bluuebunny/crossref_metadata_2025 huggingface dataset:
439. The rate of creaming of raw cows' and buffaloes' milk
Authors: Fahmi A. H.
Published: June 2009

A preliminary investigation was carried out on the effects of two ranges of temperature (room and refrigerator) on the creaming properties of cows' and buffaloes' milk. The results reported show that:

(1) While refrigerator temperature favoured the creaming of cows' milk, it greatly retarded the creaming of buffaloes' milk. This retarding effect was associated with a smaller cream-layer volume and a greater percentage of fat in the skim milk.

(2) At room temperature, the creaming of buffaloes' milk proceeded much more rapidly, suggesting that fat clumping was probably being induced.

(3) For both kinds of milk, when creamed at room temperature, the maximum values of the cream-layer volume and the specific cream-volume were found to be less than when creaming occurred in the refrigerator: reverse temperature relationships were observed in connexion with the maximum fat content of the skim milks.

In conclusion, it may be added that the observed variations in the cream-layer volume, and the fat content of the skim milks resulting from creaming at the two different temperature levels and for the varying lengths of time, would clearly result in some variability in any cheese made from such milk. This would particularly affect the yield, quality, composition and nutritive value of the cheese.
442. Variations in composition of cows' milk during a period of 12 weeks
Authors: Featherstone J. , Rickaby C. D. , Cavell A. J.
Published: June 2009

The milk from twelve individual cows in a mixed herd in Shropshire was sampled twice weekly over a period of 12 weeks, which covered the transition from winter to summer conditions of feeding. Detailed analytical results are tabulated, and certain figures presented in graphical form. In addition, bulk samples of both morning's and evening's milk were obtained and tested for fat and solids-not-fat.

On the whole the results show great individual consistency of composition, but an appreciable rise in the crude protein content of the milk from all cows took place in late April and in May, this effect being attributed to the change-over in feeding to an all-grass diet. From a consideration of the figures obtained, it is deduced that:

(1) The average composition of mid-lactation milk may differ markedly from cow to cow, but appears to be unchanged by minor alterations in the winter rations, provided these are reasonably satisfactory to begin with. There is, however, a marked increase in total protein resulting from the introduction of spring-grass feeding.

(2) The results show that a herd, although well-fed and efficiently managed, may produce milk in the late winter months, and even in the early spring, which is below the legal standard of 8·50% in s.n.f.
445. The differentiation of the lactic streptococci and their antibiotics
Authors: Hirsch A. , Grinsted Elisabeth
Published: June 2009

Twenty-three strains of lactic acid streptococci were shown to be types ofStreptococcus cremorisorStr. lactisby cultural, biochemical and serological means. The antibiotics produced by thecremorisstrains could be differentiated readily from thelactisantibiotics, of which at least five different varieties are described. A cross-test and a resistant-strain test were used to differentiate the antibiotics.
446. A note on the inhibition of an anaerobic sporeformer in Swiss-type cheese by a nisin-producing streptococcus
Authors: Hirsch A. , Grinsted Elisabeth , Chapman Helen R. , Mattick A. T. R.
Published: June 2009

Cheese of the Swiss (Emmenthaler, Gruyère, Danish-Swiss) type is popular on the continent of Europe and in America, but severe losses in ripening are caused by contamination with anaerobic sporeformers. Active gas production by the clostridia during ripening causes distension and spoiling of the cheese which becomes unmarketable.
449. The deterioration of milking rubbers: I. The effect of micro-organisms
Authors: Berridge N. J.
Published: June 2009

It has been shown that, although they are present, sulphur bacteria and streptomyces able to oxidize rubber do not affect the life of the rubber teat-cup liners of milking machines.
478. Hard cheese made from Egyptian cows' and buffaloes' milks
Authors: El-Sokkary A. M. , Hassan H. A.
Published: June 2009

1. Hard cheese of Cheddar, Derby and Manfis types was made from cows' milk and from buffaloes' milk. Buffaloes' milk curd of the Derby type was also milled at different acidities.

2. Initial acidity was higher and rate of acid development was greater in cows' milk and curd, whilst loss of fat in the whey was lower.

3. Cows' milk cheese contained more moisture, more total, soluble, and non-protein nitrogen, but less fat than buffaloes' milk cheese.

4. During ripening, the rate of acid development and protein degradation was greater in cows' milk cheese, whilst loss of moisture was usually smaller.

5. Buffaloes' milk cheese was inferior in grading quality to cows' milk cheese.

6. Attempts to improve the quality of buffaloes' milk cheese were made by altering the Derby cheese-making process as follows:

(a) ripening milk longer before renneting;

(b) modification of the milk casein/fat ratio;

(c) combining (a) and (b);

(d) modification of the casein/fat ratio plus scalding of the curd at a lower temperature and for a shorter time.

7. The last treatment (d) proved most effective and yielded cheese of very similar chemical composition and grading quality to that obtained from cows' milk.
483. The evolution of the lactic streptococci
Authors: Hirsch A.
Published: June 2009

Although milk may be considered to be the normal habitat of the lactic streptococci, their adaptation to this environment must have followed the domestication of mammals, for these organisms are not pathogenic and do not normally occur in the udder. If this reasoning is accepted, then the small biological age of these organisms logically follows, and possibly they are the youngest members of this genus.
489. The physical properties of sow's milk as a function of stage of lactation
Authors: Whittlestone W. G.
Published: June 2009

The milk from ten sows has been studied over one lactation. The density, viscosity, electrical conductivity and pH have been recorded tbroughout the lactation, and in two cases the study extended to the colostrum.
508. Note on the corrosion of aluminium dairy equipment by water
Authors: Botham G. H. , Bryson W. R.
Published: June 2009

Some few months ago the National Agricultural Advisory Service, South West Sub-Centre, encountered several farms in their area where failure to reach the required standard for designated milk appeared to be connected in some way with pronounced pitting corrosion of aluminium alloy milking buckets, and, on the suggestion of Dr A. R. T. Mattick of the National Institute for Research in Dairying, Reading, the authors of this note were given the opportunity of examining a corroded pail and of tracing the source of the corrosion, if possible.
509. Bacteriological studies on pasteurized milk
Authors: Alexander Hazel , Higginbottom Constance
Published: June 2009

1. The numbers and species of micro-organisms surviving in commercial high-temperature short-time pasteurized milks sampled direct from the cooling section of the pasteurizer have been determined and compared with those in the corresponding raw milk and in the raw milk after low-temperature pasteurization in the laboratory.

2. The geometric mean counts at 37° C. for twenty-five samples of raw, L.T. and H.T.S.T. pasteurized milks were 74,130, 1,740 and 3,200 per ml. respectively. The corresponding figures at 30° C. were 123,030, 7,080 and 8,510 per ml.

3. The percentage destruction of the bacteria was slightly smaller at all four plants for the H.T.S.T. pasteurized milks than for the corresponding L.T. pasteurized milks. The mean percentage destruction for the L.T. pasteurized milks was 97·7% for bacteria growing at 37° C. and 94·3% for bacteria growing at 30° C. The corresponding figures for the H.T.S.T. pasteurized milks were 95·9 and 93·1%.
516. A simple method for preparing crystalline rennin
Authors: Berridge N. J. , Woodward Cora
Published: June 2009

The preparation of crystalline rennin previously described (1) was somewhat long and inconvenient, but the knowledge gained about the properties of the crystals suggested that a simpler method might be successful. Since then Møgensen (2) has shown that the mere precipitation of commercial rennet with saturated sodium chloride gives a product with proteolytic properties resembling those of the crystalline material, and with enhanced milk-clotting activity per unit of dry weight. Some years previously, Hankinson (3) had also achieved considerable purification by these means. The results of an attempt to discover a simple method of crystallization are described below.
521. Normal variations in the rate of machine milking
Authors: Dodd F. H.
Published: June 2009

1. A study has been presented of the machine milking rate of 141 cows recorded in 326 lactations.

2. The coefficients of variation between cows of various measures of machine milking rate are usually in the range 30–40%, whilst the within-cow variations are of the order of 8–11%.

3. The differences between the milking rates of cows in a single herd are given, together with the distribution of these differences.

4. Milking rate declines as lactation advances, the decline being greater for fast milking cows.

5. Lactation decline in milking rate is related independently to change in milk yield and to interval since calving.
527. A study of variation in twin cattle: II. Fertility
Authors: Donald H. P. , Anderson D.
Published: June 2009

1. Results from a uniformity trial with fifteen pairs each of one-egg and two-egg twins and pairs of half-sibs are described.

2. Intra-pair variance in age at the first observed heat was less for the one-egg than for the other pairs but not significantly so. The slowest growing pairs showed delay in onset of heat.

3. 71·8% of the intervals between heats shown by unserved heifers were 17–27 days in length. No genetic variation and no individuality could be detected in either this character or the number of services per conception.

4. The variance in the gestation period was less within the one-egg than within the other pairs but not significantly so.
538. The estimation of the energy of sow's milk from fat and total solids content
Authors: Perrin Dawn R.
Published: June 2009

In studies where regular analyses of sow's milk are being made in an effort to evaluate the total energy content of the milk from sows at different dietary levels, once the composition trends of the milk have been assessed, the number of analyses can be considerably reduced and a greater number of samples handled. Satisfactory calorific values can be obtained from the estimated composition requiring analyses for fat and total solids only.
539. The effect of temperature treatment of cream before churning on the consistency of butter
Authors: Dolby R. M.
Published: June 2009

1. Measurements of hardness and ‘free-oil’ content of samples of butter from cream held at various temperatures before churning were made before and after storage. Hardness was determined by the sectility method, while free-oil content was estimated from the weight of oil exuding from thin slices of butter sandwiched between filter-papers and held at 64–4° F. (18° C).

2. Butter from cream held at 60° F. and churned at 45° F. was much softer and contained more free oil than butter from cream held and churned at 45° F.

3. If the cream was precooled to 45° F. before being held at 60° F. the butter was very slightly softer than that from cream held at 60° F. without precooling, but the difference disappeared after storage. It contained rather less free oil, but the softening point of the oil was lower. Fat losses in churning which were high where cream was held at 60° F. were reduced almost to normal when cream was precooled before being held at 60° F.

4. Cream slowly cooled to 45° F. yielded butter which was softer and contained more free oil than that from cream cooled rapidly to 45° F. and held at that temperature. The butter, however, was not so soft as that from cream held at 60° F.

5. Butter from cream held at a temperature below that at which it was to be churned did not differ significantly in hardness or free-oil content from that produced from cream held at the churning temperature.

6. Present commercial methods of cream treatment in New Zealand (rapid cooling to churning temperature and holding at that temperature) give butter of almost maximum hardness for the type of fat involved at each stage of the season.

7. More uniform consistency of butter throughout the season could be achieved only by reducing the hardness of the firmer butter and not by increasing the firmness of the ofter butter.
557. Studies of the secretion of milk of low fat content by cows on diets low in hay and high in concentrates: IV. The effect of variations in the intake of digestible nutrients
Authors: Balch C. C. , Balch D. A. , Bartlett S. , Johnson V. W. , Rowland S. J. , Turner Jill
Published: June 2009

1. Digestibility trials were conducted, and the rate of passage of hay was measured, with five Shorthorn cows during a period of normal diet and during two experimental periods in which diets low in hay and high in concentrates were given. In the first experimental period the concentrates were cubes of the wartime type sold as National Cattle Food No. 1, and containing a variety of constituents; in the second they were a mixture offlakedmaize (50%), weatings (35%) and decorticated ground-nut cake (15%). For convenience these are referred to as concentrate ‘cubes’ and ‘mixture’ respectively.

2. During the initial and final control periods the cows consumed daily 17–21 lb. hay, and about 4·5 lb. concentrates per 10 lb. of milk produced. In the initial control period the concentrates were the concentrate cubes, and in the final they were the concentrate mixture. The hay was reduced to 4 lb. daily during the two experimental periods and the remainder of the standard requirements of the animals were met by concentrates. The concentrates were the cubes in the first experimental period and the mixture in the second experimental period.

3. Seducing the hay to 4 lb. did not affect the fat content of the milk when the other food in the diet was the concentrate cubes, but there was a striking mean fall of 1·04% fat when the cubes were replaced by the concentrate mixture. This represented a loss of over 30% in the yield of fat.

4. Digestibility trials, conducted in the initial control and first and second experimental periods, indicated that the fall in milk fat content was not the result of changes in the amounts of dry matter, crude protein, ether extract, crude fibre, cellulose, cellulosans or pentosans not in cellulose digested. The essential difference between the diet of low hay with the concentrate mixture and the other diets given in this experiment was that it provided a high intake of starch yet had little of the physical property of roughage. It is concluded that depression of milk fat content results from a combination of these two factors and probably originates from changes in the physical and biochemical processes of the reticulo-rumen.

5. The intake of starch equivalent, as calculated from the intake of digestible nutrients, was close to standard requirements in all periods of the experiments, but there was a surplus of digestible crude protein.

6. The mean solids-not-fat content of the milk rose 0·48% at the time of the fall in milk fat, and this was entirely due to an increase in milk protein. After the return to normal diets the recovery of solids-not-fat was slower, but no less complete, than the recovery in milk fat.
558. The secretion of a single tracer dose of labelled iodide in the milk of the lactating cow
Authors: Glascock R. F.
Published: June 2009

1. A tracer dose of 131I in the form of radioactive potassium iodide of about 50µg. in weight has been administered to a lactating cow and the secretion of the radioactivity in the milk studied.

2. The highest activity was found in the milk on the 1st day after dosing and was only slightly lower than that expected if the iodide had been uniformly distributed throughout all the water in the animal's body.

3. The secretion of labelled iodine in the milk attained a maximum on the 1st day after dosing and thereafter declined exponentially with a half period of 1·5 days until the 9th day. The rate of secretion, though still approximately exponential, then had a much longer half period (about 10 days) but was too small to study at the dose level used.

4. Owing to the decay of the element the observed secretion of radioactivity declined more rapidly than that calculated for labelled iodine and over the first 9 days of the experiment had a half period of approximately 1·2 days. Thereafter the radioactivity declined more slowly with a half period of approximately 3·5 days.

5. From these findings it is calculated that regular daily dosing at the same rate would result in an equilibrium level in the milk about 2·3 times the maximum arising from a single dose.

6. Less than 5 % of the original dose was recovered from the milk over the period of the experiment by which time the concentration had declined to 0·5 % of its maximum.

7. The radioactivity in the milk was found to be in the chemical form of iodide ion.
561. The use of phage typing and penicillin sensitivity tests in studies of staphylococci from bovine mastitis
Authors: Price Patricia , Neave F. K. , Rippon Joan E. , Williams R. E. O.
Published: June 2009

In three heavily infected herds there were sufficient types of staphylococci to enable phage typing to be of use in distinguishing between strains present before and after intramammary infusions with antibiotics. Two phage types were rarely found in established infections in one quarter even when three or four distinguishable types were present in a herd. But two types were sometimes found in milk samples when the teat apex was unhealthy and truly aseptic sampling by the usual procedure was impractical. In quarters infected for many months phage type and penicillin sensitivity (and resistance) were found to be very stable. There were only two spontaneous replacements of one phage type by another.
566. Studies of the secretion of milk of low fat content by cows on diets low in hay and high in concentrates: V. The importance of the type of starch in the concentrates
Authors: Balch C. C. , Balch D. A. , Bartlett S. , Hosking Zena D. , Johnson V. W. , Rowland S. J. , Turner Jill
Published: June 2009

1. Three comparable groups of cows were used to investigate the effect, on milk composition and yield, of diets consisting of 4 lb. hay daily and concentrates containing 35% weatings, 15% decorticated groundnut cake and 50% of either flaked maize, maize meal or dredge corn (crushed oats and barley) respectively.

2. During initial and final control periods all the cows received 16 lb. hay daily and, per 10 lb. of milk produced, they received about 4 lb. of the concentrate mixture containing flaked maize. During the experimental period of 6 weeks all the cows received 4 lb. hay, concentrates according to milk yield, and an extra 7 lb. of concentrates daily. One group of cows received the concentrate mixture containing flaked maize, a second group the mixture with maize meal and the third group that with dredge corn. The mean daily intakes of starch for the different groups were respectively 6·0, 6·4 and 5·8 lb. per cow.

3. The diet containing flaked maize caused a marked, and that containing maize meal a small fall in the fat content of the milk, but the diet containing dredge corn was without effect. In the last 2 weeks of experimental treatment the adjusted mean fat percentage for the group of cows receiving flaked maize was 0·51 and 0·71 below the percentages for the groups receiving maize meal and dredge corn respectively. The yields of milk and of milk fat were also lower in the group receiving flaked maize than in either of the other groups, but the experimental treatments produced no changes in the milk solids-not-fat percentage.

4. This experiment has shown that when diets low in hay and high in concentrates are given to lactating cows, the type of starch in the concentrates is of great importance in determining the extent of the depression in milk fat percentage. The greater depression with flaked maize than with maize meal or dredge corn is thought to be associated with the effect of the starch on the flora of the reticulo-rumen.
600. Further observations on the volatile compounds associated with oxidized flavour in skim milk
Authors: Forss D. A. , Pont E. G. , Stark W.
Published: June 2009

The C6–C11 2,4–dienals have been identified in distillates from skim milk with oxidized flavour. The C4–C11 2–enals were isolated from the same distillates in a previous investigation. The most abundant individual compounds in the two groups were 2–octenal, 2–nonenal, 2–4–heptadienal and 2,4–nonadienal. These compounds when flavour–tested in skim milk in dilutions of 10–7–10–9 closely resembled oxidized (cardboard) flavour. It is concluded that they are the main constituents of this flavour defect and that they originate from the oxidation of the more highly unsaturated fatty acids in milk lipids.
605. Preparation of a cheese with crystalline rennin
Authors: Berridge N. J.
Published: June 2009

Kizer, Hankin, Speck & Aurand(1) have observed that the impurities associated with proteolytic enzymes are stimulating to lactic acid bacteria, and they have suggested that these substances may accelerate the ripening of dairy products. In view of these observations and suggestions an experiment begun in March 1954, on the preparation of cheese with crystalline rennin, is reported below. The results are in agreement with the suggestions of Kizer et al.
643. Penicillin in milk: III. The effect of low concentrations of penicillin on the rate of acid production by starter cultures
Authors: Berridge N. J.
Published: June 2009

In order that the results recorded in Part II of this series(1) may have meaning, it is necessary to know the effect of different low concentrations of penicillin in cheese-making. Preliminary experiments suggest that this is mainly the result of their effect on the cultures used as starters.
649. The effect of design of teat-cup liners on mastitis incidence
Authors: Dodd F. H. , Oliver J. , Neave F. K.
Published: June 2009

1. An experiment was carried out to study the effect on udder health and milk yield when half-udders of dairy cows were milked with either a moulded or an extruded teat-cup liner.

2. There was a higher incidence of mastitis in quarters that were milked with moulded than with extruded liners, but the incidence of new infection was similar for each group of quarters.

3. The types of liners used had no measurable effect on teat orifice erosion or leucocyte content of the milk, nor was the decline in milk yield with advance in lactation significantly different for the groups of quarters.

We wish to thank Dr A. T. R. Mattick and Mr A. S. Foot for advice and encouragement, and Miss H. R. Chapman for assistance in the cleaning of teat-cup liners. We are indebted to Miss M. S. Hawkins and Messrs T. M. Higgs and D. S. Simpkin for technical assistance.
684. Factors influencing the vitamin content of milk fat: VII. The possible existence of protein-bound carotenoids and vitamin A alcohol in mammary secretion
Authors: McGillivray W. A.
Published: June 2009

1. The distribution of carotenoids and vitamin A in milk-fat globules has been further investigated. The results obtained support previous observations that the carotenoid content of the fat obtained by solvent extraction from the smaller globules in milk is greater than in the fat obtained from the larger globules. It has also been shown that the vitamin A alcohol content of the extracted fat varies in the same way as the carotenoid content, but that the reverse appears to be the case for vitamin A ester.

2. It is suggested that these differences in concentration are not due to a surface layer of carotenoids and vitamin A alcohol on the fat globule but to the presence in mammary secretions, as in blood, of protein-bound forms of these substances. In support of this it has been shown that when fat is obtained by centrifuging rather than by solvent extraction, its carotenoid and vitamin A content appears to be almost independent of globule size. Furthermore, some vitamin A and carotenoids remained in the virtually fat-free serum obtained from normal milk, colostrum and pre-partum secretion and was precipitated with the various serum proteins, particularly the globulin fraction. The increased carotenoid and vitamin A alcohol content of mastitis milk may also be explained by the presence of abnormally large amounts of these protein-bound forms.

The author is grateful to the Department of Scientific and Industrial Research for a grant towards the cost of the investigation; also to the farm staff of The Dairy Research Institute (N.Z.) for assistance with the collection of milk and colostrum samples.
692. The influence of carbon dioxide on the growth of lactic streptococci
Authors: Whitehead H. R. , Jones P. A. , Robertson P. S.
Published: June 2009

The initial rate of growth ofStr. lactisandStr. cremorisin skim-milk depends upon the proportion of CO2present in solution. When CO2is constantly swept from the milk medium by a stream of CO2-free gas all strains show a very prolonged lag period. They eventually emerge from this lag period after more than 8 hr. and grow well enough to coagulate the milk within 24 hr. For optimal initial growth the lactic streptococci require the presence in solution in the milk of proportions of CO2within the range 0·2 and 2·3% by volume. Some strains have a higher CO2requirement within this range than others. Skim-milk after sterilization contains less than the optimum proportion of CO2for many strains of lactic streptococci.

Yeast extract in a proportion of about 0·5% can substitute for CO2in skim-milk.

The periodic inversion of cultures in plain skim-milk reduces the initial rate of growth of some of the streptococci, particularly those which form long chains. The reason for this is unknown. It does not occur when yeast extract is present.
697. An analysis of the performance of an ultra-high-temperature milk sterilizing plant: I. Introduction and Physical Measurements
Authors: Burton H.
Published: June 2009

The purpose of any pasteurizing or sterilizing plant is to bring about the heat inactivation of bacteria or bacterial spores. It is generally considered for convenience that the bactericidal effect takes place almost entirely in a holding period, during which the milk can be considered to be held at a fixed temperature for a minimum time. In practice, since the milk cannot be instantaneously heated and cooled, there is a progressively increasing lethal effect throughout the period when the milk is approaching its holding temperature, and a decreasing effect in the cooling period. There is, therefore, a considerable lethal effect above that due to the nominal holding time. This has been shown in a paper by Ball(1) in which methods of calculation developed for the canning industry are applied to the problem of high-temperature, short-time pasteurization of milk. The higher the final milk temperature, the greater will be the proportion of lethal effect due to the come-up time, until, at temperatures of the order of 135° C., the lethal effect during holding may be relatively slight.
699. Lactobacilli in Cheddar cheese: 1. The use of selective media for isolation and of serological typing for identification
Authors: Naylor Jill , Sharpe M. Elisabeth
Published: June 2009

A comparison of three different media, yeast dextrose agar, tomato dextrose agar and acetate agar (which is selective for lactobacilli) showed that the acetate medium was satisfactory for the isolation and counting of lactobacilli from Cheddar cheese during ripening. Lactobacilli were isolated on this medium in the early stages of ripening when the large numbers of starter streptococci growing on the other media were completely suppressed. Lactobacilli isolated were identified biochemically and serologically. Serological typing was found to be a useful method of identifying large numbers of isolates and of assessing the incidence and distribution of particular types in the cheese.

We wish to thank Dr A. T. R. Mattick for his interest and helpful advice in this work; Dr L. A. Mabbitt for preparation of the cheese samples; Miss H. R. Chapman for making the experimental cheese; and Mrs P. Jarrett for technical assistance.
700. Factors influencing the activity of cheese starters. The role of milk peroxidase
Authors: Wright R. C. , Tramer J.
Published: June 2009

1. Certain starter cultures have been found to be inhibited in the presence of milk peroxidase.

2. A high correlation has been established between the inactivation of milk peroxidase and of the inhibitory action by use of critical values of any of the following: temperature, pH, concentration of either sodium azide or hydrogen peroxide.

3. The inhibitory action can be overcome by the addition of certain reducing substances such as cysteine and sodium hydrosulphite.

4. The inhibitory action is exhibited by the corresponding separated milk and whey.

5. It is suggested that this inhibition may be due to the formation of a specific inhibitory oxidation product having a quinonoid structure.

6. The addition of 1–2% of pasteurized milk or whey to autoclaved milk caused total inhibition, whereas such additions to milk heated to 190° F. showed no such effect. This is attributed to the presence of SH groups in the latter milk capable of reducing the oxidation product.

7. It is suggested that the inhibition due to peroxidase is identical with that ascribed to lactenin 2, and that the inhibition described in our previous paper as due to ‘agglutinin’ is identical with that ascribed to lactenin 1.
706. Long survival of a streptococcal bacteriophage
Authors: Whitehead H. R.
Published: June 2009

Bacteriophage active against a lactic streptococcus was first isolated in this laboratory in February 1935. In May of the same year some batches of phage for Streptococcus cremoris strain HP were prepared by lysing the bacteria in skim-milk culture and preparing a Seitz-filtered whey as described by Whitehead & Cox(1). At that time it was not the practice to adjust the reaction of phage filtrates and the pH of the batches prepared in 1935 was not recorded. It was probably between 5·2 and 6·1 (Hunter & Whitehead (2)). Samples of four different preparations of the phage were filled into sterile tubes and sealed off in a blow-pipe flame. Two of the samples, sealed on 24 May 1935, had titres of 107 (as determined by spotting of standard loops of dilutions on a bacterial mat) and the other two, sealed on 16 July 1935 had titres of 106. The sealed tubes were stored in the refrigerator at 4–7° C.
718. Renneting and the caseinate particle: a viscometric study
Authors: Sterling C.
Published: June 2009

A viscometric study of solutions of alkaline (sodium and potassium) caseinate was made to determine the effects of renneting with and without the addition of calcium ions. There was no real viscometric effect of these treatments at high dilutions. At a higher temperature, the viscosity increment of the solutions decreased. It was suggested that particle aggregation occurs more readily at higher temperatures, leading to a greater particle symmetry as well as causing some dehydration.
719. Observations by fluorescence microscopy of casein in milk, curd and cheese
Authors: King N.
Published: June 2009

Fluorescence microscopy was applied to the examination of casein in milk, curd and cheese, to check or support the picture obtained by electron microscopy. The best fluorochroming effect was shown by thioflavine T, acridine orange, coriphosphine and basic fuchsin.

In milk, larger casein particles (0·1–0·8 μ in diameter) were rendered visible as minute nearly spherical corpuscles in lively Brownian movement. The sediment obtained on centrifuging the whole milk at about 900 g contained predominantly large particles (average diameter 0·;8 μ). On acid or rennet coagulation the casein particles aggregated to flocs, which finally formed a three-dimensional framework.

From curd or cheese freezing-microtome sections (10 μ thick) were examined. The curds which did not possess the fibrous (‘chicken-breast’) texture, characteristic for wellcheddared curd, under the fluorescence microscope displayed a granular structure, whereas curds with a pronounced fibrous texture showed a network of thin micro-fibres, particularly in sections cut along the direction of macro-fibres.

The sections (10 μ or less thick) of curd and cheese on the surface of water slowly spread out. The spreading was accompanied either by conversion of the form of casein from granular into fibrous, or by stretching of the micro-fibres in the already existing network.

The grain boundaries in curd and cheese (Cheddar, Emmental, Edam) were almost free of fat. No grain boundaries existed in process cheese.
723. The effect of level of concentrate feeding and type of roughage on milk production
Authors: Castle M. E. , Maclusky D. S. , Waite R. , Watson J. N.
Published: June 2009

1. In a short-term winter feeding trial using eight Ayrshire cows, a concentrate with a nominal starch equivalent of 68 was fed at 2 lb. and 4 lb./gal. of milk with either 16 lb. hay or 16 lb. dried grass. Silage (40 lb. per day) was also fed.

2. The weight of dry matter from grass products eaten per day was similar on all four treatments. Differences in total daily dry-matter consumption were very largely attributable to differences in the consumption of concentrate dry matter.

3. The daily dry-matter consumption as a percentage of live weight increased from 2·5 on the rations that included hay and 2 lb. concentrates per gal. to 3·2 on the rations that included dried grass and 4 lb. concentrates per gal.

4. Milk yield was significantly increased from an average of 33·5 to 37·3 lb./day when the amount of concentrates fed increased from 2 to 4 lb./gal. and also significantly increased from 33·9 to 36·9 lb./day when dried grass was fed in place of hay.

5. There was an increase of 0·9 lb. milk for each 1 lb. increase of starch equivalent plus 0·2 lb. digestible crude protein intake as a result of either increasing the rate of concentrate feeding, or of feeding dried grass instead of hay.

6. The fat content of the milk was similar on all four rations, whereas the solids-not-fat varied from 8·42% on the ration that included hay +2 lb. concentrates/gal, to 8·59% on the ration that included dried grass +4 1b. concentrates/gal. This change in S.N.F. was almost entirely in the protein fraction of the milk.

7. There was a gradation in live-weight change from -0·74 lb./day on the hay +2 lb. concentrates/gal, to +0·34 lb./day on the dried grass +4 lb. concentrates/gal.

8. After a consideration of profit margins, milk quality and live-weight changes it was concluded that both treatments B (dried grass +2 lb./gal.) and C (hay +4 lb./gal.) gave optimum and almost identical results.
725. A comparison of dried skim-milk and white fish meal as protein supplements: III. For fattening pigs fed whey without restriction under commercial conditions
Authors: Braude R. , Mitchell K. G. , Cray A. S. , Franke A. , Sedgwick P. H.
Published: June 2009

1. An experiment has been carried out under commercial conditions to compare the value of dried skim-milk and white fish meal as protein supplements in a basal meal fed to fattening pigs in conjunction with unrestricted amounts of whey.

2. There were four treatments. All pigs received 3 lb./pig/day of a basal meal, reduced to 2 lb. by the 13th week of life, plus unrestricted amounts of whey. The protein supplement in the four basal meals comprising the four treatments were: (1) 10% white fish meal, (2) 10% dried skim-milk, (3) 15% dried skim-milk and (4) 20% dried skim-milk.

There were five pens of nine group-fed pigs on each treatment, involving a total of 180 pigs. The pigs were on experiment from approximately 10 weeks of age to bacon weight. Comprehensive carcass measurements were made on all the pigs.

3. The results showed that the white fish meal in the basal meal fed with unrestricted amounts of whey could be replaced by dried skim-milk on a weight for weight basis (10%) without adversely affecting the performance of the pigs. Increasing the percentage of dried skim-milk to 15% appeared to have no advantage, but increasing it to 20% resulted in a slightly better performance of the pigs.

4. The results are discussed in relation to the findings in previous experiments and it was concluded that the evidence obtained so far strongly suggests that as a protein supplement, dried skim-milk is superior to white fish meal for the fattening pig, when compared on a protein content basis.

5. The commercial grading results of the pigs on all four treatments were quite good, with no very marked differences between any of the groups.

6. An average daily peak consumption of about 4¾ gal. whey/pig was reached by all groups of pigs during about the 26th–28th weeks of life. The growth curve and pattern of food consumption of the pigs during the experiment were compared with those in two earlier trials carried out under similar conditions, and possible reasons for some of the differences observed were discussed.
729. Characteristics of a presumptive pediococcus occurring in New Zealand Cheddar cheese
Authors: Dacre J. C.
Published: June 2009

1. Cultural and biochemical details are given of a homofermentative species of lactic acid-producing bacteria, repeatedly isolated from typical maturing New Zealand Cheddar cheese.

2. The Gram-positive cocci, occurring mainly in pairs and tetrads in acid media, are greatly stimulated in growth by the presence of yeast or tomato extracts. The organism converts glucose into inactive lactic acid and smaller amounts of acetic acid.

3. With the exceptions that the organism does not ferment trehalose and is less tolerant to low pH and high concentrations of Teepol, all its characteristics are similar to those for the genusPediococcus, in particular to the type speciesP. cerevisiaeBalcke.
The estimation of the total solids and solids-not-fat of milk from the density and fat content
Authors: Rowland S. J. , Wagstaff A. W.
Published: June 2009

The accuracy of the method specified in B.S. 734:1937 for the estimation of the total solids and solids-not-fat contents of milk from the density and fat content has been assessed by direct comparisons with the gravimetric method. A total of 2425 samples of milk, mostly from single herds, were examined in five series over different years.

The percentages of solids estimated by the density method were lower, by an average of 0·06, than those determined gravimetrically. To correct for this error, and to compensate for the lower, more accurate fat percentages arising from the recent reduction in the capacity of the Gerber milk pipette, it was proposed that the density formulae be modified to T=0·25D+l·22F+0·72 and S.N.F.=0·25D+0·22F+0·72.

These formulae were adopted in October 1957 in an amendment to the B.S. 734 published in 1955.
Making Cheddar cheese on a small scale under controlled bacteriological conditions
Authors: Mabbitt L. A. , Chapman Helen R. , Sharpe M. Elisabeth
Published: June 2009

A cover for a 40 gal. cheese vat has been specially designed to allow cheese to be made under conditions which prevent the entry of micro-organisms into the vat from the dairy environment. The technique employed is described. Using milk free from lactobacilli it has been possible to make Cheddar cheese in which no lactobacilli grew during the ripening period. An assessment of the role of these and other micro-organisms in cheese ripening should now be possible.

The technique should also be of help in other cheese investigations where control of the microflora is desired.
A proposed method for the rapid determination of lactose in separated milk and condensed whey by infra-red absorption
Authors: Goulden J. D. S.
Published: June 2009

It has been shown that the lactose concentration in separated milk can be determined rapidly with an accuracy of ±1·5% by infra-red absorption methods, using wavelengths in the 10μ region.

The method can also be used to determine lactose in condensed whey and should prove applicable to continuous recording techniques.
The effect on milk composition of feeding spring grass to cows
Authors: Waite R. , Castle M. E. , Watson J. N.
Published: June 2009

1. An experiment to investigate the seasonal increase in the solids-not-fat content of milk, which usually occurs in Britain when cows go from winter feeding to spring grazing, is described.

2. Two similar groups of cows were fed good quality winter rations at the same high level both before and after calving (about 115% of the Woodman standard after calving), until spring grass was available. One group of 7 cows was then fed for 6 weeks almost entirely on cut grass, returning to winter rations for a further 3 weeks. The control group of 6 cows continued to be fed throughout the experiment on winter rations and both groups remained indoors for the whole of the experiment. The estimated nutrient intake of both groups in all periods was kept substantially constant.

3. Changes in milk yield and composition were mainly those associated with advancing stage of lactation, and grass feeding had little specific effect. It is concluded that the increase in milk protein content which is normally observed soon after the start of spring grazing probably results from an improved plane of nutrition and not specifically from an increase in the intake of soluble carbohydrates.

4. Increases in the total nitrogen content of the milk as the experiment proceeded were contributed to uniformly by the casein, total albumin and β-lactoglobulin fractions.
The effect of heat on the vitamin B6 of milk: I. Microbiological tests
Authors: Gregory Margaret E.
Published: June 2009

1. Four test organisms were used for the microbiological assay of vitamin B6. The test organisms and the forms of vitamin B6 active for them were: Saccharomyces carlsbergensis 4228 (pyridoxine, pyridoxamine and pyridoxal), Streptococcus faecalis R ATCC8043 and Str. faecium Ø51 (pyridoxamine and pyridoxal), and Lactobacillus casei ATCC7469 (pyridoxal).

2. By simultaneous assay of the test material with the four organisms the amounts of pyridoxine, pyridoxamine and pyridoxal present were determined. The differential assay technique has been improved by the use of Str. faecium, which is more specific for measuring total pyridoxamine plus pyridoxal, instead of Str. faecalis.

3. The optimum conditions for measuring vitamin B6 in milk were studied and the differential assay technique was applied in an investigation of the effect of heat on the vitamin B6 activity of milk.

4. It was found that pyridoxal accounted for about 80% of the vitamin B6 activity of raw milk, the other 20% being due to pyridoxamine.

5. In the manufacture of evaporated milk there was a marked fall in the pyridoxal and a slight increase in the pyridoxamine content. The overall loss was some 60%.

6. On storage of evaporated and of sterilized liquid milk at room temperature there was a further loss of vitamin B6 activity. Most of the residual activity in stored evaporated milk appeared to be due to a substance other than pyridoxal or pyridoxamine, possibly pyridoxine.
The effect of heat on the vitamin B6 of milk: II. A comparison of biological and microbiological tests of evaporated milk
Authors: Davies Mary K. , Gregory Margaret E. , Henry Kathleen M.
Published: June 2009

1. For chicks and rats pyridoxine, pyridoxal and pyridoxamine were equally active in terms of the free bases when given separately from the diet.

2. Under our experimental conditions pyridoxine mixed with the chick diet was stable, but 20% of pyridoxamine, and a variable amount of pyridoxal was lost.

3. The vitamin B6 activities measured with Saccharomyces carlsbergensis, chicks and rats respectively and expressed as μg. pyridoxine/g. freeze-dried milk were: raw milk 3·4, 3·2 and 4·9; evaporated milk 1·0, 2·1 and 2·7; stored evaporated milk 0·6, 1·4 and 2·0. For the chicks the milks were mixed with the diets; they were given separately to the rats.

4. The microbiological and biological results for raw milk agreed within the limits of experimental error. For the processed milks the differences between biological and microbiological tests were statistically significant.

5. All three methods of assay showed a 45–70% loss of vitamin B6 activity on processing and a further loss of 30% of the remainder after storage for 6 months at room temperature.

We are indebted to Mr J. Rothwell, Department of Dairying, University of Reading, for preparing the evaporated milk and to Dr B. Record, Ministry of Supply, Microbiological Research Establishment, Porton, for freeze-drying the milk. We should like to thank Dr S. K. Kon for his interest in this work.
Some volatile compounds in New Zealand Cheddar cheese and their possible significance in flavour formation: II. Volatile compounds of sulphur
Authors: Walker J. R. L.
Published: June 2009

The volatile sulphur compounds present in New Zealand Cheddar cheese have been studied by means of gas entrainment and steam-distillation techniques. Hydrogen sulphide was the only sulphur compound which could be detected, and after removal of this compound from the gas stream or steam distillate only a mixture of carbonyl compounds remained. Subsequent removal of these compounds completely destroyed the original cheesy aroma of the gas stream or distillate.

The parts played by hydrogen sulphide and carbonyl compounds in Cheddar cheese flavour are discussed.

The author wishes to record his gratitude to Dr H. R. Whitehead and Dr W. A. McGillivray for their helpful advice and criticism and to Mr P. L. McLaughlin for technical assistance.
The use of an oxidation-reduction indicator to compare the oxygen permeabilities of films for rindless cheese
Authors: Dolby R. M.
Published: June 2009

Slices and blocks of cheese were coloured with aqueous methylene blue solution and vacuum-packed or wrapped in the films to be compared. The extent of bleaching of the dye after 14 days gave a good indication of the extent to which oxygen was excluded by the film. Similar results were obtained with vacuum-packed slices and with wrapped rindless cheeses.

With polythene-coated and wax-coated MSAT cellophane films there was little or no reduction of methylene blue on the cheese surface. Similar films, including a lamination of foil or MXXT cellophane, allowed complete or almost complete bleaching.
Identification of lactobacilli from Cheddar cheese by chromatography
Authors: Cheeseman G. C.
Published: June 2009

The technique of paper chromatography of bacterial extracts has been successfully applied to the routine examination of lactobacilli from cheese. One hundred and nine strains isolated on selective media have been grouped by their chromatogram patterns, and selected strains from these groups have been shown to have biochemical characteristics giving relationships which are in agreement with the chromatogram groupings. The results indicate that the technique can be used routinely for the rapid identification of strains of lactobacilli.
Production of acetone and acetaldehyde by lactic streptococci
Authors: Harvey R. J.
Published: June 2009

Seven strains of Streptococcus cremoris, four strains of Str. lactis, and one strain of Str. diacetilactis were examined for their ability to produce aldehydes and methyl ketones when grown in skim-milk. All strains were found to produce acetaldehyde and seven also produced acetone. No other aldehydes or methyl ketones were detected in any of the cultures.

A method for the quantitative estimation of mixtures of aldehydes and methyl ketones by means of paper chromatography of their 2,4-dinitrophenylhydrazones is described.