Cheeses with molds

The habit of buying pre-packaged cheeses takes the consumer away from the world of molds and cheese crusts. The product inside the package must be perfect and uncontaminated, especially if it is a fresh and soft cheese. However cheeses, at least cheeses “like we mean it”, need the work of enzymes, bacteria and molds to develop the aromatic complexity we are looking for. We talked about enzymes and lactic ferments. Now it’s time for molds.

Molds, yeasts and mushrooms

Molds and yeasts belong to the mushroom kingdom. Molds are strictly aerobic organisms (they need oxygen to develop). They are among the most widespread in the living world: more than 400,000 species have been classified, characterized by a great ability to grow and develop on the most disparate environmental conditions and substrates. Molds are different from bacteria not only because they are larger, but also because they have vegetative and reproductive bodies.

They consist of a sort of tubular sprout called “hyphae” which develops extending and infiltrating into the substrate from which it draws nourishment. The vegetative hyphae often have small dimensions, the reproductive ones on the other hand are macroscopic and develop the spores for reproduction. The production of spores is huge, even millions of units for each single hypha. There is no natural environment in which there are no mold spores.

Molds: good or bad?

Since ancient times mold and yeast, especially the latter, have been playing a fundamental role in food production: bread, wine and beer would never have been produced without the presence of yeasts; Gorgonzola, Roquefort and salami would not exist if there were no molds. In 1928, thanks to Penicillium Notatum Chrysogenum, the first antibiotics were produced, that saved several lives from diseases like pneumonia, diphtheria and gonorrhea.

Despite the previous examples describe the usefulness of molds, we cannot forget the presence of fungal microorganisms that can also be very dangerous for health, since they produce mycotoxins: toxic substances that can pollute food, making it very dangerous for the body. The major producers of mycotoxins belong to the following genera:

- Aspergillus, from which are produced various types of mycotoxins called aflatoxins (potentially present in cereals, dried fruit and milk);
- Penicillium, from which ochratoxins develop (potentially present in cereals) and patulins (which may be present in fruit juices);
- Fusarium, from which fumonisins derive (potentially present in maize).

Mycotoxins can develop on plants, both during cultivation and later in conservation, but we might also find them in products of animal origin (e.g. mycotoxins might contaminate milk when the animal is fed with “polluted” vegetables).

Molds alter food and are very visible: this aspect allows us to “protect ourselves” because we instinctively do not consume moldy foods. However if we accidentally eat a musty food we would not have immediate consequences, problems would arise only if molds ingestion was a constant in our diet. In any case, producers are obliged to control food (e.g. the presence of possible mycotoxins) before it is placed on the market, to guarantee and protect consumers’ health.

Molds and cheeses

Molds usually grow on the surface of cheeses, especially on medium/long aged ones, but also on fresh and soft cheeses, causing in this case a deterioration of the products.

There are cheeses that owe their characteristic taste to molds - which can be found in the paste (e.g. blue cheeses) or on the crust (e.g. bloomy rind cheeses) - or to yeasts (e.g. washed rind cheeses).

Blue cheese

The term “erborinato” (blue cheese in Italian) derives from “erborin”, a dialact word of Milan area to identify parsley. It describes a cheese with green-gray or blue veins in the paste, due to the presence of molds, developed during ripening.Originally the formation of the marbling was completely natural. To let the mold developing, the cheeses were left in humid environments such as caves, where molds were certainly present in fair quantities. During aging the wheels were pierced so that the molds could penetrate through the holes. Obviously there was no possibility to control the development of molds, that happened randomly, varying both in qualitative and quantitative terms. Today this technique is almost no longer used, except for some niche products. Mostly “selected molds” (e.g. Penicillium Roquefortii, Penicillium Glaucum) are added to the milk and during ripening the cheese is pierced with needles, to create a crossing for oxygen (essential condition for molds development). In this way the marbling that is obtained is rather homogeneous. Moreover, according to the molds selected, the cheese-maker can determine the color and the aroma that will be obtained at the end of the maturing.

Penicillium Roquefortii belongs to the family Trichocomaceae and produces proteolytic enzymes that act on the casein influencing the aroma. It can also produce large quantities of free amino acids (ammonia smell). Lipids, mainly hydrolyzed by lipase, release fatty acids which, in turn, act as a substrate for other enzymatic transformations. As a consequence, volatile compounds are thus released: e.g. heptanone (typical Gorgonzola smell), nonanone (herbaceous notes), 1-octen-3-ol (fungal aroma), 3-methyl-thio-propanol (boiled potato aroma).

Penicillium Glaucum also belongs to the Trichocomaceae family. Using this mold, however, you get more delicate cheeses with green veins, compared to the blue ones produced by Penicillium Roquefortii.

Another characteristic of blue cheeses is the intense action, of “lactose demolition” made by molds; lactic acid produced by lactic ferments is in turn used by molds.

During seasoning, thanks to the molds, the paste becomes compact and buttery, the crust gets rough, irregular, gray to reddish-yellow in colour depending on the environmental conditions and the taste goes from mild and buttery to spicy.

Bloomy rind cheeses

Molds used for the production of bloomy rind cheeses develop on the rind, rather than into the paste: Camembert and Brie are the best known, characterised by the development on the surface of a very thick edible felt of Penicillium Camemberti, belonging to the Aspergillaceae family.

The maturation of these cheeses, generally soft, is called “centripetal”: it goes from outside towards inside. Since Penicillium has a strong proteolytic power, bloomy rind cheeses usually have creamy undercrust. To obtain a soft paste, the surface/volume ratio must be thus in favor of the first; that’s why bloomy rind cheeses are usually low and flattened.

The evolution of these cheeses during ripening leads to the dissolution of casein with the formation of many amino radicals and ammonia. The compounds that mainly contribute to the aroma of these cheeses are isovaleric acid (“feet smell”), diacetyl (butter flavour), methane (boiled potato), butyric acid (sweat smell), 1-octen- 3-one (mushroom scent), methanethiol (cauliflower aroma).

Washed rind cheeses

The term “washed rind” defines a cheese which during ripening has been repeatedly and regularly rubbed, mainly with a solution of water and salt. In this way the crust is kept moist and becomes an ideal substratum for the development of microflora, which plays a fundamental role in seasoning. Also for washed rind cheeses maturation is “centripetal”, developing a soft undercrust and particular organoleptic characteristics.

The crust of these cheeses is mostly thin, pink to orange in colour, due to the development of yeasts and molds such as Geotrichum and Mucor. By decreasing acidity, they make the rind an ideal habitat for the development of Micrococcus and Staphylococcus (of non-pathogenic species) which also grow in presence of salt and which are orange-red pigmented. The taste of these cheeses is directly influenced by the presence of yeasts that produces some flavoring substances and facilitates the growth of the Micrococcus. Taleggio, Puzzone di Moena, Fontina, Reblochon, Raclette (just to name a few) are certainly related by notes of winery, yeast, broth, garlic, sometimes of “wet sponge” and more or less marked animal notes, but however intense and balanced by a sweet and melting paste.

As we have seen, bacteria, enzymes, molds and yeasts - although belonging to a world mostly invisible to the naked eye - have always played a fundamental role in the development of humanity. They are fully involved in food processing, sometimes degrading food, sometimes preserving it and other times making it “special” to our palate.

I like to imagine every food like a small ecosystem of microorganisms, alive and well balanced, that develop in synergy with each others.

Giorgia Barbaresco
Quality Director