Five Australian groups have attempted to correlate various compounds with the development of Cheddar flavour. Perret (1978) used vacuum distillation of grated mature Cheddar cheese followed by gas chromatography and mass spectrometry to reveal more than 150 components, including acids, alcohols, esters, aldehydes, ketones, sulphur compounds and lactones. He determined H2S, thiols and disulphides chemically to obtain the actual concentrations of sulphur compounds in the cheese rather than in the headspace. Commercial cheeses with flavour defects described as soapy, eggy, oniony and fruity were found to contain 'out of balance' concentrations of fatty acids, hydrogen sulphide, methane thiol and ethyl esters, respectively. Aston (1981, M. Appl. Sc. thesis, Queensland Institute of Technology, Brisbane, Queensland) compared normal Cheddar cheeses with cheeses manufactured using (a) mutant starters, (b) higher initial ripening temperature and (c) a combination of (a) and (b) to accelerate ripening. The cheeses were analysed at 1, 3, 6 and 9 months for (1)flavour, (2) volatile sulphur compounds (by GC/FPD of the headspace), (3) amino acids (phosphotungstic acid-soluble nitrogen) and (4) free amino acids and trichloracetic acid-soluble peptides (TCA-soluble tyrosine). Only (3) and (4) correlated well enough with flavour to be considered useful as ripening indicators. Barlow et al. (1989a, b, Aust. J. Dairy Technol., 44, 7-18) examined 54 batches of Cheddar cheese over the period of maturation. At each sampling time the cheeses were submitted to a taste panel and analysed for H2S, methane thiol, dimethyl sulphide, free fatty acids from acetic to hexanoic acids, D- and L-lactic acid, water soluble amino-nitrogen (WSN), and volatiles in the headspace over grated Cheddar cheese. The best Cheddar flavour was associated with 45-50mg/kg butyric and 20-25 mg/kg hexanoic acids. WSN, lactic acid and H2S correlated highly with Cheddar flavour. A reasonable prediction of flavour at 12 months could be made from flavour at 3 months plus H2S plus WSN. Wood (1989, M. Appl. Sc. thesis, Queensland Institute of Technology, Brisbane, Queensland) developed a method for analysis of the volatile headspace components from cheese using cryogenic sample collection. In a 20-month old cheese, methanol, ethanol, acetone, propyl formate, carbon disulphide, propan-1-ol, butanone, butan-2-ol, 3-methyl-butanal, pentan-2-one, pentanal, dimethyl disulphide, toluene, diethyl carbonate, hexanal, ethyl butyrate, ethylbenzene, o-, m- and p-xylene, alpha-pinene and an alpha-pinene isomer, dimethyl trisulphide, beta-pinene were identified. The effect of, (1) addition of neutrase, (2) use of mutant starter, (3) increased storage temperature, and various combinations of these on accelerating maturation and on the profile of headspace volatiles during maturation were examined. Dimos (1992, M.Sc. thesis, Latrobe University, Bundoora, Victoria) compared the volatiles from full-fat and low-fat (7%) Cheddar cheeses, manufactured on 4 separate occasions at the CSIRO pilot plant, over at 26-wee maturation period and found a significant straight-line relationship between actual flavour and fitted flavour calculated from: y=b(0) + b(1)x(1) + b(2)x(2) + b(3)x(3) + b(4)x(4) + b(5)x(5) where y is the fitted flavour, b(0)-b(5) are constants and x(1)-x(5) are the logs of the concentrations of H2S, heptan-2-one, butanone, delta-decalactone and propan-2-ol. This relationship held for both the full-fat and the low-fat cheese. Increases in butanone and butan-2-ol with maturation are widely reported, although high quality, mature Cheddar does not necessarily contain these compounds. Sulphur compounds, particularly CH3SH, have been shown to be essential to Cheddar flavour but are likely to be breakdown products of a highly unstable Cheddar flavour compound or compounds.
