bluuebunny/crossref_metadata_2025 huggingface dataset:
A method for the quantitative determination of individual free fatty acids in milk by ion exchange resin adsorption and gas-liquid chromatography
Authors: Needs Eric C. , Ford Graeme D. , Owen A. Jane , Tuckley Brian , Anderson Malcolm
Published: June 2009

A quantitative method for rapid routine analysis of individual free fatty acids (FFA) in milk was developed. Lipid was extracted from milk in ether and FFA were recovered by shaking the extract with anion exchange resin Amberlyst 26. The resin-bound FFA were methylated directly and the individual acids quantified, using internal standards, by gas-liquid chromatography. The properties of the resin were measured. The validity of the method was established by extraction of FFA mixtures and milk. Individual acids were, on average, found to be within 6% of the actual concentration present in the mixture. An average coefficient of variation of 4·3% was achieved for the major individual fatty acids on repeated extraction of a single milk sample.
Behaviour ofStreptococcus lactisin heat treated (80 °C for 30 min) or sterilized cow's and ewe's milk
Authors: Chavarri Francisco J. , Nuñez Jose A. , Nuñez Manuel
Published: June 2009

Generation times and acid production after 6 and 24 h by 20 strains ofStreptococcus lactisof dairy origin were determined in heat treated (80 °C for 30 min) and sterilized cow's and ewe's milk. Ewe's milk enhanced growth of the streptococci, with significantly (P< 0·001) shorter generation times and higher acid production after 6 h incubation than cow's milk, probably due to its higher vitamin content. The stronger buffer capacity of ewe's milk allowed a higher (P< 0·001) acid production after 24 h than cow's milk. A stimulatory effect of sterilization on generation time and acid production after 24 h was observed in cow's milk. However, the heat treated ewe's milk was shown to be a better substrate than sterilized ewe's milk forStr. lactis.
Use of chemical additives to improve the palatability of low fat milk
Authors: Green Margaret L. , Ridout Elizabeth A.
Published: June 2009

Milk with 1·5% fat was treated to increase its viscosity to that of whole milk on the assumption that the sensation produced in the mouth, its mouthfeel, would be improved. Selected treated 1·5% fat milks were assessed for similarity to whole milk in taste panel trials. Panelists were chosen because of their ability to distinguish between whole milk and that containing 1·5 % fat by taste in at least one of two tests. Only 34% of the persons screened were suitable. Throughout the trials, the proportion of panelists able to distinguish between the two milks served alone and in tea remained at about 50%, but rose to 80–90% for the milks in coffee. In general, addition of KOH to 1·5% fat milk to pH 7·4 and of 6 mM-citrate overcame about 75 and 50%, respectively, of the difference in mouthfeel between whole and 1·5% fat milk. Whole and 1·5% fat milks were easily distinguishable visually, but the appearance of the latter was improved by adjustment to pH 7·4.
Interrelationships of chemical composition and coagulating properties of renneted milks from dairy cows grazing ryegrass or white clover
Authors: Grandison Alistair S. , Ford Graeme D. , Millard David , Anderson Malcolm
Published: June 2009

The chemical composition and rennet coagulation properties at pH 6·4 of bulked milks from two groups of dairy cows grazing ryegrass or white clover swards were monitored over a period of 14 weeks commencing at the fifth week of lactation. There was considerable variation in the concentrations of many components and large variations in the rennet clotting time (RCT), coagulum strength and rate of syneresis. The relative proportions of αs-, β- and κ-casein were also subject to considerable variation. Many statistically significant correlations were found between concentrations of protein fractions, minerals and citrate, some of which may be of physiological significance whereas others may be incidental. The coagulum strength displayed significant correlations with concentrations of total casein, αs-casein, inorganic phosphate (Pi), whey protein and RCT, but not with β-casein or η-casein. The syneresis time was significantly related to the concentrations of fat, citrate, η-casein and the original milk pH. RCT displayed a significant correlation with the concentration of Pi.
Determining the energy of activation for the formation of lactulose in heated milks
Authors: Andrews Geoffrey R.
Published: June 2009

Time/temperature profiles were obtained for commercial ultra high temperature (UHT) and sterilized milk processing plants and for a pilot UHT plant operating under nine different conditions. Samples of milk from each process were analysed for lactulose by an enzymic method, yielding concentrations of lactulose of 4 to 118 mg/100 ml. The measured lactulose concentration could be derived from the corresponding time/temperature profile by assuming an Arrhenius relationship with an activation energy of 152 kJ mol-1, for the whole range of UHT and in-container processes examined.
Effect of reaming the papillary duct of cows' teats on keratin removal and penetrability of the duct to implantedEscherichia coliendotoxin
Authors: Schultze W. Donald , Bramley A. John
Published: June 2009

Penetrability of the bovine teat duct toEscherichia coliendotoxin solution was measured before and after reaming the duct with a polypropylene tube, a steel twist drill bit, or a fluted drill point. There was some evidence of a transient increase in penetrability for one or two milkings following reaming but most ducts were not rendered penetrable to endotoxin. Histological examination of ducts after reaming showed that although the loosely packed superficial keratin was effectively removed a continuous smooth keratin layer remained covering the epithelium. These observations are discussed with respect to the possible mechanisms responsible for maintaining the defensive barrier of the duct to bacterial penetration.
Studies on the thermostability of lactase (Streptococcus thermophilus) in milk and sweet whey
Authors: Greenberg Norman A. , Wilder Teresa , Mahoney Raymond R.
Published: June 2009

The stability of lactase fromStreptococcus thermophilusat 55 °C increased 7-fold, 2-fold and 1·5-fold in the presence of lactose, galactose and glucose respectively; maltose had no effect. Total stability over an 8 h period was more than 10-fold better in milk and sweet whey than in lactose solution, owing to the stabilizing influence of the milk proteins and the milk salts. Ovalbumin and reduced glutathione provided some extra stability but were not as effective as the milk components. In the absence of lactose the enzyme was less stable in milk and was not protected at all by sweet whey constituents. None of the milk protein fractions was as effective in the absence of lactose as when it was present. Enhanced thermostability of the enzyme in milk and sweet whey is due to contributions by all major milk components, but binding of lactose to the enzyme is the major factor controlling the extent of stabilization by other components.
Heat stability of milk: pH-dependent dissociation of micellar κ-casein on heating milk at ultra high temperatures
Authors: Singh Harjinder , Fox Partick F.
Published: June 2009

Preheating milk at 140 °C for 1 min at pH 6·6, 6·8, 7·0 or 7·2 shifted the heat coagulation time (HCT)/pH profile to acidic values without significantly affecting the maximum stability. Whey proteins (both β-lactoglobulin and α-lactalbumin) co-sedimented with the casein micelles after heating milk at pH < 6·9 and the whey protein-coated micelles, dispersed in milk ultrafiltrate, showed characteristic maxima–minima in their HCT/pH profile. Heating milk at higher pH values (> 6·9) resulted in the dissociation of whey proteins and κ-casein-rich protein from the micelles and the residual micelles were unstable, without a maximum–minimum in the HCT/pH profile. Preformed whey protein–casein micelle complexes formed by preheating (140 °C for 1 min) milk at pH 6·7 dissociated from the micelles on reheating (140 °C for 1 min) at pH > 6·9. The dissociation of micellar-κ-casein, perhaps complexed with whey proteins, may reduce the micellar zeta potential at pH ≃ 6·9 sufficiently to cause a minimum in the HCT/pH profile of milk.
Seasonal variation and characterization of Micrococcaceae present in ewes' raw milk
Authors: Bautista Lydia , Bermejo Monserrat P. , Nuñez Manuel
Published: June 2009

Samples (120) of ewes' raw milk collected over a 12-month period on arrival at the dairy and freshly drawn ewes’ milk samples (30) collected at the farm were analysed for total viable counts and staphylococci. Total viable counts reached on the average 54 × 106/ml in dairy samples and 6·0 × 105/ml in farm samples, whereas mean levels of staphylococci were 5·9 × 104/ml and 3·3 × 103/ml, respectively. A high proportion (62%) of coagulase-positive isolates from Baird-Parker agar plates was detected in spring months.Staphylococcus aureus(42%),Staph. haemolyticus(23%) andStaph. epidermidis(10%) were the predominant species in 210 characterized isolates of staphylococci from ewes' raw milk. Seven coagulase-positive, maltose-negative staphylococci could not be identified with any of the recognizedStaphylococcusspecies. EighteenMicrococcusstrains were identified asM. varians, whereas 111Micrococcusstrains of uncertain taxonomic status were separated into three groups, according to their physiological characters.
Factors affecting the ethanol stability of bovine skim milk
Authors: Horne David S. , Parker Thomas G. , Donnelly William J. , Davies D. Thomas
Published: June 2009

Milk samples from three groups of cows were taken at frequent intervals throughout lactation following autumn-, winter- or spring-calving. The ethanol (EtOH) stability/pH profile was determined for each sample and its characteristic parameters calculated. The lactational trends in these parameters were examined. Asymptotic maximum EtOH stability (Smax) was low in early lactation but rose rapidly to a value which showed no further lactational trends. Asymptotic minimum stability (Smin) for samples from autumn- and winter-calving cows showed a decrease which could be associated with the transition to summer grazing but no obvious lactational effects. The slope parameter increased slowly during lactation. The profile pK value decreased in early lactation, but thereafter increased throughout lactation giving the most obvious effect observed in direct measurement, namely an alkaline shift in the profile as lactation progressed. The EtOH stability calculated at a fixed pH of 6·6 passed through a maximum, characteristic for each cow, in the first weeks of lactation but declined steadily thereafter. This behaviour mirrors the lactational behaviour of the soluble salt balance ratio calculated from the original data of White & Davies (1958).
Production of cream from ultrafiltered milk
Authors: Scurlock Peter G.
Published: June 2009

Bovine whole milk was concentrated up to 5-fold by ultrafiltration and separated conventionally to produce protein enriched creams with fat contents ranging from 20 to 50 % (w/w). The measured viscosity of the concentrates increased with the degree of concentration. This led to inefficient centrifugal separation, as measured by the loss of fat into the skimmed milk, which was further worsened when damage to the fat globules occurred during ultrafiltration. The viscosity of the creams, at constant fat percentage, increased as the concentration factor of the milk from which it was separated rose.
An inhibitor typing scheme forStreptococcus uberis
Authors: Tagg John R. , Vugler Leone G.
Published: June 2009

A typing scheme was used to test 15 strains ofStreptococcus uberisaccording to their production of (P-type) and sensitivity to (S-type) bacteriocin-like inhibitory substances. Twelve of the strains were inhibitor producers and nine different P-types were detected. All of the strains were typable according to inhibitor sensitivity, ten different S-types being distinguished. Both the P-type and S-type designations of the strains were reproducible on repeated testing. By combination of P-typing and S-typing, highly discriminatory inhibitor ‘fingerprints’ of the strains could be obtained. This scheme would appear to have considerable potential for typing isolates ofStr. uberisas an aid to investigations into the epidemiology ofStr. uberismastitis in dairy cattle.
Effect of combined ultrasonic and heat treatment (thermoultrasonication) on the survival of a strain ofStaphylococcus aureus
Authors: Ordoñez Juan A. , Aguilera M. Angeles , Garcia M. Luisa , Sanz Bernabe
Published: June 2009

The combined effect of ultrasonic waves (20 kHz, 150 W) and heat treatment applied simultaneously (thermoultrasonication) on the survival of a strain ofStaphylococcus aureuswas studied in 0·05 m-phosphate buffer pH 6·8 and ultra-heat-treated whole milk. This combined process decreased by 63% the decimal reduction times for the heat treatment when the organism was suspended in buffer and by 43% when suspended in milk. These effects were much greater than the additive effect of the two agents considered independently.
Effect on milk production of controlling muscid flies, and reducing fly-avoidance behaviour, by the use of Fenvalerate ear tags during the dry period
Authors: Harris Jeanette A. , Hillerton J. Eric , Morant Steven V.
Published: June 2009

Fenvalerate ear tags reduced fly loads on dry dairy cattle by 95% between July and September. Fly dislodging behaviour, such as ear flicks which correlated with numbers of Musca autumnalis on the face and stamps/kicks which correlated with numbers of Stomoxys calcitrans on the legs, was also significantly reduced. There was no significant difference between the tagged and untagged groups in the total time spent grazing each day. Milk yields were not statistically significantly different, but the tagged group showed a greater increase in milk yield between lactations, of 1·45 kg/cow daily in the first 12 weeks of the lactation.
Assay of proteinases of psychrotrophic bacteria in milk using Hide Powder Azure and a simple procedure for clarification of milk
Authors: Stead Donald
Published: June 2009

The clarification of milk by addition of solutions of Triton X-100 and EDTA after digestion of added Hide Powder Azure (HPA) was found to provide a simple method of determining the extracellular proteinase activity of Gram-negative psychrotrophic bacteria in pasteurized whole milk. The light absorbance of the clarified HPA digestion product was measured directly, after a brief incubation period, and was stable to storage of samples in diffuse daylight for at least 2 d. Proteinase produced by growth in refrigerated whole milk of as few as 2·5 × 106cfu ml−1ofPseudomonas fluorescensAR11 was detected.
Ethanol stability of casein micelles – a hypothesis concerning the role of calcium phosphate
Authors: Horne David S.
Published: June 2009

The ethanol (EtOH) stability of skim milk and the stability towards aggregation of casein micelles diluted into ethanolic buffer solutions were compared using data obtained from previously published experiments. Differences in absolute stability and in relative response were observed when Ca2+ level and pH were adjusted, the buffer system results lying below those from skim milk in both cases. Increasing the ionic strength of skim milk adjusted to pH 7·0 lowered its EtOH stability whereas increasing the ionic strength of the diluting buffer increased the stability of the casein micelles. The hypothesis is put forward that the differences are due to the simultaneous precipitation of Ca phosphate when EtOH is added to skim milk. This draws calcium from the caseinate sites of the micelle, counteracting the destabilizing effects of the EtOH towards the micelle. Such removal and the consequent restructuring are kinetically controlled and micellar precipitation in skim milk finally occurs when the micellar coagulation time falls within the time scale of the restructuring reactions.
Evidence for temperate bacteriophages in two strains ofLactobacillus bulgaricus
Authors: Cluzel Pierre-Jean , Veaux Monique , Rousseau Micheline , Accolas Jean-Pierre
Published: June 2009

Lactobacillus bulgaricusstrains LT1 and LT4 previously isolated from a yogurt factory were shown to be lysogenic and inducible by mitomycin C or u.v. irradiation, induction being optimal at the beginning of exponential growth. Five indicator strains (four ofL. lactis, one ofL. bulgaricus) were found in which the two phage lysates propagated well in a liquid medium, but formed plaques on bacterial lawns less readily. Ca2+was required for the phage infection of the indicator strains to reach termination. Phage particles from each strain exhibited a comparable ultrastructural morphology under the electron microscope, having an isometric head, a triple collar and a noncontractile fibre-containing tail.
Distribution of milk in the goat mammary gland and its relation to the rate and control of milk secretion
Authors: Peaker Malcolm , Blatchford David R.
Published: June 2009

Changes with time in the distribution of milk between different storage regions of the mammary gland were studied in goats. Milk was allowed to drain from the gland through a catheter (catheter milk); the gland was then milked by hand, before (hand milk) and after the administration of oxytocin (alveolar or residual milk). The hand-milk fraction was of negligible volume. There was an essentially linear increase in the catheter- plus hand-milk fraction from 0 to 16 h. The alveolar fraction increased up to 6 h, but thereafter remained constant to 16 h. There was considerable but consistent variation between animals in the alveolar fraction as a proportion of total milk volume. The proportion of residual milk was inversely related to milk secretory rate per unit weight of mammary tissue. The hourly administration of oxytocin without milking had no apparent effect on the distribution of milk in the gland 1 h later.
Interaction between heated κ-casein and β-lactoglobulin: predominance of hydrophobic interactions in the initial stages of complex formation
Authors: Haque Zahurul , Kinsella John E.
Published: June 2009

Mixtures of κ-casein and β-lactoglobulin (β-lg) were heated at 70 °C in 20 mM-imidazole buffer, pH 6·8 containing 20 mM-EGTA. Aggregation of the κ-casein/β-lg mixture occurred within 90 s and susceptibility to hydrolysis by chymosin decreased significantly within 180 s even though covalent interaction was not detected until after 4000 s. UV-absorbance indicated initial structural destabilization of the heated κ-casein/β-lg mixture followed by a return ( > 350 s) to a spectrum comparable to the native state, indicating molecular rearrangement. Apparent hydrophobicity of κ-casein decreased 80% within 250 s compared to a 38% decrease for β-lg. Under similar conditions, the κ-casein/β-lg mixture (1:1) showed a faster (2·5 times) decrease in apparent hydrophobicity than κ-casein alone with concomitant exposure of acidic (hydrophilic) groups. The results suggested that the driving force for the rearrangement was mainly hydrophobic, i.e. entropic in origin. The tendency of heated and subsequently cooled κ-casein/β-lg to aggregate reached a maximum after heating at 70 °C for 720 s.
Protein synthesis and degradation in the mammary gland of lactating goats
Authors: Oddy V. Hutton , Lindsay Derek B. , Fleet Ivan R.
Published: June 2009

Lactating goats were given a close arterial infusion of [1-14C]leucine and [4,5-3H]4-methyl-2-oxopentanoic acid into one half of the mammary gland at 2–3 weeks and 34–39 weeks after kidding. Rates of protein synthesis, degradation and net output were determined from measurements of arteriovenous difference and blood flow using a model of leucine metabolism previously developed for muscle (Oddy & Lindsay, 1986). Protein leucine output in milk (Y μmol/min) correlated well with the difference between synthesis and degradation (X μmol/min) derived from the model:

There was substantial synthesis and degradation of protein within the mammary gland. Although only an approximate value could be obtained for the partitioning of protein synthesis and degradation between tissue and milk proteins, there was evidence of appreciable turnover of both. There was no significant difference between mammary leucine and protein metabolism in early and late lactation other than that imparted by a greater mass of mammary tissue in early lactation, although there was a tendency for greater oxidation of leucine in late lactation.
Use of light scattering techniques to study the kinetics of precipitation of mineral acid casein from skim milk
Authors: Jablonka Mark S. , Munro Peter A. , Duffy Geoffrey G.
Published: June 2009

Two light scattering methods for monitoring the precipitation of casein from skim milk (9% w/w) with mineral acid are presented. Experiments were carried out at precipitation temperatures in the range 25–53 °C and precipitation pH values in the range 3·9–5·1. The initial stages of precipitation were explored using a light fibre optics system attached to a closed-loop acid/milk mixing system. The later stages of particle formation and growth were examined using a laser doppler anemometer attached to an open-pipe flow system. It was found that there was a lag initially, followed by a period of rapid particle growth. During a third phase a dynamic equilibrium between particle growth, break-up and shrinkage was established. A model for isoelectric casein precipitation based on these observations is proposed and discussed.
Emulsifying capacity of whey proteins produced by ion-exchange chromatography
Authors: Langley Keith R. , Millard David , Evans E. William
Published: June 2009

At pH 7·0, the emulsifying capacity (Ec) of ion-exchange fractionated whey protein powders in corn oil/water systems increased with increase in protein concentration up to 0·l% (w/v), where it was maximal. At higher concentrations Ec decreased because of packing effects of the oil droplets. At low protein concentrations Ec could be determined from linear equations involving the relative concentration of the individual proteins in the powder. The surface coverage of β-lactoglobulin on the oil was ∼ 1 mg m–2. Oil droplet size and Ec were maximal at pH 4·0–6·0, corresponding to the isoionic points of the proteins.
Production of acetolactate byStreptococcus diacetylactisandLeuconostocspp.
Authors: Jordan Kieran N. , Cogan Timothy M.
Published: June 2009

The effect of several parameters on the decarboxylation of α-acetolactic acid (ALA) to diacetyl and acetoin was studied in model experiments. At temperatures > 50 °C, relatively more diacety1 than acetoin was produced. Regardless of temperature, HC1 increased the production of acetoin (58 mol% conversion at max.) and prevented the production of diacetyl. Steam distillation of ALA caused ~ 55 mol%/h conversion to acetoin and 7 mol%/h to diacetyl. Production of acetoin was proportional to the ALA concentration. Based on these results two methods for the quantitative measurement of ALA were developed. Only one of 17 strains ofStreptococcus diacetylactis (Lactococcus lactissubsp.lactisbiovar.diacetilactis, new nomenclature) and three of three strains ofLeuconostocspp. produced ALA. The implications of these findings are discussed.
Species identification of staphylococci and micrococci isolated from ewes' milk cheeses
Authors: García María Camino , Otero Andrés , García María Luisa , García María Rosario , Moreno Benito
Published: June 2009

Forty-five strains of staphylococci and 6 strains of micrococci isolated from pasteurized ewes' milk cheeses (Manchego and Burgos varieties) were identified to species level. Three strains of staphylococci were identified asStaphylococcus aureus. Amongst the 42 coagulase-negative staphylococci, 8 were novobiocin-sensitive and 34 novobiocin-resistant. The novobiocin-sensitive species found wereStaph. auricularis(5 strains),Staph. caseolyticus(2 strains) andStaph. epidermidis(1 strain). Novobiocin-resistant strains were identified asStaph. gallinarum(5 strains),Staph. xylosus(4),Staph. saprophyticus(9),Staph. cohnii(6),Staph. sciuri(1) andStaph. lentus(3). The other 6 isolates could not be identified. Only 3 strains of micrococci were identified (Micrococcus kristinae, M. variansandM. sedentarius). The possible origin of the isolates is discussed.
Effect of cleaning-in-place disinfectants on wild bacterial strains isolated from a milking line
Authors: Mattila Tiina , Manninen Merja , Kyläsiurola Anna-Liisa
Published: June 2009

Two cleaning-in-place disinfectant Systems (alkaline–acid, alkaline–CI2) were tested on wild bacteria isolated from a milking line. Most of the isolated strains were Gram-negative and capsule-positive. The effect of milk and cream on the resistance of the wild strains to the cleaning Systems was tested. Suspension tests did not show the resistance of bacteria whereas the surface test showed high resistance towards all cleaning-agents. Milk had a protective effect only on the surfaces whereas cream showed mild protection in suspension and complete protection on the surfaces. It was concluded that the growth pattern of contaminants on surfaces needs further attention and the laboratory suspension tests do not correlate with the practical situation. Disinfectant tests based on bacterial growth on the surface are of importance.
Repeatability of milk clotting aptitude evaluated by lactodynamographic analysis
Authors: Caroli Anna , Bolla Patrizia , Pagnacco Guilio , Rampilli Marco , Degano Luigi
Published: June 2009

Lactodynamographic analysis is commonly employed to evaluate the clotting aptitude of milk (Frentz, 1965; Tarodo de la Fuente et al. 1969). The individual lactodynamographic response can therefore be used in selection as a quantitative trait. The aim of this work was to estimate either the biological repeatability of the lactodynamographic response or the repeatability of the analytical method itself.
Comparison of rapid tests for assessing UHT milk sterility
Authors: Reinheimer Jorge A. , Demkow Maria R.
Published: June 2009

Samples of UHT milk were contaminated at two levels (102 and 104 cfu/ml) with 52 bacterial strains associated with spoilage. Samples were assayed, using various tests, to determine efficiency in detecting non-sterility after an incubation period shorter than that advised in standard procedures. The tests performed were colony count, titratable acidity and pH modification, organoleptic assessment, stability towards ethanol (68, 80 and 88% v/v), resazurin and nitrate reduction. After 3 d incubation at 30 °C every case was detected by the resazurin test with a good statistical probability (P = 0·999). Reliability was not so high in all other tests, even after 14 d incubation.
Studies on antimutagenic effect of milk cultured with lactic acid bacteria on the Trp-P2-induced mutagenicity to TA98 strain of Salmonella typhimurium
Authors: Hosoda M. , Hashimoto H. , Morita H. , Chiba M. , Hosono A.
Published: June 2009

The inhibitory effects of cultured milk using 76 strains of lactic acid bacteria isolated from milk products were investigated on the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3−b]indole (Trp-P2), a tryptophan pyrolysate for Salmonella typhimurium TA98. Each cultured milk sample displayed its characteristic antimutagenic effect against the mutagenicity of Trp-P2. The milk cultured with Lactobacillus acidophilus LA106 (LA2) showed the highest inhibition of 82·1% among the strains used. Milk samples cultured with Lactococcus lactis subsp. lactis, L11103 (10−3) and L11102 (KM) also exhibited higher inhibition percentages.
Effect of caprine arthritis–encephalitis virus infection on milk cell count andN-acetyl-β–glucosaminidase activity in dairy goats
Authors: Ryan Diane P. , Greenwood Paul L. , Nicholls Paul J.
Published: June 2009

Bacteriology, somatic cell counts (SCO) andN-acetyl-β-glucosaminidase (NAGase) activity determinations were conducted on milk samples collected from does in three dairy herds with caprine arthritis–encephalitis virus (CAEV) infection. In two herds, CAEV-infected does were more likely to have a subclinical bacterial infection of the udder than CAEV-free does (P < 0·05). Does with CAEV but no bacterial udder infection had significantly greater mean SCO and NAGase activity than CAEV-free does without udder infection (P < 0·01). In two herds, changes in milk SCC and NAGase associated with CAEV infection were similar to those produced by coagulase-negative staphylococcal infections. The findings confirm that indirect indicators of bacterial mastitis infection may have reduced specificity in dairy goat herds with CAEV.
Relationships between plasmin levels in rennet caseins and proteolytic and rheological changes on storage of cheese analogues made from these caseins
Authors: Mulvihill Daniel M. , McCarthy Alice
Published: June 2009

Sixteen rennet casein samples and the corresponding sixteen cheese analogues made from these caseins were obtained from a local processor. Following storage at 4°C for 6 months, pH 4·6-soluble N contents of the cheese analogues increased, while αs- and β-casein contents, elastic moduli and apparent relaxation times decreased. The β-casein and pH 4·6-soluble N contents of the 6 month old products were significantly correlated, both were significantly correlated with the plasmin (EC 3.4.21.7) contents of the corresponding rennet caseins from which the analogues were made and all three were significantly correlated with the rheological properties of the stored analogues. Of the compositional characteristics, only percent moisture in non-fat substance and percent fat in dry matter were significantly correlated (P < 0·05) with any of the proteolytic or rheological properties. The sixteen cheese analogues were also assayed at one time, when they ranged in age from 1 to 35 weeks, and highly significant interrelationships between plasmin activity, proteolysis and rheological properties were established. The results indicate that the plasmin content of rennet caseins had a significant influence on the proteolytic and rheological changes that occurred during storage of cheese analogues made from these caseins.
Secondary structures in β-casein peptide 1–42: a two dimensional nuclear magnetic resonance study
Authors: Wahlgren N. Magnus , Dejmek Petr , Drakenberg Torbjörn
Published: June 2009

Two dimensional NMR spectroscopy was used to study the structure of a peptide composed of the N-terminal 42 amino acid residues of β-casein. The peptide was obtained by enzymic cleavage using endoproteinase Asp-N. Complete sequence-specific 1H NMR assignment was performed for the peptide at three Ca2+ concentrations (0, 22 and 37 mM). The NMR results show that the peptide was highly flexible and adopted multiple conformations. No stable secondary structures were present; however, the peptide had some regions with non-random structure. The region between residues Leu16 and Asn27 adopted conformations with an increased contribution of α-helical structure, a so-called nascent helix. Two regions, Glu11-SerP15 and Lys29-Phe33 showed an increased population of conformations with extended structures. Addition of Ca2+ induced chemical shift changes for the backbone amide protons, especially around the phosphoserine region and around the suggested α-helical structure, indicating that the addition of Ca2+ stabilized the structure already present in the apo form of the peptide.
Responses of the bovine teat to machine milking: measurement of changes in thickness of the teat apex
Authors: Hamann Jörn , Mein Graeme A.
Published: June 2009

Changes in the teat apex before and after different milking treatments were measured with a spring-loaded caliper device known as a cutimeter which could detect changes in thickness of the tissues of the teat end, presumably due to congestion and/or oedema, with a high degree of accuracy (± 2%) and repeatability (r = 0·99). Teat end thickness increased with increasing vacuum level. The mean increase immediately after milking with a conventional cluster was 2% for 24 teats milked at 30 kPa, 8% at 50 kPa and 21% at 70 kPa. At these vacuum levels, the mean increases for the same teats milked with an unconventional (PKME) teatcup were 10, 18 and 25% respectively. Cyclic application of 35 kPa positive pressure to the pulsation chamber of a conventional teatcup operating at 50 kPa reduced teat end thickness by 8% compared with the mean premilking value. Although most teats returned to within ± 2% of their premilking thickness values by 1 h after milking, differences were apparent between different milking systems for up to 4 h postmilking.
A reference milk system for instrumental measurement of milk fat and protein
Authors: Clarke Timothy
Published: June 2009

A reference milk system (Clarke system) using primary reference milks made from preserved natural bovine milks (PNM) and standard reconstituted milk (SRM) has been developed to enable accurate calibration of milk analysing instruments. The PNM have values of 2, 3, 4, 5 and 6% fat and 3·5, 2·7, 3·4, 4·2 and 3·3% protein respectively and can be stored for 4 months without detectable change in fat or protein content. The above reference milk system utilizes SRM as a secondary reference milk to enable regular checking of the stability of the instrument calibration during routine testing (e.g. after every 100 samples). Over several months seven laboratories using 13 fat-testing instruments and seven protein-testing instruments achieved high levels of accuracy in weekly calibrations (coefficient of variation 1·1%) when they used the reference milk system and adhered to the prescribed calibration criteria.
Composition and structure of micellar calcium phosphate
Authors: Holt Carl , van Kemenade Mathea J. J. M. , Nelson Lowell S. , Sawyer Lindsay , Harries John E. , Bailey Raymond T. , Hukins David W. L.
Published: June 2009

Micellar calcium phosphate has the chemical composition and physicochemical properties that are consistent with it being a complex of the phosphate centres of casein with an acidic amorphous calcium phosphate. Similar acidic amorphous calcium phosphates have been prepared in the laboratory and for these, as well as for micellar calcium phosphate, the most appropriate crystalline model compound from which the short-range structure may be derived is brushite, CaHPO4.2H2O. The predicted secondary structures around sites of phosphorylation in the Ca2+-sensitive caseins often comprise an α-hclix-loop-α-helix motif with the sites of phosphorylation in the loop region. This motif may be important in linking the colloidal calcium phosphate with casein in native casein micelles.
Monitoring of B-complex vitamins in yogurt during fermentation
Authors: Kneifel Wolfgang , Holub Sonja , Wirthmann Maria
Published: June 2009

Eight commercially available yogurt starter cultures were examined for their ability to synthesize water-soluble vitamins. In order to yield comparable assaying conditions, 12·5% reconstituted whole milk was used for yogurt production throughout the experiments. When applying the traditional method of yogurt manufacture (short-time incubating at 42 °C/3–4 h) with all cultures the following vitamins were enriched during fermentation by more than 20%: thiamin (two cultures), pyridoxine (four cultures), folic acid (one culture), and biotin (two cultures). Two starter cultures were selected and used to compare vitamin profiles during the two different methods of fermentation. In contrast to short-time incubation, long-time yogurt production (30 °C/14–16 h) led to a lesser production of folic acid, but to increased concentrations of thiamin and of nicotinic acid.
Feeding calcium soaps of fatty acids to lactating cows: effect on production, body condition and blood lipids
Authors: Sklan David , Bogin Eytan , Avidar Yaakov , Gur-Arie Shai
Published: June 2009

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.
Cheddar cheesemaking from whole milk concentrated by ultrafiltration and heated to 90 °C
Authors: Green Margaret L.
Published: June 2009

Cheddar cheeses were made from milks concentrated approximately 2·3-and 3·4-fold by ultrafiltration, then heated at 90 °C for 15 s. They were compared with cheeses made from pasteurized unconcentrated milks and unheated 5·3-fold concentrates. The recoveries of fat and protein were comparable in the cheeses from heated 2·3-fold concentrates and unheated 5·3-fold concentrates and both were higher than the controls. However, fat losses were high in curds from 3·4-fold heated concentrates. The use of paired fast and slow starter strains and coagulation at 26 °C optimized the curd composition. Proteolysis and flavour development were only slightly reduced in all the cheeses from concentrated milks, perhaps aided by higher starter levels in the curd than in the controls. The structures of the curds from the heated concentrated milks were coarser than those of the controls and the curd particles fused poorly. This may explain the grainy, dry, crumbly texture in the cheeses from the heated concentrates. The texture was not improved by adding a bacterial proteinase to the curd.
Effects of cations and anions on the rate of the acidic coagulation of casein micelles: the possible roles of different forces
Authors: Bringe Neal A. , Kinsella John E.
Published: June 2009

Raw skim milk was diluted 1000-fold using distilled water or various salt solutions as specified. Smooth, hyperbolic profiles of coagulation ratev.pH for casein were calculated from recordings of turbidity (400 nm) with time. The effects of pH, cation type, anion type and cleavage ofk−casein by chymosin (EC 3.4.23.4) were determined. The maximum of pH-coagulation rate profiles decreased by 63, 85 and 94% when the skim milk diluent was changed from water to salt solutions of NaCl (100 mM), CaCl2(50 mM) or MgCl2(50 mM). The maximum of the pH–coagulation rate profile was 15 times greater when the Ca salt was changed from CaCl2to Ca(SCN)2(50 mM). The highest pH at which casein coagulation occurred increased from 4·45 to > 6·0 when Cu2+(1 mM) was included with casein micelles dispersed in CaCl2solution (50 mM). The addition of chymosin to casein micelles suspended in CaCl2solution (70 mM) eliminated the inhibition of casein coagulation by Ca2+at pH 4·5. It is proposed that ions such as Mg2+, Ca2+, and Na+, which generally associate with casein phosphate and carboxylate groups, increased the H+concentration required to initiate the coagulation of casein, because H+must displace bound Ca2+, Mg2+or Na+to reduce repulsive hydration forces between casein micelles, allowing attractive hydration forces (e.g. hydrophobic phenomena) to cause casein coagulation. Furthermore, it is proposed that ions such as Cl−, Br−,and SCN−bind to lysine, arginine and histidine groups and thereby decrease repulsive hydration forces between cationic casein micelles.
Microbial study of Casar de Cáceres cheese throughout ripening
Authors: Poullet Blanca , Huertas Manuel , Sánchez Antonio , Cáceres Pilar , Larriba German
Published: June 2009

Six batches of Casar de Cáceres raw ewes' milk cheeses were examined throughout their ripening. Three were made in winter, the others in spring. The microbial counts in the interior of the cheeses were ∼1·5 log units higher in the winter cheeses for total viable counts, lactic streptococci and leuconostocs, and >2 log units higher for total enterobacteria, coliforms and faecal coliforms in the 60 d samples. Staphylococci were not detected after day 15 of maturation in spring cheeses, but reached 1 log unit at day 60 in the interior of winter cheeses. In the surface samples, differences in microbial counts were more marked. Values of some physicochemical indices, such as pH, % moisture content and % NaCl were also determined.
Influence of milk flow rate on new intramammary infection in dairy cows
Authors: Grindal Robert J. , Hillerton J. Eric
Published: June 2009

In a series of short-term experiments cows were subjected to exaggerated bacterial challenge and accentuated milking machine conditions known to predispose to new mammary infection. The incidence of new intramammary infection was significantly greater in quarters with peak flow rates > 1·6 kg/min whether they were exposed to impacts (P< 0·05) or milking without pulsation (P<0·001). The infection rates were much lower (P< 0·001) in quarters milked with ‘pulsation and shields’ to protect against these two machine factors. Despite this, quarters with peak flow > 1·6 kg/min still showed a 12-fold increase in mastitis incidence compared with quarters with peak flow < 0·8 kg/min. Rates of milk flow have increased dramatically in the last 40 years through selection and breeding: whole udder peak flow rates in heifers have doubled from 1·9 to 3·8 kg/min. Increased emphasis, therefore, should be placed on hygiene, husbandry and milking techniques to minimize bacterial numbers at teat ends to control mastitis as the drive for higher flow rate and yield make cows increasingly more susceptible to infection. These results suggest that the benefits of reduced infection rate from mastitis control are significantly underestimated since animals are now considerably more susceptible than 40 years ago.
Proteolytic activity of two commercial proteinases from Aspergillus oryzae and Bacillus subtilis on ovine and bovine caseins
Authors: López-Fandiño Rosina , Ramos Mercedes , Fernández-García Estrella , Olano Agustin
Published: June 2009

Electrophoretic analysis of the action of two commercial enzymes, Neutrase 0·5 and MKC Fungal Protease, on whole casein and αs-, β- and κ-caseins from cows' and ewes' milk showed that Neutrase 0·5 chiefly degraded β-casein, giving rise to peptides soluble at pH 4·6 detectable by PAGE. In contrast, although MKC Fungal Protease caused intense hydrolysis of bovine β-casein, in ovine casein it resulted in more active degradation of αs- than β-casein. The latter enzyme did not produce peptides soluble at pH 4·6 detectable by PAGE. Both enzymes degraded κ-casein, yielding a breakdown product that exhibited an electrophoretic mobility similar to that of the breakdown product produced by the action of commercial rennet.
A new fermented milk using capsular polysaccharide-producing Lactobacillus kefiranofaciens isolated from kefir grains
Authors: Toba Takahiro , Uemura Hitoshi , Mukai Takao , Fujii Toshihiro , Itoh Takatoshi , Adachi Susumu
Published: June 2009

A new fermented milk was prepared by using capsular polysaccharide-producing Lactobacillus kefiranofaciens K1 isolated from kefir grains. Fermentation was carried out at 30°C for 18 h, when pH 4·5 was attained. The product had a ropy consistency and was resistant to syneresis. However, the product was given lower scores for acceptability by a consumer panel than a similar product made with Lb. delbrueckii subsp. bulgaricus.
Trials of a novel mastitis sensor on experimentally infected cows
Authors: Lake John R. , Hillerton J. Eric , Ambler Barry , Wheeler Helen C.
Published: June 2009

Numerous attempts to develop in-line Systems for the measurement of the electrical conductivity of milk as an aid to the detection of mastitis have been described. The major technical problem of fouling of electrodes exposed to milk has been overcome in the sensor tested here by use of an inductive System of measurement. The practical application of this System in the milking parlour is reported. The novel mastitis sensor has been shown to detect incipient mastitis before there are visible signs of abnormal milk. Conductivity measurements have the advantage over other diagnostic procedures in that the information is available immediately without additional effort. Normalized conductivity and milk yield variation results indicate the potential for developing a practical, automatic System for mastitis detection.
Efficiency of cleaning agents for an inorganic membrane after milk ultrafiltration
Authors: Daufin Georges , Merin Uzi , Kerherve François-Louis , Labbe Jean-Pierre , Quemerais Auguste , Bousser Charles
Published: June 2009

Cleaning of inorganic membranes after ultrafiltration (UF) of skim milk has been assessed using hydraulic, physicochemical and spectroscopic (i.r. and X-ray photoelectron spectroscopy) measurements. A cleaning sequence using hypochlorite alone or hypochlorite followed by HNO3 restored the membrane hydraulic resistance, in contrast to cleaning with HNO3 alone. When using NaOH, addition of Ca complexants (EDTA, gluconate, tripolyphosphate) and surfactants was required to obtain similar results. Three types of criteria (hydraulic, kinetic, chemical) are available to assess the effect of the sequestrant and surfactant types. In all the cases studied, traces of protein and Ca were detected on and within the membrane after cleaning. Nevertheless, it was concluded that it is possible to develop a single-step alkaline product to clean inorganic milk UF membranes if suitable surfactants and Ca sequestrants are included in its formula.
Isolation and characterization of α2-macroglobulin from mastitis milk
Authors: Rantamäki Liisa K. , Müller Hans-Peter
Published: June 2009

Whey samples were screened for the presence of the proteinase inhibitor α2-macroglobulin (α2M). From an enzymic test, α2M levels in normal whey varied in the range 0·49–0·84% of the serum level, whereas in mastitis whey the activity was markedly increased, reaching values between 0·91 and 138·5% (median 7·2%) of standard serum level. In mastitis milk samples but not in normal milk α2M was also detected by double immunodiffusion and Western blotting. The proteinase inhibitor was purified from a mastitis milk sample with high α2M activity (138·5% of serum level). In SDS-PAGE, native-PAGE and in double immunodiffusion analysis the inhibitor appeared indistinguishable from plasma-derived α2M. The α2M preparation from mastitis whey migrated essentially as native α2M, representing the ‘slow’ form of the molecule. Treatment with trypsin transformed the α2M preparation to the electrophoretic ‘fast’ form, but treatment with methylamine had only a minor effect. The receptor recognition sites were not exposed on the isolated α2M molecule but could be readily exposed by treatment of the proteinase inhibitor with trypsin, which further proved that the isolated α2M was in the entire native, functionally active state.
Characterization of the oligopeptides of Parmigiano-Reggiano cheese soluble in 120 g trichloroacetic acid/1
Authors: Addeo Francesco , Chianese Lina , Sacchi Raffaele , Musso Salvatore Spagna , Ferranti Pasquale , Malorni Antonio
Published: June 2009

The non-protein nitrogen (NPN) of samples of Parmigiano-Reggiano cheese ripened for 6 and 15 months was fractionated by ion-exchange chromatography on a Cu2+-Chelex column to separate oligopeptides from free amino acids. Peptide components were isolated by reversed-phase HPLC and identified by fast atom bombardment–mass spectrometry (FAB–MS). Only the NPN fraction of 6 month old cheese samples contained enough peptides to be further characterized. On the basis of FAB–MS spectral results, 39 oligopeptides were identified, the main components being phosphopeptides. Two sets of both intact and partly dephosphorylated peptides, accounting for a total of 19 phosphopeptides, were formed by the hydrolysis of β–casein and belonged to regions 1–20 and 6–28 of β–casein. The formation and potential role of these peptides in cheese is discussed.