Ca soaps of fatty acids (CSFA, 0·5 kg/d) were added to the diet of lactating cows for 170 d, and production, body condition score and blood lipids were examined.

Production of fat-corrected milk was increased by 1·5 kg/d owing to increase in both milk and fat production. Over 250 d lactation, production of fat-corrected milk was enhanced by 1·3 kg/d. Body condition scores were lower in cows fed CSFA in early lactation, but tended to exceed those of control cows after 80 d lactation. Reproductive performance was improved in cows fed CSFA.

Serum total lipids, phospholipids and cholesterol were increased in CSFA cows at 15 and 29 d but not at 59 d post partum. The cholesterol increase was mainly in the high density lipoprotein fraction.

With two groups of 12 cows, a procedure involving foremilking, teat washing and drying before milking was compared with no premilking preparation for its effects on mastitis and teat contamination. Half the cows in each group were deliberately infected in a single udder quarter with Staphylococcus aureus and milked alternately with uninfected cows for 9 weeks. To minimize transfer during milking all cows were milked with the use of a multi-valved claw.

Five new staphylococcal infections developed in the 12 animals in the teat preparation group compared to one in the control group. A significantly higher incidence of teat orifice colonization developed in the prepared cows compared to the control cows (17 v. 7). Foremilking and teat preparation led to transfer of staphylococci between quarters (within cow) but this was effectively prevented by the multi-valve claw in the absence of teat preparation.

A cows' milk identification test (COMIT) has been successfully developed for the detection of defined amounts of cows' milk (3–100%) in ewes' milk. The assay uses polyclonal antibodies raised in goats against bovine whey proteins. The test, an agar-gel immunodiffusion technique, uses agar plates with a printed template for correct placement of the test components (antisera discs, positive and negative milk reference discs and sample discs). The presence of cows' milk in the sample was recorded as positive when the precipitin lines appearing between the sample disc and the antisera disc fuse completely with those from the positive cows' milk reference disc. This test is reliable, practical and easy to perform in the field and in dairy factories. Furthermore, the nature and stability of the components of the test make it suitable for commercial development into kits which should be highly practical in any kind of inspection programme concerned with milk species identification.

Effects of agitation, temperature change, blood serum and heparin on lipolysis and on distribution of lipoprotein lipase (LPL) in cold-stored cows' milk were measured. All individual milks (n = 135) were susceptible to activation treatments. With ‘gentle’ treatments, induced lipolysis was strongly correlated to spontaneous lipolysis (r ≥ 0·74). In contrast, induced lipolysis in response to ‘vigorous’ treatments was more variable (0·7 > r > 0·34) and levelled off in milks with high spontaneous lipolysis. Induced lipolysis always resulted from an increase in LPL associated with cream. Strong correlations (0·79 ≤ r ≤ 0middot;94) were found between free fatty acid levels and cream LPL. All treatments (except heparin addition) also promoted lipolysis/unit cream LPL.

Cold-stored milk lipolysis was enhanced from 5- to 50-fold when milk pH was adjusted to 7–8 with NaOH, while it was greatly decreased or stopped by an adjustment to pH 6–5·5 with citric acid. Small adjustments in pH (≤ 0·5 pH unit) also affected lipolysis, but the pH of native milk was not related to spontaneous lipolysis. The binding of lipoprotein lipase to cream was a pH-dependent process with an optimum near pH 7·0. Activity of the cream lipase on cold-stored milk fat continuously increased from pH 6·6 to pH 8·5. The activating effect of heparin on cold-stored milk lipolysis reached a maximum at pH 7·0–8·0 and a minimum in native milk, while addition of blood serum gave an opposite response.

The activity of milk plasmin, plasminogen and N-acetyl-β-glucosaminidase (NAGase) and the trypsin-inhibitor capacity (TIC) were monitored in 40 quarters during the first month of lactation. TIC and NAGase activity decreased rapidly and plasmili activity more slowly during the first week. Conversely milk plasminogen increased as time elapsed from parturition. When the quality of whey was analysed as a growth medium for mastitis pathogens, a slight inhibition in the growth of Escherichia coli, Staphylococcus aureus and Streptococcus agalactiae was seen at the day of parturition. There was a distinct stimulatory effect on the growth of Str. agalactiae during the second week of lactation. No relationship was found between in vitro bacterial growth and respective plasmin or plasminogen activity in milk.

Measurements of the release of Ca, Mg and inorganic phosphate(Pi) from the casein micelles of bovine milk have been made, as functions of the pH, in the range 4·9–6·7, and at temperatures of 4, 20 and 30 °C. The results are in general agreement with earlier published studies in giving a value of 1·75–1·84 for the micellar Ca:Pi ratio. Mg appeared to behave similarly to Ca, although the amounts of micellar material were much smaller. The results on the acid-solvation of calcium phosphate are considered in relation to published quantitative studies of the pH-induced dissociation of the different types of caseins from the micelle, and of the micellar dissociation caused when micellar calcium phosphate is dissolved at neutral pH. It is evident from this that at present it is not possible to derive a universal relation between the dissociation of minerals and of caseins from the micelles at different temperatures and under different conditions.

The formation of galactose, lactulose and epilactose during heating of milk was studied. The concentration of these carbohydrates increased with pH and the severity of heat treatment. The presence of proteins reduced the amount of lactulose formed whereas it increased that of epilactose and galactose. The galactose in heated milks was derived from lactose degradation. Under the conditions studied, degradation of the Amadori rearrangement product did not result in the formation of galactose. The interaction between proteins and galactose increased the thermal stability of the monosaccharide.

The extent of cream feathering was observed in samples of six brands of instant coffee at 80 °C and classified on a scale of 0 (non-existent)–3 + (very severe). The hypothesis that it is caused by the amount of chlorogenic acid in the samples was tested. Ultraviolet spectra were recorded between 230 and 486 nm, and the amount of chlorogenic acid was measured from the absorbance at 340 nm. It was found that: (i) u.v. spectra of a given brand of coffee prepared at different concentrations could all be superimposed when concentration and dilution were taken into account, and the spectrum did not change between room temperature and 80 °C; (ii) for a given coffee a minimum amount of chlorogenic acid was needed to cause feathering, but that this amount differed by up to a factor of 10 depending upon the coffee; (iii) only two fundamental shapes of spectra were observed and coffees could be classified by a ratio, R, which lay between two ranges: 0·82 < R < 0·90 or 1·10 < R < 1·27; (iv) a knowledge of the chlorogenic acid content of a sample and the value of R appropriate to that coffee could be used to predict the occurrence of feathering.

Ultraviolet spectra of solutions of instant and filter coffees have been analysed as a linear combination of component Gaussian bands. We show that the ratio, R′, of two of these bands, one at 329 nm due almost entirely to chlorogenic acid, and the other at 272 nm due to a coffee component not appearing in the chlorogenic acid spectrum, is analogous to the ratio R (Hamboyan et al. 1989). The use of R which is easier to measure than R′ has therefore been justified on physical grounds, based on the existence of component spectral bands. Filter coffees appeared to exhibit behaviour similar to that of instant coffees.

A new method for measuring the activity of mesophilic and thermophilic lactic acid bacteria is proposed based on measuring the pH of cultures at extremely short intervals (30–90 s) during growth and calculating several kinetic parameters, i.e. the maximum acidification rate (Vm), the time and pH at which Vm occurred, the time or pH range during which the observed rates were greater than Vm/2. These were easily calculated by coupling the pH meter to a microcomputer.

An intracellular proteinase was purified from Lactococcus lactis subsp. lactis NCDO 763 after spheroplast formation from cell wall proteinase-deficient variants. The proteinase was active at pH 7·5 and 45 °C and affected by metalloenzyme inhibitors. Its specificity, determined on B-chain of insulin, was thermolysin-like. The B-chain of insulin was hydrolysed rapidly while hydrolysis of β-casein was slower. This enzyme has a Mr of ∽ 93000.

Streptococcus salivarius subsp. thermophilus (Str. thermophilus) has no group-specific antigen. HC1 extracts of 551 strains of streptococci isolated from cheese or yogurt (123 Str. thermophilus and 428 Enterococcus faecalis – Ent. faecium spp.) were examined with three type-specific antisera prepared against representatives of Str. thermophilus and also with Lancefield group D antisera. All typical (80) or atypical (43) strains of Str. thermophilus reacted with at least one type-specific antiserum and none of the enterococci reacted. Only two strains reacted with both type-specific and group antisera.

Enhanced stability of β-galactosidase (Streptococcus salivarius subsp. thermophilus) in milk is due to several milk components acting in concert. Milk salts stabilized the enzyme 3-fold compared to phosphate buffer. K+ was a better stabilizer than Na+. Omission of divalent cations, especially Mg2+, caused a marked drop in stability. Lactose stabilized enzyme stored in the frozen state but destabilized enzyme stored unfrozen. Caseinate stabilized the enzyme 8-fold in phosphate buffer but it stabilized 144-fold in the presence of lactose. In the presence of milk proteins, lactose was 25 times as effective as galactose and 100 times as effective as glucose at promoting stability; sucrose slightly destabilized the enzyme. Stability rose with increasing lactose concentration but declined with increasing enzyme concentration. In milk, soluble casein was the primary stabilizer; whey proteins and peptides had much less effect. Micellar casein had no effect on stability.

Sandwich enzyme immunoassay of Mucor miehei proteinase (from the commercial preparation Fromase) has been developed using horseradish peroxidase as a marker. The enzyme may be determined to a detection limit of 50 ng/ml. Slight cross reactions by chymosin, bovine, porcine and chicken pepsin did not affect the assay. Recovery of Fromase added to cheese extracts varied between 92 and 106%. The method was used for the determination of M. miehei proteinase in different cheese extracts.

Milk fat-coated microcapsules containing Brevibacterium linens and methionine were used to produce methanethiol, one of the volatile sulphur compounds implicated in Cheddar cheese flavour. Production of methanethiol from methionine occurred aerobically and anaerobically, but the production was 3- to 4-fold greater aerobically with most of the methanethiol being oxidized to dimethyl disulphide. About 35% of the total methanethiol was absorbed by the milk fat capsules and about 65% detected in the headspace. Levels of methanethiol began to decline at 26 °C after 24 h in milk fat-coated microcapsules. However, low temperature, such as 4–12 °C, stabilized levels of methanethiol in microcapsules over an 8-d analysis period. Optimum pH and temperature for methanethiol production were 8 and 26 °C respectively. The antioxidants butylated hydroxytoluene, butylated hydroxyanisole and ascorbic acid had negligible effects on methanethiol production.