bluuebunny/crossref_metadata_2025 huggingface dataset:
84. The Influence of Lactic Streptococci on the Ripening of Cheddar Cheese
Authors: Sherwood I. R. , Whitehead H. R.
Published: June 2009

1. The process of ripening in experimental cheeses was followed by periodic estimations of the amounts of various types of protein degradation product formed.

2. No connection between the type of nitrogen partition and the commercial quality of the ripened cheese could be traced.

3. The proteolytic powers of the various pure cultures of streptococci used as starters in the cheese vats seemed to have little influence on the rate of proteolysis in the cheeses during the ripening period. The main trend of the protein breakdown was governed by the rate and total extent of acid formation in the milk and curd during the manufacturing process. This suggests that the rennet enzyme is the principal proteolytic agent, and that the most significant function of the streptococci is the formation of acid which in turn influences the rate of action of the rennet enzyme.

4. No specific connection between the numbers of streptococci present in the cheese milk at the time of renneting and the rate of ripening of the cheese could be traced.

5. Some evidence was found tending to suggest that minor differences in the type of protein degradation occurring during the ripening period influenced the changes of bacterial flora in the cheese. Lactobacilli appeared to develop earlier where the proportion of simpler protein derivatives was high.
88. A Technique for the Determination of Lactose in Milk by the Hagedorn-Jensen Method
Authors: Blackwood Janet H.
Published: June 2009

Iodometric methods have been applied to the determination of lactose in milk by Kolthoff(1), who used freshly precipitated zinc ferrocyanide as protein precipitant, and by Fine(2) who made use of colloidal iron. The reduction of ferricyanide by reducing sugars has been used as a semi-micro method by Issekutz and von Both(3) and has been applied to the estimation of lactose in milk by Gohr(4) who also used ferrocyanide as protein precipitant.
99. The Effect of the Reaction (PH) of Milk on the Destruction of Micro-Organisms by Heat
Authors: Mattick A. T. R. , Nichols A. A.
Published: June 2009

It has been shown that alterations in the hydrogen-ion concentration of milk result in differences in the numbers of bacteria which survive the process of heating at 145° F. for 30 min. As the pH decreases the number of bacteria surviving also decreases. The possible bearings of these findings on various processes are discussed.
100. The Plate Count of Milk. Experimental Errors in the Examination of I, (a) Different Portions of the Same Sample by the Same Person, (b) Different Portions of the Same Sample by two Different Persons in one Laboratory; and II, Different Portions of the Same Milk by Ten Persons in Ten Different Laboratories
Authors: Mattick A. T. R. , McClemont J. , Irwin J. O.
Published: June 2009

(1) 419 samples were counted in each of ten stations (laboratories) in order to assess the accuracy of the plate-count method under the conditions existing in practice.

(2) When, in each count, that plate which would ordinarily be used in practice is selected for the final count, it is found that the range which would include 95 per cent, of counts in the same sample is as wide as from one-ninth of the mean to nine times the mean when inter-station differences are taken into account. For 80 per cent, of counts in the same sample the corresponding range would be from 1/(4·1) of the mean to 4·1 times the mean.

(3) Systematic differences between stations under these conditions account for between 3 and 4 per cent, of the total experimental variation.

(4) When thirty-one complete samples in which all counts were made at a dilution of 1/10 were statistically analysed separately it was found that the range which would include 95 per cent, of counts in the same sample was from 1/(3·7) of the mean to 3·7 times the mean. For 80 per cent, of counts in the same sample the corresponding range would be from 1/(2·3) of the mean to 2·3 times the mean. There were no systematic station differences.

(5) When all plates are counted at the same dilution the error is therefore much reduced and this result suggests that the systematic station differences exhibited by the 419 samples as well as some of the random errors occurring in them is due to the combining of plate counts made at different dilutions.

In effect this means that owing to the different conditions encountered during transit comparable figures for any sample could not be expected.
102. Studies on the Mycological Problems of Dairying. I. The Surface Moulding of Butter
Authors: Vernon T. R.
Published: June 2009

1. Six types of surface discolorations are described and a list is given of the fungi causing these discolorations. The fungi listed are shown to be capable of reproducing the discolorations under experimental conditions.

2. The surface moulding of butter is shown to depend largely on the weather conditions at the time of removal from cold store (temperature and humidity), and the foodstuffs available from the wrapping materials.

3. The butter, boxwood and parchment are capable, in the presence of free water, of supplying substances which stimulate the germination of fungal spores.

4. The water-soluble extract of parchment stimulates fungal germination and growth. Its value as a nutrient is masked when parchment is in contact with butter. Even a well-washed parchment is capable of supporting fungal growth.

5. The butter and the boxwood are even more important as sources of soluble food material than parchment of high “water-soluble” content.

6. Glycerine is a source of food for fungi and a glycerine-softened parchment is more liable to mould attack than a glycerine-free paper.

7. It has been shown that the softening of parchment with salt does not prevent mould attack. Two strains of Cladosporium herbarum and Penicillium sp. attacked salt-softened parchment more easily than untreated parchments.
116. Factors affecting Milk and Butterfat Secretion. II. The Colour of the Butterfat
Authors: Whetham Elizabeth O. , Hammond John
Published: June 2009

1. The colours of the butter for individual cows at the London Dairy Show have been measured on a colour scale of yellow shades on cellulose strips, and the results analysed statistically.

2. The mean values and variability curves of the ranges of butter colour in the different breeds of dairy cattle are given. Circumstances which may affect these values are indicated.

3. The two most important factors affecting butter colour are the genetic character of the cow and the method of feeding.

4. A slight increase in the shade of colour was found to occur under most of the various conditions which give rise to increased milk yield. It is suggested that this may be due to the greater intake of colouring matter (associated with the greater food intake) in proportion to butterfat produced, since increase in yield is usually associated with decrease in fat percentage.
130. Bacteriophage Phenomena in Cultures of Lactic Streptococci
Authors: Whitehead H. R. , Cox G. A.
Published: June 2009

The occurrence and isolation of bacteriophages from cultures of lactic streptococci (“starter cultures”) is described. Aeration of the milk in which the phage-infected cultures are grown is shown to have a stimulating action on the development of the phage. The characteristics of phages for lactic streptococci are described.
142. Van Oijen Modification of the Frost Little Plate Method. A Critical Investigation of van Oijen's Test for the Bacterial Content of Milk Samples
Authors: Barkworth H.
Published: June 2009

1. Van Oijen's modification of the Frost Little Plate method for estimating the bacterial content of milk has been examined and compared with the plate count.

2. The colony counting error of the Van Oijen test is about the same as that of the plate count.

3. From the results of quintuplicate tests it is recommended that 24 hours' incubation at 28°C. be used for the Van Oijen test and 72 hours at 37° C. for the plate test.

4. Thirty-one low-count samples (3000–30,000 per ml.) and thirty-one high-count samples (30,000–300,000 per ml.) were tested in quintuplicate by both methods, and statistical examination of the results shows that at both levels of count the Van Oijen test is significantly more accurate. The Van Oijen results are on the average 1–3 per cent log lower than the plate count and this difference is found to be significant.

5. In the Van Oijen test the results are based on a larger amount of milk than the plate test, and a method is given for testing whether the increased accuracy exceeds the expectation owing to increased size of sample.

6. It is noted that failure of replicate tests to reflect random distribution may be due to the variability of the technique as much as to irregularities in the actual distribution of the bacteria in the sample.

7. The effect of size of sample upon reproducibility is discussed. A true comparison of the accuracy of various methods for assessing the bacteria content of milk samples cannot be obtained unless allowance is made for variation in size of sample as between different techniques.
170. The effect of commercial sterilization on the nutritive value of milk
Authors: Kon S. K. , Henry K. M. , Ikin E. W. , Gillam A. E. , White P.
Published: June 2009

We have dealt in a previous communication (1) with the effects-of commercial pasteurization on the nutritive value of milk. We present here the results of an enquiry into the nutritional effects of the more drastic heat treatment to which milk is subjected during commercial sterilization. There is no legal definition of either sterilized milk or of the process of sterilization, but in commerce it is customary to apply the term to milk which has been heated to at least 212° F. for varying lengths of time.
178. A lipase (tributyrinase) of cows' milk. I. Occurrence, method of estimation and relationship to lactation cycle
Authors: Mattick E. C. V. , Kay H. D.
Published: June 2009

An enzyme which hydrolyses tributyrin is present in all samples of fresh cows' milk examined. A method has been developed for the determination of the tributyrinase activity of a given milk or fluid.

In milk the enzyme is present in the aqueous rather than the fatty portion. Its optimal range of activity is in the regionpH 8·2–8·7. It is rather more thermolabile than phosphatase.

Its concentration in milk varies considerably from cow to cow, and in individual healthy cows there is a fairly regular variation throughout the lactation cycle. It is highest in concentration in colostrum, then the concentration falls to a minimum at about 10 days, rising later to a figure intermediate between this minimum and the colostral value. It shows no sign of increase towards the end of the lactation period.

Its relationship to the “true lipase” of milk is discussed.
190. The effect of commercial sterilization on the nutritive value of milk. VII. Conclusions
Authors: Kon S. K.
Published: June 2009

The work carried out by us on the nutritive value of commercially sterilized milk shows definitely that certain factors are injured in the course of the heat treatment. The biological value of the proteins is slightly but unmistakably decreased, most probably because of the partial destruction of one or more essential amino-acids. Of the vitamins, vitamin C is the most markedly affected. It is decreased by half and, in view of the severity of the heat treatment, it is remarkable that the loss is not greater. The anaerobic conditions which exist during the application of the highest sterilizing temperatures may account for the survival of a part of this labile factor. Vitamin B1 also suffers serious loss, the destruction amounting to 30 % of the original value. Neither vitamin A and carotene nor vitamin B2 (flavin) are affected by the heat treatment. The fate of other components of milk was not studied by us, but experiments on rats on the effect of sterilization on the total nutritive value of milk indicates that vitamin B1 was the first limiting factor of sterilized milk.
198. The diffusion of trimethylamine oxide from the udder
Authors: Davies W. L.
Published: June 2009

On injecting a neutral solution of pure trimethylamine oxide into two quarters of an udder, the quarters increased in turgidity up to 2·5 hr. and then relaxed. The oxide diffused rapidly out of the quarters during the third and fourth hours after injection and a maximum concentration was shown in the urine at the end of the third hour. In a period of 8·3 hr., 76 % of the oxide available for diffusion was recovered from the urine.

The milk obtained 7 hr. after injection contained 7–8 mg. % of tertiary nitrogen, but the secretion had not in that time regained normal composition owing to the interference with the natural functioning of the quarters.
208. The part played by bacteria in the reduction of methylene blue in milk
Authors: Hobbs Betty Constance
Published: June 2009

1. In good quality raw milk reducing methylene blue at 37–38° C. members of the coliform group andStaph. aureuswere among the commonest organisms present at the time of reduction. Other types of staphylococci, micrococci, and certain streptococci were not infrequently present in smaller numbers. In any given milk one type of organism tended to assume predominance.

2. Using the modified test described by Wilsonet al.(1), various organisms isolated from milk at the time of reduction were examined for their rate of decolorization of methylene blue when growing in pure culture in raw “sterile” milk (milk freshly drawn from the healthy udder under aseptic conditions and having a plate count on milk agar at 37° C. of 200–300 per ml.). The most rapidly reducing organisms belonged to the coliform group. Following them, in decreasing order, cameStr. lactisand some of the faecal streptococci,Staph. aureus, Staph. albus, Staph. citreus, some micrococci, group C haemolytic streptococci and some strains ofStr. agalactiae, and aerobic spore-bearers
218. Starter cultures for cheese manufacture. Maintenance of acid-producing activity in cultures of lactic streptococci
Authors: Whitehead H. R. , Hunter G. J. E.
Published: June 2009

Single-strain cultures of streptococci used as “starters” in Cheddar cheese manufacture in New Zealand frequently suffered failure due to the apparently spontaneous appearance of bacteriophage. The trouble was cured at the Institute experimental factory by increasing the inoculum used in the starter culture from about 0·2% to 1·0–1·6%. The culture then showed a regular activity in the cheese vat from day to day for long periods of time. Field trials during the past two years have indicated that single strain cultures can be maintained for long periods also in commercial factories if the correct technique is practised.

The theory is postulated that the effect of heavy inoculation in eliminating the spontaneous appearance of bacteriophage is due to the more rapid growth of the streptococci when they are transferred to each new batch of milk, i.e. to the shortening of the lag period. Bacteriophage tends to appear whenever the lag period is prolonged as a result of light inoculation, low incubation temperature, and aeration or ageing of the milk medium. Until more is known of the nature of phage it is not possible to suggest why a prolonged lag period in the initiation of growth should favour the appearance of phage.

Under commercial conditions failures of starters occur from time to time due to faulty technique which permits the entry into cultures of extraneous phage. The source of the contamination is most probably the whey from cheese vats, since it has been shown that phage commonly occurs in the whey even in vats where acid develops quite normally within the the cheese curd. A recent case of failure, which appears to be due to some milk abnormality, indicates that there are some milk supplies in which the heavy inoculation technique described in this paper is not completely effective in preventing the appearance of bacteriophage.
230. The relation of certain lactic acid bacteria to open texture in Cheddar cheese
Authors: Sherwood I. R.
Published: June 2009

“Open” cheese were shown to evolve carbon dioxide much more rapidly than did “close” cheese. From open cheese lactobacilli or betacocci capable of producing carbon dioxide relatively rapidly could be isolated. The addition of such organisms to cheese milk resulted in the development of slit openness in the cheese. The most common types causing slit openness appeared to be gas-producing lactobacilli.
235. The enrichment ofaerogenes-cloacaetypes in milk held at low temperatures: with observations on the relative rates of growth ofaerogenes-cloacaeandb. colitypes in milk at different temperatures
Authors: Malcolm James F.
Published: June 2009

1. Seventy-five pure cultures of various types of coliform bacteria were grown in sterilized or partially sterilized milk for 24 hr. at 17° C. The cultures ofB. aerogenes, B. oxytocusandB. cloacaetypes as a rule multiplied much more rapidly than those of theB. colitypes. Similar results were obtained when twenty-nine cultures of various coliform types were grown in raw milk for 24 hr. at 17° C. There was generally little or no tendency to clumping of the organisms in the milk, even after 3 days' incubation at 17° C.

2. Forty mixed cultures, each consisting of anaerogenes-cloacaetype and aB. coli, were grown in milk for 24 hr. at 17° C. In thirty-four instances theaerogenes-cloacaetype multiplied more rapidly than theB. coli.

3. Twenty-one of these mixed cultures were also grown in milk for 24 hr. at 22, 30 and 37° C. At 22, as at 17° C, theaerogenes-cloacaetype multiplied as a rule more rapidly than theB. coli, while at 30 and 37°C. the reverse was the case.

4. Twelve specimens of bovine faeces were inoculated into raw milk and the cultures kept at 17° C. for 36 hr.Aerogenes-cloacaetypes occurring in the faeces became enriched in the milk, the coliform flora of the milk at the end of the incubation period frequently consisting chiefly of these types.

5. The greater incidence ofaerogenes-cloacaetypes in summer milk in Scotland as compared with winter milk, found in a previous investigation, may be explained by the fact that when milk is contaminated directly or indirectly with faeces, these types become enriched at the temperatures of holding commonly employed in summer. Such enrichment does not occur in winter, the holding temperature of the milk being as a rule so low that there is little or no proliferation of any coliform types. Consequently, the relative proportions of the various coliform types in winter milk tend to remain similar to those in the faeces.
237. Lactic acid bacteria in relation to cheese flavour. II. Observations on the inoculation of the milk employed in cheese manufacture with lactobacilli
Authors: Sherwood I. R.
Published: June 2009

Attempts to improve the flavour of cheese by inoculation of good quality cheese-milk (pasteurized) with selected strains of streptobacteria gave the best results when relatively small inocula were employed. Large inocula imparted a sharpness to the flavour of the cheese during the early stages of ripening, and this sharpness often persisted when the cheese was mature.

Several possible methods suitable for the propagation of lactobacilli under factory conditions were investigated. The most convenient procedure consisted in the incorporation in the starter “mother” culture (enriched with a vegetable extract) of suitable strains ofSbm. plantarum; these strains were found to grow better in association with some starters than with others.
238. The effect ofpH on growth and gas production by streptococci and lactobacilli
Authors: Davis J. G. , Thiel C. C.
Published: June 2009

ThepH ranges of growth of streptococci and lactobacilli in dextrose yeast casein digest broth have been studied. Nearly all the group I and II streptococci grew atpH 8·8, but only the enterococci grew atpH 4·8; all group III types (heterofermentative) grew atpH 4·4. Only a few lactobacilli grew atpH. 8·8 but most were able to grow atpH 4 if other conditions were favourable. The enterococci,Str. lactisandStr. cremoriscould be differentiated by the alkaline limits of growth.
240. The effect of light on the vitamin C of milk in different containers
Authors: Houston J. , Kon S. K. , Thompson S. Y.
Published: June 2009

The destruction of vitamin C in milk under the action of light was studied in different containers. Brown glass bottles showed little destruction, green glass bottles considerably more, and wax impregnated cartons still more. Nevertheless, in the latter, twice as much vitamin C survived as in clear glass bottles.
250. The influence of various factors on the fermentation end-products of the heterofermentative streptococci
Authors: Thiel C. C.
Published: June 2009

1. The influence of temperature,pH, oxygen tension and yeast autolysate on the production of by-products and the ratios of by-products formed to sugar utilized and lactic acid produced in milk by the heterofermentative lactic acid streptococci has been investigated.

2. The total production of lactic acid is increased by anaerobic conditions and low temperature. The ratio of lactic acid formed to sugar utilized is increased by anaerobic conditions and the presence of chalk.

3. The total amount of acetic acid is higher in the presence of chalk, at the lower temperatures and in yeast milk, but is decreased by anaerobic conditions. The ratio of acetic acid both to sugar utilized and to lactic acid formed is smaller at lower temperatures, in the presence of “growth factors” and chalk and under anaerobic conditions.

4. The total alcohol production is higher when yeast or chalk is added to milk, under anaerobic conditions and at lower temperatures, and similarly the ratio of alcohol formed to sugar utilized and lactic acid produced is increased.

5. Hydrolysis of residual lactose occurred in all cultures ofStr. citrovorusand with some of the other streptococci in cultures to which chalk had been added.

6. Although the heterofermentative lactic acid streptococci possess respiratory enzymes, these fail to suppress aerobic fermentation (i.e. the Pasteur effect is slight).
264. The effect of variations in the fat percentage and in the reaction (pH) of milk media on the heat resistance of certain milk bacteria
Authors: Nichols Agnes. A.
Published: June 2009

1. A review of the literature shows that the destruction of living microorganisms by heat is a complex process, and that the problem is particularly difficult when it is applied to the heat resistance of spores.

2. The problems involved in the method of heating and in the choice of a container for the inoculated substrate for heat-resistance tests are discussed, with special reference to the difficulties encountered at high temperatures such as are used in studies with spores of aerobic bacteria. Four different types of containers, namely, (a) glass capillary tubes, (b) glass ampoules or bulbs, (c) glass Pasteur pipettes and (d) corked test tubes, have been tested, and the latter were found to fulfil the necessary requirements.

3. A trial test of the heat resistance was conducted on nearly forty strains of aerobic sporeformers isolated from canned milk products, in order to obtain general information regarding the difficulties which might be expected in later and more detailed studies. Many of the strains were found to be exceedingly heat resistant. No dormancy was apparent when the spores were heated and subsequently incubated in milk products. “Skips” were only observed to any great extent among strains ofB. licheniformis.

4. Special studies of the heat resistance of three strains ofB. subtiliswhich had produced bitterness and thinning in canned cream were made. Details are given of the methods of preparing spore suspensions for these tests and of preparing the substrates for subsequent inoculation in such a way that equal concentrations of spores are present in the final subsamples.

5. The effect of the reaction of the substrate on the destruction of two of these strains ofB. subtilisby heat has been examined, but over the narrow range of pH. tested the results, which have been expressed as survival percentages, lack consistency.
273. The consistency of cheese curd at the pitching point and its bearing on the firmness and quality of the finished cheese
Authors: Blair G. W. Scott , Coppen F. M. V.
Published: June 2009

1. The pitching consistency of some 470 cheese has been determined at one factory and the data compared with the subjective judgements of a skilled cheesemaker. The smallest difference in consistency which the expert can distinguish with a reasonable degree of accuracy (threshold) is compared with those for purely elastic and viscous bodies, and it is concluded that the consistency at pitching is judged mainly from the elastic properties of the curd. The good agreement between these thresholds substantiates the hypothesis that our test for pitching consistency is closely related to the requirements of the practical cheesemaker.

2. The connexion believed to exist between firmness of curd at pitching and acidity was not substantiated, in the case of Cheddar, by a statistical examination of the available data.

3. The most usual values (medians) for pitching consistency are compared for four different factories, and it is shown that differences in technique may be associated with the same pitching consistency and produce very similar cheese, but that in other cases good cheese may be produced from very different pitching consistencies. The important thing is that the pitching consistency should be known and controlled so as to be as constant as possible under given conditions.

4. A technique is described for measuring the force required to thrust a skewer into cheese. This force (S) is highly correlated with “body” judged subjectively by an experimenter who was aware of the fact that such a correlation was to be tried. Judgements of “body” made by expert cheese graders were not so correlated, but the interpretation of their judgements was inadequate, so that no definite conclusion can be drawn.
279. The estimation of lactose in milk
Authors: McDowell A. K. R.
Published: June 2009

1. The direct volumetric copper reduction method of estimation of lactose in unclarified milk gives results which are in good agreement with those on the same milk clarified and decalcified.

2. For the polarimetric' or iodometric methods of estimation of lactose the milk is best clarified with either zinc hydroxide or cadmium hydroxide. Clarification with acid mercuric nitrate or phosphotungstic acid for the polarimetric method and with dialysed iron or phosphotungstic acid for the iodometric method gives high results owing to failure to remove interfering substances.

3. Dialysed iron, phosphotungstic acid, cadmium hydroxide or zinc hydroxide are all suitable for deproteinizing the milk for the chloramine-T method of estimation of lactose.

4. The values for lactose content of milk as estimated by the above methods show good agreement and therefore may be accepted as the true milk sugar content.
288. A simplification of the Scott Blair-Coppen test for the pitching consistency of cheese curd
Authors: Scott Blair G. W. , Scott Blair M. F.
Published: June 2009

Scott Blair & Coppen(I) have described a test for the consistency of firm cheese curd during the process of scalding and at the pitching point. This test gives the cheese maker an objective physical measure of a property which he is used to assessing subjectively by handling the curd, and should ensure a more constant condition in the curd from vat to vat and from day to day.
292. The effect of a vitamin A-rich diet on the vitamin A content of the colostrum of dairy cows
Authors: Stewart J. , McCallum J. W.
Published: June 2009

In previous papers by the authors(l,2) it was shown that the vitamin A content of the colostrum of cows varied within wide limits and that the wide range was not due to any differences in dietary, breed or date of calving in animals kept under the same conditions of management. It was also established that calves born of cows whose colostrum possessed a vitamin A content of less than 250 blue units (Moore's) per 100 ml. were more liable to infections such as white scour, navel-ill and joint-ill than were calves from cows whose colostrum had a vitamin A content of more than 250 blue units per 100 ml.
295. The problem of bacteriophage in cheese making: Part I. Observations and investigations on slow acid production
Authors: Anderson E. B. , Meanwell L. J.
Published: June 2009

That bacteriophage is the cause of much loss to the cheese-making industry of New Zealand has been shown by Whitehead(1). In New Zealand in recent years, cheese has been made almost entirely from flash-pasteurized milk with the aid of starters prepared from single-strain cultures of lactic acid streptococci (Str. cremoris). The use of such starters has been accompanied by the occasional failure of the bulk starter to clot, or, if clotted, by failure to produce the required amount of acid in the cheese vat—the latter condition being described by Whitehead as ‘pack up’. Whitehead has traced the cause of sudden failure to air-borne infection of the bulk starter by specific bacteriophage (2), the most probable source of infection being the spray from whey separators. When adequate protection from phage contamination was provided slowness in cheese making disappeared.
314. The effect of storage on the plate counts of milk and whey powders
Authors: Higginbottom Constance
Published: June 2009

It is evident from the foregoing results that decreases in count may occur during the storage of milk and whey powders. The extent of this decrease varies, however, with the type of powder and even between different samples of the same type. Further, many samples may show little or no alteration in the numbers of viable organisms surviving storage even for considerable periods.

Nevertheless, it is obviously important that for grading purposes or in relation to plant control a time limit should be fixed within which the plate count of any milk or whey powder should be determined. No data are available to show how rapidly organisms may die out during storage periods of less than 3 months, but it is tentatively suggested that all powders should normally be examined within, say, 14 days of manufacture. Unless such a limit is fixed, those samples in which the count does fall appreciably would reflect too favourably on the conditions of manufacture.
337. The supplementary relationships between the proteins of dairy products and those of bread and potato as affected by the method of feeding. With a note on the value of soya-bean protein
Authors: Henry Kathleen M. , Kon S. K.
Published: June 2009

1. The biological value of proteins at an 8% level of protein intake measured on rats by the method of Mitchell (7, 10) was 52 for white bread of 73% extraction, 76 for Cheddar cheese, 75 for a mixture of both foods when each supplied 50% of the protein, and 67 when the two sources of protein were given on alternate days. The true digestibilities were, respectively, 99, 100, 98 and 99.

2. Similar experiments with dried skim milk and dried cooked potatoes yielded biological values of 71 for potato, 89 for milk, 86 for the mixture and 81 for the substances fed separately on alternate days. The true digestibilities were, respectively, 82, 90, 82 and 87.

3. An attempt to carry out experiments of the same type with dried whey and dried potato failed because of deaths of some rats receiving the whey diet, probably because of its high content of lactose. A biological value of 76 was obtained for the potato proteins and of 70 for a mixture of whey and potato in which whey supplied 25% of the protein. The true digestibilities were, respectively, 82 and 68.

4. The biological value and the true digestibility of the proteins of a sample of edible soya-bean flour were, respectively, 73 and 90.

5. It is concluded that there is a marked supplementary relationship between the proteins of milk and potato and those of bread and cheese when the members of each pair supply equal amounts of protein and when they are given together. No supplementary relationship is exhibited when the sources of protein are given separately on alternate days.
347. The disinfection of contaminated metal surfaces with hypochlorite solutions
Authors: Neave F. K. , Hoy W. A.
Published: June 2009

Tinned trays were artificially infected withStaphylococcus aureusin diluted milk and the dried surfaces disinfected by rinsing with sodium hypochlorite solutions.

Under the conditions described, which we believe approximate those on many dairy utensils which have been imperfectly cleaned, thepH of hypochlorite solutions was found not to be a very important factor in determining their germicidal efficiency. AtpH 10 and 11, the solutions were equal to or slightly more efficient germicides than solutions at pH7.

In the destruction of 99% of the organisms on the metal trays, a solution atpH 10, containing 200 p.p.m. available chlorine was about 7 times as rapid as one with 25 p.p.m. available chlorine.
358. The effect of a high pre-heating temperature with and without ethyl gallate on the storage life of whole-milk powder spray-dried on a Gray-Jensen drier
Authors: White J. C. D. , Smith J. A. B. , Lea C. H.
Published: June 2009

1. Storage tests have been made independently in two laboratories on four samples of spray-dried whole-milk powder prepared on a Gray-Jensen plant from one batch of milk using pre-heating temperatures of 160 and 190° F. with and without the addition of 0·06–0·08% of ethyl gallate as antioxidant. The powders were packed in lacquered and in plain tinplate containers and stored at 47, 37 and 15° C, and at room temperature. Deterioration was followed by tasting tests, by determination of the amount of oxygen absorbed by the powders and by estimation of peroxide in the fat.

2. Raising the pre-heating temperature from 160 to 190° F. or the addition of ethyl gallate to the milk improved the keeping quality of the resulting powder, as measured by taste, by a factor of the order of 1½–2½ at 47° C, of 2–3 at 37° C. and of 3–4 at 15° C. and room temperature.

3. Increasing the pre-heating temperature and incorporating ethyl gallate in the milk extended the storage life of the powder by a factor of the order of 3 at 47° C., 4 at 37° C. and 8 at 15° C. and room temperature.

4. For an equivalent loss of palatability powder from high-temperature pre-heated milk absorbed appreciably more oxygen than the corresponding powder from low-temperature pre-heated milk, and the gallate-treated samples slightly more than the corresponding control powders.

5. The temperature coefficients for deterioration were slightly higher for the high-temperature powders than for the corresponding low-temperaturepowders.

6. With the two control powders storage in lacquered tinplate resulted in a small increase, of the order of 10%, in keeping properties as comparedwith storage in plain tinplate. With the ethyl gallate-treated powders no advantage resulted from the use of lacquered tinplate.
363. Studies in the bacteriology of milk: II. The staphylococci and micrococci of milk
Authors: Abd-El-Malek Y. , Gibson T.
Published: June 2009

A study of 799 cultures of staphylococci and micrococci, isolated mainly from milk, showed that according to their general character the strains could be arranged in a virtually continuous series. At one extreme is the pathogenic staphylococcus and at the other a thermoduric saprophyte. The series consists of three main groups:

(1) The staphylococcus group in which the organisms are sugar fermenters and relatively sensitive to heat. They are, mainly at least, parasites of the animal body. Four subgroups are distinguishable. In three ammonia is formed from arginine, and in two acetoin is formed from glucose. A test for acetoin production defines those mannitol fermenters which do not produce coagulase.

(2) An intermediate group in which the organisms are obligate aerobes and do not produce acid from sugars.

(3) The dairy micrococci, a group of thermoduric sugar fermenters which occur frequently on dairy equipment and in pasteurized milk. The group comprises two species conforming toMicrococcus luteusCohnemend. Lehmann & Neumann, andM. varians(Dyar) Migula.
379. The nature and quantity of fatty acids produced in butterfat by the action of micro-organisms
Authors: Richards T. , El-Sadek G. M.
Published: June 2009

1. The fatty acids have been isolated from six samples of butter made rancid with pure cultures of bacteria and moulds, and from six samples of naturally rancid butter.

2. The fatty acids have been fractionated into volatile, solid and liquid groups.

3. The mould samples produced in every case a greater total of fatty acids than bacteria under identical conditions.

4. Bacteria produced relatively less volatile acids than moulds but slightly more solid acids.

5. Of the volatile acids produced it appears that bacteria produce a greater proportion of butyric and caproic acids than moulds.

6. The liquid acids make up by far the greatest proportion of the fatty acids recovered, being in each case between 77 and 85% of the total. Of these, oleic and linoleic probably comprise the majority.
384. A note on the effect of penicillin in the reductase test for milk quality
Authors: Hunter G. J. E.
Published: June 2009

Penicillin in milk inhibits the growth of some contaminant organisms and thus may have a variable effect in the reductase test for milk quality.
386. Variations in morphology of Streptococcus lactis when grown in raw and heated milk
Authors: Morris C. S. , Edwards M. A.
Published: June 2009

1. Streptococcus lactis cultures were found to vary considerably in their morphological characters when grown in raw and heated milk.

2. This variation in morphology was found to be the main cause for the difference in colony counts between inoculated raw milk and milk heated to 70° C. for 1 hr. over a 6 hr. incubation period at 37° C.

3. Similar T.M.C.'S on inoculated raw and heated milk during incubation at 37° C. explained why the methylene-blue reduction times were the same.

4. It is thought that denaturation of protein may be responsible for the production of short chains in heated milk.

5. The by-products of growth of Str. lactis are responsible for the production of short chains in raw milk after a long incubation time at 37° C.
394. The influence of time and temperature of storage on dye-reduction tests in milk: 1. Reduction of methylene blue
Authors: Morton R. K. , Vincent J. M. , Duncan D. B.
Published: June 2009

Milks from representative producers have been used to study the influence of storage time and temperature on methylene-blue reduction times. The trends of reduction times are very well expressed as a regression function of both storage factors simultaneously, which therefore appears to describe a fundamental property of raw market milk. It thus becomes possible to compare standards in different countries and producing regions and, by the application of a rational temperature-compensation scale, to maintain reasonably constant production standards throughout the year.
395. The influence of alkalinity on the germicidal action of hypochlorites
Authors: Chaplin C. E. , Johns C. K.
Published: June 2009

Survivor curves show that, under conditions likely to be found in practice, hypochlorite solutions of low alkalinity disinfect milk films on surfaces more rapidly than those of greater alkalinity.

Dehydration of the milk film results in slower disinfection rates by both neutral and alkaline solutions.

Increasing the milk content in the film reduces the rate of disinfection and reduces the effect of the neutral solution to a greater extent than the alkaline.
414. Experiments on milking technique: 7. The effect of subjecting dairy cows, for a complete lactation, to a rigid control of the duration of milking
Authors: Dodd F. H. , Foot A. S. , Henriques Ettie , Neave F. K.
Published: June 2009

1. Thirty-eight first-calf heifers in two equal groups were subjected for complete lactations to a rigid control of the duration of milking to either 4 or 8 min.

2. The treatment had no major effect on the milking rates of either group.

3. Whilst 4 min. was insufficient time to milk out completely the udders of about half the animals on this treatment, the machines on the 8 min. treatment were generally left on for a period after milk flow had stopped.

4. There was no significant difference between the 305-day lactation yields of the two groups or in the persistency. The 4 min. treatment did, however, decrease the yield of milk and fat in early lactation.

5. The 8 min. cows had more clinical and subclinical mastitis, though they did not have a higher proportion of eroded teats nor higher Whiteside test readings.

6. Teat erosion appeared to be correlated with slow milking.
415. Factors affecting the rate of machine milking
Authors: Baxter Eleanor S. , Clarke Pamela M. , Dodd F. H. , Foot A. S.
Published: June 2009

1. A study was made of the milking of the two hind quarters of four cows by teat cup and by teat cannula at three levels of vacuum and by teat cannula at atmospheric pressure.

2. The eight quarters milked at significantly different maximum rates by teat cup but at nearly the same rate through a teat cannula, suggesting that the teat orifice is a very important factor controlling rate of milking.

3. The maximum rate of milking by both teat cup and teat cannula increased with increasing level of vacuum from 11 to 20 in. Hg. The rate of increase in the teat-cup milking was greater than in the cannula milking, suggesting that the teat orifice was stretched open at the higher levels of vacuum.

4. The average amount of strippings increased at the higher level of vacuum in teat-cup milking, due apparently to teat-cup crawl.
416. The effect of bacterial infection on the milk yield of the individual quarters of the cow's udder
Authors: Crossman Joan V. , Dodd F. H. , Lee J. M. , Neave F. K.
Published: June 2009

A study has been made of the effect of udder infections on the proportionate yield and composition of the milk of individual quarters of over 100 cows, and the data from eleven of these cows have been presented.

Typical examples have been given showing that subclinical Streptococcus and haemolytic Staphylococcus infections may persist for months and either cause a gradual reduction in the proportionate yield, and solids-not-fat percentage of a quarter or have no measurable effect, and that both types of reaction may occur simultaneously in the same udder.

Examples also show that following penicillin treatment of clinical cases caused by streptococci and staphylococci there is little recovery in the proportionate yield of the treated quarter until the following lactation, when recovery may be complete.
424. A study of lactation as affected by heredity and environment
Authors: Sikka L. C.
Published: June 2009

1. A study has been made of the interrelationships between persistency and maximum yield as components of the lactation curve, and of the importance of environment and heredity in determining the shape of the lactation curve of Ayrshire cows.

2. Persistency was defined as the linear constant of the exponential curve expressed as a percentage,maximum yieldas the highest 30-day yield as calculated from the records, andtotal yieldas the yield of milk from 15 days to 8½ months after calving.

3. The study was based on milk records computed by the official method of the Scottish Milk Records Association. The data used in much of the work was obtained from five herds of Ayrshire cows and involved 2392 lactations during the period 1920–39.

4. In an exploratory test involving 100 lactations it was found that the exponential curve fitted ninety-five of the lactation curves and that the fit was improved in forty-eight of these ninety-five curves by using the parabolic exponential curve. Five of the lactations were too erratic to be fitted by any simple mathematical curve.
425. Further investigations on the presence in raw milk of a bactericidal substance specific for certain strains of coliform organisms
Authors: Morris C. S. , Edwards M. A.
Published: June 2009

Since the publication of the original paper (1) on the occurrence of slow-reducing coliform organisms in raw milk, further investigational work has been undertaken. During the course of the work two different types of coliform organisms appeared to be responsible for the slow reduction of methylene blue: (a) those having a long lag phase of growth, and (b) those destroyed by a bactericidal substance present in raw milk.
426. Some bacteriological aspects of the deterioration of pasteurized milk
Authors: Ashton T. R.
Published: June 2009

1. Examinations have been made of milk pasteurized by the L.T. ‘Holder’ and H.T.S.T. processes using the same original bulk raw milk. In the preparation of samples care was taken to eliminate the possibility of post-pasteurization contamination. It was hoped that any differences found would be due solely to the effects of the pasteurizing processes above.

2. Samples were examined by (a) colony counts and coliform tests when fresh and after ageing at 18°C. for 24 and 48 hr., (b) methylene-blue and resazurin reduction tests when fresh and after ageing at 18°C. for 45½hr., (c) keeping quality at 18°C. to end-point of 68% alcohol and clot-on-boiling tests. All bacteriological and dye reduction tests were carried out at incubation temperatures of 37, 30 and 22°C.

3. In seven trials the experiments were repeated after storage of the original raw milk for 24 hr. at 40–50°F. (4·4–10·0°C.).

4. Some detailed examinations were made of the bacterial floras of the raw and corresponding pasteurized milks, both when fresh and after ageing.
429. Studies on Egyptian Domiati cheese
Authors: Fahmi A. H. , Sharara H. A.
Published: June 2009

In the first part of this study, brief notes are given on the better known varieties of the soft pickled group of cheese which the authors believe to be best suited to warm climatic conditions.

Domiati cheese, a variety of this group, characterized by the addition of an appreciable amount of salt to the milk prior to rennetting, is described in detail. An outline of the steps of its manufacture, the pickling process, and the effect of the amount of salt added to the milk on the composition of the resulting cheese is given.

In the second part the effects of varying additions of salt to both cows' and buffaloes' milk on rennet coagulation, rate of whey drainage, chemical composition and yield of cheese and whey were investigated.