Though the mineral constituents normally represent less than 1 per cent, of cow's milk their importance in many dairying problems is well realised. For example, the calcium-magnesium-phosphate-citrate balance is a most important factor in connection with coagulation by heat and in the alcohol test, even minute alterations in the balance producing a very marked effect.

The nitrogenous substances or albuminoids, of which animal tissues for the most part consist, and which are also found in the seeds, leaves and other parts of plants, were originally believed to be composed of one and the same organic substance called protein by Mulder about a century ago (from πρωτɛύω “I am the first”).

Curves are produced to show the proportions between morning and evening yield of milk, yield of fat, and fat per cent, in the case of individual cows milked alternatively at 6 a.m. and 9 p.m. and again at 6·30 a.m. and 3·30 p.m. In each case the intervals between milkings were 15 and 9 hours.

It is seen that when the 15-hour interval is between night and morning milkings as specified, a bigger proportion of milk is produced at the morning milking than is produced at night when the same interval is between morning and night milkings. The curves and Tables I and II show that this is quite clearly the case with the six cows in the trial.

It is apparent that, as far as winter conditions are concerned, night itself, or factors operating at night tend to high milk production of low fat content.

The influence of a number of factors on the autoxidation of butterfat has been studied. Metallic catalysts have been found to exert a great effect in hastening the reaction, their intensity being in the following decreasing order: sodium vanadate, copper lactate, iron lactate, nickel sulphate. Zinc lactate has a slight retarding action.

Ultra-violet light, hydrogen peroxide and fat peroxides have a strong prooxidative effect and to a less extent lactic acid. Curd exerts an antioxygenic effect, while humidity, glycerol, triolein, lactose, iodine, potassium iodide and the effect of pasteurisation have little or no influence.

The author wishes to thank the Auckland University College Council and Sir James Gunson for a Sir James Gunson Scholarship during the tenure of which this research was undertaken, Dr F. H. McDowall for his helpful interest in the work, and the Dairy Research Institute (N.Z.) for permission to work in their laboratories.

A study has been made of the nitrogen distribution in Kingston cheese, over a ripening period of 98 days. For the determinations, methods evolved and employed by Orla-Jensen, Barthel and others have been drawn upon. In addition, a departure has been made in applying to this study the method developed by Wasteneys and Borsook for the fractional analysis of incomplete protein hydrolysates.

Determinations were carried out on cheese of the same “make” from the day of making to the 98th day of ripening at intervals denned and recorded in the tables and figures.

Results obtained when employing the methods of Orla-Jensen and of Barthel have been complemented by the application of the Wasteneys and Borsook method, which defines the nature and the amount of various protein decomposition fractions (proteose, peptone and sub-peptone) formed as the ripening of the cheese proceeds.

Particularly striking is the finding that the difference in the results of the amide nitrogen determinations and the amino nitrogen determinations can be explained when interpreted in the light of data secured by the application of the method of Wasteneys and Borsook. The amide nitrogen curve has been found to coincide with the sub-peptone nitrogen curve, and the amino nitrogen curve to superimpose itself upon the curve depicting the sum of the subpeptone nitrogen and the peptone nitrogen.

The results of our study, subject to qualification as further data on the nature of specific enzymes may appear, suggest that after the first few hours of ripening the proteolytic breakdown in the ripening of Kingston cheese is of an associative peptic-tryptic-like nature.

1. A method is described for following the intensity of reduction (or oxidation-reduction potential) at different levels in the interior of ripening Cheddar cheese.

2. Variations in this potential throughout the course of ripening are described and mean values assessed.

3. Cheese are shown to be not homogeneous throughout their mass; outer zones of more highly oxidised condition exist near the surface of the cheese and round cracks and borings. The depth of these zones increases with the age of the cheese.

4. The values obtained can be correlated with the known bacteriological data for Cheddar cheese.

5. The significance of the data obtained in relation to cheese faults is discussed.

In Part I(1) the influence of a number of factors on the autoxidation of butterfat was investigated. It was considered of interest, however, to study the oxidation itself more fully to gain some idea of the changes taking place, and also to study certain reactions for detecting such changes.

In tallowy butter as the result of oxidation, the following differences in properties can be observed: (1) the amount of unsaturated compounds is decreased; (2) the peroxide content is increased; (3) the amount of free acid is increased; (4) the colour is bleached. Secondary changes occur simultaneously and result in the formation of aldehydes, ketones, etc.

Traces of heavy metals in amounts up to 25 parts per million have the property of inhibiting the action of lipase in butter from unpasteurised sweet cream in varying degrees depending on the concentration of the metal and on the metal itself. Copper was the most potent metal of those studied, iron, nickel, cobalt, manganese, and chromium being less active, while tin and aluminium had no effect.

The acidity produced was accompanied by fat-peroxide formation in amount varying directly with the acidity. This was attributable to the free oleic acid formed.

The depression of lipase activity by the various metals varied directly with their catalytic power in inducing fat oxidation later, and it is suggested that destruction of lipase was catalysed by the traces of heavy metals according to their varying powers of activating oxygen. Lipase as a compound naturally associated with fats might thus be looked on as a natural “antioxygen.”

1. Clean milk has been “flash” pasteurised at 165°F. Portions of the same raw milk have been treated with small amounts respectively of starter culture and lactic acid, so as to raise the acidity, before being similarly pasteurised.

2. Comparison of the whey obtained by rennetting the three raw portions has shown that those from the acidified milk contained more soluble protein than the original.

3. The differences between the raw and pasteurised milk in their coagulation time with rennin have been found to be proportionately much greater in the acidified portions.

4. These differences in coagulation time have been shown to be correlated with decreases in the amount of soluble protein found in. the whey separated from the coagulum.

5. These experimental results, together with those of other investigators, have been made the basis of a suggestion that the decreased coagulability of heated milk with rennin is partly due to flocculation of soluble milk protein upon the casein micelles.

The development of the factory-cheese industry in this, and other countries, is handicapped by the wastage of the by-product. In Great Britain alone, approximately 20,000,000 gallons of whey are produced annually by cheese factories(i), and most of it is thrown down the drains. When it is considered that whey, which constitutes half the valuable food material of milk, is so wasted, the development of the industry to even its present dimensions is a matter for surprise.

The range of the copper and iron content of 80 samples of fresh, pasteurised and sterilised milk are given. Examples of investigations on the point of entry of copper into milk during processing are given. As a minimum limit, 1·5 p.p.m. of copper in milk can be expected to produce “oiliness” in milk.

The copper content of dried milk is usually normal but the iron content is increased above that expected from the iron content of fluid milk.

Cheese made in copper vessels has a high copper content; and the iron content of cheese is variable.

Butter contains on an average about 0·5 p.p.m. of copper and 1 p.p.m. of iron. Factory made butter invariably contains more iron and copper.

The more a milk product is processed, the greater is the contamination with heavy metal.

An example of determining the amount of blood in milk by a determination of the iron content is given.

1. Two colorimetric methods for determination of copper have been described, viz. the xanthate and the sodium diethyl-dithio-carbamate. Both methods have given satisfactory results but the carbamate method has proved to be more sensitive and less liable to error from possible contamination than the xanthate method.

2. The colorimetric determination of iron by the modification of the ferric thiocyanate method has been proved to give a very high degree of accuracy and excellent results have been obtained.

3. A method of wet ashing has been described whereby organic matter is oxidised by the use of concentrated sulphuric acid and sodium nitrate and copper and iron extracted from the fat.

4. A number of results are given showing the amount of copper and iron contamination that the cream is subjected to during the course of butter manufacture, and the distribution of copper and iron in the cream, butter and buttermilk.

This study is a continuation of the investigations of Prof. Agar, Professor of Zoology, University of Melbourne, entitled “Heredity and milking function,” which appeared in the Journal of Agriculture of Victoria in January, 1926; and it deals with the inheritance of milk, butterfat percentage, and butterfat in the Victoria Stud of Red Poll Cattle owned by the Department of Agriculture of Victoria, at the State Research Farm, Werribee. The milk and butterfat records used in these investigations are the 273 day records performed under the regulations governing the Victorian Government Pure-bred Herd Test, published annually, and included in the successive volumes of the Red Poll Herd Book of Australia. They cover the period since the establishment of the Government Herd Test—1912–13 to 1929–30.

A Fresh milk supply is as essential in the tropics as it is in the more temperate regions of the world. The most fundamental of the many problems connected with tropical dairying is that concerned with the establishment of breeds of dairy cattle which will live and thrive in their environment, and produce milk; the intensity of the problem varies with the degree of severity of the climatic and environmental conditions. The manner in which this problem has been dealt with at the Government Stock Farms at Kingston, Jamaica, together with the results, is discussed in the following study. The data were collected by Mr J. Hammond from the records of the herds at these farms. To Mr H. H. Cousins, the Director of Agriculture, who has not only built up the herd to its present state of excellence but has kept also a complete record of the pedigrees and performances of all the animals, and to Dr S. Lockett, Veterinary Officer for the Department, our thanks are due for having put these records at our disposal and for communicating to us the results of their experience.

If research work in cheese ripening is to be conducted on an entirely satisfactory basis, a complete control of both temperature and humidity of the ripening room must be available.

Though temperatures are relatively easily controlled, the factor of shrinkage or loss of moisture from the cheese is a more difficult problem. Further, should such loss of moisture be an additional and variable factor due to differences in humidity of the ripening room, research work in cheese ripening is seriously handicapped. It is realised that different cheese, whether large or small, high or low in moisture, new or mature, lose moisture at different rates even though kept under exactly the same conditions of storage. Also, the identical cheese cease to remain the same due to various rates of ripening, if studied as to their loss of moisture at different temperatures.

This article records the preliminary results of an investigation of some of the causes of the variations in the yield and composition of milk. The influence of the season of the year, and the influence of climatic conditions on the average yield and composition of the milk of a herd, are discussed.

The relationships between the data are studied by means of simple corre-lation and also by means of partial correlation. The temperatures used are the average temperatures for the periods between the milkings. Thus the day-temperature is the average temperature of the interval between the morning and evening milking, and the night temperature is the average temperature of the interval between the evening milking and the next morning milking. The daily temperature is the average of these two temperatures.

The results of a routine examination of samples of commercial sterilised milk extending over a period of 15 months are given and reviewed.

Three distinct types of spoilage have been found, and each of these has been shown to be induced by a definite group of bacteria.

Representative members of each group have been isolated and examined. The majority were found to be of the type B. mesentericus, B. cereus and B. mycoides. Two types have not been identified. Of these, one has been found to be the cause of the “coconut” or “carbolic” taint, and is more fully described in Part II of this paper.

1. Normal curves of growth for dairy Shorthorn cattle from birth to 5 years of age are presented. These include height at withers, length of body, depth of chest and live weight.

2. The expression of growth by the “Relative growth rate” method is discussed and illustrated. The method is particularly suitable for expressing the growth of calves under 6 months of age.

The characters are given of the organism causing the “coconut” or “carbolic” taint of commercial sterilised milk. Although certain similarities with B. novus (Plectridium novum) Huss are shown to exist, the organism remains unidentified and the question of its identity has been reserved for a subsequent paper.

In laboratory culture the organism exists in a stable vegetative form which has resisted all efforts to induce it to sporulate. Under commercial conditions, on the other hand, it occurs in a spore form in the bottles of tainted sterilised milk.

Propagated by ordinary laboratory methods, the spore form is rapidly replaced by a vegetative race. Five serial transplants are sufficient to bring about this transformation.

Sporulation can be induced and maintained indefinitely if sporing cultures are heated at 100°C. for 30 minutes at the time of inoculation. The function of the heating process appears to be the destruction of a growth product inhibitory to the germination of the spores. This substance is associated with the growth of the vegetative form and its presence in unheated cultures is inhibitory to the germination of the spores.

Spore formation takes place at temperatures below 22°C., the spore cycle occupying 3 days at 22°C., 6 days at 15°C., and 15 days at 5°C. At higher temperatures, e.g. 30 and 37°C., it is inhibited and the normal process is replaced by an abortive effort at spore formation. The optimum temperature for the propagation of the spores is 22°C.