The copper-binding protein, caeruloplasmin, has been detected in bovine blood serum, colostrum and normal milk using immuno-diffusion techniques by comparison with a precipitating oxidase-positive system of human caeruloplasmin and anti-caeruloplasmin. The possible importance of this copper-binding protein of milk in the oxidative deterioration of milk and dairy products is discussed.

The quantities of acetaldehyde and diacetyl produced in skim-milk and MRS media are reported for strains of Streptococcus lactis, Str. cremoris, Str. diacetilactis, Str. faecalis and Str. thermophilus obtained from culture collections or freshly isolated from natural milk cultures used in cheese manufacture. The diacetyl: acetaldehyde ratio in skim-milk medium was found to be approximately 0·1:1 for Str. lactis and Str. cremoris, 0·5:1 for Str. diacetilactis (5:1 for Str. diacetilactis PIM 13 and K.2 strains) and for Str. thermophilus 0·3:1, in skim-milk medium, and 0·8:1, in MRS medium; in the latter species cultured in MRS medium the ratio varied from 3·5:1 to 0·04:1 and when cultured in milk from 1·2:1 to 0·03:1.

In both media all strains of Str. thermophilus formed more acetaldehyde and diacetyl than other homofermentative lactic streptococci.

The ratio diacetyl: acetaldehyde in 9 strains of Str. diacetilactis was found to be unsuitable for a good culture flavour.

The identification and approximate quantitative determination of methyl esters of fatty acids from commercial butterfat was obtained with a combined gaschromatograph-mass spectrometer instrument. Fifty-two components, straight chain saturated and unsaturated, as well as branched chain compounds, were identified. Seven monomethyl saturated fatty acid methyl ester isomers were identified for both C15 and C17, i.e. with chain lengths of 14 and 16 carbon atoms, respectively. Multibranched fatty acids with molecular weights of 326 and 368 were found. The results were obtained in one day.

Pent-1-en-3-ol and pent-l-en-3-one were isolated in approximately equal amounts from buttermilk obtained from oxidized cream. The two vinyl compounds were identified by combined gas chromatography and mass spectrometry. The flavour of pent-1-en-3-ol is comparatively mild being detectable in water, skim-milk, butter oil and butter at 3 pts in 106, 3 pts in 106, 1 pt in 105 and 1 pt in 105, respectively. The flavour of pent-1-en-3-one is approximately 1000 times stronger being detectable in water, skim-milk, butter oil and butter at 1 pt in 109, 3 pts in 109, 5 pts in 109 and 5 pts in 109, respectively: these concentrations are of the same order of magnitude as for the compound responsible for metallic flavour, oct-1-en-3-one.

The formation of pent-1-en-3-ol and pent-1-en-3-one is discussed.

The following compounds were isolated from best-quality Australian butter oil by high vacuum degassing, and identified by the combination of gas chromatography and mass spectrometry: the C3,5,7,9 alkan-2-ones, the C2,4,6,8,10,12 n-alkanoic acids, the C6,8,10 5-lactones (or their hydroxyacids), dimethyl sulphone, all isolated in amounts above 1 pt in 108 of butter oil, and butanone, undecan-2-one, 5-dodecalactone, diacetyl, n-nonanoic acid, a decenoic acid, methyl n-decanoate, toluene, o-methoxyphenol, a cresol, phenol, benzaldehyde, methyl benzoate and benzothiazole, all isolated in amounts between 1 pt in 1011 and 1 pt in 108 of butter oil.

No compound was isolated in an amount greater than flavour threshold, in fact most compounds were below one-tenth threshold level. However, the distillate obtained by degassing produced a very attractive creamy flavour when added to bland non-cultured butter.

The variation in deposit formation from milk of 2 herds was measured over a period of more than 12 months using a hot-wire laboratory apparatus. A marked minimum was found in May–June, with high deposit levels between September and April. There was a difference of 2 to 1 between maximum and minimum levels. The amount of deposit was not positively correlated with the mineral or protein contents of the milk, but was strongly positively correlated with fat content. It is suggested that the controlling factor is closely associated with fat content and varies with it.

In each of 5 cows, 2 quarters which had been regularly milked throughout the whole of pregnancy produced less milk in the next lactation than the other 2 quarters which had a normal dry period. The concentrations of the individual constituents in the milk of all 4 quarters of each cow were similar. The effect appears to be due to factors located within the individual quarter of the mammary gland rather than to factors such as the hormonal background or plane of nutrition which affect the whole animal.

After the suspension of milking for 2 weeks in 2 ‘experimental’ quarters of each of 4 Friesian cows, there was a reduction in the yield of milk from these quarters. Although subsequently there was a marked recovery, for the remainder of the lactation the yield was lower than that of the corresponding control quarters in which milking had not been suspended. Throughout the next lactation, in all 4 cows, the experimental quarters produced more milk than the corresponding control quarters. At the first milking after the suspension, there were marked increases in the concentrations of sodium and chloride and decreases in those of lactose and potassium in the milk obtained. Within 8 weeks, the composition recovered, and for the remainder of the experiment the composition of the milk from the control quarters was similar to that from the experimental quarters of each cow.

The effect of equal and unequal milking intervals (12 + 12, 10 + 14 and 8 + 16h) was investigated in milch ewes. The treatments were applied to 9 ewes using a double 3 × 3 Latin square. The daily production of milk and fat was unaffected by the changes in milking interval.