bluuebunny/crossref_metadata_2025 huggingface dataset:
229. Bacteriological testing of butter. New and simplified routine methods
Authors: Moir G. M. , Russell R. R.
Published: June 2009

Simple and rapid methods have been devised which utilize the minimum of apparatus and material for the routine bacteriological testing of butter. These involve the preparation of microplate cultures to obtain counts of total bacteria, “heat-resistant” bacteria, lipolytic organisms, yeasts, moulds; Grimes's method as a measure of the coliform content is also used.

The method for counting colonies of lipolytic bacteria is based upon their ability to produce round each colony a halo of white solid fatty acids in place of the clear glistening fat globules.

The new methods have been exhaustively compared with those hitherto accepted, and have been found to give satisfactory and reliable results.

A variety of comparisons has been carried out to improve still further the methods in use and to provide additional information about the nature of the bacteria contamination present in the butter. The roll-tube method seems preferable to the microplate for mould counts, and is quite suitable for yeast counts.

The results obtained confirm the view expressed by Wood & Thornton(6) that yeast and mould counts provide an inadequate criterion of factory sanitation, and should be supported at least by the total count of bacteria.

The employment of these methods has enabled large numbers of samples to be dealt with. Thus samples from most of the principal New Zealand butter factories have been regularly tested. The information so obtained has been of material value to the Dairy Division's Instructors in drawing attention to factories where sanitary conditions left room for improvement.
242. A rapid phosphatase test: (a) Adaptation of Scharer's modification to pasteurizing conditions in Great Britain; (b) A study of factors influencing the reliability of the test
Authors: Aschaffenburg R. , Neave F. K.
Published: June 2009

By adapting Scharer's “10min. field test” to British conditions of pasteurization, an accurate phosphatase test has been evolved requiring less than 1½ hr. for completion. The method is described in detail.

A small percentage of anomalies was detected when applying the new method to the examination of pasteurized samples bulked from small quantities of milk (less than 100 gallons). This led to a study of several factors thought to be the likely cause of such anomalous results.

No correlation was found between the phosphatase surviving heat treatment and the stage of lactation when milk from individual cows and from small groups of animals was tested, with the possible exception of the early stages of lactation when the enzyme concentration before and after heating was frequently found to be low.

It was observed that pasteurized milk from animals suffering from mastitis tends to give abnormally high results of the phosphatase test. The amount of residual phosphatase is subject to considerable fluctuation.
269. Experiments on the chemical enrichment of cows' milk by the administration of diethylstilboestrol and its dipropionate
Authors: Folley S. J. , Watson H. M. Scott , Bottomley A. C.
Published: June 2009

1. Diethylstilboestrol administered orally to a Shorthorn cow had no marked effect on milk yield or composition.

2. A series of injections of the dipropionate in oily solution led to a slight rise in non-fatty solids in the same cow as in 1. Single larger injections were followed by a rise in milk solids accompanied by a rapid fall in milk yield in two other Shorthorns.

3. Inunction with an ointment containing the dipropionate led to a marked increase in milk solids in a Shorthorn cow, with no change in milk yield. The effect subsided rapidly when treatment was stopped. No significant effects were produced by similar treatment of four pregnant British Friesians; on increasing the dose two of these aborted. A Guernsey cow showed a slight increase in nonfatty solids and a slight but temporary fall in milk yield.

4. Subcutaneous implantation of crystalline diethylstilboestrol led to a striking and prolonged increase in milk solids, with no fall in milk yield, in a Shorthorn cow.

5. Subcutaneous injection of an aqueous suspension of diethylstilboestrol (1 g.) was equally successful when applied to the same cow as 4, but in the next lactation. In three Ayrshires the increase in solids was accompanied by an appreciable decline in milk yield. A Shorthorn receiving 375 mg. showed a temporary rise in solids, while one receiving 225 mg. showed no effect.

6. In all cases where milk yields declined the milk solids percentage rose, but the converse did not hold. Hence the threshold dose for inhibition is apparently higher than for enrichment.

7. The threshold doses may depend on the breed; the most successful results were obtained with Shorthorns.

8. Treated cows may be difficult to get in calf subsequently, especially those treated twice.

9. Administration of large doses of diethylstilboestrol to cows in advanced pregnancy results in abortion.

10. The enrichment of the milk in favourable cases represented a true increase in the yield of solids secreted, and not merely a concentration due to reduced secretion of water.
286. The plate count and methylene-blue reduction test applied to milk
Authors: Barkworth H. , Irwin J. O. , Mattick A. T. R.
Published: June 2009

1. Defining sensitivity as the power of discriminating significantly between milks of different bacterial constitution the plate count is slightly less sensitive than the methylene-blue test observed every 5 min. and slightly more sensitive than the latter observed every half-hour.

2. The logarithm of the plate count is, in our opinion, the correct measure to use. Its coefficient of variation is slightly less than that of the methylene-blue test observed every 5 min.

3. The plate count as formerly used and the methylene-blue test as now used agree in grading in over 80% of cases.

4. Two samples whose reduction times differ by 30 min. are not significantly different. Such a difference is only significant if the result is based on the mean of duplicate tests with 5 min. observations or of triplicate tests with half-hourly observations.

5. Provided transit hazards are eliminated and standard technique is very carefully observed, there is no significant difference in results from different laboratories by either test.

6. Neither test necessarily reflects minor changes or faults in production routine. Under the conditions of our experiment the methylene-blue test was not, in cold weather, a satisfactory indicator of the numbers of organisms as distinct from ‘activity’.
287. The freezing-point of milk. I. The freezing-point and solids-not-fat content of the milk of individual cows throughout a period of lactation
Authors: Aschaffenburg R. , Temple P. L.
Published: June 2009

The results of regular determinations of the freezing-point and solids-not-fat content of the milk of three Shorthorn cows over a period of more than six months are reported.

The known constancy of the freezing-point depression was confirmed, the Δ values deviating generally by less than 2% and, in the most extreme case, by no more than 3·5% from the mean of 0·546 ± 0·002° C. No evidence was found of any influence of the state of lactation on the freezing-point depression, but a slight but definite decrease persisting for some weeks occurred at the time of year at which ample supplies of spring pasture became available to the animals.
299. Further studies on bacteriophage in relation to Cheddar cheese-making
Authors: Johns C. K.
Published: June 2009

A second outbreak of phage infection with complete cessation of acid production in experimental vats is described. Although occasional positive indications were obtained from the milk supply itself, the original source of the phage was not definitely demonstrated.

The results obtained in testing for phage appeared to be influenced by the size of milk sample examined, and by refrigerated storage for 7–16 hr. before testing.

Trouble with slow working vats in two factories which had continued over a period of 6 weeks was shown to be due to lysis of the dominant strains of the mixed culture of starter organisms by phage.

Attention is called to the need for substitution of a starter of entirely different bacterial strains when such trouble is encountered.
308. The freezing-point of milk: II. The influence of various factors and their bearing on the detection of added water
Authors: Aschaffenburg R. , Veinoglou B. C.
Published: June 2009

The results of a series of determinations of the freezing-point depressions of the milk of the individual cows of a Shorthorn herd over a period of 16 months are reported.

The relative constancy of the freezing-point was confirmed, all but two values deviating by less than 4·5% from the mean Δ values.

Significant seasonal trends were observed, especially during the spring when the supply of ample amounts of young grass may cause the production of milk with somewhat smaller freezing-point depressions.

Systematic trends in the differences between the Δ of morning and evening milk were found, the evening values being generally higher, except for the winter period, during which the cows were housed at night, when the morning Δ values became the higher. The differences appear to depend on the changes in the temperature of environment to which the cows are exposed. These observations provide an explanation for the discrepancies reported in the literature.
336. Surface activity and proteins of milk
Authors: Aschaffenburg R.
Published: June 2009

As moderate dilution causes little change in the surface tension of milk, it is shown to be advantageous to use σ-dilution curves in place of the σ-values of the undiluted fluid as a characteristic of the surface properties of milk. The complications arising from the presence of the milk fat are described, and it is suggested that the influence of the fat is of a physical rather than of a chemical nature. A study of the role of the various milk proteins shows the casein to be of great importance, whilst the heat-coagulable proteins have little influence. The serum obtained after removal of the casein and heat-coagulable proteins contains a residual fraction of protein-like material which is markedly surface active though constituting only about 3% of the total milk proteins. The surface-active material (σ-proteose) has been concentrated and isolated, and its properties are described in some detail.
346. Measurements of the rate of change of temperature in high temperature-short time pasteurization plant
Authors: Steghart F.
Published: June 2009

It has recently been claimed that in modern high temperature-short time pasteurization plant fluctuations in temperature of the order of 1° F./sec. are unusual and probably artefacts, and that an instantaneous drop is certainly fictitious.

It has, nevertheless, been shown that such rapid drops in temperature do in fact occur frequently in high temperature-short time plants of the type investigated. The plant investigated was not of the latest design incorporating devices for speeding up the control by injecting steam directly into the hot-water pipe.

Temperature changes of the order of those in question were first observed by Mattick & Hiscox(1) of the National Institute for Research in Dairying, who carried out tests on pasteurization plant using a small mirror galvanometer with a very short time constant. The maximum rates of change were, however, not observed.
351. The estimation of copper and iron in cream, butter and dry butterfat
Authors: McDowell A. K. R.
Published: June 2009

1. A method is described based on wet-ashing in micro-Kjeldahl flasks for the accurate estimation of iron and copper in 10g. samples of butter or dry butterfat or in 5g. samples of cream.

2. An acid extraction method for the routine estimation of copper and iron in dry butterfat is described. This method is shown to give a reliable estimate of the quantities of the metals present.

3. A simplified method for the estimation of iron in cream and butter is described in which the iron is first freed from its protein complex by the addition of thioglycollic acid. Copper is estimated by a similar method, but without the addition of a reducing agent. Both methods give results agreeing reasonably well with the wet-ashing method and are suitable for the routine estimation of these metals in cream and butter.
355. Cheese starter ‘recovery’ after attack by bacteriophage. (Strain dominance in multiplestrain starters)
Authors: Nichols Agnes A. , Ineson P. June
Published: June 2009

1. Three experimental starters were prepared by mixing three unrelated phaging strains ofStr. cremoris. The corresponding phages were used to determine whether changes occurred in the relative numbers of these strains on daily subculture.

The results indicated that (a) in a multiple-strain starter one strain may overgrow the others and become responsible for most of the acid produced by that starter about 1 week after mixing the strains. The starter may soon become virtually a single-strain starter. (b) Even during the day's making, one of three strains, mixed together at the time of introduction into the cheese vat, may partly overgrow the other two strains, (c) The dominance of a particular strain in a starter mixture may be affected by the temperature of propagation.
359. A note on the effect of the temperature of pre-heating of spray-dried whole milk on the biological value of its proteins
Authors: Henry K. M. , Kon S. K.
Published: June 2009

Previous work from this laboratory has indicated that the biological value of the proteins of milk is not affected by pasteurization (1), by evaporation and condensation (2) or by spray or roller-drying (3). Sterilization (4), on the other hand, caused a statistically significant decrease of 6% in the biological value; with this process heating at a high temperature is more prolonged than in the other forms of heat treatment.

It was of interest to find out whether the difference of 30°F. in the pre-heating temperature of the spray-dried whole milks described by White, Smith & Lea (5) in the preceding paper would have any effect on the biological value of the proteins.
403. The characteristics of streptococcal phages: Interaction between different races
Authors: Hunter G. J. E.
Published: June 2009

Although it is known that several phage races, capable of developing on a certain strain ofStreptococcus cremoris, exist in the surroundings of commercial cheese factories in New Zealand, only one specific race is invariably isolated from cheese or cheese whey when the culture is used as a starter. Laboratory and field evidence suggests that this particular race has a special affinity for the organism, and that its presence interferes with the growth of other races which could develop in its absence.
405. The composition of the soluble and insoluble portions of reconstituted milk powders
Authors: Waite R. , White J. C. D.
Published: June 2009

1. The mode of distribution of the constituents of centrifuged reconstituted whole-milk powder manufactured by different processes has been determined at 20 and 50° C.

2. Where considerable ‘insolubility’ exists, protein is carried into the fat layer and fat into the sediment layer in quantities directly related to the degree of ‘insolubility’. The fat in the sediment of roller powders appears to be associated almost entirely with the protein which remains insoluble at 50° C.

3. The sediments from reconstituted whole- and separated-milk powders made by different manufacturing processes have been obtained in bulk by vigorous centrifuging (14,500 ×g). Analysis of these sediments reveals considerable similarity between them, and it is concluded that a well-washed sediment would consist mainly of denatured calcium caseinate together with calcium and phosphorus in the same proportions as in normal tricalcium phosphate, Ca3(PO4)2, the calcium caseinate and most of the calcium phosphate probably being in the form of a casein-phosphate complex.

4. The accuracy of some published methods of measuring milk powder solubility has been considered, and the inaccuracies arising from the non-homogeneity of the fat and sediment layers are stressed.
Keeping quality and raw-milk grading: I. Dye tests as measures of the keeping quality of milk
Authors: Mattick A. T. R. , Rowlands A. , Barkworth H. , Hosking Zena , Kempthorne O.
Published: June 2009

The experiments analysed in this series of papers were undertaken as the result of a discussion on methods of measuring the keeping quality of milk, at a Conference of Advisory Bacteriologists of the Ministry of Agriculture and Fisheries.

Owing to the disturbance and difficulty following the outbreak of war and the dislocation of handling and distribution, a serious decline in the keeping quality of raw-milk supplies was threatened.
The phosphatase test of Aschaffenburg and Mullen: Use of permanent colour standards and comparison with the Kay-Graham test
Authors: Tramer J. , Wight J.
Published: June 2009

1. A method has been developed for measuring the intensity of colour produced in the Aschaffenburg & Mullen phosphatase test in which use is made of permanent colour standards.

2. Using this method, the relationship between this phosphatase technique and the official Kay-Graham test has been investigated.

3. The limiting standards corresponding to 2.3 Lovibond Blue Units in the KayGraham test have been established for the 30 min. and 2 hr. procedures of Aschaffenburg & Mullen.

4. The advantages of the improved technique of the Aschaffenburg & Mullen test are discussed.
432. The condition and average live and carcass weights of ‘wastage’ animals in west Wales (1943–46)
Authors: Phillips R.
Published: June 2009

1. The body size and grading of the wastage cattle have been described. It was found that the average wastage cow is relatively small in size with an average live weight of 1100 lb. or 9¾ cwt. The condition was also disappointingly poor since over one-half of the total wastage cows are in grade C or are ungraded.

2. The seasonality of the sales shows an autumn glut, which appears to increase as the grade or condition deteriorates.

3. The annual variations in body size during the 4 years are very slight, which seems to indicate that under present circumstances the region can only maintain cows of this size.

4. It was shown that the region can be subdivided into four parts in which the average body size for each section falls into one of four well-defined ranges of weight.
434. The bacteriological quality of National Dried Milk
Authors: Parsons A. T. , Fraser J. R.
Published: June 2009

This paper presents in statistical form the results of the bacteriological examination of over 1200 samples of National Dried Milk during the period 1944–9. Factors which may affect the results are discussed. The general level of bacterial quality disclosed is high, but appreciable differences are shown in the standards reached at different factories and repacking depots. No general trend with time was observed in the figures throughout the period of 6 years considered, and no correlation was observed between the counts obtained and the time which had elapsed since packing into 20 oz. tins. Between counts at 37 and at 55° C. some correlation was noted in the products of most factories and depots, and the significance of this observation is discussed. The counts obtained are compared with various standards which have been put forward or are now in operation, and ways are suggested in which the figures might be used to set up standards of bacterial quality for roller-dried milk powder in this country.
459. The deterioration of milking rubbers: II. The effect of fat
Authors: Gardner E. R. , Berridge N. J.
Published: June 2009

The presence of fat in milking machine liners is probably the chief cause of their deterioration. The primary effect of the fat is to cause softening and swelling of the rubber and greasiness of its surface; the secondary effect is to increase greatly the rate of oxidation. The primary effect may be reversed by removing the fat by solvent extraction or prolonged treatment with cold caustic soda; the secondary effect is irreversible.

Although the fat is derived chiefly from milk, rubber absorbs fat only slowly from liquid milk. Thus it is likely that most of the absorption is from milk residues remaining on liners between milkings, under conditions which favour the breaking of the natural emulsion. Such conditions would include drying, souring or other bacterial activity, and the presence of traces of detergents which act as protein denaturing agents.

Thus, if the widely recommended technique of cold or tepid rinsing is properly practised (8), fat absorption is kept to a minimum, and the life of liners will be prolonged. Under such conditions the absorption of fat from the cow's skin will be more important and methods of removal, or of prevention, such as the use of fat-resistant rubber may be advantageous.
467. Studies on variations in the solids-not-fat content of milk: III. Seasonal variations
Authors: Bailey G. L.
Published: June 2009

Seasonal changes in the solids-not-fat content of milk occur only from April to May when the level rises, from May to July when the level falls and from August to September when the level rises again.

These changes are thought to be due to changes in feeding practice.
471. The role of micro-organisms in dye-reduction and keeping-quality tests: I. The change in dominant bacterial flora during incubation at 37·5 and 22° C. and the part played by staphylococci and thecoli-aerogenesgroup
Authors: Garvie Ellen I. , Rowlands A.
Published: June 2009

1. The present work was planned to provide an explanation of the lack of correlation for individual samples between the results of dye-reduction tests at 37·5° C. and keeping-quality tests at 22° C. A special study was made of the particular part played by the staphylococci (in thirty-eight samples) and thecoli-aerogenesgroup (in thirty-seven samples) in dye reduction at 37·5° C. and in keeping quality at 22° C. A detailed study was also made of the changes in bacterial flora of twelve samples during incubation at these temperatures.

2. In milk, after overnight storage at 14° C., staphylococci were found to constitute only a small proportion of the bacterial flora, but their numbers increased during incubation at 37·5° C. (for the dye-reduction test) and at 22° C. (for the clot-on-boiling test). At the time of dye reduction staphylococci were found to constitute a major part of the bacterial flora, particularly in samples taking 5 hr. or more to reduce the dye. Although the staphylococci increased in numbers during incubation at 22° C. they constituted only a relatively small proportion of the flora at the time of the end-point of the clot-on-boiling test.

3. Initially thecoli-aerogenesgroup were found to constitute only a small proportion of the total bacterial flora. Some growth usually occurred during incubation at 37·5 and 22° C.
477. Action inhibitrice des streptocoques producteurs de nisine sur le développement des sporulés anaérobies dans le fromage de Gruyère fondu
Authors: McClintock Mary , Serres Lucie , Marzolf J. J. , Hirsch A. , Mocquot G.
Published: June 2009

La formation de gaz dans la pâte du fromage fondu, au cours de la conservation, représente un défaut assez fréquent qui entraîne le gonflement ou même l'éclatement des emballages, notamment lorsque ces derniers sont constitués par des boites métalliques.
510. Reactivation of milk phosphatase following heat treatment. I
Authors: Wright R. C. , Tramer J.
Published: June 2009

1. Commercial samples of milk of Swiss origin, sterilized by rapid heating to high temperatures, developed a positive phosphatase reaction on storage.

2. The optimum temperatures of storage for the development of this positive phosphatase reaction was 30° C.

3. These commercial samples were sterile when received and remained sterile during storage.

4. The developed phosphatase is apparently identical with the normal alkaline phosphatase of raw milk as judged by (a) heat stability, (b)pH optimum and rate of hydrolysis at different pHs, (c) comparison of results by Kay-Graham and Aschaffenburg & Mullen tests.
519. The cooling efficiences and water pressures of some surface milk coolers for farms
Authors: Scott J. K.
Published: June 2009

The main types of surface milk coolers were tested using water at 95°F. instead of milk The coolers were tested: (a) for cooling efficiency at the nominal rated flow and a range of cooling-water flows; (b) for allowable flow at 3:1 cooling-water and cooling to within 3° F. of the cooling-water; (c) for the allowable flow (lb./hr. per square foot of cooling surface) for a range of cooling-water flows; (d) for the cooling-water pressures for various rates of flow.

The results showed that no cooler reached the required efficiency at a cooling-water ratio of 3:1 or less, the temperature difference at the bottom of the cooler varying from 3·3 to 7° F. for normal coolers.

The allowable flow per square foot of cooling surface varied from 33·8 to 114 lb./hr. when cooling to 3° F. difference with 3:1 water. The corrugated plate design had higher allowable capacity at low rates of flow of cooling·water than the tubular designs. Atmospheric cooling was small.
531. The influence of live weight on milk production during the first lactation
Authors: Bailey G. L. , Broster W. H.
Published: June 2009

The relationship between live weight and lactation production was examined; records from ninety-nine animals, daughters of seven bulls, were used.

A positive relationship was found to exist within each of the seven groups and within the entire population.

The relationship did not exist between the mean values of the group.

No correlation was found between the live weights at calving of forty-seven dam/daughter pairs; the daughters were the offspring of six bulls.

It was shown that a herd breeding policy which selected animals according to their size would fail, except by chance, to improve the production of the herd.
563. The steam stripping of taints from liquids. II. Counterflow stripping with particular reference to possible use of Vacreator equipment
Authors: Scott J. K.
Published: June 2009

The considerable increase in efficiency of taint removal which can be attained by counterflow methods is shown by the extension of the algebraic and graphical methods of Part I and confirmed by experiments with the reference substances diacetyl and acetoin in water. The treatment is mainly confined to multiple contact counterflow, and several methods are suggested by which existing Vacreator equipment may be used for counterflow connexion. The effect of a feed temperature below the temperature existing in the contacting vessels is shown to increase the amount of taint removal per pound of stripping steam used. Comparative curves are given for total steam consumption for systems preheating to various temperatures with waste heat.

Results are given for experiments with a converted small size Tandem Vacreator. For diacetyl, the stripping steam used was one-tenth of that for a single contact process over the same range of diacetyl removal. Acetoin, being less volatile than diacetyl, did not show the same large steam saving.
570. A medium for the simultaneous enumeration and preliminary identification of milk microflora
Authors: Donovan Kathleen O. , Vincent J. M.
Published: June 2009

A medium has been developed that permits the viable count of milk bacteria to be combined with the determination of biochemical properties likely to be important in milk itself. This has involved the modification of standard glucose-tryptone skim-milk agar by incorporation of two indicators to detect alkali as well as acid production, substitution of lactose for glucose, and increasing the quantity of skim milk for the detection of proteolysis and casein precipitation. The medium has proved particularly valuable in the study of the thermoduric flora of pasteurized milk. The phenomenon of casein precipitation is, however, less reliably determined than are changes in hydrogen-ion concentration and proteolysis.
571. The effect of menadione (2-methyl-l: 4-naphthoquinone) on the keeping quality of milk
Authors: Higginbottom Constance
Published: June 2009

1. The addition of 1 µg. menadione/ml. to milk had no effect on the souring of the milk at 37° C. With higher concentrations of menadione the effect on the keeping quality at 37° C. varied with different milks. In some milks the clot-on-boiling stage was delayed by 1 hr. with 10 µg. menadione and by 2 to over 5 hr. with different milks containing 100 µg. menadione per ml. Some milks, however, showed no alteration in the keeping quality at 37° C. with as much as 1000 µg. menadione/ml.

2. The response of individual milks to the presence of menadione appeared to be related largely to the bacterial flora of the milk, The relative insensitivity of Gram negative rods, including coliform bacteria and of enterococci, to menadione was confirmed. Milks containing large numbers of coliform bacteria showed the least and those free of such bacteria the greatest response to menadione.

3. Menadione fed to milking cows at the rate of 100 mg·/day for a period of 3 weeks had no effect on the keeping quality of the milk when it was held at 37, 22 or 15·5° C. The time of incubation required for the milk to attain a titratable acidity equivalent to 2 ml. N/9-NaOH, to become unstable to 68 % alcohol or to boiling showed no difference between the milk from the cows given menadione and that from the control cows.

4. The menadione had no demonstrable effect on the appetite or the well-being of the cows nor on their milk yield.

5. When as much as 100 μg. menadione was given per cow per day, no menadione was detected in the milk under conditions suitable for the detection of 1 μg. menadione/ml.milk.
573. The temperature coefficient of expansion of raw milk
Authors: Short A. L.
Published: June 2009

The density of raw milk between 10 and 45°C. has been examined. The effect of composition on the expansion of raw milk has been studied and the variation of the densitytemperature coefficient quoted for different values of milk composition.
575. Colour changes in heated and unheated milk: III. The effect of variation in milk composition on the whitening and browning of separated milk on heating
Authors: Burton H. , Rowland S. J.
Published: June 2009

The effect of natural variations in the pH, and in the casein, soluble-protein and lactose contents on the whitening and browning of separated milk has been studied by holding samples of known composition, obtained from individual cows, at a temperature of 110°C. for various times and determining their reflectances after treatment.

The rate of browning, measured as a rate of loss of reflectance at a wave-length of 4260 Å., was found to depend on the pH of the milk. Apparent variations of the rate of browning with protein content are considered to have been caused by associated variations of pH with protein content in the milk from the different cows. The rate of browning varied over a range of 2:1 for the samples examined.

The whitening of milk, measured as the maximum rise of reflectance occurring on heating, was found to be much more variable, and over the same range of samples varied by 5·5:1. The soluble-protein content and pH affect the amount of whitening, but there appears to be some other factor of importance which was not covered by the chemical analyses that were made.

A considerable range of reflectances is shown by different milk samples after a fixed heat treatment. These differences are determined more by variations in the amount of whitening than by variations in the rate of browning.
579. A study of variation in twin cattle: IV. Emergence of permanent incisor teeth
Authors: Wiener G. , Donald H. P.
Published: June 2009

1. Data are presented on variation in age at eruption of permanent incisor teeth in one-egg (MZ) and two-egg (DZ) twins and in pairs of half sisters (HZ). The 1st pair of incisors erupted when animals were on average 100 weeks old and the other three pairs came at roughly 26-week intervals thereafter. Variation in age at eruption increased from 1st to 4th incisors, but the coefficient of variation remained constant at about 8%. The mean interval between eruption and complete emergence was about 5 weeks for the first three pairs of teeth and nearly 10 weeks for the 4th pair.

2. Variation in age at eruption within MZ pairs was no greater than that between left and right sides of the same animal. DZ displayed greater within-pair variances than MZ twins, and HZ pairs greater than DZ.

3. Correlations of age at eruption of teeth with body weight and with gain in weight were negative but non-significant. Age at eruption of 1st and of 3rd teeth was positively correlated with age at 1st and 2nd calving, but eruption of 2nd and of 4th teeth was not.

4. For 2nd, 3rd and 4th incisors, the intra-pair variance of the HZ group was in excess of that expected. This can be interpreted to mean that the estimates of environmental and genetic variation derivable from MZ and DZ pairs are not adequate to account for all the variation within HZ pairs.
581. The deterioration of milking rubbers: V. The effect of rubber composition
Authors: Clarke Pamela M. , Berridge N. J. , Gardner E. R.
Published: June 2009

The importance of fat absorption as a cause of deterioration in the rubber teat-cup liners of milking machines has already been demonstrated (l, 2), and it is well known that the composition of the rubber affects its resistance to fat. It was considered desirable, therefore, to see what changes in composition could usefully be made, and how these would affect fat absorption under normal milking conditions. To this end, and with the cooperation of a large number of farms and Milk Production Officers, the four experiments reported here were carried out.
601. The effect of salt and of antioxidants on the keeping quality of butter
Authors: McDowell A. K. R.
Published: June 2009

Butterfat oxidation occurred in both salted and unsalted butters during storage at 14° F. Butterfat oxidation values, after storage, were much lower in unsalted and in highly salted butters than in butters of normal salt content.

Butterfat oxidation in salted butters during storage was retarded by treatment with antioxidants. These included fat-soluble and water-soluble substances, surface-active agents and copper-complexing compounds.

Unsalted butter, salted butter and salted butter treated with antioxidants all developed ‘storage’ flavour during storage for eight months.

Many of the antioxidants added to salted butter were effective in retarding further fat oxidation and further increase in intensity of storage flavour when the butters were transferred to a temperature of 60–65° F. after storage.
604. The importance of lactobacilli in the production of flavour in cheddar cheese: I. Growth of lactobacilli in cheese serum
Authors: Mabbitt L. A. , Zielinska M.
Published: June 2009

1. The serum prepared by subjecting Cheddar cheese to pressure becomes inhibitory to the growth of lactobacilli as the cheese ripens.

2. One factor responsible for the inhibitory phenomena is the increasing osmotic pressure of the serum due mainly to the increasing amounts of amino-acids present.

3. Observations made during the ripening of a normal Cheddar cheese suggest that other factors, e.g. amino-acid imbalance, are also important.
618. Host-phage relationship of cheese starter organisms: I. Interaction of phage races with a strain ofStreptococcus lactisand its lysogenic and resistant derivatives
Authors: Czulak J. , Naylor Jill
Published: June 2009

A lysogenic culture, prepared in the laboratory from a strain ofStreptococcus lactis, was used as a cheese starter in commercial factories. It was attacked in turn by two other unrelated phage races. The lysogenic condition, which involved slight morphological and physiological changes, persisted in the subsequent forms resistant to one or both the new phage races. Acquired resistance to any one of the three phages did not protect the culture from the other two phages.

In nature such interactions between phage races and lactic acid bacteria must be constantly taking place, giving rise to similarly related strains.

Two of the three phage races produced spreading haloes around their plaques due to a lysin released during phage action. The lysin may also interfere with the survival of secondary growth after attack by these phage races. Production of this type of lysin is thus a property of the phage race and not of the bacterial strain.
621. Winter feeding of dairy cows: III. The influence on milk yield of high and low protein concentrates, each fed at two levels in addition to dried grass and grass silage
Authors: Reid D. , Holmes W.
Published: June 2009

1. In a winter-feeding experiment with eight Ayrshire cows the effects of feeding a high- and a low-protein concentrate at two rates (4 and 2 lb./gal.), in addition to dried grass and silage, were studied.

2. With these cows and the feeds used increasing the rate of concentrate feeding from 2 to 4 lb./gal. increased the total dry-matter consumption by 2 lb./day and the average milk yield by 1·2 lb./day.

3. For every 1 lb. increase in concentrate fed there was a decrease of 0·68 lb. grass dry matter eaten.

4. The level of protein in the concentrates had no effect on total dry-matter intake, and only a slight, though positive, effect on milk yield.

5. It is concluded that in this work where the diet was made up with high-quality dried grass and silage, feeding either a high- or a low-protein concentrate mixture at the rate of 2 lb./gal. milk gave the greatest profit margin per cow.
630. The determination of lactose in milk
Authors: Grimbleby F. H.
Published: June 2009

One of the most important stages governing the accuracy of lactose determinations in milk is the preparation of the protein-free serum. Factors influencing the lactose content of the serum are: (1) the complete precipitation of protein, (2) the formation of lactose-protein complexes, and (3) the degree of hydration of the protein coagulum.

Experiments are described which show how these factors are influenced by different clearing agents operating at different pH values. On the basis of the results obtained a reagent containing zinc acetate, phosphotungstic acid and acetic acid is suggested; it reduces to a minimum any errors introduced by the above factors.
637. Acid production in milk by starter cultures—The effect of peptone and other stimulatory substances
Authors: Garvie Ellen I. , Mabbitt L. A.
Published: June 2009

The rate of acid production by a slow variant ofStreptococcus cremorisin milk was raised to that of the fast parent strain when peptone or acid hydrolysed peptone were added. Lactose utilization was similarly affected. However, the stimulation took place without any change in the rate of growth. Other sources of available nitrogen gave similar results.

It is concluded that the change from a fast to a slow culture which occurs on continued transfer is due to the loss of ability to utilize the nitrogen compounds of milk.
639. Some bacteriological aspects of commercially sterilized milk: I. Incidence and nature of spoilage
Authors: Nichols Agnes A. , Candy M. R.
Published: June 2009

Samples of sterilized milk from fifteen dairies in the Midlands have been examined, and seasonal variations were detected in the incidence of mesophilic and thermophilic sporeformer contamination. Seasonal variation in the rate of spoilage at 30° C. was also apparent.

The lower incidence of contamination in summer was considered to be due to (a) less sporeformer contamination during milk production at the farm in the period when the cattle are not housed, and (b) increased processing times and temperatures in warm weather.

Cleansed milk bottles were examined and found to be an important source of contamination by mesophilic sporeformers, but the incidence of thermophiles of the type commonly found in sterilized milk was low.

Methods of reducing contamination in sterilized milk were discussed.
641. Penicillin in milk: I. The rapid routine assay of low concentrations of penicillin in milk
Authors: Berridge N. J.
Published: June 2009

Experience in the use of a rapidly growing culture of Streptococcus thermophilus for the assay of traces of penicillin in milk is described.
651. The lactose-chloride contributions to the freezing-point depression of milk: II. Examination of partial contributions over the full lactation period of two cows
Authors: Cole E. R. , Douglas J. B. , Mead M.
Published: June 2009

1. In testing the technique of using conversion factors (from determined concentration) for the calculation of the partial freezing-point depressions of lactose and chloride, regular weekly chemical analyses and freezing-point determinations have been made on the milk of one Jersey and one Friesian cow over a period of 7 months.

2. Relative constancy of freezing-point has again been noted, but slight though consistent differences were present between the milks of the two cows. No seasonal variations were observed, but changes in the freezing-point depression for the milk of one were generally associated with corresponding changes for the milk of the other.

3. Linear relationships were found and their adequacy tested between the partial depressions due to lactose and chloride for each animal. The relationships, though not statistically significantly different, differed considerably for each animal. It is suggested that formulae for the calculation of one of the constituents, lactose or chloride, from the determined amount of the other, need to be treated with caution in view of the results obtained for the two animals in this work.

For the Jersey milk it was found that 80% of the total freezing-point depression was due to the lactose and chloride content (on a fat and protein-free basis). For the Friesian milk, indications were that the lactose-chloride contribution was of the order of 75% of the total depression, but the result of statistical analysis was less satisfactory for this milk.

The co-operation of Mr J. McGibbon of the Hawkesbury Agricultural College is gratefully acknowledged. Thanks are due also to Mr J. V. Pascoe and the Dairy Farmers Co-operative Milk Co. Ltd. for their continued interest in the work.
659. Factors influencing the vitamin content of milk fat: V. Changes in vitamin A and carotenoid content of the blood plasma of cows and heifers near parturition in relation to secretion of these substances in the milk fat
Authors: Thompson S. Y. , McGillivray W. A.
Published: June 2009

1. Plasma levels of vitamin A and carotenoids prior to and following parturition have been followed in groups of cows and heifers maintained under typical New Zealand farming conditions.

2. Despite the high carotene intake prior to calving, the cows, and to a lesser extent the heifers, showed decreases in plasma vitamin A and carotenoid level at or near to parturition, the decreases in the levels for the cows being of the same order as those reported in Great Britain and the United States.

3. Although the concentration of vitamin A and carotenoids was higher in the colostrum of heifers than of cows, the total daily secretion of these components by the cows was much greater over the first few days of lactation.

4. Evidence is advanced to support the suggestion that the decrease in plasma components is related to the extra drain of colostrum synthesis rather than to any hormonal changes associated with parturition.

We are indebted to the following: the Department of Scientific and Industrial Research for financial assistance towards the cost of this investigation; Mr R. M. Patchell and the farm staff of The Dairy Research Institute for the collection of milk samples; Miss Fay Frecklington for help with much of the analytical work; one of us (S.Y.T.) to the Royal Society, the Nuffield Foundation, and the Board of The Dairy Research Institute (N.Z.) for a travelling fellowship during the tenure of which the work reported here was carried out.
666. Intramammary pressure changes in the lactating ewe: I. The nature of the pressure change under standard conditions
Authors: Whittlestone W. G.
Published: June 2009

The effect of oxytocin on the intramammary pressure of the lactating ewe has been described. The pressure curve produced by the ewe is shown to be different from both sow and cow.

An improved pressure recorder is described.
672. Variations in the solids-not-fat content of milk. Investigations into the nature of the solids-not-fat problems in the west Midlands
Authors: Griffiths T. W. , Featherstone J.
Published: June 2009

1. During the period September 1954—August 1956 monthly samples of milk were obtained from individual cows in herds selected because of known history of low solids-not-fat. Records were kept of general feeding and management. Milk was analysed for total solids, butter fat and s.n.f. (by difference). Crude protein and lactose were also estimated at three-monthly intervals.

2. Mean lactation averages were calculated for s.n.f. These showed a normal distribution around a mean of approximately 8·5%.

3. Throughout the period a high proportion of samples failed to reach 8·5%. The seasonal effect is at its worst in March and April when 70% of the samples were below 8·5%.

4. Effect of advancing lactation (uncorrected for the effect of season) agreed broadly with previously published work but marked differences in the shape of the lactation curve were found between different herds. Variations in s.n.f. are largely a reflexion of variations in crude protein.

5. Age distribution of the cows agreed favourably with published figures for the national herd, and a mean regression of s.n.f. with age gave 0·11% per year.

6. Supervision of the feeding of the herds in the investigation gave no measurable improvement in s.n.f. and no significant response was obtained from short-term trials where extra s.e. was fed.

7. There was no undue incidence of disease of the udder, either clinical or subclinical.

8. Little information could be obtained on breeding, but it is concluded that the major cause of the problem is the genetically poor potentialities of the cows as judged from the average composition of the milk they produce.
674. The lactic acid and volatile fatty acid contents of five locally made type cheeses
Authors: Barnett A. J. G. , Tawab G. A.
Published: June 2009

1. A study has been made of the development of titratable acidity, lactic acid and volatile fatty acids in five locally made type cheeses. The study of the changes involved has been made over the period of ripening up to the stage at which each type would normally be marketed. All the cheeses were made from the same batch of milk at the same time.

2. Slight modifications to the micro-column devised by James & Martin (13), and its use, have been suggested which have resulted in improved recovery of volatile fatty acids.

3. The volatile fatty acids have been determinedin totoand also as separate constituents. Formic acid has been noticed as a common constituent of the acid mixture in all the cheeses, while, over the ripening period involved and apart from unidentified acids higher than caproic, the only other volatile acids encountered have been acetic and butyric, and on one occasion iso-butyric.

4. Over the short ripening period studied, the lactic acid content of the soft cheeses rose, but after the initial rise in Pont l'Évêque and in Dutch cheese the results showed a downward trend. Fluctuations in the lactic acid content of the Smallholder cheese have been noted which compare with the corresponding findings of other workers.

5. All the results presented have been calculated on the basis of fresh cheese because this is the customary practice and comparisons with other work would be difficult if this had not been adhered to.