Chapter 15

Wine Spoilage Microorganisms

(book excerpts)

The winemaking process includes multiple stages at which microbial spoilage can occur, altering the quality and hygienic status of the wine and rendering it unacceptable. The major spoilage organisms include yeasts, bacteria, and molds. Some of the wine spoilage yeasts belong to the genera Brettanomyces, Candida, Hansenula, Pichia, and Zygosaccharomyces, but also the non-Saccharomyces yeasts species. Bacteria include lactic acid bacteria such as Lactobacillus, Pediococcus, and Oenococcus, and acetic acid bacteria such as genera Acetobacter and Gluconobacter. Mold, most notably Botrytis cinerea, is a potential problem at harvest and crush because it can lead to premature oxidation, and it makes grapes more susceptible to contamination by other microorganisms. The faults or defects caused by wine spoilage organisms include bitterness and off-flavors, and sensory visual faults, such as film formation, turbidity, viscosity, and sediments. Some of these spoilage organisms can also produce biogenic amines. The judicious use of chemical preservatives such as sulfur dioxide during the winemaking process decreases the risk of microbial spoilage, but strains vary considerably in their sulfur dioxide sensitivity. Sources of microorganisms include: grape berries, harvesting equipment, winery equipment and tools (destemmer/crusher, press, transfer hoses, pumps, valves), barrels, bungs, wine thieves, corks, and bottling lines. Some of the hot spots for contamination in wineries are: presses, tank bottom valves, ball valves (hard to clean and sanitize), oak barrels (especially around the bung hole), small fittings, transfer hoses, filters, floors, and floor drains. Factors that promote microbial growth include: sugar, malic acid, nutrients (nitrogen), high pH (greater than 3.6), high temperature, and oxygen.

Click on the following topics for more information on wine spoilage microorganisms.

Topics Within This Chapter: