The number of starter bacteria in Cheddar cheese was increased approximately 2 or 8 times by supplementing the normal starter inoculum with starter-cell suspensions which had been incubated with lysozyme in the absence of salt. Lysozyme-treated cells were also introduced into chemically acidified cheese in an attempt to achieve ripening in the absence of a normal starter culture. The added starters did not interfere with normal cheese-making by producing acid. The lysozyme-treated starter cells were lysed when the curd was salted and lysis was detected by the release of cell-free DNA and an intracellular marker enzyme (dipeptidase) into the cheese matrix. Free amino acid concentrations in maturing cheeses were increased up to 3 times compared with control cheeses. The intensity of Cheddar flavour was not increased in starter cheeses by the presence of additional lysozyme-treated starter and no Cheddar flavour developed in chemically acidified cheese containing the lysozyme-treated cells. It is concluded that intracellular starter enzymes play no direct part in flavour formation, but produce breakdown products from which Cheddar flavour compounds may be formed by other unknown mechanisms.

A method is described for determining H2S, methanethiol and dimethyl sulphide in Cheddar-cheese headspace. Cheeses ranging in age from 2 to 12 months were analysed using a gas chromatograph equipped with a photometric detector. These cheeses were presented to a trained flavour panel for the assessment of quality and intensity of Cheddar cheese flavour.

An attempt is made to correlate the concentration of sulphur compounds in the headspace with the average flavour scores. The results suggest that the flavour intensity of the cheese is related to the concentration of methanethiol in the headspace.

It has been reported previously (Annan & Manson, 1969) that chromatography of the αs-casein complex of bovine milk on columns of sulphoethyl Sephadex C-50 resulted in fractionation of the complex into a main component, αs1-casein and a number of minor components one of which was designated αs0-casein. The present communication describes the preparation of αs0-casein from unfractionated casein in an amount and state of purity which render possible its further characterization.