Cheinical Research and the Milk Industry G. C.
SUPPLÉE,
G. C. Supplée Research Corp., Bainbridge, Ν. Υ.
t h e m i l k indvistry s t a n d s as a n example 01 the value o i c h e m i c a l research . . . K e e p i n g properties have b e e n improved, n u t r i t i o n a l «pialities e n h a n c e d , and s u r p l u s e s utilized to t h e e c o n o m i c a d vantage of t h e industry a n d t o t h e dietary advantage of t h e n a t i o n M ILK is the object ive substance of a vast and complicated industrial organism in volving millions of production units and the entire consuming populace. T h e per ishability of milk and its products and their potentiality as a carrier of disease projects rigid production, processing, and distribution patterns which have been evolved largely on a philosophy of defense against microbial and spontaneous deterio ration. Application of proved bactériologie and sanitation principles is commonplace and violation of these principles is neither tolerated by the public nor sustained by the balance sheet. The subject of this address, however, relates to the chemistry of milk, rather than to sanitary procedures. It may be bluntly stat ed t hat this het erogeneous ensemble of nutritive substances is created by nature for a predestined purpose: neither the chemist nor the engineer have accomplished much as yet in improving its basic character by alteration or synthesis. Even though we designate a branch of science as dairy chemistry, it will be well t o recognize that dairy chemistry is an aggregate of interrelated technologies drawn from various specialized branches of chemistry ami biology. The objectives to be attained by research in milk chemistry are manifold—utilitarian or at the moment seemingly academic. The results of an analytical scheme designed to identify and quantitatively estimate all of the entities in milk, including trace substances, organic and inorganic, might a p pear futile and of academic interest only. However, a review of the exploratory research applied to milk or its derivatives will show that numerous findings have matured into results of significance not originally anticipated. It is quite unlikely that the first reports of the presence of copper as an inherent constituent of milk in 1919 t o 1922 were anticipated as the forerunner of subsequent research which revealed the deteriorating effects of minute traces of extraneous copper in milk products. Likewise, it could not be predicted that about 15 years following the first reports on the lecithin content of milk in the early 1900's that it would be shown that the decomposition of the choline component of t h e lecithin molecule
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into trimethylamine contributed t o the fishy flavor defect of butter which for decades had caused great economic losses t o this industry. Knowledge of the presence of tracj amounts of 7-dehydrocholesterol in milk was uninteresting and prosaic until it was shown that this entity was t h e antirachitically activable substance which was converted to vitamin D 3 when milk was exposed to ultraviolet rays. Numerous other instances could be cited illustrating the transition of a seemingly obscure research finding t o its ultimate e m bodiment in the field of applied milk chemistry. Research
totvarti
Specific
Objectives
More frequently, however, research directed to specific objectives has immediate utilitarian value. The perfection of the butterfat test by the late S. M. Babcock is an.outstanding example of diligence in the prosecution of si clear cut, preconceived objective. The Babcock test is an applicat ion of chemical research peculiar to t h e milk industry and serves as the yardstick by which the economics of this industry is measured throughout the world. Milk contains in excess of 8 5 % water and is highly perishable, i t originates a t millions of isolated sources throughout rural areas which are not susceptible t o the same degree» of siipcrvision which pre-
vails in a manufacturing establishment. These conditions were conducive to adulteration practices through addition of water and preservatives at the beginning of the century. T h e development of analytical methods a s a defense against such practices, their application, and judicious interpretation of the results were characteristic of much of the research directed t o milk at that time. T h e acceptance of milk products as staples of the dietary has developed quite empirically as a heritage and tradition of the human race. 1 lowever, t h e advent of our newer knowledge* of nutrition markedly changed the course of milk and dairy chemistry. Such organized knowledge as had previously accrued from the endeavors of the chemist consisted primarily of analytical evidence showing the gross composition of milk and its products, integrated a s to water, protein, fat, mineral, and carbohydrate content. The curiosity of the physiological chemist prompted the early research designed t o correlate t h e qualitative character of the gross constituents of milk with the nutritional needs of the animal and human organism. T h e inherent calcium and phosphorus content of milk served as an early and prominent item of investigation interrelating these constituents with a n important phase of mineral metabolism which served as the incentive for much of the subsequent research which has essentially established the calcium requirements of t h e body from infancy to maturity. Λ further example of pioneering phys iological research involving milk constitu ents relates to the qualitative variations in food proteins wherein milk proteins were shown to be nutritionally superior t o proteins from many other sources. T h e type of chemical research illus trated by the foregoing examples pro jected a general pattern of investigation of milk and its products which was greatly accelerated at the beginning of the vita min era. The discovery of vitamins pushed back the horizons of food chemis try, revealing potentialities which chal lenged the imagination of the chemist and biologist. It was natural that milk as a physiological fluid should serve as the o b ject of exploration for these essential e n tities; it is not surprising that all of t h e known vitamins have been shown to be present in greater or less degree. The e x haustive data concerning the vitamin content of milk, however, is not entirely an unmixed blessing to the industry. The primary quantitative differences in
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the levels of the various entities and t h e further variations resulting from the in constant character of cattle rations as well as those induced b}' processing procedures have revealed fluctuations in the over-all nutritive character of milk heretofore un suspected. One of the most glaring deficiencies in the vitamin complement of milk is its in herently low vitamin D content. T h e role of milk in the infant dietary and the prevalence of infantile rickets clearly pro jected a rational course of action quickly following the discovery of the synthesis of vitamin D by ultraviolet light. Produc tion of vitamin D milk by feeding irradi ated 3*east and by direct irradiation 2 0 years ago, and more recent ly by the addi tion of concentrates, represent different avenues of approach to the same end. More particularly, the advent of vitamin D milk was an epochal event in the milk industry exemplifying an affirmative phi losophy based on the concept that creative chemistry could enhance the nutritive properties of a product formerly consid ered to be unalterably fixed by nature. Even though the inherent vitamin Λ content of milk confers a significant nutri tive attribute, research has revealed sub stantial variations dependent upon the» breed of the catt le and character of the ra tion, which are obviously reflected in the processed products. Such disclosures have led to a result not originally antici pated but, nevertheless, not wholly unpre dictable—namely, the incorporation of vitamin A or its precursor in the principal competitive product of butter, oleomar garine. Recognition of the role of the cattle ra tion as a factor influencing the quantita tive levels of certain of the vitamins and trace inorganic constituents of milk has stimulated considerable research designed to lift nutritive quality and to level off variations. T h e iodine content of milk, normally measurable in parts per billion, is markedly influenced by the iodine con tent of the ration. However, evidence is not available showing whether uniformity of output can be maintained a t a desired level. Possibly a more adequate control of dental caries may be foreshadowed by the meager evidence indicating a slightly higher fluorine content of milk from cattle receiving forage from soils of high fluorine content. The ultimate applicability of the concept of ration improvement and control as a means of enhancing the nu tritive character of the general milk sup ply through the connivance of the cow re mains to be determined. At this point brief allusion should be made to the fact that numerous other inor ganic trace substances have been reported t o occur in milk, most of them detectable by spectrographic means only. Since n u tritional merit or adverse significance is attached t o only iron and copper at this time, it is unlikely that milk research will be immediately concerned with the others. V O L U M E
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Early unit installation for synthesis of vitamin Ο in fluid milk by tlirect irratliation of 6,000 quarts per hour The principle studies relating to the iron content have been concerned with the 1 to 2 parts per million present in uncontaminated milk and the possible reduction in its effectiveness in the presence of milk phos phates as an explanation of the develop ment of nutritional anemia resulting from prolonged exclusive milk diets. The cop per content of milk, normally a fractional part per million, particularly that of ex traneous origin, has imposed aggravating and embarrassing problems to the milk in dustry by virtue of its catalytic effect in accelerating oxidative deterioration in fluid milk, dry milk, and butter, particu larly. Awareness of this deteriorating effect has brought about marked changes in the character of the base metal used for fabricating milk handling equipment. These examples will serve to illustrate certain areas of research which have been imposed on one or more phases of the milk industry by the dynamic and rapidly ex panding sciences of food chemistry and nutrition. Influence in Food
of Discoveries Chemistry
The fact that specific dietary entities are better known today than ever before has aroused a consciousness of the competitive status of milk and dairy products among food staples. This situation is reflected by the research designed to improve nutri tional quality, maintain and improve or ganoleptic properties, suppress deteriorat ing changes, and otherwise cultirate con sumer appeal. Assumption of a static composition of milk or a stability of its processed products which cannot be favor ably altered and nutritionally enhanced by feeding, improved processing, or by ap propriate additions is untenable. Early in this discussion reference was made t o exploratory research and to planned objectives. Many of the objec tives relating t o organoleptic properties,
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suppression of deterioration, and profitable utilization of surpluses are of greater ur gency than long range projects dealing with nutritional improvements. The tech^ niques and procedures n o w commonplace in the production of processed dairy prod-· ucts have been adopted from t i m e t o time following some pi- - ~* of research which dis closed an import ause and effect rela tionship. This is particularly applicable to such manufactured dairy products as canned milk and dry milk. The transi tion of butter manufacture from the farm, to the centralized creamery with conse quent improvement in quality and uni formity, and the very substantial changes in the cheese industry brought about by the employment of peptizing salts in the production of processed che stabilization by dispersed milk protein; development of processed cheese through t h e use of pep tizing salts; short time, hign temperature pasteurization of fluid milk and applica tion of the same principle for the steriliza tion of evaporated milk; recognition of the influence of t h e mineral balance of milk on coagulation and physical properties of canned milk; t h e role of inherent lypolytic enzymes in the deterioration of various milk products; various interrelated re searches contributing t o t h e improvement in quality and keeping quality of butter; recognition of t h e relatively high level of riboflavin in milk and whey and the estab lishment of t h i s substance as a dietary essential; discovery of a n unidentified powerful growth stimulant in t h e nonfat portion of milk; analytical and correlated • clinical and nutritional studies relating to casein and lactalbumin with particular reference to t h e dietary and therapeutic use of hydroryzates therefrom. The extent t o which some of the fore going items m a y continue t o be of distinct and exclusive benefit t o t h e milk industry is a matter of conjecture. The direct irra diation of milk i s even n o w obsolete; the production of vitamin D milk b y the addi tion of perfected concentrates is accom plished more simply and more economi cally. T h e synthesis of riboflavin and its low cost for dietary enhancement purposes de-emphasizes t h e importance of milk a s a
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essen studies
natural carrier of this dietary essential. Rapid progress in the development of methods for the economical synthesis of the essential amino acids precludes final conclusion that these dietary substances will indefinitely remain a distinctive a t tribute peculiar to natural milk protein alone. Uses for Surplus
Production
The scope of research applicable to t h e milk industry is further broadened by t h e cyclic periods of surplus production. This situation provides the incentive for those investigations designed to develop new uses for milk or its derivatives. Aside from the proportion of the surplus which can be economically processed as canned milk, dry milk, butter, or cheese, such sur plus may be fed to stock, diverted t o proc essing centers for integration into its ma jor components, or it m a y even be wasted. Reference is now made t o the skim milk which may be literally the starting m a terial of a series of processing and inte grating steps more closely allied to t h e chemical industry than t o the milk indus try. Skim milk so utilized loses its iden tity as a food product. The following com ponents readily separated from this start ing material are: industrial casein; fluid whey which may be desiccated as such for stock feeding purposes or which may be further .integrated into lactalbumin; milk sugar; uncoagulable milk protein; and organic and inorganic phosphates. Even the mother liquor from milk sugar manu facture may be utilized as such as a source of soluble milk minerals and unknown entit ies or may be, and was for a period of time, the starting material for the recov ery and commercial production of natural crystalline riboflavin.
purposes started in isolated areas prior to any substantial accrual o f knowledge concerning the nutritional merits of this product. It is now well established as an industrial material for adhesive*, plastics, paints, and coatings and more recently as a fiber for the textile industry. The vari ous organic and inorganic compounds re active with or blended w i t h industrial casein t o impart differences in physical properties for particular uses would in it self constitute an imposing formulary. In view of the status of t h e world food supply, quantitatively and qualitatively, and the accrued knowledge revealing the importance of a good dietary protein, the competitive position o f casein for indus trial purposes versus i t s use as a food is becoming more accentuated. Casein is the first fraction removed from skim milk in the scheme o f integration heretofore mentioned. The residual whey or milk serum is the direct starting ma terial for the recovery of lactose which comprises about 75% o f the serum solids. The recovery of this product in varying degrees of purity has been a n established industrial process in this country for about 60 years. Probably o n e of t h e most sig nificant advances in lactose production during this period has been t h e perfection of methods for the commercial production of the more soluble beta anhydride type, the common form of commercial lactost· being the alpha hydrate. A considerable tonnage of beta lactose of substantially 100% purity is now produced annually, whereas lees than 20 years a g o it was avail able only as a laboratory curiosity. Whey solids, exclusive of lactose, con sist of lactalbumin, unidentified proteinaceous substances, including the little known lipoproteins of milk, enzyme sys tems, water soluble vitamins, various ni trogenous entities of low molecular weight, and substantially all of the soluble milk minerals. The lactalbumin may be read ily coagulated and separated quantita tively from fluid whey incident to milk sugar production by appropriate pll ad justment and without the admixture of
Photomicrograph of natural riboflavin commercial production from wJiey
The production of casein for industrial
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précipitants, lime, or filter aids. Such lactaibumin, with or without further purification, is suitable as the starting material for dietary and therapeutic products; such usage has greatly enhanced its commercial value during recent years. It should be mentioned at this point that the 5 to 7% of prosthetically bound lipid matter contained in this lactalbumin fraction carries about 70% unsaponifiable matter and of this portion 75 to 80% is recoverable as cholesterol—melting point 147° to 148° C. Research designed to salvage value from waste or refuse directed attention to the mother liquor or molasses from milk sugar production. Early observations revealed that this material possessed marked growth promoting properties which were further accentuated when small traces of crude rice polishings were added. At the time of these observations vitamins were merely differentiated as fat-soluble or water-soluble. The evolution of vitamin technology gradually revealed that milk sugar molasses contained numerous water-soluble vitamins, riboflavin % being present in the greatest amount. Methods for the commercial recovery of natural crystalline riboflavin from this product were perfected about 1935 and for a short time the crystalline product derived from this source was the only pure riboflavin then commercially available. The natural product, however, did not long enjoy this envied status due to the persistence and triumph of the research chemists who rapidly perfected methods for its synthesis on a mass production basis. The isolation of thiamin from a waste product and its ultimate synthesis with commensurate reduction in price followed substantially a parallel and contemporary route. Since the science of chemistry has actuated many of the features which have advanced the industrialization of milk products, one may well look to future research for an indication of further achievement. In view of the relatively meager knowledge of the reaction products which appear during spontaneous or enzymatic deterioration of dairy products, it would appear that further intensification of research in this direction is probable. The importance of oxidative and reductive factors in determining the keeping quality of certain milk products is indicated by recent evidence. Minute traces of the highly reactive sulfhydryl groups prevent the oxidation of fat in milk powder in the presence of air; however, oxidation of those groups contributes to the stale flavor defect commonly found in the stored product. The desirability of determining and controlling an optimum balance between oxidative and reductive reactions is apparent. Promising Avenues of Research The field of enzyme chemistry is expanding rapidly. Experimental evidence VOLUME
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has shown that a plurality of enzyme* acting simultaneously or in sequence, on casein and lactalbumin carrying prosthetically bound lipid matter, may hold attractive possibilities for the cheese industry. It is within the realm of possibility that the controlled used of enzymes could drastically revolutionize this branch of the dairy industry and even serve to bring into existence types of dairy products now unknown. The use of lactose for increasing the yieid of penicillin and the production of lactic acid from whey are examples wherein the carbohydrate of milk serves the fermentation industries. An obscure example of a product derived from lactose by electrolytic oxidation is calcium lactobionate calcium bromide, reputed to have particular merits as a sedative and for the alleviation of certain nervous disorders. Further development of casein and lactalbumin products for dietary and therapeutic uses may be expected. The use of casein for these products is now restricted to a few specialties with limited distribution. Casein as such for direct dietary use or as an ingredient in any widely used food is unknown notwithstanding its proved nutritional merits. The antacid properties of casein, readily predictable from its potentiometric titration curve, have not received the attention of dietitians and the medical profession which may be expected in the future. Likewise, more extensive recognition of the merits of casein in the management of peptic ulcer may be anticipated. In order to meet potential dietary and pharmaceutical uses more precise methods of production must be employed than now generally prevail. A purified dispersable dicalcium caseinate is cited as a single example which adequately meets certain dietary and pharmaceutical requirements.
Lactalbumin and casein hydrolyzates may be expected to attain more general use for pharmaceutical and dietary purposes as methods of production are further perfected Selective adsorption of certain unpalatable compounds inherent in these products is indicated as a possible means of improving consumer acceptance. A modiaed lactalbumin readily dispersible in water and possessing extremely high hydrophyllic properties has proved on limited trials to be highly efficacious in relieving edema and other complications resulting from extreme cases of protein privation. This product has also been sliown to be effective for the regeneration of blood protein, comparing favorably with beef blood serum. Clinical and nutritional evidence may be expected to sustain the presumption that lactalbumin salvaged from whey will find increasing use for dietary and therapeutic purposes. The lifting of the nutritive level of fluid market milk by the addition of vitamin D concentrates is increasing rapidly. In certain states vitamin D milk is now available in all communities of 2,500 population or over. The gradual accrual of evidence indicating the physiological importance of vitamin A and particularly the significance of body reserves is an omen indicating that its addition or the addition of its precursor to market milk may not be indefinitely delayed. In summary, the milk industry has been a prominent beneficiary of many phases of chemical research; the chemistry of milk and its derivatives is increasingly recognized as the origin of a dominate concept motivating an expanding industrialization of the production and processing of this basic food.
The
They watch him use the apparatus they had known I n cruder form, and nod in glad surprise A t instruments and laws to which they made Their contribution. They learn of better ways, And recognize familiar steps, and freely give The products of their lives. For science knows no barriers, N o demarcation lines, no tariff walls, no breaking Of its stream; and history shows that had one tried T o hide his find, self seeking fame, his thinking sprang I n simultaneous discovery from other minds, For thus does knowledge flow. White-coated before soapstone gray the chemist works, Alone, yet not alone. He is aware but dimly Of his audience, aware but dimly of the greatness * That he holds, and seeks, as they had sought before, The answers to his universe.
Chemist
White-coated before soapstone gçay, Bowed in silent concentration, The chemist works, dreamer, sceptic, philosopher. He measures, weighs, distills, and analyzes, And through his hands, That move among the glass with trained precision, Flows accumulated knowledge, gathered Through the ages; centuries of ceaseless Searching; life spans of days and nights And years consumed by that desire to know, Which since primeval time has driven man Unmercifully; knowledge forwarded in fumbling steps; Knowledge grown from knowledge sown, gleaned And winnowed, and the kernels nucleated In this quiet, thoughtful man. As he works, aware of limitation, Respectful of his tools, They who bore this treasured lore, scientists, and alchemists Doubters of the known, explorers of the dark, Crowd in spectral forms about his working bench.
» JANUARY
12,
1948
PRESENTED
before
the
AMERICAN
CHEMICAL
SOCIETT, Agricultural and Food Chemistry Division. New York, Sept. 18, 1947 (Borden Award Address).
MART COMSTOCK BAKSTOW
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