Identification of key odorants of fried cottage cheese and contribution of Galactomyces geotrichum MK017 to the formation of 2-phenylethanol and related rose-like aroma compounds

The identification of key odorants and production of 2-phenylethanol and related rose-like aroma compounds by a Galactomyces geotrichum MK01 species was examined in a fried cottage cheese. Odours were characterised as having cheesy, milky, buttery and rancid notes that were developed from 15 odorants: 2,3-butanedione, 3-(methylthio)-propanal, 3-isobutyl-2-methoxypyrazine, dimethylsulphide, dimethyltrisulphide, dimethyldisulphide, 3(sec-butyl)-2-methoxypyrazine, 1-octen-3-ol, β-damascenone, phenylacetaldehyde, 2-ethyl-3,5-dimethylpyrazine, 2-phenylethanol and phenylacetic acid, benzenemethanethiol and 5-methyl-2,3-diethylpyrazine as determined by sensory analysis and gas chromatography olfactometry. Analysis carried out after four days of cheese ripening, but before frying, indicated a distinct rose-like, honey flavour and high amounts of 2-phenylethanol, phenylacetaldehyde and phenylacetic acid. Statistical analysis demonstrated a significant correlation (P ≤ 0.05) between high amounts of rose-like compounds and the presence of the G. geotrichum MK017 species. Model experiments showed that the G. geotrichum MK017 species isolated from the fried cottage cheese was capable of biosynthesising 2-phenylethanol and related rose-like aroma compounds from l-phenylalanine.