Flavors and Fragrances

Abstract

The awareness that fungi produce enticing flavors is not new. Presumably it was their pleasant aroma that prompted the notorious Roman emperor Nero to name mushrooms “cibus deorum,” food of the gods. Not many years ago fungi were accessible for consumption if one knew how to identify edible species and had access to sites where they grew. Modern cultivation techniques have made several edible fungi much more widely available. For field mushroom, shiitake, and oyster mushroom, the three most important edible fungi worldwide, the annual production exceeds 3,400 million tons (Hobbythek, 1999). In one sense, this is an enormous agrobiotechnological production of fungal flavors. The aroma of the field mushroom (Agaricus bisporus) and of the oyster mushroom (Pleurotus spp.) originates mainly from the enzymatic oxidative degradation of linoleic acid, with 1-octen-3-ol (Figure 13.1) being the most prominent flavor compound (Venkateshwarlu et al., 1999; Husson et al., 2001). Shiitake (Lentinus edodes), which is widely consumed in China and Japan, has a very intensive aroma due to 1,2,3,5,6-pentathiepane (lenthionine; Figure 13.1) as well as sulfur containing degradation products of S-alkyl cysteine sulfoxide (lentinic acid) (Belitz and Grosch, 1987). Beyond these well known representatives, the spectrum of fungi producing flavor compounds is immense. In many cases their capability is reflected in genus or species names that point to aroma characteristics: butyrace- (butter-like), delicat- (delicious), odor-/osm- (fragrant), olid- (ambrosial), suav- (sweet), nidoros- (pungent) and foetens-/foetid- (fetid). Furthermore, trivial names in many different languages often give hints to floral, spicy, or aromatic flavor impressions. Currently, elucidation of flavor profiles either focuses on edible wild mushrooms or is employed as a tool in chemotaxonomic approaches. The volatile compounds emitted by the fruiting bodies of basidiomycetes are usually analyzed by coupled gas chromatography-mass spectrometry (GC-MS) or GC-olfactometry. Olfactometry requires dynamic headspace concentration through cryotrapping, solvent extraction, simultaneous distillation and solvent extraction (SDE), or solid phase microextraction (SPME). In an investigation of 26 basidiomycetes, more than 140 volatiles were detected, among which were mono- and sesquiterpenes, aromatics, ketones, esters, alcohols, and sulfur-containing compounds (Talou et al., 2000). In a series of 80 wild mushroom species, 34 strains synthesized a total of 28 different monoterpenes (Breheret et al., 1997). Altogether 16 aromatic compounds, which were likely to be biogenically derived from lignin of the host tree, were identified in hot water extracts of the white-rot fungus Gloeophyllum odoratum (Rosecke and Konig, 2000).