On the Determination of Volatile Thiols in Beer

Sainsbury, D. M.; Maw, George

doi:10.1002/j.2050-0416.1967.tb03046.x

Cited by 10 publications

(3 citation statements)

References 5 publications

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“…Strains grown on NA were suspended (to give an of 10) in 0.05 M-Tris-HCl buffer, pH 8.0, with L-methionine (66 m~) and incubated at 30 "C for 2 to 6 h in a Conway diffusion unit, using the method of Ruiz-Herrera & Starkey (1969). Methane thiol was trapped in 5 % (w/v) mercuric acetate in 10 % (v/v) acetic acid and estimated colorimetrically (Sainsbury & Maw, 1967). To confirm that methane thiol was being produced during incubation, portions of the mercuric acetate were acidified with 2 M-HCI to release the thiol from the mercaptide, and the head space (5 ml) was analysed by GC (Manning, 1974) with authentic methane thiol as a reference.…”

Section: Tests For Physiological Characteristicsmentioning

confidence: 99%

Coryneform Bacteria Producing Methane Thiol

Sharpe¹,

Law²,

Phillips³

1976

Journal of General Microbiology

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Recent Ivork on Cheddar cheese flavour has implicated methane thiol (CH,SH) as an important constituent of Cheddar aroma (Manning & Robinson, 1973;Manning, 1974). To determine whether this compound might be a metabolite of the bacterial flora of the cheese, isolates from milk and Cheddar cheese were examined for their ability to produce methane thiol. Among such isolates were a number of methane thiol-producing coryneform bacteria. Although methane thiol-producing bacteria have been described previously (Kadota & Ishida, I 972), we are not aware of any reports that coryneform bacteria have this ability. Accordingly these organisms are described in this paper. M E T H O DSJsolutc)s. Strains were isolated from raw milk and from homogenates of cheese curd and Cheddar cheese by enrichment using a mineral mix [containing ( 7;): K,HP04, 0.2; KH,PO,,or by direct plating on milk agar (skim-milk, 30 %; agar, 2 %). All isolates were tested for the production of methane thiol from L-methionine (see below). Positive strains were examined microscopically, and representative cornyeform bacteria were tested physiologically, and examined for the presence or absence of nieso or LL-diaminopimelic (DAP) acids and of arabinose in the cell wall.Luboratorji strains. Reference strains of A rtlirobacter tuniescens ~~1~8 9 14, Breiibacteriunz linens ~crn8546 and non-pigmented grey-white strains of coryneform bacteria, previously isolated from Limburger and Meshanger cheese by Mulder et al. (1966) and further described by Crombach (1972, I974), were included for comparison in many tests.G'cwerd ciiltiirv of' strains. Oxoid Nutrient Broth (NB) or Nutrient Agar (NA) were used. Cultures were incubated at 30 "C unless otherwise stated. Tests for physiological characteristicsCutctlrse was detected after 2 days incubation in NB, using the method of Harrigan & McCance ( I 966).Optirnirin growth tvmperatures were determined by measuring extinctions at 580 nm after growth in NB for 4 days at 22, 30, 37, and 40 "C (Lumetron Colorimeter model 401, Photovolt Corp., New York, U.S.A.).Heat resistance: cultures (0-1 ml) were inoculated into NB, heated to 60+o.r "C for 30 min, and then plated on NA.Morptiologicd changes were observed on the EYGA medium described by Cure & Keddie (1972).Aerobic growth: tested according to the method of Hugh & Leifson (1953).

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Section: Tests For Physiological Characteristicsmentioning

confidence: 99%

Coryneform Bacteria Producing Methane Thiol

Sharpe¹,

Law²,

Phillips³

1976

Journal of General Microbiology

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show abstract

“…Furthermore, beer constitutents other than volatile sulphhydryls should not interfere. [7][8][9][10][11][12][13][14][15] The procedure depends on the sweeping of any hydrogen sulphide or volatile thiols out of a sample at 37°C into a trap containing triethyl lead chloride in alcoholic solution which binds H2S and SH compounds. This sweeping is illustrated in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…In the last two decades, colorimetry, conductometry, amperometry, selective ion electrode titrimetry and gas chroraatography1«*>3i4"s-<i> 8,9,10,11,12,14 have oeen described for the analysis of hydrogen sulphide and volatile thiols in beer. The major drawbacks of these methods are that they may be insuffi ciently sensitive or not reproducible.…”

Section: Introductionmentioning

confidence: 99%