Today, the impact of yeasts on food and beverage production extends beyond
the original and popular notions of bread, beer and wine fermentations by
Saccharomyces cerevisiae (Table 1.1). In a positive context, they contribute to the fer-
mentation of a broad range of other commodities, where various yeast species may
work in concert with bacteria and filamentous fungi. Many valuable food ingredi-
ents and processing aids are now derived from yeasts. Some yeasts exhibit strong
antifungal activity, enabling them to be exploited as novel agents in the biocontrol
of food spoilage. The probiotic activity of some yeasts is another novel property that
is attracting increasing interest. Unfortunately, there is also a darker side to yeast
activity. Their ability to cause spoilage of many commodities, with major economic
loss, is well known in many sectors of the food and beverage industries, while the
public health significance of yeasts in foods and beverages is a topic of emerging
concern. This chapter defines the scope and diversity of the many beneficial and