Taxonomic and Ecological Diversity of Food and Beverage Yeasts

Abstract

Fermentation has been used for several thousand years as an effective and low-cost resource to preserve the quality and safety of foods. Apart from this primary role, fermentation adds value and enhances nutritional quality and digestibility through biological enrichment, and provides dietary enrichment through aroma and flavour production and modifying textures of food substrates. All these changes are operated by microorganisms, which, naturally present (spontaneous fermentations) or added (inoculated fermentation) in raw materials, break down complex carbohydrates and proteins into more easily digestible elements. Among the fermentation microorganisms, yeasts are undoubtedly the most important group of microorganisms that are exploited for commercial purposes. Yeasts used in food fermentation processes modify original materials organoleptically, physically and nutritionally and for this they have been used for millennia in bread-making and production of alcoholic beverages. A diversity of fermented foods, which vary according to geographical area and cultural preference, are produced across the globe and the individual and peculiar characteristics which distinguish and typify each food are determined by the expression of the wide biodiversity of the fermenting microorganisms, such as yeasts. In Western countries yeasts are involved in the production of kefir from milk, beer from barley and hops, and wine from grapes, while in developing countries, where the lack of resources limits the use of techniques such as vitamin enrichment of food and the use of capital-intensive processes for food preservation, food fermentation contributes substantially to food security. In these countries there is a wide diffusion of traditional fermented foods, produced from both edible and inedible raw materials, based on local customs and generally consumed as dietary staples. Here we report the ecology and the role of yeasts involved in fermented food and beverages, focusing on the dominant species and their effect on the product quality, summarised in Table 2.1. Chapter 2