bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.
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.