Comlek peyniri is a typical artisanal cheese in Central Anatolia. This type of cheese was made by using the indigenous lactic acid bacteria (LAB) flora of cow or ewes' milk. Majority of the samples were taken from fresh cheese because the aim was to isolate homofermentative LAB. Initially 661 microbial isolates were obtained from 17 cheese samples. Only 107 were found to be homofermentative LAB. These isolates were selected and identified by using both phenotypic and molecular methods. Phenotypic identification included curd formation from skim milk, catalase test, Gram staining and light microscopy, growth at different temperatures and salt concentrations, arginine hydrolysis, gas production from glucose, and carbohydrate fermentation. Molecular identification was based on the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of the 16S rRNA gene-ITS (internally transcribed spacer) region. By combining the phenotypic and molecular identification results, isolates belonging to each of the following genera were determined at species or subspecies level: 54 Lactococcus lactis subsp. lactis, 21 Enterococcus faecium, 3 Ec. faecalis, 2 Ec. durans, 10 Ec. sp., 15 Lactobacillus paracasei subsp. paracasei, and 2 Lb. casei strains. Technological characterisation was also performed by culturing each of the strains in UHT skim milk, and by monitoring pH change and lactic acid production at certain time intervals through the 24 h incubation. Results of the technological characterisation indicated that 33% of the isolates (35 strains) were capable of lowering the pH of UHT milk below 5·3 after 6 h incubation at 30 °C. Thirty four of these strains were Lc. lactis subsp. lactis, and only one was an Ec. faecium strain.

Seven strains of Streptococcus cremoris, four strains of Str. lactis, and one strain of Str. diacetilactis were examined for their ability to produce aldehydes and methyl ketones when grown in skim-milk. All strains were found to produce acetaldehyde and seven also produced acetone. No other aldehydes or methyl ketones were detected in any of the cultures.

A method for the quantitative estimation of mixtures of aldehydes and methyl ketones by means of paper chromatography of their 2,4-dinitrophenylhydrazones is described.

Rheological properties of reconstituted skim milk coagulated with plant coagulants Cynara cardunculus L., Cynara humilis L. and chymosin was monitored by dynamic low amplitude oscillation. There are no published reports on the modelling of the gelation behaviour of milk by plant coagulants. Three mathematical models, Scott Blair, Douillard and Carlson, were fitted to the storage modulus (G′) as function of time curves. For all coagulants, Scott Blair model was the most efficient in modelling the gelation process, and gave both the smallest residuals and standard error of residuals, Se (P < 0·0001). Douillard model gave the poorest fit and in particular it was not able to predict the initial part of the gelation curves. Carlson model had an intermediate behaviour and, in the case of chymosin, it gave results that were quite comparable to Scott Blair model. The parameters of the Scott Blair model were different for plant coagulants and chymosin. Chymosin had the longest rate constant (τ) and the time shift coefficient (ts) was also different between vegetable coagulants and chymosin (P < 0·0005). These results are in agreement with the overall trends for gelation profiles obtained for vegetable coagulants and chymosin. In the beginning of gelation both plant coagulants produced gels with slightly higher G′ values than chymosin, but after longer incubation times chymosin gels had higher G′ values. It was concluded that the Scott Blair model was the best equation to follow the gelation of milk induced by both plant coagulants as well as chymosin. Modelling is an important and useful method for comparing the gelation process in gels formed by different types of coagulants.

The efficiency of reversed-phase HPLC, capillary electrophoresis (CE), PAGE and isoelectric focusing with immunoblotting in separating ovine caseins has been evaluated. The assessment was carried out by employing electrospray ionization–mass spectrometry (ESI–MS) and matrix-assisted laser desorption ionization–time of flight as reference tools for identifying protein components. Ovine casein was fractionated by HPLC into four major peaks. With ESI–MS, each peak contained components belonging to only one of the four casein families. On-line liquid chromatography–ESI–MS allowed us to determine each fraction's composition by detecting thirteen αs1-, eleven αs2-, seven β-, and three κ-casein (CN) components. The αs1-CN and αs2-CN consisted of eight and two protein chains respectively of lengths differing through the deletion of one or more peptide sequences; they were also discretely phosphorylated as κ-CN and β-CN. By CE at pH 2·5, each casein fraction was as heterogeneous as that resulting from ESI–MS for the single HPLC-derived fractions. The separation of αs1-CN and αs2-CN proved to be excellent, with the exception of a co-migration of κ0-CN with a minor αs1-CN component and of a glycosylated κ-CN form with low-phosphorylated αs1-CN and β-CN components. Dephosphorylation of whole casein was used to reduce the heterogeneity of the native fractions and by applying currently used analytical techniques it was possible to visualize the protein moiety difference along the CE profile. CE, HPLC, and immunoblotting were all equally capable of effecting an accurate separation of the four dephosphorylated casein families. The spectra obtained by ESI–MS directly on dephosphorylated whole ovine casein samples contained the signals of the four casein families and the relative αs1-CN variants, the non-allelic αs1-CN and αs2-CN forms, dimeric κ-CN and other newly formed peptides. We suggest using this procedure for rapid characterization of whole casein.

Storage of aseptically packed UHT milk produced changes in the electrophoretic pattern of the milk caseins when the milk was stored at ambient or higher temperatures. Lower temperature storage at 4°C did not give rise to these changes.

The alterations in electrophoretic properties of the caseins appeared to be due to the action of carbonyl compounds, produced by a Maillard type of reaction, which led to changes in the charge of the protein together with some degree of polymerization. These conclusions have been drawn from results obtained on model systems of casein-lactose subjected to various heat treatments, and on casein and milk treated with acetaldehyde.

Changes in the sensitivity to calcium ions of individual caseins, whole casein and milk that had been subjected to various heat treatments or to treatment with acetaldehyde showed that all these different treatments gave rise to modified casein which, in general, became less sensitive to calcium. κ-Casein when treated alone rapidly lost its ability to protect αs1-casein from precipitation by calcium ions, while αs1-casein treated alone only gradually became more soluble in the presence of calcium. Thus, on treating whole casein there was evidence for a stability minimum when the protective ability of the κ-casein has been destroyed without a compensating gain in the stability of the αs1-casein.

The importance of these changes in relation to the stability of UHT milks has not yet been elucidated but the results indicate that cross linking between protein chains and changes in calcium sensitivity occur during long-term storage.

Changes in the level of the tissue damage marker enzyme, N-acetyl-β-D-glucosaminidase (NAGase) in quarter fore milks were found to be related to the presence and types of pathogenic bacteria present and to somatic cell counts (SCC). Minor pathogens (coagulase-negative staphylococci, Corynebacterium bovis) elicited a mild SCC increase (from a mean of 243 × 103/ml in healthy quarters to 504 × 103/ml in infected quarters) with marginal tissue damage (mean NAGase activity increased from 21 in healthy quarters to 28 in infected quarters). Major pathogens (i.e. Staphylococcus aureus, Streptococcus agalactiae, Str. dysgalactiae and Str. uberis) caused more severe tissue damage (mean NAGase of 48) and SCC increases (mean, 2803 × 103/ml). The NAGase test could also be used effectively on composite milk samples where regular monthly NAGase analysis was able to identify correctly 74% of animals having infected quarters. The possibility of combining SCC and NAGase data in order to give a more definite diagnosis of bovine mastitis is discussed.

The autolysin of Streptococcus cremoris had the specificity of an endo-N-acetylmuramidase as it hydrolysed the linkage between N-acetylmuramic acid and N-acetylglucosamine. The enzyme had no amidase or endopeptidase action. It reached highest activity in the exponential phase of growth and in the electron microscope seemed to fragment the coccal wall at the equatorial ring.

A method for lactose hydrolysis in sterile milk or whey with Saccharomyces lactis lactase is described. The properties and stability of this enzyme are very favourable for use in milk and neutral whey. The long shelf life of sterilized milk and whey products is utilized for a prolonged incubation time – one to several weeks – at room temperature. Thus, minimal amounts of enzyme are needed which makes enzyme costs very low.

Impact of milk protein composition on casein (CN) retention in curd during the milk coagulation process was studied using a model cheese making system. Individual milk samples from 110 cows in mid lactation of the Swedish Red and Swedish Holstein breeds with known genotypes of β-casein, κ-casein and β-lactoglobulin were defatted, coagulated with chymosin, subjected to syneresis and subsequent pressing simulated by centrifugation. The results indicated that κ-casein concentration of milk plays an important role in the curd formation process and initial syneresis (whey after cutting), whereas an increased CN ratio was associated with less casein in whey after simulated pressing. Increased κ-casein concentration of milk also characterized the milk samples with no measurable loss of casein in whey, compared with milk samples with casein lost in whey, both after cutting and after simulated pressing. Concentrations of αs1-casein, β-casein, and total casein in milk were positively associated with fresh curd yield, which showed a strong correlation with amount of casein retained in curd. No effect of protein genotype on fresh curd yield or casein in whey was found. The β-lactoglobulin BB genotype was associated with increased casein retention in curd, most likely due to the association of this genotype with CN ratio.

The taste-active compounds of a Camembert cheese selected for its intense bitterness defect were investigated. The water-soluble fraction (WSE) was extracted with pure water and fractionated by successive tangential ultrafiltrations and nanofiltration. The physicochemical assessment of these fractions led to the construction of a model WSE which was compared by sensory evaluation to the crude water-soluble extract, using a panel of 16 trained tasters. As no significant difference was perceived, this model WSE was then used directly or mixed with other cheese components for omission tests. Among the main taste characteristics of the WSE (salty, sour, umami and bitter), bitterness was found to be due to small peptides whose mass distribution was obtained by RPHPLC-MS (400–3000 Da) and whose taste properties are discussed.

An experiment was conducted to investigate the effects of a high concentration of vitamin E supplementation in sow diet during the last week of gestation and lactation on the performance, milk composition, and vital immunological variables and antioxidative parameters in sows and piglets. The experiment started on day 107 of gestation and lasted until the piglets were weaned on day 21 of lactation. 48 sows were divided into two groups and fed either a basal diet with 44 IU/kg of vitamin E or a basal diet supplemented with additional vitamin E, total content of 250 IU/kg. Sow milk and blood samples were obtained on day 0 (farrowing) and on day 21 of lactation. One 21-day-old piglet per litter was selected to collect plasma. Results showed that supplementation of the maternal diet with 250 IU/kg vitamin E improved the average daily gain (ADG) and weaning weight of piglets (P < 0·05), and the concentrations of immunoglobulin G (IgG) and immunoglobulin A (IgA) in sow plasma, colostrum and milk. The concentrations of fat in the colostrum and milk were significantly increased by supplementation with 250 IU/kg of vitamin E (P < 0·05). The level of plasma IgG, IgA, total antioxidant capacity (T-AOC) and catalase (CAT) were all higher (P < 0·05) in piglets from sows that were fed 250 IU/kg of vitamin E than in those from the control group. The high concentration of vitamin E supplementation to the sows enhanced the concentrations of α-tocopherol in the sow milk and plasma as well as piglet plasma (P < 0·05). In conclusion, the addition to the maternal diet of vitamin E at high concentration improved the weight of piglets at weaning, and enhanced humoral immune function and antioxidant activity in sows and piglets.

Bovine mastitis reduces the yield and quality of milk and increases the rate of culling and veterinary costs. This reduces the profitability of farm milk production but the calculation of the extent of this economic loss is complex because of the many factors involved and deficiencies in the evidence on the relationship between the disease and various production factors. This paper examines the available evidence for the UK and provides a consistent analytical framework within which the benefits arising from reduced mastitis in dairy herds constrained by quota can be considered. It is estimated that since 1970 the farms that have followed the recommended control procedures have reduced the average annual number of cases of clinical mastitis from 135 to 40 cases/100 cows each year, while the quarters remaining uninfected for a whole year has increased from 65 to 80% of the total quarters. The costs of the main control procedures (e.g. £8–60/cow for dry-cow therapy and teat dipping or spraying) are broadly covered by the reduction in clinical mastitis, leaving the benefits of reduced subclinical infection (e.g. £3810 for a 100 cow herd unconstrained by quota and achieving the average reduction in infection) as a substantial bonus. The imposition of quotas reduces the financial benefit of mastitis control but it still remains a worthwhile investment. The results of this analysis can be used to suggest maximum costs of additional new control measures produced by research. It also indicates that there is considerable value in production research which gives more precise knowledge of production Systems, thus allowing producers to respond optimally to quota cuts.

1. Under various feeding regimes the entire contents of the reticulo-rumen of fistulated Shorthorn cows were repeatedly removed, weighed, sampled and returned.

2. With cattle grazing grass/clover swards, but not with others grazing green cereals, there was a very marked tendency for less digesta to be found in the reticulo-rumen than with several winter diets.

3. An average fall of 71±24 lb. was found in the weight of a mixed herd of thirty-eight Friesian and Shorthorn cows when they were changed suddenly from winter diets to grazing. Simultaneous observations on three fistulated cows showed that 84% of such short-term variation in weight could be explained by variation in the weight of the digesta in the reticulo-rumen. It is likely that smaller, parallel variations in the weight of the contents of the remainder of the gut accounted for most of the remaining differences.

The mass flow-rate (FR) of milk from the bovine teat within individual pulsation cycles was measured by continuous computation of the average optical density of the milk–air mixture within a teatcup. Measurements during milking were made on both live and excised teats using a range of teatcup liners, vacuum levels and pulsation characteristics. During a typical pulsation cycle, soon after the start of milking, milk FR from live teats reached a peak within 100 ms of the start of the flow period and fell to about 60% of the maximum value between 0·5 and 1·5 s of flow. If the liner was held open for longer than 1·5 s, the FR typically declined a further 10% over the next 10–15 s. After 10–15 s little or no further change occurred in milk FR at normal milking vacuum levels. Milk flow from excised teats reached a steady value within 100 ms of the start of the flow period and showed no subsequent fall in FR.

Within individual pulsation cycles the changes in FR from live teats are affected by: (i) the degree of compressive load applied by the collapsed liner to the teat in the preceding cycle; and (ii) the duration of application of the compressive load. Increasing the degree of compressive load or the length of time of loading increases the peak milk FR of the next cycle by reducing the degree of congestion in the tissues of the teat surrounding the teat canal. Muscular effects are of secondary importance. The relatively small changes in milk FR associated with muscle contractions of the teat can be seen most clearly at low milking vacuum levels (below about 30 kPa) or with an unsupported teat (e.g. using a very distensible, thin-walled liner).

Hydrogen peroxide accumulated in aerated cultures of Streptococcus lactis C10, the amount depending on the sugar being utilized. When the energy source was galactose or (to a lesser extent) lactose or maltose, H2O2 reached autoinhibitory levels. With glucose, H2O2 reached levels which did not cause obvious inhibition, and then declined. Washed cell suspensions utilized several media ingredients including glucose, galactose and yeast extract as substrates for O2 uptake, but cell-free extracts utilized none of these. The only substrate which supported O2 uptake by cell-free extracts was NADH. The activity of NADH oxidase was not affected by several intermediates of carbohydrate metabolism. Evidence was obtained to show that its synthesis was regulated via induction by O2 with an overriding catabolite repression type control, when cells were grown at the expense of glucose.

A study has been made of the cultural and biochemical characteristics of heat-resistant thermophilic and mesophilic spore-forming bacteria isolated from raw and sterilized milk. The tests hitherto used in classifying this group of bacteria have been examined and some modifications suggested; as a result a simplified method of distinguishing different resistant spore-forming organisms in milk is proposed. The types of micro-organisms were few. The thermophiles were restricted to B. calidolactis and of the mesophiles B. subtilis predominated in sterilized milk and B. licheniformis in raw milk.

A C20 multibranched fatty acid earlier isolated from butterfat in trace amounts has been conclusively identified by means of mass and infra-red spectrometry and gas-liquid chromatography as 3,7,11,15-tetramethylhexadecanoic acid.

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.