Spoilage
Spoilage in wine refers to undesirable changes in aroma, flavour, or appearance that render a wine faulty or undrinkable. While all wines undergo gradual transformation during bottle ageing, spoilage is distinguished by alterations caused by microbial, chemical, or physical factors that are considered negative in quality terms.[1]
Definition and Scope
Spoilage encompasses a wide range of faults, from microbial contamination to oxidative damage. It may occur at any stage of winemaking, storage, or transport. The term is generally used for faults that make wine unmarketable, rather than the natural variability of style or maturation.[2]
Causes of Spoilage
Microbial Activity
Microorganisms are the most common agents of spoilage. Certain strains of yeast, such as Brettanomyces, produce volatile phenols associated with aromas described as medicinal, smoky, or horse-sweat.[3] Other yeasts, including film-forming types, can develop on the wine surface, especially if protective levels of Sulphur dioxide are not maintained.
Bacteria also play a role: lactic acid bacteria may lead to excessive diacetyl, imparting buttery aromas, or contribute to mousiness. Acetic acid bacteria, often in the presence of oxygen, are responsible for high levels of volatile acidity, a sharp vinegar-like fault.[4]
Chemical and Physical Factors
Oxidation is one of the principal non-microbial causes of spoilage, marked by browning in white wines and loss of fruit character. Excessive exposure to oxygen, whether during winemaking or in faulty closure systems, accelerates this process.[5]
Heat damage, known as “cooked” or “maderised” character, may occur when wine is stored at high temperatures. Light-strike, a condition caused by exposure to ultraviolet light, produces unpleasant aromas resembling wet wool or cabbage, particularly in delicate white wines bottled in clear glass.[6]
Common Forms of Spoilage
- Volatile acidity (VA): Caused mainly by acetic acid bacteria, producing vinegar-like aromas. - Brettanomyces: Yeast contamination leading to phenolic and animal notes. - Sulphide faults: Hydrogen sulphide and mercaptans create odours of rotten eggs or onion. - Oxidation: Loss of freshness, browning, and nutty flavours. - Microbial haze or sediment: Uncontrolled microbial growth leading to visual defects.[7]
Prevention and Management
Preventing spoilage requires rigorous control of conditions throughout production and storage. Hygiene in the winery, effective use of sulphur dioxide, controlled fermentation temperatures, and exclusion of oxygen are critical safeguards.[8] Monitoring of microbial populations, along with careful storage and transport under cool, dark, and stable conditions, helps reduce risks of post-bottling spoilage.[9]
Modern analytical techniques, such as gas chromatography and DNA-based assays, allow early detection of spoilage organisms before sensory faults appear. Winemakers may also apply corrective measures, including sterile filtration or micro-oxygenation, to stabilise wine quality.[10]
See also
References
- ↑ Robinson (ed.), The Oxford Companion to Wine, 2015.
- ↑ Jackson, Wine Science, 2020.
- ↑ Ribéreau-Gayon et al., Handbook of Enology, Vol. 1, 2006.
- ↑ AWRI, “Wine faults: microbial spoilage”, awri.com.au.
- ↑ Jackson, Wine Science, 2020.
- ↑ Zoecklein et al., Wine Analysis and Production, 1999.
- ↑ Robinson (ed.), The Oxford Companion to Wine, 2015.
- ↑ Ribéreau-Gayon et al., Handbook of Enology, Vol. 1, 2006.
- ↑ Jackson, Wine Science, 2020.
- ↑ AWRI, “Wine faults: microbial spoilage”, awri.com.au.