bluuebunny/crossref_metadata_2025 huggingface dataset:
A study of surface hydrophobicity of milk proteins during enzymic coagulation and curd hardening
Authors: Peri Claudio , Pagliarini Ella , Iametti Stefania , Bonomi Franco
Published: June 2009

The formation of hydrophobic sites on the surface of casein micelles as a consequence of rennet action has been followed through the binding rate of a fluorescent probe and its distribution between a free and an ‘aggregated’ protein fraction. The variation of this parameter has been related to clotting time and curd hardening kinetics.

Results show that a first aggregation of casein through hydrophobic sites interaction began as soon as rennet was added to milk. At the natural pH of milk, the sol-gel transition occurred when all the casein micelles were already involved in large aggregates. This was not the case with slightly acidified milk (pH 6·5 and 6·3) where clotting occurred well before the first aggregation step had been completed. The surface hydrophobicity of casein continued to increase in the curd due to continuing enzymic action and structural rearrangements. When this process has been completed the hardening of curd proceeds at an accelerated pace until it reached its maximum asymptotic value.
Titration – a rapid method for the determination of proteolysis in cheese
Authors: Ollikainen Pia
Published: June 2009

Titration is an old method used for the determination of acidic and basic groups of a molecule. Several metabolic end-products in cheese are compounds with acidic or basic groups, e.g. propionic, acetic and lactic acids, amino acids, amines and ammonia. A number of colorimetric and fluorometric methods have been used to study proteolysis in cheese; some are time-consuming with several steps, and certain of the reagents are hazardous.

We have used acid-base titration for analysis of the products of proteolysis in Swiss-type cheese. The titration system was that originally developed for use in silage analysis (Moisio & Heikonen, 1989) and applied to cheese it has proved to be useful, easy and rapid with an accuracy similar to that achieved by colorimetry.
Influence of static and dynamic teat characteristics and milking time on udder health in Norwegian Red Cattle
Authors: Rønningen Odd , Reitan Arne Dagfinn
Published: June 2009

A field survey with 70 cows in 15 herds was carried out to find a possible correlation between the depth of teat penetration into the teatcup liner during milking, and udder health. The investigation showed that the depth of penetration into the liner of fore teats was positively correlated with the fore teat end hardness (P < 0·01), and with the frequency of clinical mastitis for the whole udder (P < 0·1). The investigation also showed that the teat end height above the floor was negatively correlated with mean cell count for the previous year (P < 0·001), and with the prevalence of subclinical mastitis in rear quarters (P < 0·05).
Changes in the physical properties of ultra high temperature processed buffalo milk during storage
Authors: Sharma Dinesh K. , Prasad Deoki N.
Published: June 2009

Buffalo milk collected within 4 h of milking was standardized (4·5% fat and 8·5% SNF) and processed in an ultra high temperature plant at 5 °C intervals. Changes in viscosity, free tyrosine and sedimentation were measured over 6 months at 15 and 30 °C. We suggest that an interaction probably occurred in the casein and whey proteins (β-lactoglobulin) and caused changes in the physical and chemical qualities of these milks during storage. Variations in the casein particle sizes were observed in the milks during storage by electron microscopy.
A method for assessing loss in milk yield due to subclinical mastitis
Authors: Oshima Masaharu , Yoshida Tatsuyuki , Koyama Kohei , Moriyama Taminori
Published: June 2009

A method for assessing the loss in quarter milk yield due to subclinical mastitis is proposed. It is based upon two indices calculated from quarter milk yields and results from the assessment of mastitis obtained by measurement of the electrical conductivity of milk. The results were obtained from the cows through repeated quarter-milkings during several months of lactation. The grade of abnormality of a quarter with subclinical mastitis was expressed by the first index, the mean quarter difference of electrical conductivity of milk produced by the quarter (mQdEC, 25 °C). The reduction in milk yield of a quarter presumed to be due to subclinical mastitis was expressed by another index, the quarter yield ratio, R, which is that percentage of normal milk yield produced by a quarter with mastitis. Examination of the relationship between these two indices showed that subclinical mastitis caused a reduction in milk yield in the affected quarters. From the linear regression, it was found that ~3% reduction in quarter milk yield occurred for every 1 x 10–4 S/cm increase in the mQdEC of the quarter with presumed subclinical mastitis.
Relationship between amplitude and phase measurements of photoacoustic signal in the infrared region and water concentration in condensed milk
Authors: Martel Richard , Paquin Paul , Bertrand Lionel
Published: June 2009

Photoacoustic signals in the near infrared region (~ 2·75 μm) have been investigated using amplitude and phase information to determine their effectiveness in estimating the water content of milk. The results obtained showed a good correlation between the photoacoustic signal and water concentration (R2 = 0·98) even though photoacoustic saturation was present in the range of wavelengths studied. However, this is not recommended as a fast technique for water determination because of inherent phase fluctuations in the samples analysed.
Effect of mastitis on plasminogen activator activity of milk somatic cells
Authors: Zachos Teffi , Politis Ioannis , Gorewit Ronald C. , Barbano David M.
Published: June 2009

This study was conducted to examine the effects of mastitis and stage of lactation on plasminogen activator (PA) activity in milk somatic cells. An assay System, which measures the plasmin-mediated hydrolysis of the chromogenic substrate D-valyl-leucyl-lysinep−nitroanilide, was used to assess PA activity present within milk somatic cells. Milk cell associated PA activity was increased (P< 0·05) by 50% in the presence of fibrin fragments. This suggests that milk somatic cells contain tissue PA which, unlike urokinase PA, is preferentially activated in the presence of fibrin fragments. An increase of the milk somatic cell count from < 5 × 104 to > 106cells/ml resulted in an 8-fold increase in PA activity per cell. Elevated levels of PA activity were associated with milk somatic cells isolated from mastitic quarters obtained from cows in early (<4 months in lactation) or late lactation (>8 months in lactation). We conclude that PA activity is increased during severe mastitic inflammation. Although the physiological function of this enzyme is as yet unclear, we propose that it may be involved in the conversion of plasminogen to plasmin, contributing to the higher levels of plasmin occurring in milk isolated from mastitic quarters.
Comparison of the ability to bind lipids ofβ-lactoglobulin and serum albumin of milk from ruminant and non-ruminant species
Authors: Pérez M. Dolores , Puyol Pilar , Ena José Manuel , Calvo Miguel
Published: June 2009

The interaction of sheep, horse, pig, human and guinea-pig whey proteins with fatty acids has been studied. Using gel filtration and autoradiography, it was found that sheepβ-lactoglobulin and serum albumin from all species had the ability to bind fatty acidsin vitro. Sheepβ-lactoglobulin, isolated from milk, had ˜ 0·5 mol fatty acids bound per mol monomer protein, and albumin from sheep, horse and pig contained ˜ 4·5, 2·9 and 4·7 mol fatty acids/mol protein respectively. However,β-lactoglobulin from horse and pig milk had neither fatty acids physiologically bound nor the ability to bind themin vitro. Albumin was the only whey protein detected with bound fatty acids in these species as well as in human and guinea pig. This suggests that the ability of ruminantβ-lactoglobulin to bind fatty acids was not shared by the same protein of non-ruminants.
Fractionation of whey protein components through a large pore size, hydrophilic, cellulosic membrane
Authors: Mehra Raj K. , Donnelly William J.
Published: June 2009

Whey protein solutions of different chemical compositions were filtered through a large pore size ultrafiltration membrane (molecular mass cut-off 100 kDa). The influences of pH, ionic environment and Ca chelation on the performance characteristics of the membrane (filtration rate, total and individual whey protein permeability) were examined. Increase in pH in the range 5·0-10·0 resulted in a gradual increase in filtration rate and individual whey protein permeability. The presence of Ca in the whey protein solution had a negative effect on the performance characteristics of the membrane. Addition of EDTA to protein solution improved the filtration rate but had no effect on the protein permeation. Fractionation of the low molecular mass whey proteins (β-lactoglobulin and α-lactalbumin) from high molecular mass proteins (bovine serum albumin, lactoferrin and immunoglobulins) was best achieved at pH 8·0.
Purification and identification of TGF-β2-related growth factor from bovine colostrum
Authors: Tokuyama Yukiko , Tokuyama Haruhiko
Published: June 2009

Bovine colostrum contains transforming growth factor (TGF)-β-like activity. High levels of this activity are found in early colostrum (within 12 h after parturition); however, it decreases rapidly after 30 h. In this study, the activity in early colostrum was purified by a sequence of decaseination, DEAE-Sephacel chromatography, Sephadex G-100 gel filtration, precipitation at neutral pH, further gel filtration and reversed-phase FPLC. A homodimeric 23 kDa protein was identified that retained the TGF-β-like activity. Its activity was completely neutralized by a specific anti-TGF-β2 antibody. These results indicate that the TGF-β-like growth factor found in bovine colostrum is chemically and antigenically related to TGF-β2. The physiological roles of the TGF-β2-related growth factor are discussed.
Oscillatory rheological study of the gelation mechanism of whey protein concentrate solutions: effects of physicochemical variables on gel formation
Authors: Tang Qingnong , McCarthy Owen J. , Munro Peter A.
Published: June 2009

The thermal gelation of a commercially available whey protein concentrate was studied by oscillatory rheometry using a Bohlin rheometer. Gelation time increased with decreasing protein concentration with a critical protein concentration (at infinite gelation time) of 6·6%. The effect of temperature in the range 65–90 °C on gelation time was described by an Arrhenius equation with an activation energy of 154 kJ/mol. Gelation time was a minimum at pH 4–6, the isoelectric region of the whey proteins. Small additions of NaCl or CaCl2 dramatically decreased gelation time. Higher protein concentrations always produced higher storage modulus (G′) values after any heating time. Loss modulus (G″) v. time curves exhibited maxima at relatively short times for protein concentrations of 30 and 35%. G′ values for 10% protein concentration increased with temperature for heating times up to 59·5 min. G′ values at 59·5 min for 25% protein concentration were higher at 78 °C than at either 85 or 90 °C. The results are discussed in terms of current theories for biopolymer gelation.
Flow behaviour of low solids fresh cheeses
Authors: Korolczuk Jozef
Published: June 2009

A computerized, coaxial cylinder viscometer, controlled by a function synthesizer, was used to study the stress characteristics of acid fresh cheeses containing 7·5–8·5% protein and 0–20% fat in total solids, as a function of shearing time (0–3600 s) and of shear rate (0–4·5 s–1). For a given shear rate the stress diminished with time, following an exponential equation. The hypothetical final stress level (Sf for the shearing time t = ∞) represented about half its initial value (Si). For four cheese samples, the time required for the stress to become equal to Sf + (Sf – Sf)/e was 340–560 s. The stress-shear rate relation indicated shear thinning behaviour. The effect of shearing time showed that the material was thixotropic. The cheeses exhibited plastic flow. The initial and final stress levels were hyperbolic functions of the shear rate. Bingham final yield stress (for t = ∞) was 14–50 Pa. It was 15–25% higher for increasing than for decreasing shear rate. Bingham viscosity (for t = ∞) was between 2 and 6 Pa s. It was 10–20% higher for decreasing shear rate. The initial level of Bingham viscosity was ˜ 30% higher than its final value.
Methods for the determination of aroma compounds in dairy products: a comparative study
Authors: Xanthopoulos Vassilis , Picque Daniel , Bassit Naïma , Boquien Clair-Yves , Corrieu Georges
Published: June 2009

Several methods used for sample preparation and for the determination of volatile flavour compounds in dairy products were tested. Steam distillation was an advantageous method for isolating volatile substances. The extraction yields for acetaldehyde, ethanol and diacetyl were >90%, and acetoin was partly separated from diacetyl. After steam distillation of the sample, gas-liquid chromatography was found to be a rapid method for the determination of acetaldehyde, ethanol and diacetyl in a wide range of concentrations corresponding to those found in dairy products. However, the lower limits for reproducible measurements were high (250, 1250 and 65 μM respectively). From the same sample, colorimetry was shown to be an accurate method for the detection of low levels of diacetyl and acetoin (12 and 57 μM respectively). Diacetyl interfered in the colorimetrie determination of acetoin. However, the interference was < 10% when the diacetyl: acetoin molar ratio was < 0·033. Dynamic head-space gas chromatography proved to be a sensitive method for acetaldehyde and diacetyl determination when a ‘purge and trap’ injector and a capillary column were used. The ranges suitable for determination lay between 25 and 100 μM for acetaldehyde and between 2·9 and 11·4 μM for diacetyl. Acetoin was analysed by HPLC on a cation-exchange column and detected by refractometry for concentrations ranging from 250 to 4000 μM.
Inhibitory effect of dairy products on the mutagenicities of chemicals and dietary mutagens
Authors: Cassand Pierrette , Abdelali Hasnaa , Bouley Christine , Denariaz Gerard , Narbonne Jean F.
Published: June 2009

The antimutagenic effects of uninoculated milk and milks cultured withBifidobacteriumorLactobacillusstrains towards the mutagenicity induced by two direct mutagens, 4-nitroquinolineN-oxide and 2-nitrofluorene, and three dietary indirect mutagens, aflatoxin B1, benzo(a)pyrene and quercetin, were investigated using thein vitro Salmonella typhimuriumtest. Each cultured milk sample and control milk had a significant antimutagenic effect, to an extent varying with the mutagen used. Uninoculated milk had a greater inhibitory effect than cultured milks towards dietary indirect mutagens.
Effect of yogurt feeding on the small and large intestine associated lymphoid cells in mice
Authors: Perdigón Gabriela , Rachid Mirta , De Budeguer Marta V. , Valdez Juan C.
Published: June 2009

The effect of giving yogurt supplements to Balb/c mice on the various gut-associated lymphoid cells was studied. Animals were fed for 2, 5, 7 and 10 consecutive days. The different lymphoid cell types were identified and counted by haematoxylin–eosin staining of histological slices. The numbers of cells secreting IgA, IgG and IgM and the numbers of T lymphocytes were determined by direct immunofluorescence. The degree of activation of the intestinal macrophages in the small intestine was assessed by measuring the β-glucuronidase (EC 3.2.1.31) released into the intestinal fluid, and also by a histochemical method. Throughout the feeding period, there were no histological alterations in the gut, but there was marked cell infiltration, mainly of plasma cells and lymphocytes. The number of macrophages on the small intestine increased significantly after feeding for 2 d, while the β-glucuronidase activity was only slightly higher that of the controls. After a 7 d feeding period, the number of IgA secreting cells increased, while the values for cells secreting IgM and IgG and for T lymphocytes remained similar to those of the controls. The effect of giving yogurt on lymphoid cells associated with the large intestine was mainly on the numbers of IgA secreting B cells and T lymphocytes, with a marked increase during the whole feeding period in the latter type of cell. Since giving yogurt mainly enhanced the IgA secreting B cells in both small and large intestines, this increase would strengthen the host's defence mechanisms in the intestinal mucosa. Although the number of macrophages was increased, there was no enhancement in their activity, which might have harmed the host by producing an inflammatory response.
Effect of polyphosphate binding on the chain dynamic of caseins: investigation by differential scanning calorimetry and thermally stimulated currents
Authors: Lamure Alain , Pommert Jean-François , Klaebe Alain , Lacabanne Colette , Perie Jean-Jacques
Published: June 2009

Samples of caseins having different Ca contents as used in cheese processing were analysed by techniques using differential scanning calorimetry and thermally stimulated currents (TSC) before and after treatment with Na poly-phosphate, a food additive used in the manufacture of processed cheese. These techniques revealed structural changes induced by the salt, and the different types of water molecules associated with the protein are evident. This characterization is in agreement with results obtained by other techniques, particularly X-ray diffraction of proteins. Transmission electron microscopy of the same samples confirmed that the changes observed by TSC were associated with an unravelling of the protein.
Isolation and partial purification of astringent compounds from ultra-high temperature sterilized milk
Authors: Harwalkar Venktesh R. , Boutin-Muma B. , Cholette H. , McKellar R. C. , Emmons D. B. , Klassen G.
Published: June 2009

Astringent off-flavours were observed in commercial samples of UHT-milk heated by direct-steam injection. The off-flavour components from these milk samples were isolated by the chloroform-methanol extraction procedure of Harwalkar & Elliott. The astringent-tasting components in these extracts were partly purified by isoelectric precipitation at pH 7·0 and by size exclusion chromatography on Sephadex G-50 columns. The extracted off-flavour components and the partly purified samples were further analysed by FPLC using a Mono-Q anion exchange column and PAGE. The FPLC and PAGE patterns of the extracts from astringent and non-astringent samples of milk showed marked differences and the astringent flavour correlated with one of the fractions resolved by FPLC. This fraction was found to be heterogeneous by PAGE. The astringent off-flavours in UHT-sterilized milk were γ-casein-like breakdown products of casein.
The level of bitterness and solubility of hydrolysates produced by controlled proteolysis of caseins
Authors: Vegarud G. E. , Langsrud T.
Published: June 2009

A series of hydrolysates from commercial sodium caseinate and rennet casein were prepared using different commercial proteolytic enzymes. Increasing degree of hydrolysis, DH, resulted in markedly changed solubility of the products. The level of bitterness varied with the enzyme used. Non-bitter hydrolysates of sodium caseinate were obtained with a DH of 10–12 and protein solubilities of 99%. The rennet casein hydrolysates exhibited low levels of bitterness and high solubility (90%), even at high DH values (DH = 55).
Phosphorylation of casein components by Tyrosine-specific protein kinases
Authors: Yoshikawa Masaaki , Shimada Masamitsu , Miyamura Tsuyoshi , Takeya Tatsuo , Chiba Hideo
Published: June 2009

The phosphorylation of different caseins by a number of tyrosine-specific kinases has been studied. The different kinases showed a range of specificities, suggesting differences in recognition mechanisms. The site of phosphorylation of αs2-casein by one phosphorylase has been identified, and compared with analogous sites in other proteins.
A 1H-NMR study of bovine casein micelles; influence of pH, temperature and calcium ions on micellar structure
Authors: Rollema Harry S. , Brinkhuis Jan A.
Published: June 2009

The influence of pH, temperature and Ca depletion on bovine casein micelle suspensions in D2O containing simulated milk ultrafiltrate was studied by 1H-NMR spectroscopy.

In the pH range of 5·8–7·5 the spectrum of the micelles showed very little pH dependence, indicating that no changes occurred in the dynamic behaviour of the proteins constituting the micelle.

The NMR spectrum of casein micelles was strongly temperature dependent, particularly in the temperature range of 60–98 °C. Increase in temperature resulted in a strong increase in spectral intensity concomitant with changes in the spectral characteristics. In micelle suspensions these changes were reversible, and indicated that at clevated temperatures the rigid structure of the casein micelle started to melt, leading to an increased mobility of appreciable parts of the proteins in the micelle.

Ca depletion of the casein micelles by addition of EDTA resulted in an increase in spectral intensity, which arose from the presence of casein components in the serum phase, The spectrum of these serum phase particlcs resembled closely the spectrum of a solution of total casein in simulated milk ultrafiltrate and was quite different from the spectrum of casein micelles.

The implications of these results with respect to models of the structure of bovine casein micelles are discussed.
Dissociation and reassociation of enzyme-treated caseins under high pressure
Authors: Ohmiya Kunio , Kajino Tsutomu , Shimizu Shoichi , Gekko Kunihiko
Published: June 2009

The effects of pressure on the association states of enzyme-treated casein molecules were studied by monitoring the turbidity of the solutions under pressures up to 3000 kg/cm2. β-Casein polymers, partly degraded with immobilized trypsin, dissociated with increasing pressure up to a critical pressure (e.g. 1200 kg/cm2) and then reassociated under the higher pressure up to 3000 kg/cm2, following a parabolic turbidity-pressure curve. In the case of chymosin-treated κ-casein, a similar pressure dependence of turbidity was found under the same pressure conditions. Based on these results, the pressure effects on dissociation and reassociation of casein molecules were discussed in terms of the volume change of water around their hydrophobic moieties.
Production of methanethiol in milk fat-coated microcapsules containingBrevibacterium linensand methionine
Authors: Kim Sun C. , Olson Norman F.
Published: June 2009

Milk fat-coated microcapsules containingBrevibacterium linensand methionine were used to produce methanethiol, one of the volatile sulphur compounds implicated in Cheddar cheese flavour. Production of methanethiol from methionine occurred aerobically and anaerobically, but the production was 3- to 4-fold greater aerobically with most of the methanethiol being oxidized to dimethyl disulphide. About 35% of the total methanethiol was absorbed by the milk fat capsules and about 65% detected in the headspace. Levels of methanethiol began to decline at 26 °C after 24 h in milk fat-coated microcapsules. However, low temperature, such as 4–12 °C, stabilized levels of methanethiol in microcapsules over an 8-d analysis period. Optimum pH and temperature for methanethiol production were 8 and 26 °C respectively. The antioxidants butylated hydroxytoluene, butylated hydroxyanisole and ascorbic acid had negligible effects on methanethiol production.
Associations between the bovine major histocompatibility complex (BoLA) and milk production in Icelandic dairy cattle
Authors: Simpson S. Patricia , Oddgeirsson Olafur , Jonmundsson Jon V. , Oliver Robert A.
Published: June 2009

Associations between BoLA type and milk production were investigated using information from 80 Icelandic cattle from four dairy farms in Iceland. The specificity w6 reduced milk, fat and protein yield. Although w6 has been shown to be associated with increased susceptibility to mastitis, there is no evidence to suggest that the reduced yields here were due to mastitis. The association may be due to increased disease susceptibility or due to a direct effect of BoLA Class I antigens.
Glycoproteins in the heat- and acid-stable fraction of ovine milk
Authors: Alichanidis Efstathios , Michaelidou Alexandra-Maria
Published: June 2009

Affinity chromatography on a concanavalin A–Sepharose support was used to isolate two glycoprotein fractions from a heat- and acid-stable fraction of ovine milk. One of these glycoprotein fractions was purified by rechromatography on DEAE-cellulose to essentially a pure protein yielding a single band on gel electro-phoresis. The apparentMrof this glycoprotein (GP2) as estimated by electrophoresis was 50500. It contained 8·88% carbohydrate and 0·61% P. The other glycoprotein fraction (GP3) contained 0·53% P and 17·76% carbohydrate including sialic acid, mannose, galactose, fucose, galactosamine and glucosamine. It appeared on electrophoresis in acrylamide gels as a slow-moving broad band. On similar treatment in the presence of sodium dodecyl sulphate it revealed four glycoprotein zones with apparentMrof 15200, 18300, 23500 and 25300. Both GP2 and GP3 contained low amounts of aromatic and sulphur-containing amino acid residues and large amounts of Asp, Glu, Ser and Leu. GP3 is similar in some respects to the bovine milk heat- and acid-stable fraction constituent, component 3.
HPLC and GLC analysis of the triglyceride composition of bovine, ovine and caprine milk fat
Authors: Barron Luis J. R. , Hierro M. Teresa G. , Santa-María Guillermo
Published: June 2009

A total of 116 molecular species of triglycerides were identified in milk fat, using a combination of HPLC and GLC. Triglyceride composition was predicted from the random composition, which was calculated on the basis of the mole fractions of the main fatty acids making up the total triglyceride fraction. The qualitative composition of the milk fat was similar in cows', ewes' and goats' milk. In all three milks the partition number of the main triglycerides was 46, but the proportions of the triglycerides with partition numbers of 34, 38, 42, and 48 exhibited substantial differences among the milks of the three species.
Accelerated ripening of Cheddar cheese with the aminopeptidase of Brevibacterium linens and a commercial neutral proteinase
Authors: Hayashi Kiyoshi , Revell Dean F. , Law Barry A.
Published: June 2009

Partly purified extracellular aminopeptidase from Brevibacterium linens was used to accelerate Cheddar cheese ripening. It was found that although the aminopeptidase was unstable in acidic buffer, it was highly stable in Cheddar cheese; negligible amounts of the enzyme activity were lost during 3 months' maturation. A better score for flavour in sensory analysis of enzyme-treated cheese was obtained by the combination of the aminopeptidase and a commercially available metalloproteinase (Neutrase) than by the metalloproteinase alone.
Interactive effect of H2S production from cysteine and methanethiol production from methionine in milk-fat-coated microcapsules containing Brevibacterium linens
Authors: Kim Sun C. , Kim Misun , Olson Norman F.
Published: June 2009

The interactive effect of two of the major Cheddar cheese flavour compounds, H2S and methanethiol, was studied in milk-fat-coated microcapsules containing Brevibacterium linens, cysteine and methionine. Two substrates, cysteine and methionine, were either co-encapsulated with B. linens or encapsulated separately with B. linens and mixed together. The production of H2S from cysteine in microcapsules was slightly reduced by the methanethiol produced from methionine. However, the presence of H2S stabilized methanethiol produced from methionine in milk-fat-coated microcapsules and subsequently increased the level of methanethiol. Without H2S, the methanethiol in milk-fat-coated microcapsules disappeared rapidly after 48 h. By making separate microcapsules at each optimum environment and mixing together, the cells could operate in the protected and ideal environment of the microcapsules to form products that diffused out and acted as reactants with products from other microcapsules.
Calcium ion activities of cooled and aged reconstituted and recombined milks
Authors: Augustin Mary-Ann , Clarke Phillip T.
Published: June 2009

Milk powders were subjected during manufacture to the following treatments: low-, medium- or high-heat, indirect or direct UHT preheat, or no preheat. The Ca2+ activity–pH profiles of reconstituted milks (9% total solids, TS) in the pH range 6·06–6·98 and reconstituted concentrated milks (19·6% TS) and recombined concentrated milks (26% TS, 18% SNF, 8% fat) in the pH range 6·27–6·69 were determined. Statistical analysis of the results using a (– In Ca2+ activity) transformation was used to quantify the effects of pH, preheat treatment and fat incorporation on Ca2+ activity. pH had a dominant effect on Ca2+ activity and the effects of preheat treatment and fat incorporation were small in comparison. Depending on the batch of milk used for preparation of powders, pH accounted for 98·8–98·9%, 96·4–96·7% and 93·7–97·3% of the total variation in Ca2+ activity in reconstituted milks, reconstituted concentrated milks and recombined concentrated milks. The corresponding contributions of preheat treatment to variation in Ca2+ activity were 0·26–0·47%, 0·34–1·67% and 0·24–0·40%. The addition of fat to reconstituted concentrated milk to yield recombined concentrated milk with the same SNF: water ratio resulted in 0·03–3·71 % variation in Ca2+ activity. The results suggested that differences in heat stability among powders subject to different preheat treatments are not likely to be linked to Ca2+ activity.
Elevation of bovine serum C-reactive protein and serum amyloid P component levels by lactation
Authors: Morimatsu Masami , Watanabe Atsushi , Yoshimatsu Kumiko , Fujinaga Toru , Okubo Masahiko , Naiki Masaharu
Published: June 2009

C-reactive protein (CRP) and serum amyloid P component (SAP), which are known to increase in sera from humans and many other animals with acute inflammation caused by infection, toxic drug administration or injury, were previously purified from bovine serum. These serum levels were determined by enzyme-linked immunosorbent assay (ELISA) using specific antiserum to bovine CRP or SAP which was prepared by immunizing rabbits and goats with each purified protein. Among 68 healthy Holstein cows, 45 non-lactating cows had levels of CRP and SAP of 20·6±1·4 and 27·6 ± 1·3 μg/ml respectively; 23 lactating cows had higher levels of CRP and SAP (76·0±13·6 and 38·3±5·5 μg/ml respectively). In the latter group, there was a high correlation between milk yield and serum CRP levels (P <0·001). From these observations, it was assumed that lactation might stimulate CRP synthesis rather than SAP synthesis in bovine liver as an acute phase reaction, and that CRP might be called a lactation-associated protein.
Xanthine oxidase/dehydrogenase in mammary gland of mouse: relationship to mammogenesis and lactogenesisin vivoandin vitro
Authors: Hayden Thomas J. , Brennan Denise , Quirke Katherine , Murphy Paddie
Published: June 2009

Xanthine oxidase/dehydrogenase (XO/XDH) increases at mid gestation in mammary gland but not in liver of the mouse and remains elevated until the pups are weaned at 20 d post partum. The increase in enzyme activity is due neither to alteration in activators or inhibitors nor to a production of a variant enzyme with altered catalytic properties. The increase is precededin vivoby a surge of prolactin-like activity (placental lactogen) in plasma, and prolactin is required for induction of XO/XDH in explant culturein vitro. Induction of XO/XDHin vivoandin vitroprecedes the full histological differentiation of the gland. In addition, induction of XO/XDHin vitrooccurs more rapidly and at lower concentrations of prolactin than does histological differentiation. Thus although XO/XDH is present in milk, increased XO/XDH activity is an early event in mammogenesisin vivoandin vitrorather than a terminal component of differentiation.
Evidence and characterization of temperate bacteriophage inStreptococcus salivariussubsp.thermophilusSt18
Authors: Carminati Domenico , Giraffa Giorgio
Published: June 2009

Lysogenic strains ofStreptococcus salivariussubsp.thermophiluswere studied using induction with mitomycin C (MC). The induction and presence of temperate phage were investigated carrying out tests on sensitive strains, electron microscopy and phage DNA analysis. Forty-fiveStr. salivariussubsp.thermophilusstrains were subjected to induction with MC and growth of the various cultures was evaluated. Only one strain of those tested showed lysis after adding MC, thus indicating a possible lysogenic state, 0·5μg MC/ml being the optimal dose. Two Φ18 phage-sensitive strains out of 45 were isolated in which this phage behaved as virulent, causing lysis of the culture in broth, but no lysis plaques on agar medium were detected. The St18 strain was cured by u.v. irradiation but no mutants sensitive to the Φ18 phage were found among the clones non-inducible by MC. The presence of phages having a hexagonal isometric head and a long non-contractile tail in the lysate obtained after inducing the St18 strain was confirmed by examination under the electron microscope. Study of the phage DNA showed a genome size of 40·9 ± 0·5 kb without cohesive end fragments. In addition, the restriction map of the phage genome was constructed. This study has demonstrated lysogeny inStr. salivariussubsp.thermophilusand also that several phage infections ofStr. salivariussubsp.thermophilusstarters may have an ‘endogenous’ origin.
Heat stability of recombined milk: influence of lecithins on the heat coagulation time-pH profile
Authors: McCrae Catharina H. , Muir D. Donald
Published: June 2009

Two types of lecithin, namely egg and soya lecithin, were investigated as potential stabilizers of recombined milk. They were incorporated into recombined milk both before and after homogenization (20·7 MPa; 60 °C). Their presence at homogenization changed neither mineral equilibria nor homogenization efficiency. However, heat stability varied significantly irrespective of batch of low-heat skim milk powder used in recombined milk. The variation in heat stability depended on type of lecithin. Soya lecithin proved to be a very effective stabilizer. It improved heat stability over a wide pH range (6·3–7·1) and the effect occurred even when the lecithin was added after homogenization. In contrast, egg lecithin destabilized the system to heat at pH < 6·7 by converting a Type A into a Type B heat coagulation time-pH profile if it was incorporated before homogenization; after homogenization it had no effect. The effects of both egg and soya lecithin on the heat stability of recombined milk strongly suggest that interactions occur between phospholipids and milk protein.
Computer simulation of the hydraulic milking method
Authors: Butler M. Clare , Grindal Robert J.
Published: June 2009

A mathematical model of the interactions within a milking machine teatcup has been developed, which describes the relationship between liner wall movement, pressures and flow rate when milking without an air inlet. It is based on equations of motion for a column of incompressible fluid and requires a second-order, non-linear differential equation to be solved. Incorporating a non-return valve allows hydraulic milking to be modelled, and the comparison between predicted and measured pressures, flow rates and liner wall movement when milking hydraulically is shown. The model can be used to optimize milking conditions to reduce vacuum peaks, improve liner opening and thus maximize flow rate.
K+ and Cl− transport by mammary secretory cell apical membrane vesicles isolated from milk
Authors: Shennan David B.
Published: June 2009

The transport of K+ (Rb+) and Cl− by membrane vesicles isolated from bovine milk has been studied using ion-exchange column chromatography. K+ (Rb+) and Cl− accumulation by the vesicles was time-dependent and was almost abolished by 0·1% Triton X-100, suggesting that uptake represents ‘real’ transport rather than binding. K+ (Rb+) uptake was influenced by the anion in solution in a manner suggesting that influx is sensitive to changes in vesicle membrane potential. Similarly, Cl− uptake was found to be sensitive to vesicle electrical potential: Cl− influx was enhanced by inside positive potentials. Cl− uptake was not saturable with respect to external Cl−. The results suggest that K+ (Rb+) and Cl− cross the apical membrane by way of conductance pathways. The similarity between ion transport by skim milk membrane vesicles and that of the apical aspect of the intact mammary epithelium suggests that the former may be a good model to study solute transport by the apical membrane of mammary secretory cells.
Different bacteriophage resistance mechanisms inStreptococcus salivariussubsp.thermophilus
Authors: Larbi Dejla , Decaris Bernard , Simonet Jean-Marc
Published: June 2009

Streptococcus salivariussubsp.thermophilusstrain NST5 exhibited a temperature-dependent defence mechanism against the virulent bacteriophages φ.B1.2 and φA1.1. It was active at 42 °C but not at 30 °C as demonstrated by a significant increase of both plaque size and efficiency of plaquing. This defence mechanism did not affect host-dependent phage replication and did not interfere with phage adsorption to NST5. These results suggest that it interfered with phage development. The phages φT33, φT58, φD1, φT21 and φT9, belonging to the same phage type as φB1.2, were examined for their ability to infect NST3 and NST5. Restriction modification systems of different specificity were detected in NST3 and NST5; host-dependent phage replication was detected at 30 and 42 °C; an abortive defence mechanism was detected in NST5 which was active at 42 °C, but not 30 °C, and was independent of restriction modification action or interference with phage adsorption. Our investigations of phage-host interactions showed that the twoStr. salivariussubsp.thermophilusstrains studied avoided attack by related bacteriophages by evolving at least three different resistance systems.
Identification of a new molecular form of human α-lactalbumin
Authors: Maynard Françoise
Published: June 2009

α-Lactalbumin (α-La) is a protein found in the milk of all mammalian species and is involved in lactose biosynthesis in association with galactosyltransferase (Brodbeck et al. 1967). The primary structure of α-La from several species such as bovine (Brew et al. 1970), human (Findlay & Brew, 1972), and goat (McGillivray et al. 1979) has been determined. Hall et al. (1982) have established the nucleotide sequence and the organization of the human α-La gene (Hall et al. 1987).
Effects of prolonged treatment of lactating goats with bovine somatotropin on aspects of adipose tissue and liver metabolism
Authors: Vernon Richard G. , Faulkner Anne , Finley Eric , Watt Paul W. , Zammit Victor A.
Published: June 2009

The effects of prolonged (22 weeks) treatment of lactating goats with bovine somatotropin on the metabolism of adipose tissue and liver has been investigated. Somatotropin treatment resulted in smaller adipocytes, decreased rate of fatty acid synthesis and decreased total acetyl-CoA carboxylase activity of adipocytes, but with no change in the proportion of this enzyme in the active state. The rate of acylglycerol glycerol synthesis from glucose of adipocytes tended to decrease as did total glucose utilization by the tissue. Glucose conversion to lactate was unchanged by somatotropin treatment but glucose conversion to other products was decreased. Maximum response of adipose tissue to insulin was unchanged but the sensitivity to insulin decreased on somatotropin treatment. Treatment with somatotropin had no effect on basal lipolysis and decreased maximum response to the β-agonist isoproterenol, but this probably reflects the rate of isoproterenol-stimulated lipolysis varying with cell volume in adipocytes. No apparent change in response either to α2-adrenergic agonists or to adenosine was apparent. The number of β-adrenergic receptors was unchanged in adipocyte membranes but the number of α2-adrenergic receptors increased. The rate of hepatic gluconeogenesis in vitro, the activity of key gluconeogenic enzymes and the modulation of the rate of gluconeogenesis by butyrate were unchanged except for the effect of this latter agent on gluconeogenesis from propionate. Hepatic ketogenic activity, as indicated by the activity of carnitine palmitoyl-CoA-transferase-1 and the concentrations of carnitine and acyl carnitines, was unchanged by treatment. Thus at the end of a prolonged period of treatment with somatotropin in lactating goats, lipid synthesis in adipose tissue is still decreased but no effects on liver lipid and carbohydrate metabolism were apparent.
Microparticle-enhanced nephelometric immunoassay for caseinomacropeptide in milk
Authors: Prin Christine , Bari Nezha El , Montagne Paul , Cuilliere Marie-Louise , Bene Marie-Christine , Faure Gilbert , Humbert Gerard , Linden Guy
Published: June 2009

A microparticle-enhanced nephelometric immunoassay has been developed for the determination of caseinomacropeptide (CMP) in bovine milk. It is based on the nephelometric quantification of the competitive immunoagglutination of a microparticle–CMP conjugate with an anti-κ-casein (κ-CN) antiserum. This one step immunoassay was sensitive (detection limit in reaction mixture, 16μg/l), accurate (linear recovery of CMP in dilution overloading) and reproducible (CV 7–14% for within and between run precision). Because of the specificity of the polyclonal antiserum used, it was necessary to separate CMP from κ-CN by ultrafiltration before the quantification of bovine milk CMP. Under the conditions of milk ultrafiltration used, κ-CN was entirely retained (> 99·5%) but the concentration of CMP measured in milk ultrafiltrates was underestimated (by ∼25%) compared with its concentration in whole milk. Microparticle-enhanced nephelometric immunoassay of CMP, with a calibration range from 0·32 to 20 mg/1 for 20- fold diluted milk ultrafiltrate, allowed contamination of bovine milk by rennet whey as low as 5 ml/1 to be detected. Applied to ultrafiltrates from milk stored at 4 °C, this immunoassay also detected proteolysis of κ-CN not revealed by measurement of κ-CN concentration in milk. A statistical lower limit of 3·21 mg/1 was determined as the increase in CMP concentration in milk ultrafiltrates that indicated probable κ-CN proteolysis in the milk sample. Previously demonstrated to be an easy to perform method for assaying the main proteins of bovine milk, microparticle-enhanced nephelometric immunoassay thus also appeared to be appropriate to quantify CMP so as to detect slight contamination of milk by whey and to indicate the proteolysis of κ-CN during milk storage at low temperature.
Bovine milk procathepsin D and cathepsin D: coagulation and milk protein degradation
Authors: Larsen Lotte B. , Benfeldt Connie , Rasmussen Lone K. , Petersen Torben E.
Published: June 2009

Cathepsin D is an indigenous aspartic proteinase in bovine milk. By competitive enzyme-linked immunosorbent assay the amount of immunoreactive cathepsin D and procathepsin D in bovine skim milk was estimated to be 0·4 μg/ml. Immunoreactive cathepsin D purified from whey consisted of a small fraction of mature cathepsin D, but the major form was the proenzyme procathepsin D. A preparation of bovine milk procathepsin D was, like mature cathepsin D, able to degrade purified αs1-, αs2-, β- and κ-casein and α-lactalbumin, while β-lactoglobulin was resistant to cleavage. The cleavage sites in these proteins were determined and compared with those of chymosin. Cathepsin D was capable of generating the αs1-I, β-I, β-II and β-III fragments originally described from the action of chymosin on the respective caseins, and these fragments were subjected to further proteolysis. Cathepsin D was also able to liberate the caseinomacropeptide from purified κ-casein, and to coagulate bovine skim milk. This demonstrated that milk contains an indigenous coagulation enzyme present mainly in the whey fraction.
Cholesterol oxidation in butter and dairy spread during storage
Authors: Nielsen Jacob H. , Olsen Carl Erik , Jensen Claus , Skibsted Leif H.
Published: June 2009

In a dairy spread (800 g lipid/kg, 10 g salt/kg) based on 750 g milk fat/kg and 250 g rapeseed oil/kg fat in 15 g extruded catering packaging, there was a more significant accumulation of cholesterol oxidation products than in butter (minimum 800 g lipid/kg, 12 g salt/kg) in 10 g extruded catering packaging when stored at 4 or at 20 °C. There was a lag phase of 7 weeks in cholesterol oxidation in dairy spread stored at 4 °C, while no lag phase was observed for storage at 20 °C. Total concentrations of oxysterols were, however, very similar for dairy spread stored at 4 and 20 °C after 13 weeks storage (∼ 12 μg/g milk lipid); storage at – 18 °C almost prevented cholesterol oxidation (∼ 4 μg/g milk lipid). For butter, cholesterol oxidation was less pronounced at 4 °C (< 3 μg/g milk lipid) than at – 18 °C (∼ 4 μg/g milk lipid) and 20 °C (∼ 7 μg/g milk lipid). 7-Ketocholesterol was the dominant oxidation product, with 1·3 and 5·7 μg/g milk lipid in butter and dairy spread respectively after 13 weeks storage at 4 °C.
Effect of medium-chain fatty acids in mould ripened cheese on the growth ofListeria monocytogenes
Authors: Kinderlerer Judith L. , Matthias Helen E. , Finner Paul
Published: June 2009

Listeria monocytogenesandList. innocuawere isolated from commercial soft ripened and blue-veined cheeses manufactured in France, mainly from Brie cheese made from unpasteurized milk. Five isolates wereList. monocytogenesserotype 1/2 and two wereList. innocua. Examination of Bleu d'Auvergne cheese with the cryoscanning electron microscope showed that many conidia spores were present in the blue veins in close contact with the cheese surface. There were few conidia spores in the Brie, mostly on the outside of the cheese but not in contact with the surface. High concentrations of free dodecanoic (lauric) acid (1·77–2·50 g/kg cheese) and tetradecanoic (myristic) acid (2·54–6·38 g/kg cheese) were found in the veins of the blue cheese, but concentrations in the white regions were much lower. Free lauric and myristic acids were not detected in the Brie cheeses. There was no difference in the overall fatty acid composition of the fat in the surface ripened and blue-veined cheeses, although higher concentrations of free medium-chain fatty acids were found in a blue cheese compared with a surface ripened cheese. The pH and fat content were higher in regions with obvious fungal growth, the blue veins of Fourme d'Ambert and the rind of Brie. Free lauric acid dissolved in butteroil inhibited multiplication in broth at pH 7·0 of a test strain ofList. monocytogenesisolated from Bleu d'Auvergne. Some inhibition was seen with hexanoic, octanoic, decanoic and tetradecanoic acids. We suggest that the presence of localized concentrations of free medium-chain fatty acids (dissolved in the fat) in the blue veins of blue mould ripened cheese could act as natural preservatives and inhibit the growth of listerias in conditions where (if present), one would otherwise expect them to grow.