Spoilage mousiness

Unfortunately, uncontrolled MLF also presents a risk of wine spoilage by compounds that can produce off-flavours (including acetic acid, volatile phenols and mousiness) or that may be hazardous to human health (such as ethyl carbamate and biogenic amines). The most important aspects of the development of LAB and MLF in wines are dealt with in this chapter. 

There is no available method to remove this taint effectively (Lay 2004). The removal of precursors (L-lysine and ethanol) is not feasible. As it depends on microbial activity, the preventive measures are similar to those suggested for volatile phenols when there is the risk of D. bruxellensis infection. The prevention of spoilage by heterofermentative lactic bacteria usually advised, like decreasing wine pH values and rapid inactivation by sulphur dioxide, once malolactic conversion is finished, should also be effective against bacterial mousiness. 

Brettiness". "Volatile phenols can be considered as natural components in wines and beer, or as spoilage compounds when present in excessive amounts" (84). Brettanomyces species can produce both mousiness and, at low concentrations of volatile phenolics, also "a distinct aroma described variously as cider-like, spicy, dove-like or phenolic... formed toward the end of fermentation" (84). The ethyl phenols produced can exceed the sensory threshold 16-fold (85), producing wines, at high concentrations of volatile phenolics, with distinct "barnyard", "stable", and "animal" phenolic odors (85-87). Wines with high concentrations of phenolic odors are deemed "Bretty" by tasters. 

Heterofermentative lactobacilli have been associated with the mousy defect in wines (Costello et al., 2001 Heresztyn, 1986). This type of spoilage is characterized by the development of an offensive odor that renders a wine... 

Lactobacillus is also an important group of spoilage organisms, especially in foodstuffs high in sugars. In addition, they are responsible for the production of mousy flavours in wine, and may also cause spoilage in meat. 

This fault is associated with wines rather than musts because synthesis of these compounds requires the presence of ethanol (Heresztyn, 1986). As the aroma threshold in wine is very low, 1.6(lg/L (Riesen, 1992), very little growth of these bacteria is required to potentially spoil a wine. Sponholz (1993) suggested that mousiness is not a common problem, but low-acid wines with insufficient SO2 can be more prone to spoilage. Lay (2003) reported that different cultures of Brettanomyces formed a distinctive mousy taint in the presence of lysine or ammonium phosphate under both aerobic and anaerobic conditions. 

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