bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seasonal variations in the total nitrogen, non-protein nitrogen and urea nitrogen contents of Friesian and Jersey milk
Authors: McDowell A. K. R. 
Published: June 2009

SummaryA large number of samples (433) from the milk of Friesian herds was taken during the period November 1968 – September 1969, and a smaller number (159) from Jersey herds during the dairy ‘season’ September 1969 – April 1970, and analysed for total nitrogen (TN) and for non-protein nitrogen (NPN). The Friesian milk sample varied in TN from 0·456 to 0·624% (average 0·531 ± 0·021%) and in NPN from 0·024 to 0·054% (average 0·035 ± 0·004%). The Jersey samples varied in TN from 0·467 to 0·718% (average 0·584 ± 0·036%) and in NPN from 0·022 to 0·051% (average 0·033 ± 0·006%).The average NPN value for all the milks was 0·034 ± 0·005%.There was a seasonal trend in NPN and TN for the Jersey and in TN but not in NPN for the Friesian milks. The proportion of NPN as a percentage of TN varied widely – for the Friesian samples from 4·9 to 10·2% (average 6·46%) and for the Jersey samples from 3·7 to 8·7% (average 5·74%).Urea N also was estimated in 125 of the Friesian and in all the Jersey milk samples. It varied from 0·012 to 0·029% (average 0·020 ± 0·004%) in the Friesian and from 0·009 to 0·031% (average 0·020 ± 0·004%) in the Jersey samples. For all the milks the urea N as a percentage of NPN varied from 33 to 79 (average 56·5%).It is suggested that values for ‘protein content’ of milk should refer only to ‘true’ protein ((TN – NPN) × 6·38) and that in the absence of an analytical result for NPN the use of an average value such as that above would be justified.
An in-line milk sampler for determining the numbers of bacteria derived from teat surfaces and udder infections of cows milked in recorder machines
Authors: McKinnon C. H. , Cousins Christina M. , Fulford Rosemary J. 
Published: June 2009

SummaryA simple in-line milk sampler is described for determining the bacterial contamination from the udders of cows milked in recorder machines. When sterilized, and used with a sterile cluster, it collects a milk sample bacteriologically representative of the cow's total yield and it can be used with minimum disruption of the milking routine.
Mechanics of the teat and teatcup liner during milking: information from radiographs
Authors: Mein G. A. , Thiel C. C. , Akam D. N. 
Published: June 2009

SummaryFor radiographic studies of the teat and teatcup liner during milking, quarters were infused with a suspension of propyliodone in milk. Simultaneous recordings of vacuum within the liner, in the mouthpiece chamber and in the pulsation chamber, and recordings of liner-wall movement, were made in conjunction with the radiographs.The studies indicated that the sudden decline in milk flow-rate at the end of the period of peak flow-rate from each quarter, and the concurrent changes in the appearance and position of the teat in the liner, result from a fall in teat sinus pressure. This fall in pressure follows the partial closing of the milk passageway between the teat and udder sinuses. The changes initiating the closing of this connexion seem to occur above the teatcup and are associated with the declining amount of milk in the udder.The teat is elongated by 33–50% as it enters the liner and further stretching of the skin of the teat throughout milking is negligible. Thus, increase in the depth of penetration of the teat into the liner is due to more of the teat entering the top of the liner.The force exerted on the teat by the closed liner, which is greatest near the end of the teat, usually appears to increase near the end of milking. The force acting against the inner surface of the open liner barrel is greatest during the peak flow-rate period and it appears to be fairly uniform over most of the area of contact.
Residual milk yield as affected by dose and time of injection of oxytocin
Authors: Thompson P. D. , Paape M. J. , Smith J. W. 
Published: June 2009

SummaryA study was made, using Holstein cows, of the relationship between (1) the dose of oxytocin administered; (2) the time between milking and intravenous (i.v.) injection and (3) the time between injection and withdrawal of residual milk. Effectiveness of each dose for removal of residual milk was expressed as the percentage of residual milk in the quarter which was withdrawn by a test milking. The total amount of milk in the quarter was determined by giving a large dose of oxytocin and a second test milking, which then indicated the volume of milk missed by each combination of dose and delay times. It was found that delay before injection had no consistent influence on the effectiveness of the test dose; however, an increased delay after injection required an increase in the test dose for removal of a constant percentage of residual milk. The mean dose required for 75% removal increased from 6·3 mu/kg bodyweight to 57 mu/kg bodyweight as the time from injection to removal of residual milk increased from 5 to 30 min. The doses which produced removal of 75% of the residual milk in at least 50% of the quarters tested were 5, 10 and 40 i.u. for delays between injection and removal of residual milk of 5, 15 and 30 min respectively.
Adsorption, latent period and burst size of phages of some strains of lactic streptococci
Authors: Keogh Barbara P. 
Published: June 2009

SummaryThe host–phage reactions of 20 strains of lactic streptococci currently used in cheese manufacture, and the phages active on them, were studied under a variety of conditions. The phages of the lactic streptococci conformed in their behaviour with the general behaviour of phages for other bacterial species. The burst size of phages which attack one strain of starter culture varied widely and also varied when one phage attacked different host strains. The burst size of a phage was also influenced by the host on which it was previously propagated. An increase of temperature from 30 to 37 °C the latent period, but it increased, decreased, or had no effect on the burst size. This increase in temperature also usually decreased the percentage adsorption of phage. Rennet at a concentration of 0·02 % significantly reduced the percentage adsorption of phage in sterile reconstituted milk and also in tryptone yeast-extract broth.
Proteolysis detection in milk: II. The effect of preincubation of raw and laboratory pasteurized bulk milk samples on tyrosine value and its relationship with bacterial populations
Authors: Juffs H. S. 
Published: June 2009

SummaryA study is reported of the effect of preincubation of raw and laboratory pasteurized bulk milk samples on the tyrosine value (TV) of milk and its relationship with bacterial populations. For raw samples, mean TVs before and after preincubation for 20±2 h at both 25 and 30 °C differed (P < 0·001). After preincubation at 30 °C, the TV of 47 % of raw samples exceeded that considered to represent the upper limit of variation in the TV of a normal bulk milk supply. At this temperature, however, there was no indication that proteolytic psychrotrophs were a major contributor to increased TV. With preincubation of raw samples at 25 °C, an increase to above the upper limit of variation occurred in only 20 % of samples; however, proteolytic psychrotrophs appeared more active at this temperature. In similar samples preincubated after laboratory pasteurization, large increases occurred in TV after 20 ±2 h at 30 °C, while at 25 °C the increases were much smaller and of the order found for preincubated raw samples. The results showed, however, that nonpsychrotrophic bacteria were also the principal source of proteinase giving rise to increased TVs in laboratory pasteurized samples.
Influence of dietary proteins on rennin and pepsin content of preruminant calf vell
Authors: Garnot Pascaline , Valles E. , Thapon J.-L. , Toullec R. , Tomassone R. , Ribadeau-Dumas B. 
Published: June 2009

SummaryStudies were undertaken to determine the influence of dietary proteins on the rennin and pepsin contents of preruminant calf vell. Three groups of 12 Friesian calves were each fed either milk proteins, whey proteins or a 50:50 mixture of these 2 diets. They were slaughtered at a constant weight of 150kg and their vells collected and dried. Another group of vells was obtained from 8 animals that had been fed milk proteins in a separate experiment. The extraction of the abomasal enzymes was carried out at acid pH, and the extracts were quantitatively analysed for rennin and pepsin by DEAE-cellulose column chromatography. Qualitative analyses were also performed by agarose-acrylamide gel electrophoresis. The only enzymes observed using this last method were rennin and bovine pepsin II. Statistical analysis of the quantitative enzyme determinations indicated a trend for the vells from calves fed diets containing casein to be richer in total activity and in rennin, while the level of pepsin remained approximately constant. It seems that casein may induce the secretion of rennin. However, further experiments will be necessary to confirm this. Important differences were observed between the 2 groups of veils from calves given the same diet, but grown in slightly different conditions.
Effects of intramammary arterial infusion of non-essential amino acids and glucose in the lactating goat
Authors: Mepham T. B. , Linzell J. L. 
Published: June 2009

SummaryThree experiments were carried out on 2 lactating goats, in which mammary arterial plasma amino-acid concentrations were elevated by the infusion of a solution of non-essential amino acids into a carotid artery supplying a transplanted mammary gland. In a fourth experiment a solution of glucose was similarly infused. In some cases the increased arterial concentrations of amino acids resulted in their increased mammary uptake, and in a depression of glucose uptake. However, infusions of neither amino acids nor glucose resulted in increased milk protein yield. Infusion of [U-14C]glutamic acid in one experiment demonstrated gluconeogenesis from glutamate carbon within the mammary gland. The results are discussed in relation to data obtained in another laboratory, from which it has been claimed that non-essential amino acid supply may limit milk protein synthesis. The present results provide no confirmation for the claim.
The effect of phosphates in lowering the amount of deposit formation during the heat treatment of milk
Authors: Burdett Marion 
Published: June 2009

SummaryThe addition of small amounts of phosphate salts reduced the amount of deposit formed from heated milk, both in laboratory experiments and during the operation of a practical ultra-high-temperature heat-exchanger. Sodium pyrophosphate was much more effective than the other phosphates tested. Reasons are suggested for these observed effects.
Properties of aseptically packed ultra-high-temperature milk: III. Formation of polymerized protein during storage at various temperatures
Authors: Andrews A. T. 
Published: June 2009

SummaryThe formation of protein polymers in ultra-high-temperature (UHT)-treated milk during storage at various temperatures was examined by gel filtration. The extent of polymer formation was found to depend on both storage time and temperature. After some months of storage at the higher temperatures of 30 and 37°C, the extent of polymerization of the caseins and whey proteins due to reactions of the Maillard type was several times greater than the heat-induced changes resulting from the UHT processing itself. After storage for 6 months the following proportions of milk proteins were found to exist in the form of covalently bound polymers: 50% at 37°C, 40% at 30°C, 26% at 20°C and 21% at 4°C. In addition, further amounts of polymer were formed by disulphide bonding, the contribution of such polymers diminishing gradually in a temperature-dependent manner during storage due to continuing polymerization reactions. It appeared that αs1-casein may be preferentially involved in these polymerizations with β-casein reacting at a somewhat slower rate. Polymerization and associated reactions modifying molecular charge led to the expected alterations in electrophoretic mobility and a loss of definition in the bands due to the various protein components. Measurements of proteolytic breakdown indicated only very small increases in trichloroacetic acidsoluble fragments, suggesting that proteolysis was of minor significance.
Accelerated cheese ripening: a method for increasing the number of lactic starter bacteria in cheese without detrimental effect to the cheese-making process, and its effect on the cheese ripening
Authors: Pettersson H.-E. , Sjöström G. 
Published: June 2009

SummaryA method is outlined for accelerating ripening in Swedish semihard cheese by increasing the number of lactic starter bacteria present in the cheese without impairing characteristic texture and flavour. In addition to the normal starter inoculum, suitable lactic starter bacteria whose lactic-acid-producing activity had been greatly reduced by previous sublethal heat treatment, were added to the cheesemilk. When suspensions of streptococci and lactobacilli cultivated at a constant pH were heated at 59 and 69°C respectively acid production was retarded by 5–10 h, which was found to be sufficient for the cheese-making. Proteolysis was lowered only 10–30% by these heating temperatures. Bacterial cell suspensions, prepared by the methods outlined and added to the cheesemilk, were incorporated in cheese curd to extents depending on the amount added and the type of starter. The number in the final cheese could be increased to a maximum of 4–5 times that of control cheese. No adverse effect of the extra starter bacteria on pH, fat content and water content of cheeses 24-h old was observed. Proteolysis, measured as the increase in trichloroacetic acid and phosphotungstic acid (PTA)-soluble N, increased with increasing number of cells in the cheese. Organoleptic judgements showed a positive correlation (r= 0·81) between taste and PTA-soluble N, which in turn was influenced by the number of cells in the final cheeses.
Observations on the microscopic crystalline inclusions in Cheddar cheese
Authors: Brooker B. E. , Hobbs D. G. , Turvey A. 
Published: June 2009

SummaryIn ripening and mature Cheddar cheese, 2 distinct types of birefringent microscopic crystalline inclusions are found. One of these is an irregularly shaped large aggregate of needle-like crystals (LAC). The histochemical demonstration of Ca in the LAC together with their total absence from cheese made with δ-gluconic acid lactone (GAL) instead of starter bacteria suggests that they are composed of Ca lactate.The other type of inclusion is a smaller aggregate of crystals (SAC). They are more numerous than the LAC and are concentrated in areas which probably correspond to the lines of curd particle fusion. The SAC appear in cheese immediately after pressing and increase in number until the cheese is about 1 month old. They can be detected in unsalted, milled curd after 1 d and are present in large numbers in cheese made with GAL. These observations together with histochemical evidence that they may contain phosphate groups suggest that the SAC are probably composed of Ca phosphate. Their location in spaces between the fat and casein phases of the cheese indicates that they crystallize from pockets of residual whey. Each SAC is composed of a large number of very long (maximum length 4·5 μm), thin (maximum diam. 25 nm) crystals each of which is covered by a thin layer of electron-dense material tentatively identified as casein.
Selection and some properties of phage-resistant starters for cheese-making
Authors: Marshall R. J. , Berridge N. J. 
Published: June 2009

SummaryClones ofStreptococcus lactisand ofStr. cremorisresistant to some bacteriophages that could virtually annihilate the parent strains were selected by plating very large numbers of the bacteria in the presence of the phage. Some of the resistant strains were shown to form acid rapidly in milk and to be satisfactory for cheese-making. They were not lysogenic. Adsorption of the phage to which the parent culture had been sensitive still occurred with 3 strains but not with 4 others. Rates of mutation from phage sensitivity to phage resistance were determined for 2 original strains ofStr. lactisand were found to be of the same order as the rates quoted in the literature for other mutations. The mutation rates of phages to forms which could attack the resistant strains were too low to be measured.
The effect of lipolytic Gram-negative psychrotrophs in stored milk on the development of rancidity in Cheddar cheese
Authors: Law B. A. , Sharpe M. Elisabeth , Chapman Helen R. 
Published: June 2009

SummaryThe highest incidence of lipolytic activity among the psychrotrophic Gram-negative flora of commercial raw milks was found in strains ofPseudomonas fluorescensandPs. fragi.The lipases of all of the lipolytic strains remained wholly or partly active after heat treatment at 63°C for 30 min. Two of the strains tested further had lipases which retained 20–25% of their activity even when heated at 100 °C for 10 min. Cheeses made from milks in which strains or a single strain of lipolytic Gram-negative rods (GNR) had been allowed to multiply to > 107colony forming units/ml became rancid after 4 months even though the GNR had been killed by pasteurization. The rancidity was characterized by a soapy off-flavour in cheeses containing free fatty acid concentrations from 3 to 10 times higher than those in control cheeses made from stored milks with low counts of GNR. Strong rancidity could be reproduced by adding the culture supernatant of a pre-grown lipolytic strain, but not the washed cells, to milk and pasteurizing it immediately before cheese-making, demonstrating the extracellular nature of the rancidity-inducing lipases.
The effect of concentration on the heat stability of skim-milk
Authors: Muir D. D. , Sweetsur A. W. M. 
Published: June 2009

SummaryA progressive change takes place in the heat stability of skim-milk during concentration. At the maximum in the coagulation time (CT)–pH profile of milk concentrated to over 20% of total solids (TS) the total N depletion curve changed from single- to 2-stage and CT became insensitive to the addition of urea. Furthermore, addition of β-lactoglobulin to skim-milk concentrates destabilized the heated milk whilst the opposite effect was observed in the presence of sulphydryl-group blocking agents. As a result of these observations, it has been suggested that the mechanism of coagulation in concentrated milk is similar to that which occurs within the minimum of the CT–pH profile of skim-milk at normal levels of TS.
Reductive methylation of lysine residues in casein
Authors: Olson N. F. , Richardson T. , Zadow J. G. 
Published: June 2009

SummaryThe effect of reductive methylation on the properties of αs-, β- and κ-caseins was studied using preparations of these proteins in which 20 or 60% of the lysyl residues had been reductively methylated. This modification appeared to affect the physicochemical properties of the protein to an insignificant extent and in particular, electrophoretic mobility, sensitivity to precipitation by Ca2+and solubility of Ca salts of individual proteins were only slightly altered. The use of caseins which had been subjected to methylation with radioactive formaldehyde is suggested as a potentially valuable method for the study of protein interactions.
Formation of methanethiol by bacteria isolated from raw milk and Cheddar cheese
Authors: Law Barry A. , Sharpe M. Elisabeth 
Published: June 2009

SummaryStrains of coryneform bacteria which produce methanethiol from L-methionine in laboratory culture have been isolated from Cheddar cheese and raw milk Many Gram-negative raw milk isolates includingPseudomonas fluorescens, Ps. putida, Ps. fragi, Ps. aureofaciens, Acinetobacter, AeromonasandSerratia marcescensalso produced methanethiol. Representative strains of coryneforms and pseudomonads produced methanethiol only from free L-methionine; glycyl-L-methionine and D-methionine were not degraded. The aerobic nature of the methanethiolproducing bacteria and the instability and alkaline pH-dependence of their thiol producing enzymes explained their failure to increase methanethiol concentrations in experimental cheese, even when large numbers (5 × 107/g milled curd) of pregrown cells were added. Other commonly occurring cheese bacteria such as starter streptococci, micrococci or lactobacilli either did not produce methanethiol or produced only traces. It is concluded that the methanethiol normally present in Cheddar cheese is unlikely to be the product of bacteria or their enzymes.
An improved method for the preparation of crystalline β-lactose and observations on the melting point
Authors: Itoh Takatoshi , Katoh Mineo , Adachi Susumu 
Published: June 2009

SummaryAn improved method for preparing β-lactose crystals was developed by heating a supersaturated solution of lactose under reflux. The product obtained by this method yielded large well-defined crystals.Differential thermal analysis was used for the characterization of β-lactose. The thermograms of β-lactose obtained when heating conditions were similar to those used in the conventional measurement of the melting point gave an endothermic peak at 229·5–230 °C. A marked difference was observed between the peak temperature on the thermogram and the melting point (m.p.) of β-lactose (252–252·2 °C) given in the literature. The method for determining the m.p. of β-lactose was reexamined in detail and previously reported values could not be confirmed. By application of the conventional method for determining m.p. of organic substances, 229·5 °C (dec.) is proposed as the m.p. of β-lactose.
Serological and fluorescence studies of the heat stability of bovine lactoferrin
Authors: Baer Augustin , Oroz Marko , Blanc Bernard 
Published: June 2009

SUMMARYThe heat denaturation of Fe-saturated lactoferrin (If) and Fe-free lactoferrin (apo-lf) was studied using the methods of micro-complement fixation and fluorescence. It was established that the change in conformation of apo-lf, induced by iron binding, conferred a higher heat stability to the molecule: the changes were observed at temperatures above 40 °C for apo-lf and above 60 °C for If. The Fe-binding ability of the protein was partially independent of the degree of denaturation. Fluorescence analyses indicated that tryptophan residues were probably not directly involved in the metal binding. There was no evidence of antibodies interfering with the binding sites.
The formation of γ-caseins during cooling of raw milk
Authors: Reimerdes Ernst H. , Herlitz Erika 
Published: June 2009

SUMMARYIt has been shown that there is a time-dependent transfer of β-casein and the milk serine proteinase system from micelles to milk serum with change of temperature from 38 to 4 °C. It has been established that the γ-caseins can be formed by proteolytic degradation of β-casein. By a simple extraction technique, the very hydrophobic γ-casein fraction was separated from stored milks (26 and 4 °C) and estimated quantitatively. The results showed that the proteolytic degradation of β-casein is faster at 4 °C than at room temperature and this can be explained by the immobilization of enzyme and substrate at the micelle surface at higher temperatures (26 °C).The results indicate that irreversible changes during cooling for short periods do not cause problems in milk processing, but the formation of γ-caseins and phosphopeptides may influence the technological properties of raw milk stored for more than 48 h.