Production of Sulfur Flavors by Ten Strains of Geotrichum candidum

Abstract

Ten strains of Geotrichum candidum were studied on a liquid cheese model medium for the production of sulfur compounds which contribute to the aroma of cheeses. The volatile components produced by each cultured strain were extracted by dynamic headspace extractions, separated and quantified by gas chromatography (GC), and identified by GC-mass spectrometry. It was shown that four strains of this microorganism produced significant quantities of S-methyl thioacetate, S-methyl thiopropionate, S-methyl thiobutanoate, S-methyl thioisobutanoate,S-methyl thioisovalerate, andS-methyl thiohexanoate. This is the first example of the production of these compounds by a fungus. In addition, dimethyldisulfide, dimethyltrisulfide, dimethylsulfide, and methanethiol, which are more commonly associated with the development of cheese flavor in bacterial cultures, were also produced by G. candidum in various yields, depending on the strain selected. The potential application of these strains in cultured microbial associations to produce modified cheeses with more desirable organoleptic properties is discussed.

Methylthioacetaldehyde, a possible intermediate metabolite for the production of volatile sulphur compounds from -methionine by Lactococcus lactis

“…The identity of the unknown metabolite was confirmed by GC-FTIR analysis. Reaction mixtures (5 ml) or fractions collected from HPLC analyses, were analysed using a headspace analyser (HP 7695A purge and trap concentrator; Hewlett-Packard, Palo Alto, CA) coupled to a gas chromatograph (HP 6890, Hewlett-Packard) and a mass spectrometer (HP 6890A quadrupole mass spectrometer, Hewlett-Packard), as previously described by Berger et al [15]. The electron impact energy was set at 70 eV and data were collected in the range 29-300 atomic mass units at a rate of 1.68 scans s À1 .…”

“…Olfactometry analysis was performed as described by Berger et al [16] but both dynamic headspace apparatus used for extraction and chromatographic separation conditions were as described by Berger et al [15].…”

“…After incubation for 5 h at 37°C, the reaction mixtures were analysed for VSCs production by Headspace-GC-MS analysis as described above. VSCs were quantified using the DMDS (Acros, F-93191 Noisy-Le-Grand Cedex, France) standard calibration curve established with the area of specific ion m=z ¼ 47 [15]. The nonvolatile metabolites produced from KMBA were analysed by HPLC as described above but with only UV detection.…”

“…The fifth compound had a different odour that was described as green apple, fruity, floral, aldehyde, almond, mushroom and acetaldehyde. Its mass spectrum was as follows: m=z 92 (1), 91 (1), 90 (58), 63 (5), 62 (5), 61 (100), 48 (4), 47 (25), 46 (23), 45 (48), 42 (8), 35 (25), 29 (15), with the number in parenthesis indicating the relative intensity of ions. This compound truly corresponds to the unknown product X observed by HPLC analysis (Fig.…”

Sulfur compound production by Geotrichum candidum from l-methionine: importance of the transamination step

“…Culture samples were analyzed for VSC content. Five ml of the culture broth (medium and biomass) was extracted and analyzed using a dynamic headspace GC-MS analyzer (HP7695A Purge and Trap concentrator, Hewlett Packard) as previously described [2].…”