bluuebunny/crossref_metadata_2025 huggingface dataset:
443. Keeping quality and raw-milk grading: III. Comparison of keeping quality tests and dye tests in milk control (results of a field trial)
Authors: Rowlands A. , Hosking Zena
Published: June 2009

1. The results discussed in this part of the report were obtained by examination of milk samples taken at approximately fortnightly intervals throughout a period of one year from 298 farms in eight widely separated areas of England and Wales. The samples were examined by the routine resazurin test, the methylene-blue (4½/5½ hr.) test, the methylene-blue (½ hr.) test and the temperature-compensated keeping quality test using clot-on-boiling (c.o.b.) to determine the end-point. For the first three tests, the treatment of the samples and the standards applied conformed to those prescribed officially for these tests in England and Wales. Details are given of the treatment of samples and testing procedure for the temperature-compensated c.o.b. test. With this test two standards, equivalent to a residual keeping quality at 22° C. of 21 and 24 hr. from 9 a.m. on the day of collection of the milk from the farms, for both evening and morning milk were used.

2. The results are analysed on the basis of the proportion of farms and of samples passing or failing the different tests, the effect of shade atmospheric temperature on the incidence of failures and the relationship between the standards imposed by the c.o.b. tests and the official methylene-blue (4½/5½ hr.) test.

The proportion of farms and of samples passing each test was much higher in winter than in summer and was directly related to the prevailing shade atmospheric temperature. However, a proportion of farms was consistently able to comply with the standards. No more than 5% of the total failures by any test could be ascribed to the 60 (20%) best farms, whereas the 60 (20%) worst farms were responsible for as many as 37–60% of the total failures from the 298 farms.
444. The production of antibiotics by streptococci
Authors: Hirsch A. , Wheater Dorothy M.
Published: June 2009

From raw and pasteurized milk and cheese, human, bovine and pig faeces, human nose and throat swabs, 553 pure cultures were isolated and tested by a cross-streak technique on agar. From the same sources, but without isolation and purification of the cultures, 510 samples were also tested by spotting individual colonies with a test-organism culture ofStreptococcus agalactiae. A further 8016 samples were tested after enrichment by a quick assay usingStr. cremorisas the test organism. The samples examined failed to reveal antibiotic producing streptococci with the exception of some strains ofStr. lactiswhich produced nisin.
452. Bacteriological tests for milk sampled during distribution to the consumer
Authors: Rowlands A. , Hosking Zena
Published: June 2009

1. This survey was undertaken to select a test for the official examination of the keeping quality of milk, both raw and pasteurized, sampled during its distribution to the consumer. Forty-five laboratories in England and Wales collaborated in the survey and together tested 20,159 samples during the year May 1949–April 1950.

2. Failures with each test were lower in winter than in summer, and increased with increasing shade temperature. However, the proportion of failures for all samples tested in any one month at maximum shade temperatures up to 70° F., or even 75° F., was not appreciably higher than at temperatures up to 65° F. Of the samples examined during June to September, 62% were taken on days when the maximum shade temperature exceeded 65° F.

Whatever test is used for the control of milk it is reasonable to expect that at least 75% of samples taken during a given period should reach the required standard. Because of the lower incidence of failures in winter than in summer, this requirement should apply to tests done during a period of 6 months rather than one of a year.
461. ‘Broken’ or ‘bitty‘ cream in raw and pasteurized milk
Authors: Stone M. Jean , Rowlands A.
Published: June 2009

Of 161 cultures of aerobic sporeformers isolated from raw and pasteurized milk 96 were found to be B. cereus, 27 B. mycoides, 17 B. subtilis, 11 B. sphaericus, 3 B. megatherium, 2 B. pumilus, 1 B. firmus and 4 were unidentified strains.

Typical broken cream followed by rapid sweet curdling of sterile milk was produced by 36 of 39 strains of B. cereus and 5 strains of B. mycoides examined. Three strains of B. cereus failed to produce broken cream. These 3 strains were atypical in that they failed to produce lecithinase, unlike the remaining 93 strains isolated during this study. Other species of aerobic sporing bacilli tested, including 17 strains of B. subtilis, 10 of B. sphaericus, 2 of B. megatherium, 2 of B. pumilus and 1 of B. firmus, all failed to produce broken cream and in fact produced no visual change in milk within 48 hr. at 22° C.

Under the conditions of our experiments, 48 out of 60 samples of fresh farm milk and 12 out of 14 samples of freshly bottled pasteurized milk developed broken cream within 18 hr. at 22° C. followed by sweet curdling within a further 24 hr. Strains of B. cereus or B. mycoides were isolated from all samples showing broken cream, but only 3 atypical strains of B. cereus were isolated from the 14 samples which did not develop the fault.

It seems that the production of broken cream is in some way associated with the production of lecithinase by B. cereus and B. mycoides. This view is supported by the fact that three non-lecithinase producing strains of B. cereus were also unable to produce broken cream. However, attempts to reproduce the fault by adding a concentrated culture filtrate to sterile milk or cream were unsuccessful.

Because of the widespread distribution of spores of B. cereus and B. mycoides in both raw and pasteurized milk, the absolute prevention of broken cream does not seem possible, but preliminary observations suggest that maintenance of milk at 5° C. or lower from the time of pasteurization until delivery to the consumer may sufficiently delay the onset of the fault to obviate the difficulty in practice except in very hot weather in households where insufficient care is taken to keep milk cool.
476. Observations on the influence of inhibitory substances produced by the lactobacilli of Gruyère cheese on the development of anaerobic spore-formers
Authors: Hirsch A. , McClintock Mary , Mocquot G.
Published: June 2009

1. The failure of clostridia to produce a butyric acid fermentation, when known to be present in Swiss-type cheese, is discussed.

2. It is suggested that inhibitory substances produced by the predominating lactic flora of young cheese are partly responsible for the suppression of the fermentation.

3. Details are given of the techniques used to investigate this supposition.

4. The evidence was obtained by examining fifty-one samples of Gruyère cheese, 78% of which were contaminated with clostridia. 85% of the samples contained inhibitory lactobacilli.

5. In 30% of the samples the inhibitory phenomena were sufficiently marked to give clear zones of inhibition againstStaphylococcus aureuswhen a suspension of cheese was placed in penicillin cups.

6. Inhibition ofClostridium butyricumwas demonstrated with pure cultures of lactobacilli. The cultures could grow at temperatures from 30 to 50° C, but were inhibitory only at certain temperatures of incubation which appear to be a strain characteristic.

7. The inhibitory substance(s) concerned is not nisin because it is acid and heat labile.
485. The effect of temperature on the development of broken cream
Authors: Stone M. Jean
Published: June 2009

Three strains ofB. cereuswere grown in milk at nine different temperature combinations. Broken cream could be prevented by holding milk at 5° C. or lower for 24 hr. before transferring to 15 or 18° C. for a further 24 hr., but with a subsequent period of storage at 22° C. the fault was not prevented. Broken cream developed after storage at 10° C. followed by 18 and 22° C., but not in milk kept at 10° C. and then transferred to 15° C. After preliminary storage at 15° C. the fault appeared within a further 24 hr. regardless of the subsequent storage temperature.

With two strains ofB. cereusit was observed that pasteurization accelerated spore germination and hence the development of the fault. With low levels of inoculum there was delay in the appearance of the fault with one strain of the organism.

In twenty-four samples of commerically pasteurized milk it was shown that the fault could be controlled by refrigeration at 5° C. before distribution except when the subsequent temperature was allowed to rise to 22° C.

Contrary to the suggestion made by Davis (15) preliminary observations indicate that the growth ofB. cereusand the development of broken cream is not inhibited by the presence of acid-producing organisms such asStr. lactis.
486. The action of the lecithinase of Bacillus cereus on the globule membrane of milk fat
Authors: Stone M. Jean
Published: June 2009

An effect simulating broken cream in whole milk was produced when Bacillus cereus was grown in washed cream at 22° C. A similar but less marked effect was obtained when a concentrated culture filtrate of B. cereus was added to washed cream.

Microscopic examination of washed cream to which B. cereus or its concentrated filtrate had been added showed that the fat-globule membranes had been broken down. The hydrolysis of lecithin in washed cream in which B. cereus had grown was demonstrated by qualitative estimation of free choline.

Since these results could not be reproduced when a non-lecithinase-producing strain of B. cereus or its concentrated culture filtrate was added to washed cream, it appears that the hydrolysis of the lecithin of the fat-globule membrane is at least partly responsible for the formation of broken cream.
490. The distribution of fat-globule size in sow's milk: II. The influence of stage of lactation
Authors: Whittlestone W. G.
Published: June 2009

The fat-globule size distribution patterns have been determined throughout lactation for ten sows and through the colostrum phase for two.
491. The effect of pre-heating milk at 230° F. (110° C) on the keeping quality of spray-dried whole milk
Authors: White J. C. D. , Waite R. , Hawley H. B. , Clark J. G. , Henry Kathleen M.
Published: June 2009

1. Three samples of spray-dried whole milk were made from milk pre-heated at 190, 230° and 230° F. with regenerative cooling to 190° F., in an A.P.V. H.M. Paraflow Heat Exchanger and dried in a Kestner plant. The powders were packed in plain tin-plate cans and stored at 17, 37 and 47° C. The keeping quality of the powders was determined by examination at intervals for palatability, absorption of oxygen and peroxide value of the fat. The biological value and true digestibility of the protein of the powders were estimated in rat-feeding experiments initially and after 6 months' storage. The breadmaking properties of the powders were also examined.

2. The keeping quality, biological and baking tests showed that the three milk powders were very much alike, and that no advantage was gained by raising the preheating temperature of the liquid milk from 190 to 230° F.
496. The associative growth of Bacillus cereus and Streptococcus lactis in milk
Authors: Garvie Ellen I. , Stone M. Jean
Published: June 2009

It has been found that when three strains of Bacillus cereus are grown in turn with each of two strains of Streptococci lactis and two strains of the coli-aerogenes group, the growth of the spore-formers is neither suppressed nor stimulated. It has been confirmed, however, that the spore-former is unlikely to develop if the milk is held at 15°C. or below. Broken cream results if marked growth of B. cereus occurs. A nisin-producing strain of Str. lactis did not retard the development of the spore-former in milk, but after initial increase the numbers of B. cereus decreased. Broken cream was not prevented.
498. Some group N streptococci isolated from raw milk
Authors: Garvie Ellen I.
Published: June 2009

A number of strains of streptococci falling into serological group N which could not be identified as eitherStreptococcus lactisorStr. cremoriswere isolated during a study of the bacterial flora of raw milk (1). These organisms were dominant in milk incubated at 22°C. until the end-point of the clot-on-boiling test in three out of the twelve samples examined and, apparently, had played a major part in their spoilage. Similar strains were isolated in smaller numbers from the samples aged under other temperature conditions.
511. Observations on the serological typing of group N (‘lactic’) streptococci
Authors: Briggs C. A. E. , Newland L. G. M.
Published: June 2009

1. Agglutinating type sera were prepared in rabbits for fourteen representative strains in a collection of sixty-eight group N (‘lactic’) streptococci.

2. Common type antigens, distinct for each named species, were found in strains ofStr. lactis(inhibitory varieties),Str. diacetilactisandStr. cremoris.

3. Certain individuals in each of the named ‘groups’ contained additional heterologous antigens, some of which were identical to heterologous (but not the common) antigens in strains of other groups.

4. Quantitative differences in the representation of common antigens were also found.

5.Str. lactisOJ andStr. cremorisHP were shown to be mirror images of each other so far as their type antigens are concerned, containing two common type antigens in inverse proportions of 4:1 respectively.Str. lactisOJ possesses the ‘cremoris group’ type antigen, and the implications of this observation are discussed.
515. Cheddar-cheese flavour and its relation to tyramine production by lactic acid bacteria
Authors: Dacre J. C.
Published: June 2009

1. Cultures ofStr. faecalis, L. plantarumand a strain ofLeuconostoc, when added to cheese milk, all brought about an increase in Cheddar flavour intensity in the resultant cheese.

2. Examination of the cheeses for tyramine content showed that the formation of the amine bore no relationship to the increases in flavour intensity. The production of tyramine appeared to be merely incidental in the cheese-ripening process.

3. A survey among the lactic acid bacteria disclosed only one species containing a significant amount of the L( – )-tyrosine decarboxylase enzyme—L. brevis. This species added to cheese milk causes an objectionable ‘yeasty’ flavour in the final cheese.
522. Automatic apparatus for drawing the milk-ejection curves of dairy cows under controlled milking conditions
Authors: Whittlestone W. G. , Phillips D. S. M.
Published: June 2009

An improved milk-flow recording instrument is described which is completely controlled by the milking operations in an experimental dairy and which automatically indicates the end of milking in terms of a predetermined rate of milk flow. The instrument makes possible the recording of milk-ejection curves without changing the milking routine or requiring an additional operator in the milking shed.
528. The inhibition of micro-organisms by raw milk: II. The separation and electrophoretic examination of two different inhibitory fractions
Authors: Auclair J. E. , Berridge N. J.
Published: June 2009

The two substances previously assumed to be necessary for the bacteriostatic action of raw milk have been concentrated and separated from one another. Electrophoretic experiments have shown that the preparations, though highly active, are still far from pure and that it should be possible to obtain material of much greater potency.
545. Studies of the secretion of milk of low fat content by cows on diets low in hay and high in concentrates: II. The effect of the protein content of concentrates
Authors: Balch C. C. , Balch D. A. , Bartlett S. , Cox C. P. , Rowland S. J. , Turner Jill
Published: June 2009

1. Twenty cows were used in an experiment to compare the effect of five different diets on the fat and solids-not-fat content and yield of milk.

2. During initial and final control periods all the cows received 18 lb. hay daily and about 4 lb. of a balanced concentrate mixture (crude protein 16·5%) per 10 lb. of milk produced. In the experimental period, which lasted 7 weeks, a control group of four cows remained on this diet. Two similar groups received daily only 4 lb. hay and about 6 lb. extra concentrates; in these groups the concentrates contained 22·3% crude protein. The remaining two groups received similar treatment except that the concentrates contained only 11·6% crude protein. In addition, 10 1b. macerated delignified straw pulp (containing 1 lb. crude fibre) were given to half the cows receiving each type of concentrate. At the end of the experiment the cows were turned out to grass.

3. With the diets low in hay and high in concentrates there was a fall in the fat content of the milk, with some variability in the response of individual cows (see 4 below). With the concentrates high in protein, the fall appeared to be rather slower than with those low in protein, but by the sixth and seventh weeks of experimental treatment it was estimated to be 0·67% fat with high and 0·72% fat with low protein concentrates. The experiment showed, therefore, that serious falls in fat content may occur in cows early in lactation with diets of 4 lb. hay and concentrates containing 22·3 or 11·6% protein. The addition of a limited amount of crude fibre as straw pulp brought about no recovery in milk fat content.

4. The extent of the depression brought about by the change to diets low in hay diminished with advancing stage of lactation.
551. Variations in the fat content of human milk during suckling
Authors: Whittlestone W. G. , Perrin Dawn R.
Published: June 2009

It has been shown that human milk, like cow's milk, increases in fat content during suckling. The increase is not associated with any systematic change in fat globule size distribution. Human milk fat globules, like those of the cow, have been shown to cluster at body temperature. These facts support the theory that the increase in fat content during suckling is due to the fine ducts filtering out the larger globule clusters.
556. The use of seaweed meals in concentrate mixtures for dairy cows
Authors: Burt A. W. A. , Bartlett S. , Rowland S. J.
Published: June 2009

The relative effects upon milk yield and composition of three concentrate mixtures containing 10% of two types of seaweed meal (Ascophyllum nodosum and Laminaria cloustoni) and an oatfeed-salt mixture, have been observed.

Each cow received daily a basal ration of 30 lb. marrowstem kale and 18 lb. hay for maintenance and the first 1½ gal. of milk and 31½ lb. concentrates for each gallon thereafter.

No significant effects of treatment upon milk yield or fat percentage were observed.

The milk produced on the oatfeed-salt mixture had a slightly but significantly higher solids-not-fat content than that on the mixtures containing seaweed meals.

The results showed that seaweed meals have a nutritive value no greater than that of a mixture of 7 parts oatfeed and 1 part salt, which had an estimated starch equivalent of only 39.

In view of the relatively high cost, low palatability and low nutritive value of seaweed meals, their possible use in the feeding of dairy cows appears very limited.
560. The incidence of penicillin in milk supplies
Authors: Storrs F. C. , Hiett-Brown Winifred
Published: June 2009

1. In surveys carried out in the summer of 1951, 1·4% of churn milk contained penicillin in one group of tests and 2·8% in another. Bulk milk was free from this antibiotic.

2. In a further survey carried out in the winter of 1953, 3·2% of composite churn milk contained penicillin. Bulk milk was again free, but small aggregates of a few supplies used for making bulk starters sometimes contained penicillin.

3. Of twenty samples of milk and seven of whey examined during 1951–3, and which were implicated in starter failure, only two milks and one whey contained penicillin in significant amounts.

4. The rate of excretion of penicillin from the composite milk of a herd containing thirty-seven treated cows was determined. Milk up to the fifth milking contained sufficient penicillin to cause starter inhibition.
576. The volatile compounds associated with oxidized flavour in skim milk
Authors: Forss D. A. , Pont E. G. , Stark W.
Published: June 2009

Using chromatographic techniques, a number of compounds was isolated from the steam distillates of skim milk containing oxidized (cardboard) flavour. The following compounds were definitely identified: acetone, acetaldehyde, n–hexanal, crotonaldehyde, and the C5 to C11 2-unsaturated aldehydes. Presumptive evidence for the presence of several 2,4-diunsaturated aldehydes of medium chain length was obtained also. Acetaldehyde and acetone were also isolated from normal skim milk; these two compounds appear to play no part in the defect.

2-Enals, in particular the C8 and C9, were considered to be the principal flavour-determining compounds. In milk at dilutions of 1 part in 107 to 109 they impart an oxidized type of flavour resembling that known as cardboard. Evidence was obtained that 2,4-dienals were also present and they produced a similar flavour.

It may further be deduced that cardboard flavour in milk is caused by the preferential oxidation of di- and polyunsaturated fatty acids.
578. The composition of the milk of the blue whale
Authors: Gregory Margaret E. , Kon S. K. , Rowland S. J. , Thompson S. Y.
Published: June 2009

The detailed composition of samples of milk from three blue whales (Balaenoptera sibbaldi) is reported in terms of total solids, fat, solids-not-fat, total protein, casein, soluble proteins, non-protein nitrogen, lactose, chloride, ash, calcium, phosphorus, sodium, potassium, magnesium, vitamin A, thiamine, biotin, riboflavin, nicotinic acid, vitamin B6, pantothenic acid and vitamin B12.

The composition of the milk of the whale is compared with that of other species.
580. The deterioration of milking rubbers: IV. Fat in milk liners
Authors: Cooper J. H.
Published: June 2009

Following the earlier papers in this series ((1)–(4)) further work has been carried out on the fats and greases which attack milking rubbers. The sources from which they come have been investigated and an estimate made of the composition of the fatty material obtained from used milk liners.
584. Spore-forming organisms in commercial sterilized milk
Authors: Grinsted Elisabeth , Clegg L. F. L.
Published: June 2009

A study has been made of the cultural and biochemical characteristics of heat-resistant thermophilic and mesophilic spore-forming bacteria isolated from raw and sterilized milk. The tests hitherto used in classifying this group of bacteria have been examined and some modifications suggested; as a result a simplified method of distinguishing different resistant spore-forming organisms in milk is proposed. The types of micro-organisms were few. The thermophiles were restricted toB. calidolactisand of the mesophilesB. subtilispredominated in sterilized milk andB. licheniformisin raw milk.
602. Experiments in cheesemaking without starter
Authors: Mabbitt L. A. , Chapman Helen R. , Berridge N. J.
Published: June 2009

Cheese has been successfully made from raw and pasteurized milk by a process similar to that employed for Cheddar or Cheshire-type cheese but omitting the starter inoculum.

In the preferred method gluconic acid lactone was used as the acidifying agent during the setting of the curd and after milling.

The flavour of the best products was acceptable to a number of people not necessarily experienced in cheese-tasting, but it was different from that of normal Cheddar.

No improvement in flavour was achieved by inoculation of the cheese milk with a strain of L. casei and L. brevis.

Further detailed investigation is needed to perfect the process and to determine whether its use in industry is justified or desirable.
603. Development of serologically identified lactobacilli added to cheese made without starter
Authors: Sharpe M. Elisabeth
Published: June 2009

Lactobacilli are found in large numbers in cheeses of many varieties, and it is therefore believed that they are concerned with the development of flavour. In investigating this, Mabbitt(1) made cheese without starter, adding strains of lactobacilli to the cheese millr to determine whether flavour would then develop. The serological types of the lactobacilli were known, and the present paper describes the serological methods of identifying the strains of lactobacilli which were recovered from the cheese with those which were added.
607. Winter feeding of dairy cows: I. The influence of level and source of protein and of the level of energy in the feed on milk yield and composition
Authors: Holmes W. , Waite R. , MacLusky D. S. , Watson J. N.
Published: June 2009

1. The effect of feeding levels of protein and energy appreciably higher than the Woodman standards on the yield and composition of the milk from twelve Ayrshire cows has been studied in two winter-feeding experiments.

2. In the first experiment the S.E. of the concentrate ration was held constant at 63½% and the D.C.P. content adjusted to 10, 15 and 17%. The 10 and 15% D.C.P. concentrates derived their protein from home-grown feedingstuffs, whereas the 17% D.C.P. concentrate was a bought-in commercial mixture. Feeding the three levels of D.C.P. led to no statistically significant differences in milk yield, milk composition or live-weight gain, although the commercial mixture (17% D.C.P.) resulted in milk with a slightly lower fat content.

3. The second experiment reversed the feeding conditions of the first, i.e. D.C.P. was held constant at 16% and three concentrates were fed which contained 59, 67 and 75% S.E. respectively. The two rations of higher S.E. content gave significantly more milk than the low S.E. ration and tended to give slight increases in live weight. There was a slight increase in the S.N.F. content of the milk when the S.E. of the concentrate was raised from 59 to 67% S.E. This was due almost entirely to an increase in the protein content of the milk. There was no further increase in S.N.F. with the 75% S.E. concentrate, and this latter concentrate produced milk with a slightly lower fat content.

4. Comparison of costs and returns showed that the cheap low protein concentrate, ration C, even though it gave the least milk, yielded the highest profit. It was shown, however, that at any reasonable fixed cost of starch equivalent the most profitable level of feeding above the Woodman maintenance standard was 3–3·3 lb. S.E./10 lb. of milk of 3·8–4·0% fat. Alternatively, the total ration should be 110–117% of the Woodman standard.
608. Winter feeding of dairy cows: II. Dried grass produced in spring and in autumn compared with other concentrates and with spring grazing
Authors: Holmes W.
Published: June 2009

1. Two experiments were carried out to compare spring-dried grass and autumn-dried grass. In both experiments a 3×3 Latin square changeover design was used with periods of 4 weeks. In the first the control ration was a home-grown concentrate mixture (S.E. 58, D.C.P. 12·5%), in the second a high-quality mixture of imported feeds (S.E. 73·5, D.C.P. 16·6%). The concentrates or dried grass were fed in addition to a basal ration which supplied only the maintenance requirements of the cow.

2. In both experiments the milk yield from spring grass was 3–5% higher than that from autumn grass, but the differences were not statistically significant. In Exp. 1 the yield from the home-grown mixture was the same as from spring grass. The yield from the imported mixture in Exp. 2 was significantly higher than from both grass rations. There was a significant increase in milk yield when the cows went on to spring grazing in Exp. 1.

3. Expression of the feed input as a percentage of the Woodman standards showed that the level of feeding was similar in all three rations in the first experiment, and that the increased milk yield from the high-quality ration in the second experiment could be explained by the increased level of feeding which it gave. It was considered that the increased yield on spring grazing might have been caused simply by an increase in the amount of nutrients consumed.
612. Steam distillation of taints from cream: II. Investigations on commercial equipment with use of diacetyl and acetoin as reference substances
Authors: McDowall F. H.
Published: June 2009

The extent of removal of the reference substances diacetyl and acetoin from water and cream in the Vacreator under varied conditions of operation has been investigated.

1. It was not affected by change in diameter or length of the uptake-pipe, or, with water, by changing the position of the equilibrium-valve to the top of the uptake-pipe or by introduction of the steam at the bottom of the pasteurizer bend instead of at the normal steam inlet.

2. It was affected only slightly by inclusion of baffles in the uptake-pipe, to provide a more intimate contact of steam and cream.

3. With diacetyl in water it was not affected by introduction of the major proportion of the steam via the infuser connexion, and with diacetyl in cream it was not affected until the proportion of steam introduced via the infuser was greater than 50% of the total amount of steam used. With acetoin in both water and cream there was a progressive slight reduction in extent of reference substance removal with increase in proportion of steam introduced via the infuser.

4. With diacetyl and acetoin in water it was not affected by increase in rate of flow of steam and cream at constant intensity of treatment.

5. With diacetyl it was not affected by temperature of steam distillation over the range 138–197°F., but with acetoin there was a progressive reduction in extent of removal with decrease in distillation temperature.

6. Steam is most effectively used if it is applied in separate stages instead of in one stage, i.e., a multiple Vacreator uses steam more efficiently than a single-unit machine. This effect is more marked with diacetyl, which has a high equilibrium coefficient, than with acetoin, which has a low coefficient.

7. The equilibrium coefficient computed from steam treatment of diacetyl solutions in the Vacreator is of the same order as that determined by the laboratory continuous equilibrium vaporization apparatus.

8. The efficiency of cream-deodorization equipment may be lowered by condensation of vapour back into the liquid, e.g. by use of excess cooling water in the Vacreator jackets.

9. There are indications that removal of diacetyl from cream is somewhat slower than from water.

The thanks of the author are due to Mr J. K. Scott for helpful discussion, to Mr E. R. Elley who did the analytical work, and to Mr B. Le Heron for assistance in the operation of the Vacreator and collection of samples.
619. Host-phage relationships of cheese starter organisms: II. Effect of phage activity on heterologous strains of lactic streptococci
Authors: Naylor Jill , Czulak J.
Published: June 2009

A reaction closely resembling the nascent phage phenonomenon was studied. When lysing the homologous strains ofStr. lactis, two phage races were found to be capable of simultaneously inducing lysis of a heterologous strain and of other phage-resistant homologous strains. Seitz filtered potent lysates of the homologous strains also caused lysis. Subjecting the lysates to a temperature of 60°C. for 5 min. destroyed the lytic activity on heterologous strains but did not inactivate the phage.

These two phage races produced haloes around their plaques while a third phage, unable to induce lysis of heterologous cultures, showed no haloes. Addition of I3-to the medium suppressed the appearance of haloes, providing further evidence that they are due to the production of bacterial lysins.

Evidence was obtained to show that several other possible mechanisms were not responsible for the observed lysis, and it was concluded that a heat-labile lysin or lysins capable of destroying the heterologous strain was produced during lysis of the homologous strain. The relationship of this to the nascent phage and other similar phenomena observed elsewhere is discussed.
626. Udder infections in the ‘dry period’: IV. The relationship between the new infection rate in the early dry period and the daily milk yield at drying-off when lactation was ended by either intermittent or abrupt cessation of milking
Authors: Oliver J. , Dodd F. H. , Neave F. K.
Published: June 2009

1. Records were collected from a herd where many cows were producing relatively high daily yields of milk at the time of drying-off. Animals giving 7 lb. of milk or less daily were dried off by intermittent milking, and those giving over 7 lb. daily were dried off by ‘stop’ milking. The data from 113 dry periods were analysed so that a comparison could be made of the new infection rate in the early dry period according to level of production at drying-off.

2. The new dry-period infection rate was found to increase with yield at drying-off. This was not due to age differences between the groups of cows.

3. The rise in total infection rate with yield was due mainly to an increase in Str. agalactiae infections.

4. A high proportion of clinical quarters were detected in the dry period by the cowmen.

5. The yield in the lactation following the dry period studied was not related to yield at drying-off.

6. New dry-period infections were significantly (P <0·01) more numerous in quarters of cows that had been hand-stripped during lactation compared with quarters of machinestripped cows.
628. Further studies of immersion cleaning of milking equipment
Authors: Thiel C. C. , Clegg L. F. L. , Clough P. A. , Cousins Christina M. , Akam D. N. , Gruber Marie
Published: June 2009

Further studies of immersion cleaning have shown that no deposition of calcium soap and inorganic calcium salts occurs if the immersion solution contains ethylene diamine tetraacetic acid. Compared with results for the previous year there was a marked improvement in the bacteriological state of liners as a result of the absence of calcium deposits. It has also been shown that the addition of tetramethylthiuram disulphide to the rubber mix from which liners are made gives useful bactericidal properties. The intensity of the bactericidal action was little reduced after liners had been in farm use for 4 months.
632. Reactivation of milk phosphatase following heat treatment: IV. The influence of certain metallic ions
Authors: Wright R. C. , Tramer J.
Published: June 2009

1. Reactivation of alkaline milk phosphatase is affected by the presence of ions, Mg2+, Zn2+and Mn2+being activating and Cu2+, Ni2+and Co2+being inhibitory.

2. Cu2+will inhibit reactivation induced by Mg2+, but has no effect upon Zn2+-induced reactivation.

3. Using washed cream, either alone or in admixture with boiled whey treated with cationic resin, reactivation occurs in the presence of added Mg2+, but not when Zn2+is added.

4. Experiments with EDTA. confirm that metallic ions play a part both in alkaline phosphatase activity and in reactivation.

5. It is suggested that either Mg2+or Zn2+or both play a part in reactivation.
635. The estimation of the total volatile fatty acids in cheese
Authors: Barnett A. J. G. , Tawab G. A.
Published: June 2009

An extraction method is described for determining the volatile fatty acids in cheese. The method, dependent upon Soxhlet extraction and micro-distillation, is speedy with regard to actual manual operation and gives results in accordance with those obtained by lengthier established methods.
640. Some bacteriological aspects of commercially sterilized milk: II. Type of sporeforming bacteria isolated
Authors: Candy M. R. , Nichols Agnes A.
Published: June 2009

Cultures of sporeforming bacteria isolated from commercially sterilized milk were examined and seasonal variations in the incidence ofB. subtilis/B. licheniformisstrains were apparent which may account for the increased rate of spoilage at 30° C. during the winter.

B. subtiliswas the most common mesophilic sporeformer isolated, and under favourable conditions it produces rapid digestion of milk.

Thermophilic sporeformers are frequently present, and usually produce a firm acid clot in milk held at temperatures favourable for their growth. The classification of the thermophiles isolated is uncertain and a review of the classification of the aerobic thermophilic sporeformers in general is required.

Cl. thermosaccharolyticum, a gas-producing thermophile, was isolated from sterilized milk.
647. Winter feeding of dairy cows: IV. The influence of four levels of concentrate feeding in addition to a basal ration of grass products on the production obtained from milking cows
Authors: Holmes W. , Reid D. , MacLusky D. S. , Waite R. , Watson J. N.
Published: June 2009

1. An experiment is described which assessed the effects on the production obtained from milking cows, of feeding a concentrate with a starch equivalent of 64 at four levels (0, 2, 4 and 6 lb./gal. of milk produced), in addition to a basal ration with limited amounts of hay and dried grass and with silage fed ad lib.

2. The total daily dry-matter intake of the cows increased from 2·2 to 2·7% of the live weight as the rate of concentrate feeding was increased from 0 to 6 lb./gal., despite a reduction in the amount of roughages consumed.

3. For each increase of 1 unit in silage dry-matter percentage, there were increases of from 1·18 to 0·42 lb. of silage bry-matter intake per cow per day as the level of concentrate feeding increased. For each increase of 1 lb. in silage dry-matter intake there was an increase of l lb. in total dry-matter intake per cow per day.

4. The average daily milk yield per cow increased from 22·2 lb. when no concentrates were fed to 27·6 lb. when 6 lb. concentrates were fed per gallon of milk produced. This is an increase of 0·9 lb. milk/lb. increase in starch equivalent intake. A significant difference in response was found between higher yielding and lower yielding groups of cows. The higher yielding group gave an increase of 1·1 lb. and the lower yielding group only 0·6 lb. milk/lb. increase in starch-equivalent intake.

5. At the general level of feeding and of milk yields obtianed in this experiment, no evidence of diminishing returns in milk production was detected when the rate of concentrate feeding was increased.

6. The content of solids-not-fat in the milk rapidly increased from 8·3% when no concentrates were fed to 8·6% when 4 or 6 lb. of the concentrates were fed per gallon of milk produced.

7. When concentrates were fed at the rate of 0 and 2 lb./gal. declines in live weight as well as in the yield and solids-not-fat content of the milk were noted, while at 6 lb./gal. there was an unnecessary gain in live weight. It is concluded, therefore, that with the particular animals and roughages used in this experiment, the optimal level of concentrate feeding was 4 lb./gal.
648. Weight Changes in grazing cows
Authors: Balch C. C. , Line C.
Published: June 2009

1. Under various feeding regimes the entire contents of the reticulo-rumen of fistulated Shorthorn cows were repeatedly removed, weighed, sampled and returned.

2. With cattle grazing grass/clover swards, but not with others grazing green cereals, there was a very marked tendency for less digesta to be found in the reticulo-rumen than with several winter diets.

3. An average fall of 71±24 lb. was found in the weight of a mixed herd of thirty-eight Friesian and Shorthorn cows when they were changed suddenly from winter diets to grazing. Simultaneous observations on three fistulated cows showed that 84% of such short-term variation in weight could be explained by variation in the weight of the digesta in the reticulo-rumen. It is likely that smaller, parallel variations in the weight of the contents of the remainder of the gut accounted for most of the remaining differences.
653. A calorimetric study of milk, cream and the fat in cream
Authors: Phipps L. W.
Published: June 2009

Specific heat data have been obtained for separated milk, whole milk, cream (15% fat content) and the fat in cream, under certain well-defined experimental conditions. With standardized techniques of sample preparation, the results were repeatable within the errors of the experimental methods employed.

An examination of the effects on the specific heat curves of milk fat of different modes of thermal treatment has provided information on the melting and solidification behaviour of the fat. The degree of dispersion of the fat in cream has been shown to be an important consideration.

My thanks are due to Miss H. R. Chapman of the Institute dairy, for supplying milk and cream samples, and to Mr J. H. Prentice and other members of the Physics department for useful discussion.
654. A rapid method for estimating the size distribution of fat globules in cream
Authors: Dolby R. M.
Published: June 2009

The proportion of fat present in cream as small globules (approximately 1 μ and under) is estimated from the proportion of the total fat which remains in the serum when a sample of the cream, diluted to 10% fat, is centrifuged at 60° C. for 30 min. at 3000 r.p.m.

The fat present as large globules (7 or 8μ and over) is estimated by finding the proportion of the fat which rises 1 cm. in 60 min. when the cream, diluted to 10% fat, is held at 60° C. in a modification of the Andreasen particle-size apparatus in which the jar is replaced by a conical flask and the tip of the sampling pipette is held 1 cm. from the flat bottom of the flask.

The thanks of the author are due to Dr F. H. McDowall for helpful advice and criticism and to Miss R. P. Johnson for assistance with the experimental work.
658. Factors influencing the vitamin content of milk fat: IV. The source of milk fat vitamin A and carotene
Authors: McGillivray W. A.
Published: June 2009

1. The effect of varying levels of vitamin A ester in the blood plasma of cows on the levels of vitamin A ester in their milk fat has been investigated.

2. The milk fat levels reflect plasma levels, but it appears that, irrespective of the immediate carotene or vitamin A intake of the animals or of their liver reserves, some of the milk fat vitamin A ester is derived from vitamin A of other than immediate dietary origin.

3. It is suggested that the bulk of the plasma carotene contributes little to the level of carotene in the milk fat. The latter derives mainly from the carotene of immediate dietary origin which, during transport from the intestines to the storage organs, is associated with dietary fat and vitamin A ester in the chylomicrons.

The author is grateful to the Department of Scientific and Industrial Research for a grant towards this investigation; also to Mr M. R. Patchell and the farm staffs of The Dairy Research Institute (N.Z.) and Massey Agricultural College for assistance with the feeding and dosing of the animals and the collection of milk samples. The assistance of Miss Fay Frecklington with some of the experimental work and of Mr A. C. Glenday with statistical examination of the results is also acknowledged.
671. The association between the fat percentage of cows' milk and the size and number of the fat globules
Authors: King J. O. L.
Published: June 2009

Milk samples were collected, between 17 April and 30 May 1956, from fifty-six Ayrshire and forty Friesian cows, which had been calved for between 45 and 165 days, when they were running out at grass day and night. The results showed that differences in the fat percentages of their milk were accompanied by corresponding variations in the average diameter of the globules in both breeds and in the numbers of globules per cu.mm. in the Friesian cows. These changes were not significant for either variant because there were some individuals in which changes in fat percentage appeared to be accounted for by either an increase in fat globule diameter or an increase in the number per cu.mm. with correspondingly low figures for the other variant.
673. Bacteriology of Cheddar cheese: A study of starter organisms in manufacture and maturing
Authors: Dawson D. J. , Feagan J. T.
Published: June 2009

1. The trends of starter bacteria population during the manufacture and maturing of Cheddar cheese have been investigated. Fourteen strains consisting of Str. lactis, Str. diacetilactis and Str. cremoris have been studied.

2. Physiological and morphological characteristics of the fourteen strains were examined.

3. Population studies during manufacture showed that the three species of starter organism attain quite different maximum populations and at different stages of the cheesemaking process. Str. lactis (4500 millions/g.) and Str. diacetilactis (2900 millions/g.) reached their maximum half way through Cheddaring, whereas Str. cremoris (960 millions/g.) reached its maximum at milling.

4. Str. lactis was shown to maintain its maximum population until the cheese left the press, whereas Str. diacetilactis and Str. cremoris steadily declined after reaching their maximum.

5. Counts of the different starter cultures used showed considerable variation between and within strains, particularly in the case of Str. cremoris.

6. No relationship was shown to exist between acidity development and starter populations developed.

7. The study of cell distribution in the cheese curd has shown that whereas Str. lactis and Str. diacetilactis gave an even scattering of diplococci, Str. cremoris showed colony formation.

8. Str. lactis strains maintained a high but declining population during maturing of the cheese, the starter beginning to die out gradually after 8 weeks. Str. diacetilactis showed similar trends but at lower populations levels. Str. cremoris, on the other hand, gave much lower populations, the starter dying out rapidly after 2 weeks, and virtually disappearing at 8 weeks.

9. Persistence of starter bacteria in the cheese appears to be correlated with salt tolerance and chain length.

10. Starter bacteria isolated from the cheese made with Str. lactis have shown a low proportion of slow acid-producing types in contrast to a high proportion found with Str. cremoris.

11. The non-starter bacteria in the cheese were found to consist on the average of 30% micrococci and 70% lactobacilli. Negligible numbers of other genera were isolated.
678. The effect of variations in nutrient intake upon the yield and composition of milk II. Factors affecting rate of eating roughage and responses to an increase in the amount of concentrates fed
Authors: Burt A. W. A.
Published: June 2009

1. Rates of eating hay, kale and concentrates and responses to a 3 lb. increase in the daily concentrate allowances when roughage was rationed on a ‘group’ basis, were measured in fourteen Ayrshire cows and fifteen heifers.

2. There were significant differences between animals, between days, and significant cow × period interactions, in rates of eating in both groups. The cows were a more variable group and generally ate faster than the heifers. Although the rate of eating fresh kale tended to decrease with increasing dry-matter percentage, the rate of eating kale dry matter was positively and significantly related to the dry-matter percentage.

3. There were positive associations between the rates of eating of the three different foods, and of these with live weight, but no effects of milk yield or stage of lactation, and no marked effects of climatic conditions could be detected.

4. The errors in the determination of mean rates of eating were such that observations made on 4–5 days gave satisfactory comparisons of individual rates of eating.

5. Reponses in milk yield to additional concentrates were positively correlated with milk yield, and no independent effects of stage of lactation could be detected. Responses by the heifers were less then those of cows giving similar yields.

6. Responses in solids-not-fat percentage were greatest in those cows with inherently low percentages.

7. There was no relationship between rates of eating roughage and responses of milk yield to additional concentrates, but live-weight responses and, to a lesser extent, solids-not-fat responses were negatively correlated with rates of eating in the cows. It was concluded that the level of feeding, system of management and the roughage:concentrate ratio used were such as to eliminate the effects of rates of eating roughage upon milk yields, if indeed such effects exist.