bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative micelle structure: II. Structure and composition of casein micelles in ovine and caprine milk as compared with those in bovine milk
Authors: Richardson B. C. , Creamer L. K. , Pearce K. N. , Munford R. E. 
Published: June 2009

SummaryThe casein micelles of sheep (Ovis aries), goat (Capra hircus) and cow (Bos taurus) milks have been examined by electron microscopy. The ovine micelles were smaller than bovine micelles, most being below 80 nm diam. The caprine micelles were either large (c. 200 nm diam.), easily sedimented and electron-dense, or small (below 80 nm) and similar to the ovine micelles. Examination of the micelles using the freeze-etch technique showed, however, that they were all composed of subunits of similar dimensions (10–15 nm diam.).Electrophoresis of the caseins showed that there were differences between them, with the caprine casein containing a smaller proportion of its protein in the more mobile components. The mineral contents of the milks were also different, but these were apparently related to the different pH and casein contents of the milks. It is likely that the diiferences in micelle size distribution are determined by the physical and chemical properties of the casein components.
Thermal conductivity of creams
Authors: Fernández-Martín F. , Montes F. 
Published: June 2009

SummaryThermal conductivities of creams of about 20, 30 and 40 % fat were measured at several temperatures between 5 and 75 °C. Because of the meagre data on cream, special attention was given to the prediction of conductivity using different mathematical models. An equation was derived for the thermal conductivity of cream as a function of temperature and volume fraction of the fat phase.
Effect of thiocyanate on mammary gland growth in rats
Authors: Pyska H. 
Published: June 2009

SummaryIn growing rats from 3 weeks to 3 months old, 0·1 % potassium thiocyanate (KSCN) decreased the plasma protein-bound iodine level by 47 % and the total DNA in the mammary gland by 11 %, but had no effect on the total KNA. Administration of thiocyanate in the form of 0·1, 0·3 and 0·5 % KSCN during pregnancy and 14 d of lactation lowered the protein-bound iodine level by 48–66 %, the total DNA by 11–47 % and the total RNA by 14–63 %, depending on the KSCN dosage. The 14-d-old litters of rats receiving thiocyanate weighed 4–41 % less than those in the control group.
Localization of glycosylated κ-casein in bovine casein micelles by lectin-labelled gold granules
Authors: Horisberger Marc , Vonlanthen Monique 
Published: June 2009

SummaryThe localization of glycosylated k-casein in isolated bovine casein micelles was investigated at the ultrastructural level with gold granules labelled with the Ricinus communis lectin specific for galactose. No evidence was obtained for the presence of glycosylated k-casein on the surface of glutaraldehyde-fixed micelles whether or not they had been treated with neuraminidase. Glycosylated k-casein was mainly located in the bridging network interconnecting the micelles and appeared to be loosely associated with the micelles. When thin sections of micelles were marked, no clear-cut evidence was observed for the presence of intramicellar glycosylated k-casein.
Preparation and properties of rennets from lamb's and kid's abomasa
Authors: Anifantakis Emmanuel , Green Margaret L. 
Published: June 2009

SummaryLamb and kid rennets were prepared by extraction of dried abomasa with 6% (w/v) NaCl-2% (w/v) H3BO3 and activation of the proenzymes at pH 2·0. Each gave one zone of precipitation on casein-agar gel diffusion, enabling them to be differentiated from calf rennet and pig pepsin. After agarose gel electrophoresis, the proteinase activity of lamb rennet occurred in chymosin and pepsin bands only, whereas kid rennet contained an additional proteinase of intermediate mobility. Relative to their milk-clotting activities, lamb and kid rennets contained less pepsin and were less proteolytic on both haemoglobin at pH 1·8 and casein at pH 5·3 than calf rennet. The milk-clotting activities of lamb and kid rennets increased less with decrease in pH and were more stable to storage at both the pH value of maximum stability and lower pH values than that of calf rennet. Neither cathepsin activity nor lipolytic activity on milk fat was detected in any of the 3 rennets, but lamb rennet caused slight hydrolysis of tributyrin.
Multiple modification/restriction systems in lactic streptococci and their significance in defining a phage-typing system
Authors: Boussemaer Jean Pierre , Schrauwen Peter P. , Sourrouille Jean Louis , Guy Philippe 
Published: June 2009

SummaryThe reactions between 6 strains of mesophilic lactic streptococci and their respective phages were studied quantitatively. Of 30 nonhomologous reactions, the bacteria were fully sensitive in 4 and restricted the phages in 23. A mathematical model was developed that was used to identify at least 4 and probably 5 modification restriction (M/R) systems of which up to 3 were found in the same strain. The model was based on 24 measured values and correctly predicted the values of 5 others. One of the 3 negative reactions was shown to be due to a restriction beyond the limit of detection, a second was due to lysogeny or lack of adsorption, but was shown to have the predicted value when the homologous phage was modified on the host of the challenging phage. In the last reaction a measurable restriction was predicted, but could not be proven by means of a modified phage. These results suggest M/R to be one of the main defenses of the lactic streptococci against their phages. They explain why host range is not a useful criterion in the classification of phages and suggest a rational approach to the definition of a starter rotation.
Effect of teat skin disinfection on the rate of infection and interval to infection in cows exposed to high levels of Staphylococcus aureus
Authors: Sheldrake Richard F. , Hoare Roderic J. T. 
Published: June 2009

SummaryAll teats of a herd of lactating cows were contaminated after each milking with Staphylococcus aureus. Two teats of each cow were subsequently dipped in an iodine solution, while the remaining 2 teats were not dipped. For cows with a single infection the interval to infection in dipped and undipped quarters was 64 and 60 d respectively, while for the first infected quarter of cows with multiple infections the interval to infection in dipped and undipped quarters was 50 and 39 d respectively. For the second quarter infected in cows with multiple infections, the period between the first and second infection was 21 and 12 d for dipped and undipped quarters respectively. It is suggested that while teat skin disinfection was effective in reducing the rate of new infection, it had little effect on the process of infection in those quarters becoming infected. The occurrence of an infection in one quarter doubled the rate of infection in the other quarters.
Effect of milk concentration on the nature of curd formed during renneting – a theoretical discussion
Authors: Dalgleish Douglas G. 
Published: June 2009

SummaryUse of a model of the renneting reaction has led to the definition of the amounts of soluble casein present in milks of different concentrations, at the time of clotting. It is shown that, although the clotting time (RCT) is relatively little affected by the concentration of milk by ultrafiltration, the proportion of casein which is soluble at the RCT is highly dependent upon the concentrations of both milk and rennet. This may affect the structure of the curd.
A differential scanning calorimetric study of the thermal behaviour of bovine β-lactoglobulin at temperatures up to 160 °C
Authors: de Wit Jacob N. , Klarenbeek Gijsbert 
Published: June 2009

SummaryThe thermal behaviour of β-lactoglobulin was studied by differential scanning calorimetry (DSC) in the temperature range 40–160 °C. The DSC curves revealed, in addition to the usually observed denaturation peak near 80 °C, a distinct endothermal peak between 130 and 150 °C. When the pH was increased from 6·5, the area under the peak near 80 °C (denaturation heat) decreased significantly, whereas the peak area near 140 °C increased. The temperature of maximum heat absorption in the peaks near both 80 and 140 °C gradually increased as the pH decreased. Addition of sugars and variation of the heating rate both caused a temperature shift of the endothermal heat effect at 140 °C, similar to that at 80 °C. No peak near 140 °C was observed when β-mercapto-ethanol was added to the β-lactoglobulin solution before scanning. The origin and nature of the high temperature denaturation peak is discussed in terms of conformational changes of the protein.
Development of structure and texture in Cheddar cheese
Authors: Green Margaret L. , Turvey Alan , Hobbs David G. 
Published: June 2009

SummarySamples of curd and cheese, taken throughout cheese-making with milks concentrated to different extents, were examined by light microscopy and by scanning and transmission electron microscopy. The mature cheeses were analysed for textural parameters by instrumental and sensory means. The protein was packed in larger, more compact areas and the fat was more segregated in the curds and cheeses from the more concentrated milks. The protein network increased in coarseness in proportion to the concentration factor of the milk, the relative differences being the same throughout cheese-making into the mature cheese. Thus, the basic structure of the protein network was laid down during the curd firming process and was not fundamentally altered later in cheese-making. The fat/protein interfaeial area in the cheese and the changes in structure during maturation decreased as the concentration factor of the milk increased. The instrumental firmness, cohesiveness and force and compression required to cause fracture, and the sensory firmness, crumbliness, granularity and dryness of the cheese all increased as the concentration factor of the milk increased. The adhesiveness declined and there was little change in elasticity, with increase in milk concentration factor. The textural differences were related to the smaller fat content, lower level of proteolysis, stronger links in the protein matrix and reduced capacity of the fat and protein phases to move relative to each other in the cheeses from the more concentrated milks.
Effect of intravenous supplements of L-methionine on milk yield and composition in cows given silage-cereal diets
Authors: Chamberlain David G. , Thomas Phillip C. 
Published: June 2009

SUMMARYEight cows in mid lactation and receiving a diet of perennial ryegrass silage and barley (70:30 on a DM basis) were given intravenous supplements of l-methionine (8 g/d). The methionine treatment had no significant effect on milk yield, protein content or lactose content, but increased milk fat content and yield by approximately 10% (P < 0·05).
Effect of oxygen on the keeping quality of milk: II. Effect of available oxygen on bacterial spoilage and oxygen uptake
Authors: Schröder Monika J. A. 
Published: June 2009

SUMMARYThe effect of limiting the amount of O2 present in commercially pasteurized milk on bacterial growth and on the keeping quality of the milk was investigated. No increase in bacterial count of laboratory pasteurized milk during storage for 9 d at 5 °C was observed and O2 consumption due to bacterial activity was low. In commercial pasteurized milk containing post-pasteurization contamination (PPC) growth of strict aerobes was encouraged by high O2 content while that of coliforms was less dependent on O2 level. The amounts of headspace (HS) O2 consumed in milk with PPC growth were large. Reducing the dissolved O2 content of commercial pasteurized milk stored in O2-impermeable containers without HS had little effect on bacterial activity and shelf-life.
Factors affecting the ethanol stability of bovine milk: V. Effects of chemical modification of milk protein
Authors: Horne David S. , Parker Thomas G. 
Published: June 2009

SUMMARYThe effect of chemical modification of milk protein on the ethanol (EtOH) stability of skim-milk has been investigated. Modification of lysine residues by reaction with anhydrides increased the EtOH stability whereas amidation of carboxyl groups destabilized the milk. Lysine modification also counteracted destabilization induced by Ca2+ addition. By using multiple linear regression techniques these latter effects can be accounted for in terms of the changes they bring about in micellar charge. These results provide a further verification and an extension of the previously proposed mechanism for EtOH-induced coagulation of skim-milk.
Some factors affecting the post clotting development of coagulum strength in renneted milk
Authors: Storry John E. , Ford Graeme D. 
Published: June 2009

SUMMARYEffects of pH, added Ca, rennet concentration, temperature, concentration and dilution of milk, on rennet clotting and coagulum development have been investigated. Rennet clotting time (RCT) was decreased by reduced pH, by increased temperature and by increased concentrations of rennet or added Ca. Only extremes of concentration or dilution of milk increased RCT. Strength of milk coagulum at 1 h after RCT was increased by reduction in pH and by increased concentrations of added Ca. Increased temperatures decreased coagulum strength whereas increased rennet concentrations had little effect. A curvilinear relationship between total casein concentration and coagulum strength was found for Friesian and Jersey milks. Two phases of coagulum development after clotting were observed. Changes in pH particularly affected the first phase whereas changes in temperature particularly affected the second. Effects of rennet, casein and Ca were similar for both phases.
Detection by Warburg manometry of compounds stimulatory to lactic acid bacteria
Authors: Webb Leslie E. 
Published: June 2009

SUMMARYThe effect of aqueous algal extract, yeast extract casein peptone and meat peptone on acid production by 4 strains of lactic acid bacteria was tested manometrically using a milk–bicarbonate medium. A strain-dependent stimulation of the bacteria was detected after 4 h incubation. After fractionation of an aqueous extract of the green algaScenedesmus obliquuson a Sephadex G25 column, 2 fractions with stimulatory activity were found usingStreptococcus lactisas the test organism. One of the peaks of activity, confined to shortening of the lag phase, was due to hypoxanthine which, however, had only a slight stimulatory effect in conventional milk souring tests. The manometric method provides a sensitive and rapid test for detecting compounds with biological activity in µg amounts, but it should be accompanied by milk souring tests for interpretation of the type of stimulation involved.
Effect of teat washing on the bacteriological contamination of milk from cows kept under various housing conditions
Authors: McKinnon Charles H. , Fulford Rosemary J. , Cousins Christina M. 
Published: June 2009

SummaryThe effect of different methods of teat washing on bacterial contamination and sediment levels of the milk of cows kept under 3 housing conditions was studied. By use of an in line milk sampler and steam sterilized clusters the bacterial contamination from the teats after udder preparation was determined directly.The results show that, even under the same housing conditions and teat washing treatments, considerable variation in bacterial counts and sediment level occurred. Overall, washing with hypochlorite (600 mg/1 available Cl) and drying with a paper towel gave total counts that were significantly lower than were obtained with the other 4 treatments. The aerobic spore count, in which thermoduric flora predominated, was greatly reduced by drying the teats, but the inclusion of hypochlorite in the wash water had little effect. Coliform contamination was very low (∼ 1/ml) even where the cows' teats were heavily soiled and were not washed.The sediment levels in the milk again showed wide variation and occasional high values (3 mg/l) were recorded for washed cows. In marked contrast to its effect on the bacteriological results, drying had little effect on reducing the sediment.
Relationship between the level of N-acetyl-β-D-glucosaminidase (NAGase) in bovine milk and the presence of mastitis pathogens
Authors: Kitchen Barry J. , Kwee W. Seng , Middleton Gordon , Andrews R. Jeffrey 
Published: June 2009

SummaryChanges in the level of the tissue damage marker enzyme, N-acetyl-β-D-glucosaminidase (NAGase) in quarter fore milks were found to be related to the presence and types of pathogenic bacteria present and to somatic cell counts (SCC). Minor pathogens (coagulase-negative staphylococci, Corynebacterium bovis) elicited a mild SCC increase (from a mean of 243 × 103/ml in healthy quarters to 504 × 103/ml in infected quarters) with marginal tissue damage (mean NAGase activity increased from 21 in healthy quarters to 28 in infected quarters). Major pathogens (i.e. Staphylococcus aureus, Streptococcus agalactiae, Str. dysgalactiae and Str. uberis) caused more severe tissue damage (mean NAGase of 48) and SCC increases (mean, 2803 × 103/ml). The NAGase test could also be used effectively on composite milk samples where regular monthly NAGase analysis was able to identify correctly 74% of animals having infected quarters. The possibility of combining SCC and NAGase data in order to give a more definite diagnosis of bovine mastitis is discussed.
Milk yield in rats in relation to activity and size of the mammary secretory cell population
Authors: Knight Christopher H. , Docherty Ann H. , Peaker Malcolm 
Published: June 2009

SummaryAn attempt was made to partition changes in milk yield during lactation in the rat between changes in the size of the secretory cell population and changes in cellular activity. Groups of rats were studied on d 2, 7, 14, 21 and 28 of lactation. Milk yield increased between d 2 and 7, less markedly between d 7 and 14 and decreased between d 14 and 21. Milk secretion had apparently ceased on d 28. Total mammary DNA (DNAt) and RNA (RNAt) increased from d 2 to 14. It is concluded that of the increase in milk yield between d 2 and 14, an increase in cell population accounted for 75% and an increase in cellular activity for 25%. A decrease in activity appeared to be entirely responsible for the decrease in yield between d 14 and 21.
Isolation of bovine milk fat globule membrane material from cream without prior removal of caseins and whey proteins
Authors: McPherson Avis V. , Dash Mary C. , Kitchen Barry J. 
Published: June 2009

SummaryBovine milk fat globule membrane (MFGM) material was isolated from cream by a new technique which did not involve removal of caseins and whey proteins before destabilization of the fat globules. These components were removed by centrifugation of the membrane material extract through a concentrated sucrose solution (52·5% (w/v) sucrose in 10 mM-Tris HCl buffer, pH 7·5). Membranes collected at the sample–sucrose interface, while whey proteins remained in the supernatant and caseins migrated into the concentrated sucrose solution. The yield of membrane material using this procedure was 25% less than that from conventional methods. This reduced yield was due mainly to lower levels of lipid material, in particular triglyceride. Electrophoretic analysis showed that the polypeptide composition of ‘unwashed’ membrane material was similar to that of conventionally prepared MFGM. This method is particularly suitable for the isolation of membrane material from milks and dairy products in which the fat globule stability is reduced or unknown.
Some observations on the behaviour of dairy cattle using cow-activated out-of-parlour concentrate dispensers
Authors: Little William , Harrison Roger D. 
Published: June 2009

SummaryHoused dairy heifers (62 cows) were fed concentrates exclusively through variable-time, out-of-parlour dispensers. They were observed to visit the dispensers on average 20·4 times/d but significantly less frequently (13·9 times/d) shortly after calving. The dispensers were occupied for 25·8% of the night (22.00–06.00 h) compared with 30·4% of the day (06.00–22.00 h). This difference was small but significant, whereas the differences between the proportion of night and day spent standing (32·5 v. 66·2%) or eating silage (4·8 v. 24·7%) were noticeably greater. In a herd of ∼ 80 cows in which the daily average number of visits to the dispenser was 20·5/cow there was a significant decrease in the number of visits/d (y) with increasing time after calving (x) where y = 23·4–0·030x (r = 0·88). Some cows repeatedly visited the dispensers more frequently than others (range 13·2–34·9±5·3 visits/d, giving a repeatability of 0·58). Cows in a grazing herd (∼ 60) visited the dispensers on average 14·6 times/d during an average 3·6 visits to a cubicle house to which they had continuous access. The number of visits to the dispensers (y) again decreased with increasing time after calving (x) where y = 22·7–0·072x (r = 0·45). The average time spent in the cubicle house (z) also decreased as the days after calving (x) increased (z = 8·4 – 0073x+0·000203x2, r =–0·66). All cows, however, stayed in the cubicle house during periods of heavy rainfall.
Some attributes of twin-bearing British Friesian and Canadian Holstein cows recorded in England and Wales
Authors: Wood Peter D. P. 
Published: June 2009

SummaryThe production of milk, fat and protein of 37216 mothers of twins was compared with that of 1691 127 mothers of single calves of Black and White breeds of cattle recorded in England and Wales. At every parity, the mothers of twins produced more milk, fat and protein than the mothers of single calves. The proportion of twin-bearing cows retained increased with parity, from 0·67% at first calving to ∼ 4·0% at the tenth or eleventh calving. More mothers of twins achieved 305 d of lactation subsequently than mothers of single calves, although their inter-calving intervals were not generally longer.
Effects of κ-casein genetic variants and lactation number on the renneting properties of individual milks
Authors: Schaar Johan 
Published: June 2009

SummaryThe effects of κ-casein genetic variants, lactation number, pH and casein content on the renneting properties of individual milks were studied. Rennet coagulation time (RCT) and curd firmness were determined with the aid of a lactodynamograph and the results statistically analysed. Renneting properties were strongly related to κ-casein variants and lactation number, with κ-casein B and higher lactation numbers giving shorter RCT and increased curd firmness, the effects on curd firmness being more pronounced. The effect of κ-casein variant on RCT could be eliminated by reducing pH and adding CaCl2 to the milk samples. The effect on curd firmness was not altered by this treatment, however. The results show that the renneting properties of individual milks are to a considerable degree genetically controlled.