bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sources ofStreptococcus uberisin the dairy herd: I. Isolation from bovine faces and from straw bedding of cattle
Authors: Bramley A. John 
Published: June 2009

SUMMARYDuring an outbreak of mastitis due toStreptococcus uberisthe organism was frequently isolated from samples of straw bedding used by the cattle. More than one millionStr. uberis/g straw were isolated from 36% of samples. The organism was also recovered from 34% of samples of bovine faeces, but usually in low numbers. An examination of straw samples collected from cattle yards on 32 other dairy farms demonstrated that this was not an isolated occurrence sinceStr. uberiswas found in 24% of samples from 56% of the herds. No correlation was found between counts ofStr. uberisand coliforms. The significance of these observations is discussed.
Effect of oxygen on the keeping quality of milk: I. Oxidized flavour development and oxygen uptake in milk in relation to oxygen availability
Authors: Schröder Monika J. A. 
Published: June 2009

SUMMARYOxidized flavour developed in whole milk only through the catalytic effect of either Cu or light. The O2 requirement for the 2 processes differed as did the characteristics of the off-flavours produced. Cu-induced oxidized flavour was described as ‘cardboardy’ and light-induced oxidized flavour was ‘painty’. Light-induced oxidized flavour increased in intensity with O2 loss, and could be prevented in stored milk by restricting access of O2. In UHT milk with a dissolved O2 content of 6·6 mg/1, and in the absence of access of further O2, light-induced oxidized flavour did not develop; similarly, O2 uptake of 7·5 mg/1 in in-bottle sterilized milk exposed to fluorescent light did not result in flavour formation. When light-induced oxidized flavour developed consistently in whole milk none developed in skim-milk, indicating the lipid source of the flavour. In contrast Cu-induced oxidized flavour development was not associated with high O2 uptake. Although nearly complete deoxygenation of whole pasteurized milk contaminated with Cu prevented the formation of the flavour, moderate deoxygenation resulted in even greater flavour intensity than non-deoxygenation. The 2 oxidized flavours also differed in relation to ascorbic acid (AA) oxidation. Light-induced oxidized flavour developed only after AA oxidation was complete, whereas Cu-induced flavour developed with AA still present. AA oxidation was greatly accelerated through the effects of both Cu and light. In milk free from Cu contamination and protected from light, after AA oxidation (plus SH group oxidation in the case of UHT milk) was complete, no further loss of O2 occurred, even during prolonged storage at 5°C, despite the presence of large O2 concentrations. However, at 20°C, a small consumption of O2 was measured, and this was associated with stale flavour.
Effect of psychrotrophic post-pasteurization contamination on the keeping quality at 11 and 5 °C of HTST-pasteurized milk in the UK
Authors: Schröder Monika J. A. , Cousins Christina M. , McKinnon Charles H. 
Published: June 2009

SummaryThe keeping quality of commercial HTST-pasteurized milk and laboratory pasteurized milk from a common bulk raw supply has been investigated for 5 dairies. Spoilage occurred at levels of total bacterial counts around 107 colony forming units/ml, but with a slightly higher off-flavour threshold for the commercial milks than the laboratory pasteurized milks. The predominant microflora at spoilage and the type of off-flavour produced differed between the 2 types of milk. Raising the storage temperature from 5 to 11 °C caused a slight shift in the spoilage microflora and led to an average reduction in the shelf life of the laboratory pasteurized milk from 28 to 6 d and of the commercial pasteurized milk from 13 to 5 d. Changes in the level of post-pasteurization contamination (PPC) were reflected in changes in keeping quality, particularly at 5 °C. However, the greatest improvements were found in the absence of PPC.
A survey of sources of heat-resistant bacteria in milk with particular reference to psychrotrophic spore-forming bacteria
Authors: McKinnon Charles H. , Pettipher Graham L. 
Published: June 2009

SummarySamples of winter bedding and summer pasture, rinses of teats and milking equipment, and milk samples from bulk tanks from 4 farms were analysed bacteriologically for total count (TC), thermoduric count, total spore count (TSC) and psychrotrophic spore count (PSC).In bedding and pasture samples the TSC comprised the main component of the thermoduric flora but was less than 0·1 % of the TC. The PSC formed ∼ 1 % of the TSC in winter bedding and ∼23 % of the TSC in pasture. For pasture, the PSC: TSC ratio was highest for the upper layer of soil and lower for the grass and deeper layer of soil. The TSC formed 5% of the thermoduric flora in rinses of milking equipment and only a very low PSC was obtained. The TSC of farm bulk tank milks was higher in the winter than the summer but the PSC was similar in both seasons. This was due to an increase of ∼9 times in the PSC:TSC ratio for milks in summer compared with winter. The PSC in raw and commercially pasteurized milks from a local creamery showed a similar seasonal trend.
Relation between micelle size and formation of soluble casein on heating concentrated milk
Authors: Aoki Takayoshi , Kako Yoshitaka 
Published: June 2009

SummaryIn order to examine the influence of micelle size on the formation of soluble casein brought about by heating concentrated milk, casein micelles were separated into 3 fractions by differential centrifugation. The micelles were dispersed in the ultrafiltrate of skim-milk and the preparations were concentrated to 1/2·5 of the original volume. When the concentrated milk samples were heated at 135–140 °C, a larger amount of soluble casein was formed from smaller micelles than from larger micelles. Only a slight effect on the formation of soluble casein on heating was observed when colloidal calcium phosphate (CCP) was removed from the large micelles to a level lower than that associated with the small micelles or when the CCP in the small micelles was increased to a level higher than that of the large micelles. The soluble caseins formed on heating from different sizes of micelles were similar in composition. The fact that the formation of soluble casein on heating was affected by micelle size may be ascribed to variation in the κ-casein content of micelles rather than to variation in CCP content.
Proteolysis of caseins and the proteose-peptone fraction of bovine milk
Authors: Andrews Anthony T. , Alichanidis Efstathios 
Published: June 2009

SummaryThe proteolysis of highly purified samples of αs1-, αs2-, β-and κ-caseins by porcine plasmin and by bovine plasminogen with urokinase has been examined principally by gel electrophoresis. The resulting peptide band patterns were compared with those of total proteose-peptone (TPP) samples prepared from fresh and stored raw and pasteurized milk, and also with those obtained during the natural course of proteolysis by indigenous enzymes in milk during storage. TPP was found to contain at least 38 components detectable by a single electrophoresis run. Apart from residual traces of whey proteins and intact caseins nearly all of these components were fragments of caseins produced by indigenous plasmin, with products from the breakdown of αs1- and β-casein predominating. Over 90 % of TPP has been accounted for in this way. A fragment consisting of residues 29–105 of β-casein was isolated and characterized from both stored milk and from plasmin digests of β-casein. This fragment was a relatively major product of the natural proteolysis occurring during storage of milk, but contrary to a report in the literature it was not the same as proteose-peptone component 8-slow. Since many of the components of TPP resulted from proteolysis, the composition of TPP was found to vary according to the time and temperature of storage of the milk from which it was prepared. Thus, while the proteose-peptone fraction of milk can easily be defined operationally it cannot be rigorously defined in terms of its composition unless the history of the milk is also defined.
Lipid composition of milks from cows with experimentally induced mastitis
Authors: Needs Eric C. , Anderson Malcolm 
Published: June 2009

SummaryChanges in milk lipid composition were measured during the course of mastitis infections induced in cows by infusion of eitherEscherichia coliendotoxin orStreptococcus agalactiaeinto 2 quarters of the udder; untreated quarters were used as controls. Experiments were divided into 3 distinct phases: a pre infusion period during which several samples were collected before infusion; a post infusion period following infusion and corresponding to the occurrence of elevated cell counts in milk from infused quarters; a recovery period followed after a short pause and represented the return of the cell count in milk from infused quarters to the level in the corresponding controls.Milk total fatty acid composition was unaffected by the infusion. Free fatty acid (FFA) composition did, however, undergo some alteration. There was a significant increase in long-chain saturated acids in milk from infused quarters relative to the corresponding controls during the post infusion period. FFA concentration (mequiv./100 g fat) also increased significantly during this period although the net increase was only slight. Phospholipid and cholesterol concentrations were significantly higher post infusion in milk of infused quarters.The results suggest that changes in concentration and composition of those milk constituents synthesized and secreted by the mammary epithelium occur after secretion in the alveolar lumen and milk ducts.
A procedure for the complete clarification of milk of various species and its suitability for use with colorimetric measurements
Authors: Owen A. Jane , Andrews Anthony T. 
Published: June 2009

SummaryBovine, caprine, ovine and human milks have been clarified by addition of Triton X-100 and EDTA followed by a short incubation. Generally, addition of 4·2% Triton X–100 and 5·4% EDTA was sufficient and with skim-milk samples no dilution was necessary. With whole milks some dilution and greater amounts of Triton X-100 or longer incubation times or higher temperatures were required. These factors were interrelated to some extent and the optimum conditions will be determined by convenience and any particular requirements of the experiment. The attainment of optically transparent milk samples greatly facilitates colorimetric measurements; as examples we have shown that total protein may be estimated by the biuret reaction, NH2groups measured with 2,4,6-trinitrobenzene sulphonic acid and SH groups by reaction with 5, 5′-dithiobis(2-nitrobenzoic acid). Acid phosphatase activity in bovine milk was followed colorimetrically by reaction withp-nitrophenyl phosphate to demonstrate the suitability of the clarification procedure in the measurement of enzymic reactions.
Observations onCorynebacterium bovisinfection of the bovine mammary gland: I. Natural infection
Authors: Honkanen-Buzalski Tuula , Griffin Tony K. , Dodd Frank H. 
Published: June 2009

SummaryData from experiments in 55 commercial herds have been examined to study the patterns ofCorynebacterium bovisinfection. Such infections are most common in herds that are not subjected to regular control methods but their commercial significance appears to be small. In herds using teat disinfection and dry cow therapy levels of infection with this organism are low. There is no evidence from these data to suggest thatC. bovisinfections protect the udder against invasion by a major pathogen. On the contrary these infections do not persist when major pathogens invade.
Influence of 2-mercaptoethanol on heat stability of concentrated whey-protein-free milk and formation of soluble casein
Authors: Aoki Takayoshi , Kako Yoshitaka 
Published: June 2009

SummaryThe heat coagulation time (HCT) of concentrated whey-protein-free (WPF) milk measured at 120 and 130 °C was reduced toby addition of 5–20 mM-2-mercaptoethanol (ME). However, although the amount of soluble casein formed on heating was doubled by addition of ME, the shape of the HCT–pH profile was affected only slightly. The proportion of κ-casein in the soluble casein from heated concentrated WPF milk containing ME was very high, though it was somewhat lower than that of the soluble casein from heated concentrated WPF milk containing no ME. No solubilization of colloidal Ca phosphate was observed in either unheated or heated concentrated WPF milk on addition of ME. These facts suggest that ME probably promotes the formation of soluble casein with release of κ-casein from micelles on heating, thus destabilizing the casein micelles.
Effect of residues of five disinfectants in milk on acid production by strains of lactic starters used for Cheddar cheesemaking and on organoleptic properties of the cheese
Authors: Dunsmore David G. , Makin Debbie , Arkins Richard 
Published: June 2009

SUMMARYThe inhibitory effect of five disinfectants on acid production byStreptococcus lactisandStr. cremorisCheddar cheese starters was compared using two techniques, a laboratory scale fermentation tube test, and pilot scale cheese manufacture. Threshold inhibition concentrations (partial, total) of disinfectants (mg/1) on acid production observed in the fermentation tube were: peracetic acid/H2O2(0–5, > 600) iodophor (75–220, > 400), quaternary ammonium compound (QAC), (20–30, > 200), acidic anionic (60–120, 600–1200), and Na hypochlorite (400–1000, > 1000). Threshold inhibition concentrations (partial, total) observed in the cheese vat were (mg/I); peracetic acid/H2O2(0–5, 5–35), iodophor (15–30, 75–200), QAC (10–20, > 200), acidicanionic(30–120, > 600), and Na hypochlorite (35–400, > 400). Flavour threshold concentrations in the cheese at 4 weeks were (mg/l): peracetic acid/H2O25, iodophor 8, QAC 20, acidic anionic 12, and hypochlorite 50. It is concluded that problems in cheese manufacture are unlikely to occur with hypochlorites, iodophors, and acidic anionics, but that care should be taken when using QAC and peracetic acid as sanitizers. A correlation coefficient of 0918 was computed between the two methods of determining partial acid inhibition (P< 0·005).
Effect of ACTH and oxytocin treatment on lactoferrin and citrate in cows' milk
Authors: Thomas Alex S. A. , Fell Lloyd R. 
Published: June 2009

SUMMARYSix dairy cows were treated before milkings with either oxytocin (Pitocin, 20 i.u.) or ACTH (Synacthen, 150 i.u.), principally to determine their effect on the ratio of citrate:lactoferrin concentrations in the milk. With ACTH treatment, after 3 d milk yield and citrate concentration decreased significantly, lactoferrin and bovine serum albumin (BSA) concentrations increased significantly. Somatic cell counts (SCC) increased temporarily in the milk of three of the cows which previously had > 100000 cells/ml. Lactoferrin yield remained fairly constant but citrate yield was significantly reduced. The citrate: lactoferrin molar ratio decreased from 1373 to 606. With oxytocin treatment, after 4 d milk yield first increased and then significantly decreased, citrate concentration decreased significantly while there were no significant changes in lactoferrin or BSA concentration or in the yield of any other milk constituents. The citrate: lactoferrin molar ratio decreased from 1621 to 1301. There were no significant changes in SCC either during treatment or 4 d after treatment but there was a significant rise at 16 d after treatment. It was concluded that in lactating cows both hormones affected citrate and lactoferrin concentrations in the direction that would improve the antibacterial properties of milk, but that this was accompanied by adverse effects on milk secretion. The extent of the change was not sufficient to be likely to produce inhibition of coliform bacteria.
Epimerization of lactose to free lactulose in heated model milk solutions
Authors: Greig Barry D. , Payne Gerald A. 
Published: June 2009

SUMMARYThe kinetics of the epimerization of lactose to lactulose were determined for two ‘model milk’ solutions, one containing lactose and the other lactose and lysine. The lysine was added to lactose to determine whether amino groups of proteins act as base catalysts promoting the production of free lactulose. The presence of lysine actually reduced the rate of production of free lactulose, presumably by the formation of amino-sugar complexes. The rate of production of free lactulose over the range of processing conditions was shown to be first order for both systems. Thermal effects on lactose were shown to be complex. The epimerization of lactose to lactulose was reversible and both sugars were thermally decomposed to their monosaccharides. The difference in the rate of production of free lactulose between the lactose, and the lactose and lysine solutions was also observed in processed milk and its ultrafiltrate (protein free).
Methods for making kefir and fermented milks based on kefir
Authors: Marshall Valerie M. , Cole Wendy M. 
Published: June 2009

SUMMARYFlavour, aroma and appearance of milks fermented with commercially available kefir grains were compared with similar characteristics of heat treated (90 ΰC/30 min) milks that had been fermented with aroma producing starters in addition to the kefir grains. The starters used were either a mixture ofStreptococcus lactissubsp.diacetilactisandLeuconostoc cremoris(lactic culture) or ofStr. thermophilusandLactobacillus bulgaricus(yogurt culture).Two methods of fermentation were investigated involving removal of the grains followed by (i) a second fermentation of the kefir with the aroma-producing organisms and (ii) combining the kefir with aroma-producing organisms for use as a starter to ferment a further sample of heat-treated milk. Products were assessed by a taste panel and marked for acceptability. Addition of lactic or yogurt cultures resulted in products with increased mean scores for aroma and more acceptable flavours.
Short-term associations between disease and milk yield of dairy cows
Authors: Lucey Stephen , Rowlands G. John , Russell Alexander M. 
Published: June 2009

SUMMARYShort-term associations between disease and milk yield were studied in 1594 lactations occurring between 1977 and 1982 in 732 Friesian, Ayrshire and Holstein crossbred cows. Statistically significant differences in milk yield between one week before and one week after clinical diagnosis were observed for ketosis (5·l kg/d), hypomagnesaemia (4·1 kg/d), mastitis occurring after peak yield (2·1 kg/d) and lameness (1·1 kg/d). Milk yield declined for as much as 2–4 weeks before diagnosis of disease, and total losses in milk yield associated with ketosis or hypomagnesaemia were estimated to be 60–70 kg. No significant differences were found for endometritis or for mastitis when it occurred before peak yield. Milk yield was suppressed for about 4 weeks after calvings with retained placenta, but there were no corresponding effects of dystocia or hypocalcaemia on milk yield. It is suggested that if automatic daily milk recording is available it may be possible to detect deviations from normal, and hence detect subclinical disease 2 or more weeks before its clinical appearance.
Separation of casein aggregates cross-linked by colloidal calcium phosphate from bovine casein micelles by high performance gel chromatography in the presence of urea
Authors: Aoki Takayoshi , Kako Yoshitaka , Imamura Tsuneaki 
Published: June 2009

SUMMARYHigh performance gel chromatography of the casein micelles disaggregated by 6 m-urea was carried out on a TSK-GEL G4000SW column using 6 M-urea synthetic milk serum as the effluent. The eluate was divided into two fractions. Fast eluted fraction 1 decreased from 67·5 to 57·3% on reduction of casein micelles and was not observed in reduced colloidal phosphate-free casein micelles. Fraction 1 from reduced casein micelles contained 1·7 times as much Ca and Pibound to casein as did whole casein micelles, while fraction 2 essentially contained only bound Ca. These facts indicated that fraction 1 of reduced casein micelles consisted of the casein aggregates cross-linked by colloidal Ca phosphate (CCP). Polyacrylamide-gel electrophoresis showed that fraction 1 of reduced casein micelles contained more αs1- and αs2-caseins and less β-casein than whole micellar casein. No κ-casein was detected in fraction 1 of reduced casein micelles. It is suggested that the ester phosphate groups of casein are the sites for interaction with CCP.
Development of an objective method for assessing the mechanical strength of casein curd
Authors: Jablonka Mark S. , Munro Peter A. 
Published: June 2009

SUMMARYAS the break-up of weak curd during processing leads to fines losses, the mechanical strength of acid casein curd is important. When different techniques were investigated to evaluate objectively the strength of acid casein curd a plate extrusion method was found to require the least preparation of the curd and to give rapid and reproducible results. The optimum condition for mechanical testing of samples was after acidulation or after cooling for 2h at 25 °C.
Effect of precipitation temperature and pH on the mechanical strength of batch precipitated acid casein curd
Authors: Jablonka Mark S. , Murno Peter A. 
Published: June 2009

SUMMARYThe precipitation stage in acid casein manufacture controls the initial strength of the casein curd, which is an important factor in determining fines losses during processing. A plate extrusion method was used to determine the mechanical strength of casein curd, precipitated batchwise at temperatures from 25 to 53 °C over a pH range of 3·9 to 5·1. Curd strength was determined either immediately after acidulation or after cooling for 2 h at 25 °C. Curd was stronger immediately after acidulation than after cooling and increased in strength as precipitation temperature and pH were increased. Curd precipitated at high temperature and high pH was mechanically strong, had a large particle size, and had high total solids and Ca contents. The relationship between these curd properties is discussed, and it is concluded that Ca retention at high precipitation temperature and pH is largely responsible for the characteristic curd properties under these precipitation conditions.
Effects of iodate, hydrogen peroxide and dichromate on the denaturation of whey proteins in heated milk
Authors: Marshall Richard J. 
Published: June 2009

SUMMARYThe effect of heating raw milk at 75 °C for 30 min and at 95 °C for 15 s in the presence of varying concentrations of three oxidizing agents on the denaturation of total and individual whey proteins was measured. At 75 °C, ±-lactalbumin could be protected against denaturation by both iodate and H202 and ²-Lactoglobulins A and B by H202 and dichromate. However, at concentrations above ∼ 15 MM, the oxidizing agents tended to increase denaturation. At 95 °C, where the extent of whey protein denaturation was much reduced in the absence of oxidizing agents, little or no protective effect was observed. It is suggested that H202 may prove a suitable alternative to iodate in reducing deposits in ultra high temperature plants.