Biodiversity and the survival of autochthonous fermented products.

Abstract

Many microorganisms isolated and characterized during the past century have received considerable attention from the pharmaceutical and/or food fermentation industry because of their potential biotechnological interest. Lactic acid bacteria (LAB), particularly those belonging to beneficial and nonpathogenic genera (Lactococcus, Lactobacillus, Leuconostoc, Oenococcus, and Streptococcus), have traditionally been used in the food industry. They also play an essential role in the dairy industry due to the tremendous level of human consumption of several important fermented products, mainly cheese and acidified/fermented milks. In the USA, more than 4.6 million tons of cheese and more than 1.3 million tons of yogurt were produced in 2005 [1], whereas in the European Community (EU-25) more than 8 million tons of cheese and 6.9 million tons of acidified/fermented milk were produced in 2003 [3]. These figures correspond to a global sales value that surpasses US$ 28.44 billion, with the global sales value of cheese representing about 30% of total dairy-product sales [2]. Nowadays, more than 500 kinds of cheese are manufactured worldwide, and the many varieties are derived from modifications in cheese-making techniques. However, the fermentation process whereby milk is transformed into cheese has not changed to any great extent since humans discovered the process as a means of preserving food (the fermentation of milk dates back to ~3000 BC). Cheese is a dynamic biochemical product and, unlike many processed food products for which stability is essential, it undergoes significant changes during ripening. The unripe curds of many varieties of cheese have bland and largely similar flavors. However, the sequential actions of cheese microbiota and the interactions among the different microorganisms during the ripening period result in the flavor compounds that characterize each variety. Acidifying lactococci species usually occur as dominant bacteria early in the ripening process. Afterwards their numbers decrease as they give way to lactobacilli, which, due to their higher versatility for fermentation, can survive in cheeses at stages when concentrations of major carbohydrates and free water decrease, whereas the sodium chloride load increases. Apart from the above-mentioned major genera of LAB, other bacteria, including non-starter LAB and non-lactic-acid bacteria, as well as some fungi (yeasts, moulds), staphylococci, micrococci, coryneform bacteria, and propionic acid bacteria, which develop in the product particularly during the maturation phase as secondary microbiota, are often responsible for the intensity of flavor in many dairy products. The production of a wide range of antagonistic primary and secondary metabolites, including organic acids, diacetyl, CO2 and even bacteriocins, affects the complex dynamics of microorganisms in cheese. Thus, a well-founded understanding of the microbial balance in this special living ecosystem is essential to improve older varieties of cheese and to develop new ones. Due to the dairy market’s continuous growth, commercial cultures have conventionally been selected to obtain greater quantities of product, homogeneous quality of the end product, and short production times, with the final goal of satisfying the preferences of consumers. Most varieties of commercially important cheeses are manufactured worldwide by means of commercial starter cultures of generic composition (including acidifying and aromatic diacetyl-producing lactococci strains and sometimes also leuconostocs and lactobacilli strains). In Europe, Asia, Africa, and Latin America, however, there are regions where fermented products are still manufactured traditionally. In global markets, these fermented products are now highly appreciated and are considered to be of premium value because of their flavor characteristics, which are not found in varieties of cheese produced industrially. In Europe, such products are elaborated according to well-established rules governing the production of registered designations of origin. Protected designations of origin (PDOs) apply to foodstuffs that are produced, processed, and prepared in a given geographic area using recognized