Odours of Fungi

When you enter a damp cellar, open a packet of mushrooms or go for a walk in the woods in the autumn, you will often smell the chemical activities of fungi. Although many of the more pungent smells of decay are associated with bacterial activity, fungi make a characteristic, often more musty , contribution. The volatile compounds of mushrooms contribute to their organoleptic properties. Other compounds behave either as insect attractants or as feeding deterrents. Yet others contribute to the relationship of a fungus with its competitors. 

Other compounds that have been detected in mushroom volatiles include a range of Cg alcohols, their esters and oxidation products and various other compounds such as benzyl alcohol, benzaldehyde, acetone, ethanol, ethyl acetate, 

3-methylbutanol, 2,4-nonodienal and 2,4-decadienal together with, surprisingly, tetrachloro-l,4-dimethoxybenzene (drosophilin A methyl ether) (7.58). 

Many other edible mushrooms produce oct-l-en-3-ol and other Cg compounds together with different metabolites that give them their characteristic taste. The ratio of the Cg compounds may vary. 3-Methylbutanal, 3-methylbu-tanol, benzaldehyde and phenylacetaldehyde, together with 1- and 2-phenyl-ethanol, have been detected in Boletus edulis. 

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Many coumarins are found in plants and a comprehensive review is available (78FOR(35)i99). Coumarin has a pleasant taste and odour and was used for flavouring until its toxic action on the liver was discovered. Among other coumarins which have toxic effects on mammals are a group called aflatoxins, e.g. aflatoxin Gi, (221), which are secondary metabolites of fungi of the Aspergillus genus. Some of these compounds have been present in animal feeds and caused deaths of the animals. In contrast, other coumarin derivatives,... 

The odours of sandalwood and cedarwood and their resistance to attack by fungi and insects have made them prized articles of commerce for both construction and decorative purposes for thousands of years. Similarly the oils derived from the woods have a long history of use in perfumery. 

PVC-P materials, such as flooring and roofing material, can be prone to microbiological attack in humid or damp conditions. This is due to the fungi using the plasticiser at the surface of the article as a food source. This can lead to partial discolouration (pink colour or black specks) which can further cause a tacky surface where dirt can accumulate. Unpleasant odours may also be a consequence. 

Boron has some exceptional performance characteristics including low mammalian toxicity, activity against fungi and insects, and low cost. A further advantage of boron is its ability to diffuse into green timbers that normally would resist traditional pressure treatment. Also, wood treated with borates has no colour and no odour... 

Fungi also emit VOCs, which are responsible for their odour. More than 500 VOCs have been identified from different fungi. One of the commonly produced VOCs, ethanol, is very volatile and acts as a potent synergiser. 

A relation was found between the odour intensity and the concentration of bacteria on the inside of the humidifier (Fig. 9). The odour intensity increases with increasing number of bacteria. This was not the case for other locations in an HVAC system. A similar correlation could not be found for fungi. 

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