CHEESE 2001 – Cultures: One, No One, One Hundred

Almost all cheeses are swarming with life: in one gram of cheese, up to one milligram can be composed of micro-organisms. The complex interactions between micro-organisms, primary materials and production conditions transform a relatively flavorless substance – milk – into an incredible variety of cheeses. These cheeses differ in shape, texture, color, odor and flavor. As with all fermented milk products with ancient origins lost in time, man learned to benefit from micro-organisms in the production of cheese long before he learned of their existence. For thousands of years, cheese-makers have conditioned the development of micro-organisms in cheese by permitting, favoring, or preventing its contamination by bacteria, yeasts, and molds. Cheese-makers controlled the development of these elements through the management of the conditions of the cheese-making and cheese-aging, inhibiting them or favoring them by changing the substrate in which they lived (making it more or less acid, more or less salty, or more or less rich in nutrients.) It is only in the last hundred or so years that microbiologists have studied the role of micro-organisms in food and that their ideas have changed, for better or worse, the method of cheese production.
The microbiology of cheese production may be studied with widely different approaches, and with various degrees of sophistication. From a microbiologist’s point of view, a cheese is (or should be) a world with four dimensions: diverse stocks, diverse species, diverse populations, and diverse communities of micro-organisms occur with time – they are changed – and they in turn change their environment, the cheese. Therefore, different cheeses require or permit different approaches with regards to the study of and to the manipulation of the microflora. In mass-produced cheese, standardized and often destined for use as ingredients in the production of other foods and not for consumption as such, it is possible, and even convenient to aim for the maximum simplification of the microflora. Thus, biodiversity is minimized with the regular pasteurization and of the use of culture starter made from well-defined ingredients. With typical artisan cheeses, instead, the complexity and richness of microflora cannot be reduced without a greatly reducing flavor. To make pizza cheese, a few stocks derived from one or two species of micro-organism (one) or the use of citric acid (none) will be enough. To create a typical artisan cheese – that miracle of flavor – one needs many diverse species, and each species must have many stocks (one hundred thousand). Today, the molecular approach to microbial ecology gives us the opportunity to study and to describe with an ever-increasing accuracy the microbial diversity of cheese. Above all, we must resist the temptation to face the problem in a purely descriptive and passive manner. From one side, the complexity of the microflora is not necessarily a guarantee of the production of fine cheeses, and often results in variations in product quality that often cannot be controlled. From the other side, the pressures of an increasingly homogenizing method of production push typical artisan cheeses into a narrowing niche. Using powerful techniques of “finger-printing” is already possible, and necessary, to construct a microbiological “identity cards” for typical artisan cheeses. These “identity cards” can be used to defend typical artisan cheese from mass-production. However, this purely defensive strategy is not enough. The new molecular approaches at a community level must be taken advantage of not only to dynamically study microbial ecology, but also to link information about the composition of the microflora in a product with its chemical and sensory characteristics. Only by following this strategy will we have the tools to involve and govern these complex interrelations with the same consistency with which we are able to produce cheeses with drastically simple microflora.

Eugenio Parente is currently an Associate Professor in the Agriculture Department at the University of Basilicata where he teaches Industrial Microbiology and Applied Microbiology in the field of Animal Production. He specializes in research into cheese microbiology and he is a columnist for the magazine Caseus.

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