental Microbiology 69:3540-48, June 2003)

Stephan Reebs is a professor of biology at the University of Moncton in New Brunswick, Canada, and the author of Fish Behavior 'n the Aquarium and in the Wild (Cornell University Press).