bluuebunny/crossref_metadata_2025 huggingface dataset:
Once daliy milking of dairy cows: relationship between yield loss and cisternal milk storage
Authors: Knight Christopher H. , Dewhurst Richard J.
Published: June 2009

The proportions of milk stored in the gland cistern (cisternal) and within secretory alveolar tissue (alveolar) were determined for a group of ten cows in mid lactation, yielding ∼ 20 kg milk/d. As a proportion of total milk, cisternal milk, measured at 8 h after milking, ranged from 0·09 to 0·53. Milking frequency was then reduced from twice daily to once daily on two occasions, first for 1 week and then, 2 weeks later, for 2 weeks. Milk yield was reduced during once daily milking in all cows, by an average of 22·8% during the first week (P < 0·001). The amount of decrease varied among cows in a way that was unrelated to pretreatment yield, but the immediate decrease was significantly and inversely correlated with cisternal milk proportion (r = 0·81, P < 0·01). When milking reverted to twice daily, yield recovered to a value not significantly different from pretreatment, and the degree of recovery was inversely related to cisternal milk proportion (r = 0·74, P < 0·01). With the exception of one cow, yield decreases correlated well between the two periods of once daily milking. When treatment weeks were disregarded, lactation persistency (the rate of decline in yield with time) was unaffected by once daily milking. The results show that the ability of individual cows to tolerate once daily milking is related to their cisternal storage characteristics; yield is reduced less in cows that store a greater proportion of their total milk production within the cistern. Once daily milking for up to 2 weeks had no lasting effect on milk yield or lactation persistency, suggesting that there had been no detrimental effect on udder development.
Tryptic phosphopeptides from whole casein. II. Physicochemical properties related to the solubilization of calcium
Authors: Berrocal Rafael , Chanton Serge , Juillerat Marcel A. , Favillare Blaise , Scherz Jean-Claude , Jost Rolf
Published: June 2009

Casein phosphopeptides (GPP) were produced by tryptic hydrolysis of sodium caseinate and further purified by precipitation and chromatography on QAE-Sephadex A-25. Their physico-chemical properties were compared with the properties of an enzymically dephosphorylated equivalent preparation (DPP). Binding of Ca2+ to the peptides was measured using a Ca selective electrode and was found to increase with pH and to show 1/1 stoicheiometry Ca/Porg in CPP at pH 6·5 a.nd 7·6. Klotz plots indicated equivalent binding sites at these two pH values, but some heterogeneity was seen at pH 3·5. In contrast, DPP did not bind significant amounts of Ca2+.

CPP effectively inhibited the formation of insoluble calcium phosphates at different Ca/P ratios. The effective CPP concentration was 10 mg/1 and complete stability of calcium phosphate solutions was obtained at about 100 mg/1. This stabilizing effect was dependent on the presence of organic P.
Heat-induced changes in sodium Caseinate
Authors: Guo Mingruo , Fox Patrick F. , Flynn Albert , Mahammad Kais S.
Published: June 2009

Chemical and physical changes that occur in Na caseinate (at 1 or 2% in water, pH 7·0) on heating in the range 120–150 °C were investigated by polyacrylamide gel electrophoresis, ion-exchange and gel-permeation chromatography, light scattering, u.v. spectroscopy, amino acid analysis, and the formation of pH 4·6 and 12% TCA-soluble N and 12% TCA-soluble P. The electropherograms of heated samples were smeared and indistinct suggesting intermolecular aggregation which was not reversed by 6 M-urea or SDS and indicating covalent bond formation; αs2-casein was especially sensitive. Aggregation was confirmed by ion-exchange chromatography and light scattering. Fragmentation of the caseins also occurred on heating, as indicated by the formation of pH 4·6 and 12% TCA-soluble N and by gel filtration. Formation of soluble N and dephosphorylation followed first-order kinetics. Concentrations of available lysine and available methionine were reduced by 10–15% on heating at 140 °C for 30min; chemical assays for arginine and tryptophan indicated increases, suggesting interference. Ultraviolet spectroscopy indicated a slight apparent increase in aromatic residues after heating at 140 °C for up to 60 min.
Tryptic phosphopeptides from whole casein. I. Preparation and analysis by fast protein liquid chromatography
Authors: Juillerat Marcel A. , Baechler Robert , Berrocal Raphael , Chanton Serge , Scherz Jean-Claude , Jost Rolf
Published: June 2009

Tryptic phosphopeptides were obtained from whole bovine casein by chromatography on the anion exchange resin QAE-Sephadex A 25. Salt gradient elution of the column allowed separation of non-phosphorylated peptides from phosphorylated species. The preparations obtained contained at least seven distinct phosphopeptides of which the following casein fragments were identified: αs1(43–58):2P, αs1(59–79): 5P, αs2(46–70): 4P, β(1–28): 4P, β(2–28): 4P, and β(33–48): 1P. Fast protein liquid chromatography (FPLC) on Mono Q HR 5/5 resin showed that the phosphopeptides were eluted in the same order as from the QAE-Sephadex resin. However, on the analytical column HR 5/5 the fragments αs1(59–79): 5P and β(2–28): 4P, having the same net charge under the conditions of chromatography, co-eluted, whereas they were at least partly separated on the preparative column HR 16/10. Following enzymic dephosphorylation, the peptides eluted at lower salt strength in the gradient. FPLC on Mono Q resin thus permitted dephosphorylation to be monitored and intermediates between the parent species and the fully dephosphorylated peptide to be identified.
Chemical prediction of water activity in processed cheese
Authors: Esteban María A. , Marcos Andrés
Published: June 2009

By linear regression analysis, a highly significant negative correlation (r = −0·96) was found between the mean ash concentration values (g/100 g moisture) and water activity (aw) of six types of processed cheeses (low-fat, semi-fat, fat, extra-fat, double fat and special). The regression equation aw = 0·9951 − 0·0032* (ash), applied to 40 cheese samples, yielded aw values which differed by < 0·005 aw units from those measured experimentally in 75% of the samples. The maximum differences between the calculated and experimental aw values (found in only two samples) were ±0·01 aw units.
Automatic method to quantify starter activity based on pH measurement
Authors: Spinnler Henry E. , Corrieu Georges
Published: June 2009

A new method for measuring the activity of mesophilic and thermophilic lactic acid bacteria is proposed based on measuring the pH of cultures at extremely short intervals (30–90 s) during growth and calculating several kinetic parameters, i.e. the maximum acidification rate (Vm), the time and pH at which Vm occurred, the time or pH range during which the observed rates were greater than Vm/2. These were easily calculated by coupling the pH meter to a microcomputer.
Effects of dehydration and arginine vasopressin infusions on the production of milk and the morphology of the goat udder
Authors: Dahlborn Kristina , Hilali Jamal Hossaini , Rodriguez-Martinez Heriberto
Published: June 2009

Lactating goats were subjected to dehydration and to infusions of arginine vasopressin (AVP). Dehydration decreased milk production significantly but no changes were observed on the day of AVP infusion. The levels of AVP in plasma reached the same magnitude during both experimental procedures. AVP-immunoreactivity was immunocytochemically detected by light (peroxidase-antiperoxidase technique) and electron microscopy (immuno-Au technique on to glutaraldehyde-fixed, resin-embedded sections) in the mammary gland but not in the control experiments. In addition the cisternae of the rough endoplasmic reticulum in the secretory alveolar cells underwent significant swelling in response to the experimental procedures.
A method for determination of macropeptide by cation-exchange fast protein liquid chromatography and its use for following the action of chymosin in milk
Authors: Léonil Joëlle , Mollé Daniel
Published: June 2009

Cation-exchange chromatography on a Mono S column (Pharmacia) was used to separate macropeptide from whey proteins. Macropeptide was eluted by 0·1 M-NaCl in a 20 mM-KCl–HCl buffer, pH 2. This technique was suitable for quantitative determination of macropeptide in rennet whey and also for following the action of chymosin on κ-casein in skim milk. Precipitation at pH 4·6 was used to remove residual caseins and to keep macropeptide in solution. In comparison with other methods for determining macropeptide, the present one eliminates the need for pretreatment of samples with trichloroacetic acid (TCA) and allows the recovery of all the macropeptide. Quantitative determination of macropeptide in the 8% TCA-soluble fraction by cation-exchange chromatography showed that only 50–75% of the macropeptide was recovered. This chromatographic technique could also be applied for isolating and producing whole macropeptide on a preparative scale.
Interquarter comparison of markers of subclinical mastitis: somatic cell count, electrical conductivity,N-acetyl-β-glucosaminidase and antitrypsin
Authors: Jensen Niels Einar , Knudsen Kim
Published: June 2009

We have evaluated the usefulness in mastitis diagnostics of new diagnostic measures using the continuous nature of the variation in quarter milk samples of four inflammatory markers: somatic cell count,N-acetyl-β-glucosaminidase (EC 3.2.1.30), electrical conductivity and antitrypsin. A two-way analysis of variance was performed for each of the inflammatory markers on results from 273 cows sampled six times at 14 d intervals. Adjustment for the individual cow's mean removed approximately half the total variation for all four markers, indicating that comparisons in marker levels between quarters without taking the cows' overall level into account, as is done in diagnostic keys based on fixed threshold, is a rash procedure. After adjusting for the individual cow means, the total variation of the marker observations was partitioned in three sources of variation: between the four quarter levels, between different sampling days, and the experimental error, i.e. the variation within each quarter over-the study period. As expected, the variation between quarters accounted for the largest percentage of the variation (44–65%). In contrast the variation between days was only 16–34% and of the same magnitude as the experimental error. These figures can profitably be taken into account when designing experiments in future mastitis research studies. They imply that mastitis diagnostics based on quarter milk samples collected over time will be influenced only slightly by random biological variation and that the same relative differences that exist in marker levels between the four quarters of a cow as a rule will be disclosed irrespective of sampling day. Thus, the udder health state is relatively stable when determined by these inflammatory markers. In addition to simple correlations between markers measured on the same day, correlations of the logarithm of the interquarter ratios and of the experimental errors were computed. Stronger associations between the markers emerged and these correlations reflect more precisely than simple correlations the real diagnostic relations of the markers.
31P nuclear magnetic resonance spectra of milk from various species
Authors: Belton Peter S. , Lyster Richard L. J.
Published: June 2009

The31P nuclear magnetic resonance spectra of milk from goats, sheep, a rabbit, a baboon and a human were examined and compared with the spectrum of cows' milk. Most of the peaks observed could be assigned to phosphorus compounds already known to be present in such milks. However, rabbit milk was found to contain unexpectedly large amounts of phosphate esters, and to have only low levels of alkaline phosphatase (EC 3.1.3.1) activity. In addition, an unknown compound was detected in baboon milk and in some samples of sheep and goat colostrum. This compound was not identified, but may be a mixed anhydride such as 1,3 diphosphoglyceric acid. The results show that changes during lactation may be followed by31P nuclear magnetic resonance and that the technique may be of value in authentification of samples.
Effects of long-term deep-freeze storage on the condition of the fat in raw sheep's milk
Authors: Needs Eric C.
Published: June 2009

Effects of long-term deep-freeze storage on the stability of fat in raw sheep's milk were assessed by measuring free fatty acid (FFA) concentrations, lipoprotein lipase activity and the amount of solvent-extractable fat. Portions of milk from three herds were frozen and stored at – 12, – 20 and – 27 °C. There was a gradual increase in FFA during 6 months storage, the rate of lipolysis being affected by storage temperature and differences between herds. After 6 months storage the residual lipase activity was only 2% (– 12 °C), 11% (– 20 °C) and 24% (– 27 °C) of the initial activity in fresh milk. The potential for lipolysis in the stored samples, after they were removed from storage and allowed to thaw to 4 °C, gradually fell as storage time was prolonged. This may be due to the loss of lipase activity.
New type of Domiati cheese of potential benefit to people with high blood cholesterol
Authors: Abou-Zeid Nadia A.
Published: June 2009

Part of the milk used for manufacturing Domiati cheese was replaced by buttermilk at rates of 0, 20, 30, 40, 50 and 60%. The fat and SNF contents were standardized at 5 and 10% respectively. The hypocholesterolaemic effect of buttermilk when incorporated into cheese was tested with rats by including cheese manufactured with and without buttermilk mixed in their diet at a rate of 30% for a period of 60 d. When the diet containing Domiati cheese free from buttermilk (control cheese) was given to rats, there were highly significant increases in serum and liver cholesterol. However, when part of the milk used in manufacturing Domiati cheese was replaced by buttermilk the increases in serum and liver cholesterol concentrations were reduced. These reductions were proportional to the proportion of buttermilk incorporated in the milk used to manufacture the cheese. When 50% of the milk used for Domiati cheese was replaced by buttermilk the hypercholesterol-aemic effect of Domiati cheese was nullified and the serum and liver cholesterol concentrations were restored to their normal values. The effect of replacing 50% of the milk used in the manufacture of Domiati cheese by buttermilk on the quality of the cheese was tested periodically during the ripening period. The buttermilk improved the flavour of the cheese whilst only slightly affecting its ripening.
Calcium, phosphate and citrate in human milk at initiation of lactation
Authors: Kent Jacqueline C. , Arthur Peter G. , Retallack Robert W. , Hartmann Peter E.
Published: June 2009

The onset of copious milk secretion (lactogenesis II) in women occurs between 1 and 3 d after birth, and during this period the composition of breast milk changes. During the first 5 d of lactation we measured the concentrations of total, diffusible and ionized Ca (Catot, Cad, Ca2+), diffusible phosphate (Pid), diffusible citrate (Citd) and lactose in the breast milk. On day 1 after birth the concentrations (mean ± SEM) were Catot, 5·71±0·30 mM; Cad, 2·66±0·19 mM; Ca2+, 2·90 ±0·18 mM; Pid, 0·26±0·16 mM; Citd, 0·25±0·03 mai and lactose, 76±11 mM. Between day 1 and day 4 the concentration of Catotincreased 1·7-fold to 9·56 ±0·39 mai, Cadincreased 1·8-fold to 4·75±0·26 mM, Ca2+decreased by 20% to 2·33 ± 0·13 mM, Pidincreased 6·6-fold to 1·69±0·11 mM, Citdincreased 20-fold to 5·06±0·21 mM, and lactose increased 2·3-fold to 173±4 mM. A high correlation has been found between [Cad] and [Citd] in the milk of both ruminant and non-ruminant species, which show a wide range in concentrations of [Cad] and [Citd], and the data fit a simple physicochemical model of ion equilibria in the aqueous phase of milk. The results of the present study confirm the relationship between [Cad] and [Citd] in human milk, even during lactogenesis II when the composition of the milk is changing very rapidly.
Machine-induced teat tissue reactions and infection risk in a dairy herd free from contagious mastitis pathogens
Authors: Zecconi Alfonso , Hamann Jörn , Bronzo Valerio , Ruffo Gianfranco
Published: June 2009

Machine-induced changes in teat thickness were measured in a randomly selected group of 22 cows from a commercial dairy herd consisting of 110 cows during an experiment lasting 1 year. Half the cows used were free from mastitis whereas the remainder had at least one quarter infected by environmental pathogens. Teats were classified according to a threshold change in teat end thickness of 5%. The relationships between quarter infection or teat duct colonization and teat end thickness changes induced by machine milking were investigated. Teats with > 5% change in thickness had significantly increased teat duct colonization and a slight, non-significant, increase in quarter infection. We conclude that machine-induced changes in teat end thickness are predisposing factors for teat duct colonization by environmental pathogens. This may provid: an increased new infection risk, especially when hygiene is poor.
Changes in structure of the bovine milk fat globule membrane on heating whole milk
Authors: Houlihan Avis V. , Goddard Philippa A. , Kitchen Barry J. , Masters Colin J.
Published: June 2009

The effects of heat-induced interactions between milk fat globule membrane components and skim milk proteins in whole milk on the structure of the membrane were examined by isopycnic sucrose density gradient centrifugation and by using Triton X-100 as a membrane probe. Skim milk components were incorporated into all the lipoprotein fractions separated by density gradient centrifugation. High density complexes, higher in density than those found in the natural milk fat globule membrane, were formed during the heat treatment. Losses of natural membrane polypeptides from the medium and low density lipoproteins were observed on heating. Heating whole milk also altered the rate of release of membrane components by detergent, with decreases in protein released and an increase in phospholipid constituents released. Studies on washed cream indicated that some of the changes in the membrane on heating whole milk occurred due to the heat treatment alone, independent of the interactions with skim milk proteins.
Inhibition of proliferative responses of mouse spleen lymphocytes and rabbit Peyer's patch cells by bovine milk caseins and their digests
Authors: Otani Hajime , Hata Isao
Published: June 2009

The modulating effect of bovine milk casein components and their digests on the proliferative responses of mouse spleen lymphocytes and rabbit Peyer's patch cells induced or not induced by mitogens has been studied with a colorimetric assay using 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. All the casein components and their digests tested had little mitogenic effect on the proliferative responses of mouse spleen lymphocytes and rabbit Peyer's patch cells. Intact κ-casein significantly inhibited the proliferative responses of mouse spleen lymphocytes and Peyer's patch cells induced by mitogens such as lipopolysaccharide fromSalmonella typhimurium, concanavalin A, phytohaemagglutinin and pokeweed mitogen. In contrast, intact αsl-casein and β-casein had little effect. κ-Casein had an inhibitory effect after digesti on by pancreatin or trypsin, but not after pepsin or chymotrypsin digestion. Both pancreatin and trypsin digests of αsl-casein and -casein significantly inhibited the proliferative responses of mouse spleen lymphocytes and rabbit Peyer's patch cells induced by mitogens, whereas pepsin and chymotrypsin digests of both caseins were without effect. Moreover, the trypsin digest of each casein component had an inhibitory effect on mouse spleen lymphocyte proliferation in the absence of mitogen. Since trypsin is a major proteinase in pancreatin, the substrate specificity of trypsin seems to be important for the formation of the inhibitory peptides from casein components. These observations suggest that intact κ-casein and some peptides formed from milk casein components by the action of trypsin may suppress the immune responsiveness of neonates.
Restrained molecular dynamics study of the interaction between bovine κ-casein peptide 98–111 and bovine chymosin and porcine pepsin
Authors: Plowman Jeffrey E. , Creamer Lawrence K.
Published: June 2009

The cleavage of bovine κ-casein at the Phe105–Met106* bond by chymosin or pepsin is the first stage in casein micelle coagulation and casein digestion. The nature of the interaction of the peptide His98–Pro–His–Pro–His–Leu–Ser–Phe105–Met–Ala–Ile–Pro-Pro-Lys111 with chymosin and porcine pepsin was investigated using molecular modelling and energy minimization techniques. This study verified and extended a proposed model that electrostatic binding (involving His98, His100, His102 and Lys111 or Lys112) at either end of the active site cleft of chymosin is important for the positioning of residues 103–108 in the cleft. The peptide conformation remained unchanged in going from solution to binding into the active site cleft, with the exception that optimum binding of substrate to chymosin required the isomerization of the His98–Pro99 peptide bond from the trans to the cis conformation. The study also identified an acidic region in porcine pepsin that is in a position to form strong electrostatic interactions with the histidines at the N-terminus of the peptide.
Formation of acid-heat-induced skim milk gels in the pH range 5·0–5·7: effect of the addition of salts and calcium chelating agents
Authors: Goddard Simon J. , Augustin Mary-Ann
Published: June 2009

The effects of pH and added salts or chelating agents on the gel strength and dynamic rheological properties of acid–heat-induced gels made from reconstituted skim milk (200 g solids/l) were investigated. Gel strength increased as pH was lowered between 5·75 and 5·15 except in the range pH 5·45–5·25 where a local maximum in gel strength was obtained at pH 5·35. Gel characteristics were affected by addition of salts or chelating agents but each of their effects was different, depending on the final pH of the milk gel. The addition of CaCl2 or chelating agents (Na2HPO4, disodium citrate or the disodium salt of EDTA) which affected micellar calcium phosphate, non-sedimentable casein and Ca2+ activity in different ways all resulted in decreased gel strength at pH 5·5. The addition of CaCl2 or MgCl2 caused a decrease in tanδ (ratio of the viscous modulus G″ to the elastic modulus G′) whereas disodium citrate or the disodium salt of EDTA addition caused an increase and Na2HPO4 addition did not cause a change. The addition of NaCl (up to 50 mM), which causes an increase in ionic strength but has no effect on non-sedimentable casein and Ca2+ activity, decreased gel strength but did not change tanδ. The addition of a range of other salts (KCl, NH4Cl, NaSCN, NaNO3 or Na2SO4) also decreased gel strength at pH 5·5.
Effects of intraruminal infusion of propionate on the concentrations of ammonia and insulin in peripheral blood of cows receiving an intraruminal infusion of urea
Authors: Choung Jai-Jun , Chamberlain David G.
Published: June 2009

To test the hypothesis that propionate can reduce hepatic capacity to detoxify ammonia, effects of the inclusion of propionate in intraruminal infusions of urea on the concentrations of ammonia, other metabolites and insulin in peripheral blood were investigated in two experiments with non-lactating dairy cows. Both experiments were of a 4 × 4 Latin square design with four animals, four treatments and four experimental periods of 7 d; feed was given in two equal meals each day, all intraruminal infusions were given for 1 h at the time of the morning feed, and propionic acid was partly neutralized with NaOH. In Expt 1, the treatments were a basal diet of pelleted lucerne and chopped hay alone or with the following infusions (g/d): urea 80, propionic acid 350, urea 80 plus propionic acid 350. The inclusion of propionate in the urea infusion markedly increased (P < 0·001) the concentration of ammonia in plasma compared with infusion of urea alone. Moreover, the inclusion of urea with the propionate infusion abolished (P < 0·01) the increase in blood insulin level seen with the infusion of propionate alone. In Expt 2, less severe treatments were imposed, the aim being to reproduce metabolic loads of propionate and ammonia that might be expected from a diet of high-protein grass silage rich in lactic acid. The treatments were a basal diet of grass silage alone or with the following infusions (g/d): NaCl 145, NaCl 145 plus urea 50, propionic acid 200, urea 50 plus propionic acid 200. Effects were less pronounced than in Expt 1 but, in the period immediately after infusion, similar effects were seen. It is concluded that propionate–ammonia interactions may have potentially important effects on milk production especially for diets with high proportions of grass silage containing high levels of protein and lactic acid.
Effects of heat treatment and acidification on the dissociation of bovine casein micelles
Authors: Law Andrew J. R.
Published: June 2009

The effects of heat treatment and subsequent acidification of milk on the distribution of proteins, Ca and Pi, between the serum and micellar phases were examined using ultracentrifugation. After heating milk at 85 °C for 10 min, and storing for 22 h at 4, 20 or 30 °C, there was a marked increase in the concentration of κ-casein in the serum. At 4 and 20 °C there was also slightly more β-casein in the serum from heat-treated milk than in that from the corresponding raw milk. The whey proteins were extensively denatured, and were almost equally distributed between the supernatants and micellar pellets. After storage for 22 h the distribution of Ca and Pibetween soluble and colloidal phases in heat-treated milk was similar to that in raw milk. After acidifying heat-treated milk by the addition of glucono-δ-lactone and storing for 22 h at 4, 20 or 30 °C there was progressive solubilization of colloidal calcium phosphate with decreasing pH, and at pH 5·0 almost all of the Ca and Piwas present in the serum. At 20 °C, and even more so at 4 °C, serum concentrations of the individual caseins increased considerably with decreasing pH, reaching maximum levels of about 25 and 40% of the total casein at pH 5·7 and 5·5 respectively, and then decreasing rapidly at lower pH. Compared with raw milk, maximum dissociation in heat-treated milks stored at 4 and 20 °C occurred at higher pH, and the overall levels of dissociation of individual caseins from the micelles were lower. At 30 °C, the concentrations of individual caseins in the serum of heat-treated milk decreased steadily as the pH was reduced, and did not show the slight increase found previously for raw milk. The role of the denatured whey proteins in interacting with κ-casein and in promoting aggregation of the micelles on acidification is discussed.
Enumeration of starter cultures in fermented milks
Authors: Ghoddusi Hamid B. , Robinson Richard K.
Published: June 2009

Some media available for the isolation and enumeration of starter cultures employed for the manufacture of cheese, yogurt and bio-yogurt were examined. Reddy's medium or a modification of Elliker's medium was found to be most satisfactory forLactococcusspp., while trypticase phytone yeast (TPY) agar with a mixture of antibiotics proved suitable for the discrete enumeration ofBifidobacteriumspp. The inclusion of Prussian blue (PB) in reinforced clostridial medium or tryptone proteose peptone yeast extract (TPPY) agar gave excellent differential counts for the starter bacteria in yogurt even when the culture was imbalanced, while TPPY (PB) agar allowed the visible separation of all four of the organisms that might be found in a typical bio-yogurt, namelyLactobacillus delbrueckiisubsp.bulgaricus, Streptococcus thermophilus, a,Bifidobacteriumsp. andLb. acidophilus. It was noted that variation among different strains of any given species could change the expected reactions, so for quality control purposes the suggested media may need to be modified to cope with the specific cultures in use.
Simultaneous recording of oxytocin release, milk ejection and milk flow during milking of dairy cows with and without prestimulation
Authors: Bruckmaier Rupert M. , Blum Jürg W.
Published: June 2009

The effects of manual teat stimulation compared with stimulation by the liner of a conventional milking machine and the influence of milk ejection on the course of milk flow during the entire milking were investigated. Twelve cows were milked with or without prestimulation on three quarters and milk flow was recorded while intramammary pressure (IMP) was recorded in the left front quarter and blood samples for the determination of oxytocin (OT) were taken at 1 min intervals. OT concentrations increased very similarly in response to manual teat stimulation or liner stimulation and remained elevated during the entire milking procedure. Milk flow curves were generally bimodal without stimulation and not bimodal during milking after prestimulation. Milk yield was not significantly lower in milkings without than with stimulation, whereas machine-on time was prolonged and peak milk flow rate was reduced during milking without stimulation. Time to reach milk flow plateau, time to reach peak flow rate and IMP profiles were similar in both treatments if time was calculated from the start of stimulation. IMP increased similarly in response to manual or liner teat stimulation. In milkings with and without prestimulation IMP did not reach its maximum until the start of milking. In bimodal milk flow curves the second increase of milk flow occurred concomitantly with the start of IMP increase; ejection IMP generally occurred concomitantly with the milk flow plateau. In some cases during milking without prestimulation only small and transient OT release was observed. In response, IMP did not increase to its maximum and increased further in response to a stripping-related OT release. During the course of milking IMP decreased slightly because of the emptying of the three milked quarters. After the end of milking, and with OT concentrations decreasing to the premilking values, IMP again decreased slightly to another plateau, probably owing to myoepithelial relaxation. Thus the course of milk ejection, i.e. the IMP profile, influenced milk removal markedly during early milking.
Survival and residual activity ofLactobacillus acidophilusfrozen cultures under different conditions
Authors: Foschino Roberto , Fiori Enrico , Galli Antonietta
Published: June 2009

Eight strains of theLactobacillus acidophiluscomplex were subjected, as concentrated cultures in skim milk, to different freezing treatments (rapidly in liquid nitrogen and more slowly in cold air at −30 °C), then stored at −80 and −30°C for 9 months. Survival was determined by plate counting with and without bile salts or sodium chloride at the highest tolerated concentration for each strain, to distinguish the undamaged population from the total population. Fermentative activity was measured as total lactic acid production by thawed cultures under standard conditions. Higher survival rates and greater activity were always obtained by storing cultures at −80 °C, but most strains stored at −30°C also survived well. Analysis of variance revealed that the viability of the frozen cultures was affected more by storage temperature than by cooling rate. Selective media were unable to distinguish the active population from the total surviving population. The correlation between values for activity and survival with selective media was poor.
Aggregation of β-lactoglobulin studied by in situ light scattering
Authors: Hoffmann Marion A. M. , Roefs Sebastianus P. F. M. , Verheul Marleen , van Mil Peter J. J. M. , De Kruif Kees G.
Published: June 2009

In situ light scattering, where light scattered from a sample is measured directly while the sample is heated in the instrument, is presented as a simple and effective technique for studying the heat-induced aggregation of β-lactoglobulin. This technique was shown to be applicable not only to monitoring the initial aggregation steps, but to following the overall aggregation process with time. The experiments gave results similar to measurements carried out after a heat-quench treatment, but were more informative. From experiments on a standard NIZO β-lactoglobulin sample, a strongly desalted standard NIZO sample, different genetic variants of β-lactoglobulin and a mixture of these, we concluded that the standard NIZO sample was suitable for studying heat-induced aggregation. This sample has been investigated more extensively. Results with β-lactoglobulin (10–100 g/1) at 65 °C fitted a kinetic model for the denaturation and aggregation of β-lactoglobulin. This model, which held for β-lactoglobulin dissolved in water at near neutral pH and at 60–75 °C, recognizes an initiation, propagation and termination reaction, by analogy with polymer radical chemistry. It gave a quantitatively correct description of the dependence of the scattering intensity on the initial β-lactoglobulin concentration. Salt composition, pH and temperature strongly influenced the aggregation of β-lactoglobulin. Particle size increased with salt concentration in the range studied (up to 20 mM-NaCl and 1·0 mM-CaCl2). When the pH increased from 6°9 to 8·0 particle size was strongly reduced, whereas it strongly increased when pH was lowered to 6·2. Between 61·5 and 70 °C temperature did not affect particle size, whereas aggregation rate strongly increased. These effects could be incorporated in the kinetic model via the reaction constants of the reaction kinetic pathway.
New crystal form of β-lactoglobulin
Authors: Rocha Thales L. , Brownlow Sharon , Saddler Keith N. , Fothergill-Gilmore Linda A. , Sawyer Lindsay
Published: June 2009

The milk whey protein β-lactoglobulin has been isolated from ovine milk, purified and crystallized in a form suitable for X-ray crystallography. The crystals, which diffract to 1·9 Å resolution, belong to the trigonal space group P3121 with unit cell lengths a = b = 99·8 Å, c = 67·7 Å and unique angle γ = 120·0°. Although there have been many crystal forms reported for bovine β-lactoglobulin, none has been reported with these unit cell parameters. A preliminary native data set has been collected and a molecular replacement solution obtained, using the structure of dimeric bovine β-lactoglobulin as the search model. The importance of the ovine structure in relation to that of the bovine is discussed.
Proteinases in normal bovine milk and their action on caseins
Authors: Andrews Anthony T.
Published: June 2009

Native proteolytic enzymes in good quality normal bovine milk readily hydrolyscd the caseins during incubation or storage, producing the γ-caseins, proteosc-peptone components 5 (PP5) and 8-fast (PP8F) and a considerable number of other unidentified fragments, many of which were also subsequently found in the proteose-pcptone fraction. The rate of casein hydrolysis was greater in pasteurized than in raw milk, with β-casein being slightly more susceptible to attack than αs1-easein. Measurements of γ-cascin and proteose-peptone formation have been made and it was found that PP5 was an intermediate product that was subject to further proteolysis while PP8F was a stable end-product. With the exception of component 3 (PP3), virtually all constituents of the proteose-peptone fraction increased during storage and appeared to be products of the action of proteolytic enzymes. Further evidence was obtained from the effects of various inhibitors that the principal proteinase of normal milk is plasmin, but slight differences were apparent between the protein breakdown patterns induced by storage and by added plasmin, which was consistent with the presence of more than one proteinase. Incubations in the presence of soya bean trypsin inhibitor to prevent plasmin action clearly revealed that another enzyme(s) was also involved.
Isolation and some properties of extracellular heat-stable lipases fromPseudomonas fluorescensstrain AFT 36
Authors: Fox Patrick F. , Stepaniak Leszek
Published: June 2009

Aeration increased the growth and lipase production in milk byPseudomonas fluorescensstrain AFT 36, isolated from refrigerated bulk milk. A heat-stable lipase was isolated from a shaken milk culture of this microorganism by DEAE-chromatography and gel filtration in Sepharose 6B. The lipase-rich fraction from DEAE cellulose contained 3 lipases that were separated by gel filtration; only the principal lipase, which represented ∼ 71 % of total lipolytic activity, was characterized. The purified enzyme showed maximum activity on tributyrin at pH 8·0 and 35 °C; it had aKmon tributyrin of 3·65 mM. and was inhibited by concentrations of substrate > ∼ 17 mM. The enzyme was very stable over the pH range 6–9; it was relatively heat-labile in phosphate buffer in the temperature range 60–80 °C, where it was stabilized significantly by Ca2+. It was, however, very stable at 100–150 °C: theDvalues at 150 °C were ∼ 22 s and 28 s in phosphate buffer and synthetic milk serum respectively; the correspondingZvalues in the temperature range 100–150 °C were ∼ 40 and ∼ 42 °C and theEafor inactivation were 7·65 × 104J mol-1and 6·97 × 104J mol-1respectively.
Effects of fat concentration on the homogenization of cream
Authors: Phipps Leslie W.
Published: June 2009

A study has been made of the interdependence of the volume fraction and the degree of dispersion of the fat in creams subjected to single-pass homogenization. The effects of fat volume fraction φ could be incorporated into a semi-empirical correlation of the homogenizing variables established previously. In general, as φ increased from a low value the mean fat globule diameter at first decreased, reached a minimum and subsequently increased. The total area of the fat interface/m.l. volume when the globule diameter was a minimum proved to be independent of the homogenizing pressure and had a value of approximately 1·1 m2; the interface of maximum area was greater than this and, in contrast, its magnitude was pressure-dependent.

The overall results have been interpreted in relation to the variability of the disruptive energy within the homogenizing valve, competing effects of globule coalescence and hindered break-up, and the surface-active properties of the milk proteins.
Factors affecting the ethanol stability of bovine skim-milk
Authors: Horne David S. , Parker Thomas G.
Published: June 2009

The ethanol (EtOH) stability characteristics of skim-milk concentrates were found to be governed by their chloride ion content. This effect appeared to be largely one of ionic strength. At pH values around 7·0 and above, EtOH stability showed a linear decrease with increasing chloride content but at pH values < 7 the relationship was non-linear. This empirical observation allows the EtOH stability of a skim-milk concentrate to be predicted from simple measurements on the original milk sample. Moreover, predicted increases in the EtOH stability of concentrated milks were obtained when the levels of monovalent ions in the system were reduced either by dialysis before or after concentration or by ultrafiltration.
Antagonistic activity of Debaryomyces hansenii towards Clostridium tyrobutyricum and Cl. butyricum
Authors: Fatichenti Fabrizio , Bergere Jean L. , Deiana Pietrino , Farris Giovanni A.
Published: June 2009

A study of the inhibitory action of Debaryomyces hansenii (31 strains) on Clostridium tyrobutyricum (5 strains) and Cl. butyricum (2 strains) on laboratory media showed that Deb. hansenii inhibited the growth of these organisms, and that this effect was due not only to competition for nutrients but also to the production of both extra-and intracellular antimicrobial metabolites. The inhibitory effect varied with strain and occurred whether the yeasts were grown aerobically or under reduced O2 tension.
Fouling of a plate heat exchanger used in ultra-high-temperature sterilization of milk
Authors: Lalande Marc , Tissier Jean-Pierre , Corrieu Georges
Published: June 2009

The composition and weight of deposit formed in all sections of an ultra-high-temperature milk sterilization plant were determined. Deposits formed in the preheating, heating and cooling sections during sterilization of pasteurized whole milk were analysed for dry matter, protein, fat and mineral contents. The weight and composition of components of the deposit varied in different sections of the plant and with the heating temperature. Two categories of deposit could be distinguished: one in the preheating section consisting of (w/w) protein 50%, minerals 40% and fat 1% and another in the heating section consisting of minerals 75%, proteins 15% and fat 3%. Concerning the rate of formation of these deposits, a comparison of the results with those obtained for pasteurization shows that fouling was more rapid during pasteurization of raw milk than during sterilization of previously pasteurized milk. Hypotheses concerning mechanisms of formation of protein deposition are discussed.
Effect of pasteurization temperature on the keeping quality of whole milk
Authors: Schröder Monika J. A. , Bland Michael A.
Published: June 2009

The keeping quality (KQ) of whole milks pasteurized at 72 °C, 78 °C or 83 °C for 20 s and stored at 12 or 7 °C was examined by assessment of the naturally contaminating thermoduric microflora and of the numbers of Gram-negative rods, a single strain of the latter being introduced deliberately by post pasteurization inoculation. A pasteurization temperature of 83 °C reduced the KQ at 7 °C by about 15% compared with pasteurization at 72 °C or 78 °C, with a 2 d loss in the absence, and aid loss in the presence, of the post pasteurization contamination. The KQ of milks stored at 12 °C was not significantly affected by the pasteurization temperature. Milks pasteurized at 78 °C tended to have a slightly better KQ than those pasteurized at 72 °C, especially at 7 °C. However, pasteurization at both 78 °C and 83 °C caused a reduction in cream rising and considerably increased the risk of cream plugging.
Effect of storage, light and homogenization on the colour of ultra heat treated and sterilized milk
Authors: Andrews Geoffrey R.
Published: June 2009

The rates of change in light reflectance and in CIELAB tri-stimulus colour values were compared for direct and indirect ultra heat treated (UHT) and sterilized milk in glass and polyethene bottles stored under different conditions. The rate of change of milk reflectance was higher at shorter wavelengths and the milk colour changed more rapidly at 30 and 37 °C than at room temperature. Sterilized milk in polyethene bottles was bleached when stored in an illuminated cabinet. The colour of skimmed milk changed more rapidly than that of whole milk. The rate of change in reflectance of direct UHT milk above 590 nm was found to be higher than in other milks. A statistical interaction was found between the fat content and the storage temperature for the CIELAB values. The homogenization pressure used in processing UHT milk samples did not affect the rate of change of the milk colour. The main implication of these findings may be that milk colour cannot be used to assess the heat treatment of a milk when the age or storage conditions of the milk are unknown.
Effects of variations in somatic cell count on the rennet coagulation properties of milk and on the yield, composition and quality of Cheddar cheese
Authors: Grandison Alistair S. , Ford Graeme D.
Published: June 2009

Cheddar cheeses were prepared from low somatic cell count (SCC) milks and from milks containing 10, 20 and 30% added high SCC milk to give modestly elevated SCC. Increased SCO in the milk were associated with a reduction in the coagulum strength and an increase in moisture content of the cheeses. Cheese texture was affected significantly as judged both by the findings of an assessment panel and by instrumental physical measurement. The panel scores for flavour were also slightly altered. It was concluded that even a small increase in SCC is detrimental to cheese composition and quality, although no significant effects on yield were detected. Relationships between cheese yield, composition and properties, coagulation properties and composition of the milk were also studied. Yield was related to the total solids and fat in the milk but not to the coagulation properties or the flavour or texture of the cheeses. Coagulum strength, cheese composition and cheese texture were strongly interrelated.
Increased milking vacuum in teatcups fitted with non-return valves
Authors: Andrews R. Jeffrey , Mein Graeme A. , Williams David M.
Published: June 2009

An experimental non-return valve was fitted in the short milk tube so that flow was permitted only in one direction, away from the teat. Liner movement was minimal because no air admission to the liner above the valve was provided. The extent of liner opening therefore depended on the amount of milk extracted within a pulsation cycle and on any air leakage past the liner mouthpiece. Milking experiments using four cows showed that the mean vacuum level in nominally open liners of valved teatcups during peak milk flow was 8·6 kPa higher than in conventional teatcups. Bench tests showed that the increase in liner vacuum (LV) depended on the nominal plant vacuum level, the pressure difference between initial LV and maximum pulsation chamber vacuum, the liner elasticity and mounting tension. The main source of energy available to raise LV above the nominal plant vacuum is the release of strain energy, stored within the liner during the collapse phase of each pulsation cycle.
Studies on the Morphology and Systematics of Plant and Soil Nematodes mainly from Andhra Pradesh. I. Tylenchoidea
Authors: Singh Sunita D.
Published: June 2009

Descriptions of four new tylenchs belonging to different genera are given : (1)Tylenchus (Tylenchus) holochmatusn.sp., (2)Tylenchorhynchus varicaudatusn.sp., (3)Trichotylenchus trilokiaen.sp., (4)Helicotylenchus pteracercusn.sp. The material of the first described species was collected in North India and that of the other new species in South India. Systematic features of new species are fully discussed and compared with those of the related forms.

Detailed descriptions are given ofTylenchorhynchus digitatusandPratylenchus indicusdescribed by Das (I960) from Hyderabad. The material was collected from type locality but from different hosts.Tylenchorhynchus curvusWilliams, 1960, is recorded from India.

Species reported as causing damage to economically important plants in Hyderabad are :Hoplolaimus seinhorstiLuc, 1958, parasitic in cauliflower;Pratylenchus thorneiSher and Allen, 1953, parasitic in maize andRotylenchulus reniformisLinford and Oliveira, 1940, parasitic in grape vines.
Composition and structure of helminth communities in eels Anguilla anguilla from Italian coastal lagoons
Authors: Kennedy C.R. , Di Cave D. , Berrilli F. , Orecchia P.
Published: June 2009

The composition and diversity of total and intestinal helminth component and infracommunities were determined in eels Anguilla anguilla from four shallow coastal lagoons near Rome. The lagoons differed principally in respect of their salinity. Only Lake Burano still received an input of freshwater, and both freshwater and marine helminth species were found in eels. In the other three lagoons all helminth species were marine or euryhaline and communities were dominated by digeneans. At component community level these three lagoons were far more similar to each other than to Lake Burano, but this distinction almost disappeared at infracommunity level. Species richness and diversity declined with increasing salinity at component community level but not at infracommunity level. Despite the changes and differences in helminth community composition, intestinal helminth infracommunity structure was very similar in all four lagoons and to that in eels from freshwater localities in Britain. The findings thus provide further and unexpected support for the view that some factor(s) other than supply side ones must be operating to produce the fundamental structural similarity in helminth communities in eels.