bluuebunny/crossref_metadata_2025_split huggingface dataset:
A survey of the microflora of raw and pasteurized milk and the sources of contamination in a milk processing plant in Addis Ababa, Ethiopia
Authors: Mahari Tadesse , Gashe Berhanu A. 
Published: June 2009

SummaryThe microorganisms present in raw and pasteurized milk and the sources of contamination in the milk after it had arrived at the processing plant in Addis Ababa were studied. The lowest count registered for raw milk samples was 4 × 107cfu/ml while the highest was 1 × 109cfu/ml. Pasteurized milk had mesophilic aerobic counts of 7 × 105cfu/ml as it left the pasteurizing unit, but the population increased 2- to 4-fold as a result of subsequent contamination. Of the total counts in raw milk, psychrophilic, thermoduric and thermophilic organisms made up 98·l, 1·4 and 0·5% respectively. In pasteurized milk, the amounts were 53·0, 39·5 and 7·5% respectively. Samples of milk pasteurized in the laboratory contained only 74·5% thermoduric and 25·5% thermophilic organisms. The isolates mostly belonged to the generaBacillus, Streptococcus, Lactobacillus, Arthrobacter, Alcaligenes, AeromonasandPseudomonas. Cocci were more predominant than rod-shaped bacteria. Of the rod-shaped bacteria, 73% were Gram-negative. The utensils holding the raw and pasteurized milk and the plastic sheets used for bagging the pasteurized milk contributed unusually high numbers of bacteria which were either thermoduric or thermophilic. More isolates were obtained from the pasteurized than the raw milk. The keeping quality of the pasteurized milk was found to be much lower than that of the laboratory-pasteurized milk.
A 43Ca and 31P NMR study of the calcium and phosphate equilibria in heated milk solutions
Authors: Wahlgren N. Magnus , Dejmek Petr , Drakenberg Torbjörn 
Published: June 2009

SummaryCasein micelle suspensions, colloidal Ca phosphate-free casein solution and simulated milk ultrafiltrate (SMUF) were studied using high-resolution 43Ca and 31P NMR in the temperature range 4–64 °C. Only one 43Ca and one 31P signal was obtained for each solution. Signal intensities and line widths varied with the environment and were affected by the redistribution of Ca and P during heating and cooling. Based upon the temperature-dependent broadening of the 43Ca signal, five different Ca environments were discerned in the heated milk fractions. The Ca state, induced by heating of a casein-containing milk salt solution, differed from both the state of Ca present in micellar colloidal Ca phosphate and from the state of Ca induced by the heating of SMUF.
Characteristics of ruminant mammary epithelial cells grown in primary culture in serum-free medium
Authors: Winder Steven J. , Turvey Alan , Forsyth Isabel A. 
Published: June 2009

SummaryCells were obtained from the mammary glands of sheep and cows by collagenase–hyaluronidase digestion. Characterization of cells as epithelial was by reaction with a monoclonal antibody to cytokeratin. A subpopulation of spindle-shaped or stellate cells reacted with a monoclonal antibody to desmin and may be related to myoepithelial cells. The development is described of a simple serum-free culture system for these cells on gels of rat tail (type 1) collagen. A commercial medium (M199) was used, buffered with Hepes and with bovine serum albumin as the sole protein supplement, plus fibronectin for the first 18 h only as an attachment factor. The cell cultures showed stimulated DNA synthesis in response to mitogens on attached gels and also responded as floating cultures to lactogenic hormones with production of α-lactalbumin.
Isolation and characterization of 3-deoxypentulose and its determination in heated milk
Authors: Troyano Esperanza , Olano Agustin , Jimeno Maria Luisa , Sanz Jesus , Martínez-Castro Isabel 
Published: June 2009

SummaryThe presence of 3-deoxypentulose in heated milk is reported. This compound has been isolated from alkaline solutions of lactose and characterized by spectroscopic and Chromatographie techniques. Gas Chromatographic analysis of free monosaccharides of milk revealed two peaks corresponding to 3-deoxypentulose in commercial sterilized milk samples, in a concentration range of 30–50 mg/1. Its concentration increased with temperature and length of time of processing.
Multinuclear NMR study of the pH dependent water state in skim milk and caseinate solutions
Authors: Mariette François , Tellier Charles , Brule Gerard , Marchal Philippe 
Published: June 2009

SummaryThe effects of decreasing pH and micellar calcium concentrations of reconstituted skim milk and caseinate solution were studied by 1H and 17O NMR spectroscopy. The proton transverse relaxation rate 1/T2 of skim milk decreased as the pH decreased, reaching a minimum at pH 5·3. However, as the pH fell sodium caseinate solution showed a continuous increase in 1/T2, with no minimum. Analysis of proton relaxation as a function of the interpulse time in the CPMG (Carr-Purcell-Meiboom-Gill) sequence demonstrated that both the proton exchange mechanism and ‘bound’ water contributed to proton relaxation in skim milk. The study of 17O relaxation rate as a function of pH confirmed the change in protein hydration upon acidification. Increasing the amount of EDTA showed that the proton transverse relaxation rate of skim milk decreased until a plateau was reached when the micellar calcium was totally solubilized. With excess EDTA the relaxation rates of skim milk and caseinate solution were identical. A strong correlation was also found between the pH dependent relaxation rate and the solubilization of micellar phosphorus as detected by 31P NMR. Together, these results suggested that aggregation of caseins by calcium and colloidal calcium phosphate is mainly responsible for the excess hydration in skim milk micelles.
Process integration study of a milk powder plant
Authors: Robertson Lindsay J. , Baldwin Alan J. 
Published: June 2009

SummaryA study was undertaken of the heat exchange possible in a milk powder plant consisting of milk treatment, a four-effect evaporator fitted with a thermovapour recompressor and a spray drier fitted with a fluidized bed secondary drier. The study utilized the techniques of process integration analysis and grand composite curve matching. Of particular interest was the optimum utilization of vapours within the evaporator. It was shown that with a minor redesign of the evaporator, and utilization of some vapour in the milk treatment section of the plant, a 6% reduction in total energy consumption of the milk powder plant was possible. If heat exchange between inlet and outlet air of the spray drier was not considered practical, preheating spray drier air with vapour from the evaporator resulted in a 10% reduction in energy consumption. Other minor heat exchange possibilities were also revealed. It was concluded that the use of vapour from the evaporator, and increased steam consumption in the evaporator, may lead in some designs to decreased plant thermal energy consumption overall. As well as the process integration study, formulae are presented for calculating the change in thermal economy of an evaporator when vapour is extracted for use in other sections of the plant. The use of process integration studies needs to be given consideration in overall design of energy-intensive dairy plant.
Yield and composition of milk from lactating mares: effect of body condition at foaling
Authors: Doreau Michel , Boulot Sylviane , Chilliard Yves 
Published: June 2009

SummaryThe yield and composition of milk from nursing mares were studied during the first 2 months of lactation in two groups of six and five saddle mares respectively made thin or fat before foaling, then fed ad lib. post partum. Milk yield did not significantly vary with body condition (16·5 and 15·4 kg/d for fat and thin mares respectively). Milk from fat mares had a higher fat content than milk from thin mares; the reverse was found for protein. The composition of milk fat was modified: milk of fat mares was poorer in short- and medium-chain fatty acids (C8-C14). Milk fat output was affected by body condition: 252 and 187 g/d for fat and thin mares respectively. This can be explained by a difference in lipid mobilization, as shown by variations in non-esterified fatty acids.
Measurement of teatcup liner wall movement
Authors: Butler M. Clare , Adley Nicholas J. D. 
Published: June 2009

SummaryA technique for monitoring the movement of the teatcup liner during milking, using video recordings, has been investigated. The liner was videoed through a transparent shell and the recordings were subsequently processed frame by frame by an image analyser. The width of the liner and its variation with pressure difference across the liner walls were calculated at several locations along the liner length, and analysis of these results allowed the pressures at which the liner buckled and the walls touched to be determined and some estimate of the degree and duration of liner collapse to be made.
Characteristics ofα–aminoisobutyric acid transport by lactating rat mammary gland
Authors: Shennan D. B. , McNeillie S. A. 
Published: June 2009

SummaryThe transport of α-aminoisobutyric acid (AIB) by lactating rat mammary tissue has been examined. AIB uptake by mammary tissue was via both Na+-dependent and Na+-independent pathways. AIB uptake via the Na+-dependent pathway was inhibited by (methylamino)isobutyric acid (MeAIB) whereas AIB uptake via the Na+-independent pathway was blocked by 2-aminobicyclo[2, 2, 1]-heptane-2-carboxylic acid (BCH). A small fraction of AIB influx persisted in the presence of both MeAIB and BCH. The Na+-independent moiety of AIB uptake was strongly inhibited by phenylalanine, tryptophan, leucine, isoleucine and methionine. AIB efflux from mammary tissue slices was found to be both Na+-dependent and Na+-independent. Trans-stimulation of AIB efflux by other amino acids was not observed; in contrast, external phenylalanine, tryptophan and leucine inhibited AIB efflux. The results are largely consistent with the presence of systems A and L in lactating rat mammary tissue. However, the Na+-independent fraction of AIB transport may represent transport via a tissue specific form of system L.
Retinol determination in milk by HPLC and fluorescence detection
Authors: Jensen Søren Krogh 
Published: June 2009

SummaryA simple and rapid method for determination of retinol in whole milk is described. Milk (400 mg) was diluted with a water–methanol–ethanol mixture (55:9:36 by vol.) and saponified with potassium hydroxide in a culture tube. Retinol was extracted into 10ml heptane-di-isopropyl ether (3:1) of which 100 μl was injected into the HPLC. Fluorescence detection ensured the specificity and sensitivity. The critical points in the analysis were the extraction of retinol from fatty samples and the instability of retinol towards photo-oxidation and air oxidation in alkaline solvents. There was an average recovery of 98·5 ± 2·4% and a CV of 3·6%.
Thermal inactivation of γ-glutamyltranspeptidase and Enterococcus faecium in milk-based systems
Authors: Patel Shailam S. , Wilbey R. Andrew 
Published: June 2009

SummaryUntreated whole milk, skim milk, sweetened milks, sweetened and unsweetened creams and ice-cream mixes were preincubated with a culture of Enterococcus faecium, then subjected to heat treatment in a pilot-scale plate heat exchanger using a hold of 15 s at 76°C. The liquids were examined for γ-glutamyltranspeptidase (GGTP) activity and total streptococcal count before and after heat treatment and the results plotted against water activity (aw). There was a good correlation between reduction in GGTP activity, destruction of streptococci and aw, demonstrating the potential of the enzymic assay for assessing the severity of HTST heat treatments above the minimum for pasteurization.
Consequences of diagnostic errors in mastitis therapy trials
Authors: Morant Steven V. , Dodd Frank H. , Natzke Roger P. 
Published: June 2009

SummaryThe effect of errors that occur in the diagnosis of intramammary infectious mastitis on the precision of experiments measuring the efficacy of mastitis therapy has been investigated. Diagnostic errors within the range found by experienced workers can create large biases in the apparent cure rate of therapy particularly at cure rates of less than 0·5. Using confirmed methods of diagnosis rather than single samples and reducing the probabilities of false positive and false negative diagnoses to 0·01 and 0·05 respectively, the biases in the apparent cure rates are reduced to acceptable levels. A method is given for calculating the rates of occurrence of false positive and false negative diagnoses from the results of trials using confirmed diagnoses. These errors cannot be calculated from therapy trial data when diagnosis is based on single milk samples.Because the bias in the measurements of the cure rate is greatest at the lowest levels of elimination, estimates of spontaneous recovery in untreated quarters have the greatest error. For this reason experiments incorporating an untreated control group of infected quarters usually reduce the precision of the therapy trials. An experiment in which the efficacy of a test product is measured relative to a reference product has advantages. It minimizes the difficulties arising from scale of measurement, diagnostic errors and herd differences in response rate, and makes possible comparisons between trials. Further investigations are required on the importance of spontaneous recovery, particularly for studies of Escherichia coli therapy and dry period therapy. The results of this investigation have relevance to all types of mastitis investigation that measure the change in mastitis status of udder quarters, i.e. new infection rates.
Study of the fouling of a mineral microfiltration membrane using scanning electron microscopy and physicochemical analyses in the processing of milk
Authors: Vetier Claudine , Bennasar Michel , de la Fuente Blas Tarodo 
Published: June 2009

SummarySoluble proteins and Ca and P salts in the fouling deposit on a mineral microfiltration membrane obtained in static conditions were analysed and compared with those found using dynamic filter conditions in a laboratory pilot installation for milk processing. The serum milk proteins were retained by the porous micellar deposit under both static and dynamic conditions, resulting in progressive fouling of the dynamic micellar membrane, enabling milk to be processed with a mineral microfiltration membrane. Ca and P salts increased fouling probably by allowing better adsorption of casein micelles on the alumina and by acting as intermicellar bonds in the deposit. Fat globules modified porosity, permeability and resistance to matter transfer of the deposit. The dynamic conditions gave a deposit of the same type and structure as with the static conditions although made thinner by the velocity effect.
Surface and emulsifying properties of caseins
Authors: Dickinson Eric 
Published: June 2009

SummaryThe properties of adsorbed films of αs1-, β- and κ-casein and sodium caseinate are compared at the planar oil–water interface, at the surface of emulsion droplets, and at the surface of polystyrene latex particles. Attention is directed towards understanding (i) the relationship between the molecular characteristics of the caseins and their surface activities and surface viscosities at the oil–water interface, (ii) the nature of competitive adsorption between the caseins (particularly αs1- and β-), and (iii) the effect of Na and Ca ion concentrations on electrophoretic mobilities and flocculation behaviour.
Surface properties of the bovine casein components: relationships between structure and foaming properties
Authors: Lorient Denis , Closs Brigitte , Courthaudon Jean Luc 
Published: June 2009

SummaryIn order to optimize the use of caseins as surfactants, the surface tension, foaming capacity and stability were measured as a function of pH, ionic strength, protein concentration and polarity (modified by covalent binding of carbohydrates). We found that the caseins differ in their behaviour at the air/water interface with β-casein showing the greatest ability to decrease surface tension and to produce foams, due probably to its amphipathic structure. In experiments carried out at pH values close to pI, with low ionic strength and constant solubility (optimal conditions for foam formation), we observed a high surface hydrophobicity, a good accessibility and flexibility of peptidic side chains (evaluated by proteolysis), and a high foaming capacity parallelled by increased surface pressure. Foam stability of caseins was low compared to those of globular proteins such as β lactoglobulin.
Application of fractal concepts to the study of caseinate aggregation phenomena
Authors: Horne David S. 
Published: June 2009

SummaryThe concepts of fractals and fractal dimension are introduced and applied to the description of the disordered structures of colloidal aggregates. It is demonstrated that the structure of the aggregates produced by ethanol de-stabilization of casein micelles can be quantitatively characterized by a fractal dimension. The values measured are compared to literature predictions from various computer studies simulating different models of the aggregation process.
Lipase redistribution in cows' milk during induced lipolysis: I. Activation by agitation, temperature change, blood serum and heparin
Authors: Cartier Philippe , Chilliard Yves 
Published: June 2009

SummaryEffects of agitation, temperature change, blood serum and heparin on lipolysis and on distribution of lipoprotein lipase (LPL) in cold-stored cows' milk were measured. All individual milks (n = 135) were susceptible to activation treatments. With ‘gentle’ treatments, induced lipolysis was strongly correlated to spontaneous lipolysis (r ≥ 0·74). In contrast, induced lipolysis in response to ‘vigorous’ treatments was more variable (0·7 > r > 0·34) and levelled off in milks with high spontaneous lipolysis. Induced lipolysis always resulted from an increase in LPL associated with cream. Strong correlations (0·79 ≤ r ≤ 0middot;94) were found between free fatty acid levels and cream LPL. All treatments (except heparin addition) also promoted lipolysis/unit cream LPL.
Theoretical analysis of ultraviolet spectroscopic studies on the feathering of cream in coffee
Authors: Pink David A. , Hamboyan Lucie , Aboud Helen 
Published: June 2009

SummaryUltraviolet spectra of solutions of instant and filter coffees have been analysed as a linear combination of component Gaussian bands. We show that the ratio, R′, of two of these bands, one at 329 nm due almost entirely to chlorogenic acid, and the other at 272 nm due to a coffee component not appearing in the chlorogenic acid spectrum, is analogous to the ratio R (Hamboyan et al. 1989). The use of R which is easier to measure than R′ has therefore been justified on physical grounds, based on the existence of component spectral bands. Filter coffees appeared to exhibit behaviour similar to that of instant coffees.
Extraction of plasma triacylglycerols by the mammary gland of the lactating cow
Authors: Thompson Gordon E. , Christie William W. 
Published: June 2009

SummaryThe fatty acid content of triacylglycerols (TG) in arterial and mammary venous blood plasma has been analysed in five cows that were close to peak lactation. The fatty acids in arterial TG were extracted by the mammary gland in amounts 14:0 < 16:0 < 18:0and 18:0 > 18:1n – 9 > 18:2. The difference of extraction between palmitate and stearate was similar in different TG species. The fatty acid 18:1n – 7, which was largely the trans isomer, was extracted more than 18:1n – 9. Significant amounts of phytanic acid were acylated in plasma TG, but not extracted by the mammary gland.
Extent of damage to amino acid availability of whey protein heated with sugar
Authors: Desrosiers Thérèse , Savoie Laurent 
Published: June 2009

SummaryThe effect of heat treatments, at various water activities (αw), on digestibility and on the availabilities of amino acids of whey protein samples in the presence of lactose was estimated by an in vitro digestion method with continuons dialysis. Four αw (0·3, 0·5, 0·7 and 0·97), three temperatures (75, 100 and 121 °C) and three heating periods (50, 500 and 5000 s) were selected. The initial lysine: lactose molar ratio was 1:1. Amino acid profiles showed that excessive heating of whey (121 °C, 5000 s) destroyed a significant proportion of cystine at all αw, lysine at αw 0·3, 0·5 and 0·7, and arginine at αw 0·5 and 0·7. At αw 0·3, 0·5 and 0·7, protein digestibility decreased (P < 0·05) as the temperature increased from 75 to 121 °C for a heating period of 5000 s, and as the heating time was prolonged from 500 to 5000 s at 121 °C. Excessive heating also decreased (P < 0·05) the availabilities of ail amino acids at αw 0·3, 0·5 and 0·7. The availabilities of lysine, proline, aspartic acid, glutamic acid, threonine, alanine, glycine and serine were particularly affected. Severe heating at αw 0·97 did not seem to favour the Maillard reaction, but the availabilities of cystine, tyrosine and arginine were decreased, probably as a result of structural modifications of the protein upon heating. Heating whey protein concentrates in the presence of lactose not only affected lysine, but also impaired enzymic liberation of other amino acids, according to the severity of heat treatments and αw.
Contribution of plasmin to Cheddar cheese ripening: effect of added plasmin
Authors: Farkye Nana , Fox Patrick F. 
Published: June 2009

SummaryPlasmin (EC 3.4.21.7) was added to cheese milk to assess its contribution to Cheddar cheese ripening; the activity of plasmin in the cheese was increased by levels ranging from 1·5 to 6 times that in the control cheeses. Even at the highest level of added plasmin, no activity was found in the whey. β-Casein was degraded faster in the experimental cheeses than in the controls, and the concentration of γ-caseins increased concomitantly. The total N in the water-soluble extract was up to ˜ 20% higher in the experimental than in the control cheeses but phosphotungstic acid-soluble N was not affected by the plasmin activity in the cheese. Several differences were apparent in the gel electropherograms of the water-soluble extracts of the experimental and control cheeses; some peptides were present at higher concentrations in the former, others in the latter, suggesting that plasmin contributes to both the formation and degradation of water-soluble peptides in cheese. The organoleptic quality of the plasmin-enriched cheeses was judged superior to that of the controls and ripening was considerably accelerated; a plasmin level 3–4 times the indigenous value appeared to be optimal. No bitterness was detected in any of the cheeses.
New αs2-casein variant from caprine milk
Authors: Chianese Lina , Mauriello Rosalba , Intorcia Nunziatina , Moio Luigi , Addeo Francesco 
Published: June 2009

SummaryA new αs2-casein variant was isolated from goat milk by means of covalent chromatography. With gel electrophoresis at alkaline pH, the αs2-casein variant showed a double band with the highest anodic mobility amongst the casein components. The mobility of the isolated αs2-casein variant was similar to that occurring in three individual samples of whole casein. Two dimensional electrophoresis revealed a more pronounced heterogeneity of this protein. Developing the two dimensional plate with polyclonal antibodies obtained against the four main bovine casein fractions, we demonstrated that the variant in question belongs to the αs2-casein family. Since the αs2-casein fractions, immunospecifically developed, spread along two different zones on the gel, it was concluded that a heterozygous αs2-casein form was present in the sample.