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Butter Production

( Originally Published 1939 )



TECHNOLOGY

Cream production. Cream for the manufacture of butter is mostly produced by farmers who are engaged primarily in other lines of agriculture. Most farmers keep a few cows as a source of regular income throughout the year. They usually do not provide themselves with either the knowledge or the equipment to produce cream of the quality that could be produced if they were really dairy-minded. This situation hampers the application of improved methods. Educational work is slow where the incentive is lacking.

The invention and wide distribution of the farm cream-separator were a great stimulus to the production of cream. Whereas in the past the farmer had had to haul his milk to the creamery every day, now he could separate the cream on his farm and deliver it only once a week or even less frequently. This was easy on the farmer but hard on the cream. Usually the farmer did not have proper storing facilities. The cream soured and often became grossly contaminated.

The keen competition among butter manufacturers forced the selling price of butter closer to the rising cost of cream. Continuation in business was possible only to those firms which operated on a large-volume basis where the small percentage of profit was compensated for by the very large volume of output. This forced the creameries to reach farther and farther for their supplies. This in turn increased the time between the production of the cream and its delivery to the factory. Such conditions led to the development of very large centralizers (as these creameries were called) which drew on the cream supply from hundreds of miles.

In the meantime a new movement got under way. The rapid development in the knowledge of proper ways to handle dairy products and the increasing influence of the great agricultural colleges, experiment stations, and universities, together with the educational work of the creameries, have all operated to stimulate the development of a great dairy industry, founded on modern principles of sanitary production, scientific operation, and economic administration of high-class dairy farms and butter factories. The cream is produced on farms which are stocked with tuberculin-tested cattle and which are equipped to cool the cream quickly so as to deliver it to the creameries while it is fresh.

Still another force has been at work to improve production conditions. This is the influence of eastern health laws and regulations on, and also consumer demand for, quality products. As the eastern markets have expanded in their increased consumption of butter, cheese, and ice cream, the demand for cream of high sanitary quality likewise has increased. Producers throughout the butter country have learned that, when they meet the exacting eastern requirements, they can sell their cream at better prices. This has led to the scattered introduction throughout the whole country of cream-production practices on a par with milk-production practices anywhere.

Cream procurement. The competitive urge for volume has led to the development of several systems of securing cream.

A few creameries still buy their cream in the form of whole milk which is delivered daily by the farmer. Such a practice yields a high-grade product because the cream is made fresh, and the farmer is in direct and frequent contact with the creamery-plant operators and quality-control men. However, such a procedure is economically possible only where the milk supply is large and is concentrated in a relatively restricted area.

The so-called cream route system is in extensive use. The hauler operates a route which visits every farm and collects the cream for delivery to the creamery. He may operate on a commission basis, or he may be a creamery employee. He may receive both a salary and a commission. In any event, he comes into direct contact with the farmer, weighs, samples, and often tests the cream, and delivers or ships it to the creamery. If the hauler is quality-minded, he can exercise a potent influence to impress the farmer with the need of exercising care to produce a good quality of cream.

The whole-milk creamery which had to reach great distances for a supply of cream found it economical to establish skimming stations where the farmers delivered their whole milk for plant separation of the butterfat. The cream was then shipped to the creamery, and the skim milk was returned to the farmer. As the introduction and use of the farm separator led more and more to the farm separation of butterfat, the skimming station has been displaced by the cream station. This is nothing more than an assembling place where cream can be brought by the nearby farmers for testing, weighing, and purchase by the station operator. This man is often more interested in using the station as a means to secure the merchandise trade of the farmers than he is in using his influence to get the patron to produce a better quality of cream. The station itself may be one of several in a town, thus competing for volume and often compromising on quality.

The independent cream buyers and the farmers' cooperative marketing associations also procure cream and sell it to creameries. However, they are unstable factors in the industry, and their operations are in general not conducive to as much improvement in quality.

Many producers ship their cream directly to the butter factories. They have the disadvantage that they are not in direct contact with the plant people, and there is a tendency to hold cream too long before shipment. But they do have the great advantage of getting clean cans, and they are in contact with the plant managements through correspondence.

Cream-improvement program. As a result of the keen competition for volume, procurement people have generally been more interested in quantity than quality. If a shipper's cream were rejected, he would have no difficulty in selling it at a flat price to a neighboring competing procurement operator, regardless of whether the butter made from it scored 89 or 92. Such practices were demoralizing to any constructive effort by officials and butter manufacturers to improve the quality of the cream supply. Two movements have recently been inaugurated which are having a helpful influence, namely, the grading of cream and the activity of regulatory officials in the enforcement of cream standards.

When cream is graded on quality, a premium is paid for the better cream. This benefits the manufacturer because he makes a higher-scoring butter which brings a better price. It benefits the farmer also because he gets a better price for his cream and builds a stronger market for his product. The basis of the grading differs in several states. Some base it on the acid content of the cream; others, on the acidity and certain organoleptic qualities; and still others, on the age of the cream. These efforts are largely voluntary within the industry, although the states are gradually adopting cream grading laws with a price differential of one or two cents between successive grades. Their influence to improve quality is indicated by the results in the application of the Indiana 4-day plan. Some experimental runs showed that the score of butter made from the cream 4 days old was 1 1/4 points higher than that made by regular ungraded cream. The secret of this enhanced score lies in the fact, demonstrated by Parker and Whitaker, that cream delivered within 4 days of its production has not undergone the microbiological deterioration or biochemical change which is attendant on cream that is a week or 10 days old. The movement is growing, and greatly improved conditions in the quality of cream are reported.

Creamery butter-making procedure. Sampling and grading. Cream is delivered to the butter plants mostly in 5- and 10-gallon cans. It must be very carefully graded for quality, and be sampled for the determination of the butterfat content. The ability of the cream grader on the receiving platform to place the cream properly into the several classes determines, in large measure, whether or not the plant will operate at a profit. If he allows too much off-grade cream to go into the manufacture of his top-grade butter, he lowers his butter score and the price that his butter will bring. On the other hand, if he selects too closely, he will find himself loaded up with a large amount of low-grade cream to make into butter at a lower price as compared with a relatively small amount of high-grade cream to make into his regular production. This is a costly situation if he paid the same price for all his cream, good or bad.

The grading of cream is based largely upon its flavor. The only way to determine this is to taste the cream. In some places, grossly insanitary practices are followed. The operator may dip his hand or finger into the can, lick it off, and wipe the remainder back into the can. Modern plants now provide a short glass rod and a sanitary dental spittoon. The rod is dipped into the cream and then passed to the mouth so that the cream can be tasted in a sanitary manner. The rod is washed in running hot water, and the tasted cream is expectorated into the bowl for discharge to the sewer.

Since the inauguration of the extensive government program for the improvement in the cleanliness of cream and butter, equipment has been installed for effectively straining extraneous matter out of incoming cream. Like the straining of milk, this removes the tell-tale signs of such contamination.

Neutralization and treatment. Experience has taught that there is an optimum acidity at which cream can be churned to make it into the best butter. Also, there may be flavors in the cream which would carry over into the butter unless they were removed from the cream before it is churned. Reducing the acidity improves the keeping quality of the butter. This procedure is called neutralization, although it is not such literally because the acidity is adjusted to about 0.15-0.3 percent as lactic acid, depending upon the subsequent treatment.

There has been some criticism of this practice of neutralizing cream on the ground that it constitutes a sophistication by covering up inferiority, and an adulteration by the addition of foreign substances. Such a specious argument loses cogency because no fraud is involved. The treatment is an established trade practice, performed openly, commended and encouraged by the dairy departments of the state experiment stations and dairy research organizations, and necessary for the marketability of possibly three-fourths of all the butter consumed in this country. It is only by this procedure of procurement and processing that a large volume of all kinds of cream from a wide variety of sources can be made into butter of good keeping quality and fairly dependable uniformity. The market demands such a constancy for its stability. This neutralization of cream for butter making has been a powerful factor in the development of the creamery-butter industry in this country. However, it is to be expected that when economic and sanitary conditions in the butter industry improve, this practice will decline.

Sometimes a cream may have a strong flavor imparted by certain feeds or weeds eaten by the cow. This can often be removed by pressure processing. Briefly, such treatment involves rapid heating under pressure followed by release of the heated cream in a vacuum which volatilizes the off-flavors.

Pasteurization. After the cream is neutralized, it is usually pasteurized. This kills any disease germs which may have been in the cream, and also the mixed flora of microorganisms, thereby increasing the keeping quality of the butter and improving the flavor. Cream is usually pasteurized at a temperature of 150° F. for 30 minutes, or 160° F. for 15 minutes. Some plants flash-pasteurize at approximately 180° to 190° F. This extra treatment is believed to inactivate any harmful enzymes.

A process has been developed for pasteurizing cream under a vacuum at temperatures from 200° to 250° F. or higher, making the cream practically sterile and greatly improving the flavor. The use of such high temperatures without spoiling the cream is made possible by the briefness of the heat treatment. The cream travels at a speed of about 3 to 5 pounds per second past a given point under a pressure of 10 pounds or more, and then is suddenly and "explosively" expanded into a heated vacuum chamber, thereby being cooled immediately. The process is covered by U. S. patents 2,022,419 and 2,022,420.

Ripening. Sour or ripened cream makes a butter with a more pleasing flavor and aroma, as well as a more constant and dependable score, than that made without this treatment. The cream is inoculated with selected bacterial cultures, and is then held at the desired temperatures to obtain the proper combination of acidity, organoleptic properties, and keeping quality. If too high an acidity is developed, the butter may not keep well, particularly if it is salted. Practice has shown that a ripening acidity of about 0.30 to 0.45 percent is about as high as is safe for unsalted butter to insure the optimum flavor with good keeping quality, while an acidity below 0.2 percent is desirable generally for salted butter.

The ripening process involves much more than the production of lactic acid. This acid is non-volatile, and imparts but little "bouquet." The microorganisms break down the constituents of cream into a number of characteristic chemical compounds, the most organoleptically significant of which are the volatile acids, certain esters, and particularly the chemicals diacetyl, acetylmethylcarbinol, and 2,3-butylene glycol. The diacetyl content in normal low-flavored butter is about 0.1-0.3 p.p.m.; in medium flavor, 0.4-0.8; and in full flavor, 0.9-2.0, although these limits have not been established. The ratio of the weakly flavored parent product acetylmethylcarbinol to the organoleptically significant diacetyl is about 15 to 1.

Proper ripening is probably the most delicate operation in butter manufacture. The cream must be held within rather narrow limits of temperature variation. It must be adjusted in its citric acid con-tent to correct for the loss which this valuable microbic food sustained from attacks of microorganisms in the raw cream. The period of ripening is determined by the kind of butter desired (salted or unsalted), the season of the year, and sectional influences. The handling of the starter requires a careful selection of the proper kind of milk. The cultures themselves must be accorded the bacteriological care which is necessary to keep them free from contamination and at the same time effectively viable.

The starters (butter cultures) themselves are usually not pure cultures of a single organism. A good starter contains predominantly bacteria of the type Streptococcus lactis which produce lactic acid. Other organisms are known to be necessary to form the aromatic constituents. Hammer 2 and his associates have conducted such extensive investigations in this field that their report that these accessory organisms are S. citrovorus and S. paracitrovorus must be taken as authoritative.

Color. The characteristic yellow color of butter is acquired from material in the feed of the cow. The effectiveness of its conversion into butterfat pigment is largely a characteristic of the breed. When the cows are on spring and summer pasture, their food is rich in the carotene and xanthophyll of the fresh green feed, but in the fall when the pasture vegetation is dying off and in the winter when the stock food consists of hay and other dry feed, there is not much coloring matter to be absorbed by the butterfat. Therefore, butter is more highly colored in the spring and summer, and much less colored in the fall and winter. Such differences in color militate against the maintenance of consumer demand. Stable markets are built on constancy of quality and consumer acceptance. The only way that this uniformity of color can be maintained is to add coloring material to the cream just before churning. This necessity is recognized by the federal butter statute. No color is used except that which is approved by the U. S. Department of Agriculture. The amount added varies according to the natural color of the butter, but an average figure might be considered to be one ounce to every 100 pounds of milkfat.

In recent years there has developed such an increasing demand for light-colored butter that the deeper-shaded butter is actually discounted on the market. Efforts have been made to bleach butter. The deep rich yellow shades which formerly were so highly prized are now actually a detriment in some markets.

Churning. This process consists of violently agitating the (ripened) cream so that the milkf at separates from the cream in the form of small grains or granules of butter which grow larger until the maximum degree of "gathering" has been effected. On the farm, the churn often consisted of a vertical cylinder in which the dasher was worked up and down. In large plants, the churn usually consists of a horizontal cylinder which rotates on its horizontal axis so that the cream is violently agitated and thrown against the baffles and walls.

Butter factories are usually equipped with combined churns which are constructed to churn the cream to butter and also to "work" the butter. These may produce from 800 to 1000 pounds of butter in every batch, completed in about 40 to 50 minutes. A small glass window in the end of the churn allows the operator to observe the condition of the batch during the churning operation. When the butter granules have reached the desired size, the rotation of the churn is stopped, and the buttermilk is drained off. In order to free the butter granules from adhering buttermilk, they are washed with water in the churn. Clean, cool, potable water at the proper temperature is added, and the churn is rotated several times. The wash water is drawn off, and the butter is allowed to drain. The washing may be repeated several times if the quality of the butter requires it. Inasmuch as the water dissolves and leaches out some of the volatile aromatic constituents, it follows that butter made from high-quality cream should not be washed much, whereas butter made from lower grade cream can be washed more exhaustively to advantage.

Salting. Butter is salted to impart a salty taste, to enhance its natural flavor, and to improve its keeping quality. Heavy salting will obscure some of the delicate desirable flavors, whereas light salting will accentuate objectionable ones. Well-made salted butter is widely accepted. Most of the salted butter sold contains about 2 to 2.5 percent of salt. Great care is exercised to use salt of proper taste and solubility. When the salt content is below about 2 percent, its inhibiting effect on the growth of microorganisms is unimportant. A salt content of about 3 percent is equivalent to a brine strength of about 19 percent in the butter serum, and this concentration is effective to preclude microbic growth.

Working. After the churning is completed and the salt added, the butter is given a treatment known as "working." The object is to distribute the moisture and salt uniformly, to secure evenness of color, to impart the desirable texture of plasticity, to break down any granular properties, and to adjust the content of moisture. All these properties are obtained by forcing the butter between parallel rotating rollers to impart a kneading action, or by rotating the churn so that the butter simply falls and is worked by concussion against the sides of the churn.

Packing. The standard package for bulk butter has been called the 60-pound wooden tub, but it actually holds 62-64 pounds. Before the butter is packed into the tubs, they are steamed to kill the germs and to open up the pores. Then hot paraffin is applied by spray or brush. This treatment protects the surface of the butter pack from mold spoilage and reduces shrinkage from loss of moisture. The tubs are then lined with parchment liners, and the bottoms are protected by parchment circles. After the butter has been packed into the tubs, parchment circles are placed on top to protect the butter from contact with the wooden tops and reduce the tendency toward surface taints. Great care is exercised to pack the butter solid so as to avoid leaving any air pockets where mold might develop or brine might collect. When the butter is cut into prints, it is wrapped in parchment paper and sometimes again in waxed paper, and then packaged in paraffined cartons.

The parchment liners and wrappers for salt butter are usually sterilized by boiling in brine solution. Those for unsalted butter are soaked in boiling hot water.

Storage. On account of its delicate flavor and chemical instability butter will undergo changes in quality unless it is promptly and effectively refrigerated. It will keep in good condition for many months with very little, if any, noticeable deterioration at temperatures be-low 0° F. Most of the butter for storage is packed in May, June, and early July, and is consumed within the year.

Several factors contribute to the deterioration of butter on pro-longed storage. Air slowly oxidizes it with attendant development of a tallowy flavor. Light enhances this effect. If the cream is exposed to such metals as copper and iron, appreciable amounts may dissolve and be carried into the butter where they seem to intensify oxidation. Eight parts per million of copper is a heavy contamination. Germ life contributes its share to the deterioration of butter. The residual content of acid and the several enzymes all catalyze harmful effects. Some of the desirable aromatic constituents themselves undergo ad-verse chemical changes. However, it has been found that there is no appreciable loss of vitamin A and D in Australian and New Zealand butter made from either sweet or acid cream, even when stored for two years.'

Whipped butter. Butter can be slightly warmed and vigorously whipped with air until the color becomes lighter, the texture soft and plastic, the flavor slightly intensified, and the volume greatly increased. This admixture of air does not seem to increase the rate of deterioration if the product is kept cold. Such a product spreads well on bread if not used too cold.

Renovated butter. Butter of low grade, known in the trade as packing-stock butter, can be improved in quality and "dressed up" for marketing by subjecting it to processing or "renovating." This is a legitimate industry which is licensed to operate under heavy taxation and strict supervision by the Bureau of Internal Revenue of the Treasury Department and the Bureau of Dairy Industry of the Agri-culture Department. The butter is melted so as to draw off the brine for straining out the curd and other insoluble material, and then is deodorized by blowing air or steam through it. It is then cooled and churned with fresh cream, and is finally worked and packed for market like other butter.

RELATION TO THE PUBLIC HEALTH

The milkfat comes directly from the churned cream by draining off the non-fat buttermilk portion as completely as possible. The water con-tent comes from the moisture in the residual traces of buttermilk which escaped the washing process, and also from the water which replaced the buttermilk. The curd is the residual trace of coagulated milk protein which is occluded in the butter granules; it contains the protein and lactose from the remaining traces of buttermilk. The salt was added at the time of manufacture.

Nutritional value. About 10 1/2 quarts of milk are required to make 1 pound of butter, concentrating the butterfat about 21 to 1. It has a calorific value about twice that of proteins and carbohydrates, averaging about 3300 calories per pound. Like all the fats, butterfat is easily and almost completely digested. Its content of the unsaturated fatty acids, linoleic and linolenic, gives it an important role in supplying these essentials of proper nutrition, although they vary over a wide range according to season and feed of the cow.

Butterfat contains the important vitamin A in large amounts .4 For the physiological effects of deprivation of this vitamin, see the discussion on page 24. During the World War, serious nutritional disturbances (manifested particularly in diseases of the eye) were suffered in Denmark, caused by the substitution by these thrifty people of oleomargarine substantially free from (or low in) vitamin A for butter rich in that vitamin.

The golden yellow color of butter is due mostly to its content of carotene, the precursor in the body of vitamin A. The amount varies with the content in the feed. The vitamin itself is colorless. There-fore, the color of a butter is not necessarily a measure of its vitamin A content. Different breeds of cows possess congenital differences in their ability to convert the carotene into the vitamin and to put color into their milk. Those herds which secrete the fat with a higher yellow color tend to put more carotene and less vitamin A into the fat than the others, and so produce a more highly colored fat. However, since the differences in butter color which can be produced by different kinds of feed are much greater than those which occur among different breeds on the same feed, the natural golden yellow color of milkfat is, in general, a fairly good index of vitamin A activity. Pasteurization does not adversely affect the vitamin A content. In the interest of the public health, it is deplorable that there is such a large demand for light-colored butter. This movement is directed away from the nation's best source of vitamin A. The deficiency will have to be made up from some other source or the public health will suffer even more severely than it does now.

Butter also contains appreciable amounts of vitamin D. This vitamin participates in the assimilation of calcium and phosphorus. It has the role of locking, so to speak, these elements into the proper tissues, and reduces their tendency to escape in the elimination functions. This property makes the vitamin particularly important for building bones and teeth, and maintaining the blood with the proper mineral content of these elements.

Both vitamin A and D vary over a threefold range from their low values in the winter to high values in summer. The pasturage of the herds and their exposure to the summer sun enable them to secrete these dietary essentials in their milk, and to substantiate the popular conception of the generally superior nutritive quality of highly colored June butter.

Epidemiology. Tuberculosis. A large amount of laboratory work has been done on the viability of pathogenic organisms in butter. Schroeder and Cotton 7 reported that studies by several workers indicated that tubercle bacilli will live in butter for periods ranging from 12 days to 8 months. This wide divergence of results led them to conduct a careful study wherein they found that cream from milk infected with the tubercle bacillus may contain large amounts of these organisms which survive in salt butter (1 ounce of salt to 1 pound of butter, kept at 60° F.) for 41/2 months or longer. They proved their point by guinea-pig inoculations. They consider that salt is weakly inimical to the viability of tubercle bacilli but that dependence should not be placed on this property because the salt is not distributed absolutely uniformly throughout the butter.

Mohler, Washburn and Rogers quote Swithinbank and Newman as reporting that, out of 496 samples of market butter in England, they found 76 samples or 15.2 percent to contain tubercle bacilli. They quote Schroeder and Cotton (Bur. Animal Ind. Circular 153) that tubercle bacilli remain viable for at least 160 days in salted butter when kept without ice in a house cellar. Mohler and his associates made salted butter out of milk from tuberculous udders, and also out of milk which had been inoculated with tubercle bacilli. All the milks were found to be highly infective as determined by inoculation into guinea pigs. The butter itself communicated tuberculosis to guinea pigs both by ingestion and by subcutaneous inoculation. Samples were stored at -10° F. and were virulent by inoculation after 6 months, and by eating after 3 months. Unsalted butter made at the same time was found to be equally infective.

Tanner lists the results of 44 investigations on the incidence of tubercle bacilli in butter 9 from which he concludes that tubercle bacilli may remain viable in butter for long periods (12 days to 6 months) but not as long as in cheese.

Edington gives in detail the method he used to examine 40 samples of imported butter. He found one of the Danish samples to be positive for tubercle bacilli. He considers such a finding to be surprising since these butters are believed to be made from pasteurized cream, although he recognizes that the butter may have become infected after manufacture.

The danger of contracting tuberculosis from butter made from unpasteurized cream is becoming less as the bovine tuberculosis eradication program nears completion, and the proper control of pasteurization is advanced.

Undulant-fever organisms. Fitch and Bishop 11 report that Van der Hoeden examined 20 samples of sour-cream butter from naturally infected milk and found it to contain no organisms of Brucella abortus. They refer to Lerche as having isolated this organism 5 times from 14 samples of butter made from infected cream, and once from 11 samples of buttermilk. These investigators themselves separated cream by gravity from the milk of cattle known to be shedding the organism. This milk or cream was not pasteurized. While it was still sweet, it was made into butter, one half of which was unsalted and the other half was salted to 3 percent. By guinea-pig inoculation, the Brucella abortus was isolated from the buttermilk, the salted butter, and the unsalted butter.

Carpenter and Boak mixed suspensions of several strains of Brucella abortus with melted butter, salted to 1.5 percent, and injected samples into guinea pigs. The organisms remained viable from 32 days to 142 days but not after 192 days. Guinea pigs injected with samples from 17 different lots of market creamery butter of unknown history showed no evidence of the infection at necropsy. Cream of 40 percent butterfat content was inoculated with this organism and stored at 8° C. Two of the test organisms were viable for 8 days and 2 for 10 days.

Typhoid fever. Tanner 13 has reviewed the work of numerous investigators on the presence of typhoid organisms in butter. The experimental evidence as to how long the organisms will remain viable in artificially infected cream and butter is contradictory. Some work shows that the organisms are viable in sweet-cream butter for 10 days but not for 15 days, and in sour-cream butter for 7 days but not for 10 days. Other work showed that the organisms were alive for 3 weeks. Another observer found that in only 1 out of 8 experiments did the typhoid germs in salted butter survive for a longer period than 10 days. Unsalted butter contained viable typhoid organisms for several months.

Washburn 14 inoculated cream just before churning, then worked and salted the butter, and placed it in cold storage. Samples were withdrawn every 2-3 days. Living colonies were found on the one hundred and fifty-first day after its manufacture.

Boyd 15 reports 7 cases of typhoid fever traced to butter from unpasteurized cream which came from a farm where there was a per-son suffering from the disease. In another outbreak, there were 10 cases from unpasteurized cream made into butter. He quotes Hill as reporting a typhoid and also a diphtheria outbreak traced to butter from infected cream supplies.

Other organisms. Berry 16 reports the work of other investigators who found the typhoid bacillus in buttermilk after periods of 3-10 days, and who show that tubercle bacilli may be in unpasteurized buttermilk offered for sale. Bruck found viable typhoid organisms in butter from infected cream after 27 days. The experiments of Hill in Minnesota showed that diphtheria organisms can live in butter for a month. Berry studied the viability of several types of pathogenic bacteria in butter by inoculating broth cultures into sweet cream and then making counts periodically on suitable media. In almost every case there was an immediate decline in numbers.

At a salt content of 6 percent, E. typhosa and S. paratyphi grew slightly, and S. schottmülleri abundantly. At 9 percent salt strength, none grew. S. aertrycke and Esch. coli reacted similarly to S. schottmülleri in butter.

Rosenau, Frost, and Bryant IT collected 25 samples of butter (mostly prints) in Boston, and found coliform organisms in 6 samples (total bacteria counts in these were high), streptococci in 14 samples, no Clostridium welchii (B. welchii), and tubercle bacilli in 2 out of 21 samples tested. Some of the highest-priced and highest-scored samples contained, in addition to the tubercle bacilli, large numbers of bacteria, particularly streptococci, per gram. They state that price is no guarantee of safety, and recommend the pasteurization of cream for butter making.

The presence of staphylococci, discovered in milk by Barber in 1914 and confirmed by investigators since then,19 has apparently been noted in butter. Fanning reports 19 an outbreak involving 70 persons, 2 of whom died, from eating butter which contained Staphylococcus aureus. There was sudden onset of epigastric pain, vomiting, diarrhea, and collapse, with no increase in the pulse rate and with normal or subnormal temperature. Samples of the suspected butter were consumed in normal amount by a human volunteer who developed a mild diarrhea with bright yellow stools.

Armstrong and Parran 20 have cited several epidemics traced to butter. An outbreak of diphtheria was traced to a carrier of disease on a farm. An epidemic of typhoid fever was caused by a carrier who made and sold butter to a grocery. In another typhoid epidemic, all who became ill had used butter or buttermilk from a single lot of infected raw cream produced on a farm which had a case of typhoid fever.

Pasteurization of cream for butter making. Although no figures are available, it is quite probable that most of the creamery butter manufactured in the United States is made from pasteurized cream. However, large amounts of butter are made from cream that is not pasteurized. Trimble 21 reports that 15 states produce more farm-made butter than creamery butter, i.e., 65,000,000 pounds against 36,000,000 pounds, respectively, and that in 1932 over 5,500,000 pounds more farm butter were produced than in 1929. The 1934 Census shows that 23 states produced more farm-made butter than creamery butter, and 28 states made 37,000,000 pounds more farm butter than in 1929. Altogether, probably 500,000,000 pounds of country butter are still produced in the United States.

The pioneer in this country in the pasteurization of cream for but-ter making was H. E. Schuknecht. When he began to do this in 1896, he encountered the usual opposition to innovation. Butter makers said that good butter could not be made from pasteurized cream and that the markets would not accept it. They said that the butter was flat in flavor and had no grain. However, after such changes in processing as necessary, and as the result of persistent effort, the superior quality of such butter began to be recognized. The export trade was the first avenue for its marketing because this butter had uniform and long-keeping qualities. Now, the great bulk of creamery butter is pasteurized, and there is a growing tendency to re-quire this as a public-health measure.

Oldenbusch, Frobisher, and Shrader showed that 50 percent cream inoculated with E. typhosa, beta hemolytic streptococci from scarlet fever and septic sore throat, and tubercle bacilli could be effectively pasteurized at a temperature of 145° F. for less than 3 minutes, and at 143.5° F. for less than 7 minutes.

The Commission on Milk Standards 24 has reviewed the sanitary situation in the butter industry and has recommended that butter should be graded on the basis of its sanitary quality and market score, and that in the interest of the public health the cream used in the manufacture of butter should be pasteurized.

Biochemical effects. The shipment of cream from long distances for butter making, together with a lack of cooling facilities on many farms, has led the industry to accept cream which may run from 0.2 to 1.5 percent acidity, averaging around-0.5. This acidity is caused by the growth of enormous numbers of microorganisms in the cream Other microbic metabolic decomposition products may also be formed, imparting various desirable and undesirable properties. Some of these are the desirable volatile constituents which are so important for imparting the proper flavor and aroma to' the butter. Others are the undesirable carbohydrate and protein decomposition products which impart bitterness and various. other off-flavors, as well as properties which may be physiologically harmful. Most of these microbic effects are also deleterious to the keeping quality of the butter.

However, their possible undesirable effects are almost entirely eliminated in the manufacturing processes. The high acidity is neutralized with lime or carbonate of soda or bicarbonate of soda. Off-flavors are removed in large measure by pasteurization, enhanced sometimes by special supplementary treatment with steam. Bitter and other flavors in the water phase (skimmed-milk portion) are largely eliminated in the draining off of the buttermilk from the churn and finally removed by washing the butter with pure water. The micro-organisms themselves are killed by the pasteurization process. None of these treatments imparts any property which has been shown to be at all harmful to health.

Unless butter is made from high-grade materials and is kept under refrigeration, it spoils rapidly. The usual temperature of commercial storage is about -5° F., and that of iceboxes and refrigerators in grocery stores and homes is about 50° F. The factors that contribute to spoilage are the microbiological content of the cream before its pasteurization, the amount of acid, the time and temperature of pasteurization, the salt content, the microbic flora, the temperature of storage, and the chemical effects of light, air, and metals.

CONTROL MEASURES

Standards and regulations. Definition. It is common practice to require a minimum standard for the milkfat content of butter, and sometimes a maximum standard for the moisture content. The U. S. Congress in the act of March 4, 1923, defined the composition of butter, and this definition is the basis for the standards used by the U. S. Food and Drug Administration:

Butter. The food product usually known as butter, and which is made exclusively from milk and cream, or both, with or without common salt, and with or without additional coloring matter. It contains not less than 80 percent by weight of milkfat, all tolerances being allowed for.

Most of the states have enacted the same standards, although a few require 82.5 percent fat, and some add a moisture standard. Usually this is set at 16 percent as a maximum. When this moisture standard is enforced, it automatically compels the butter maker to produce but-ter which contains appreciably more than 80 percent milkf at because of the impossibility of leaving enough of the other ingredients to ac-count for the intervening 4 percent. However, usually only the milk-fat standard is enforced.

Proposed grades for churning cream. The U. S. Department of Agriculture has issued standards for grades 27 of churning cream. It classifies cream on the basis of its acidity, flavor, and value to make butter of given scores ranging from 93 and above to 88 and below. This enables a producer to sell on quality and to secure a price commensurate with the care taken in the production, thereby creating an incentive for the farmers to market a better quality of cream.

Cream from accredited areas. Several cities, including Indianapolis, Cleveland, Chicago, and others, have prohibited the sale of but-ter which comes from other than officially accredited tuberculin-tested areas. The Board of Health of Chicago requires that butter for sale there shall be labeled to read: " Made of cream from healthy herds from officially accredited tuberculin-tested areas." The State Board of Agriculture of Utah, on January 15, 1937, adopted a regulation prohibiting the importation into that state of any dairy product (mentioning butter specifically) which did not come from cattle free of tuberculosis. The elimination of tuberculous cattle from modified ac-credited areas is gradually extending this protection over the entire country.

Extraneous material. Butter should be made from clean cream which was produced in a cleanly manner. However, many shipments contain impurities similar to those which often get into milk, namely: mold, insects, straw, leaves, dust, feathers, animal hairs, and other such extraneous material. In the fluid-milk industry, so much educational and regulatory effort has been expended by the supervisory agencies of the industry and government that milk producers have learned to give increasing care to the sanitary handling of milk, and to strain out all possible extraneous material that may get in. Similar regulatory pressure has been directed recently to the sanitary improvement of the production practices in the butter industry. These efforts include the examination and seizure of both cream and butter. Clarke states 28 that, in the summer and fall of 1934, 3.51 percent of all cream examined was condemned, whereas in the period from July to September 1935, only 2.70 percent was condemned, indicating improvement. These condemnations were distributed as follows: cheesy 42 percent, moldy 23 percent, putrid 21 percent, yeasty 8 percent, rancid 3 per-cent, and containing extraneous matter 2.7 percent. The percentage condemnations of all cans of cream examined in 1937 and 1938 were 2.8 and 2.7 respectively. Although sanitary conditions are much better, extensive changes in the methods of procurement and handling are considered to be essential before this industry can be said to be in a satisfactory condition.

Fortified flavor. Various commercial products have been offered to the butter industry for addition to butter to improve its aroma (or "nose" as it is called in the butter trade) . However, when this quality is developed too far by natural cultural means, the butter does not keep well. The addition of the artificial flavor, diacetyl, does not cause so rapid a deterioration of the butter. However, the addition of too much imparts a "chemical" taste which is recognized even by the layman as making the butter too strong. Its addition to butter is considered by the Food and Drug Administration and some other regulatory officers to be a violation of the law. However, this is disputed by some authorities who contend that it is in the same category of acceptable trade practices as neutralization of cream and the use of bacterial starter cultures for ripening cream.

Scoring. Butter is not bought on the basis of its composition but exclusively on its organoleptic qualities, that is, its taste, flavor, appearance, and texture. To assist traders to arrive at comparable grades, a standard procedure for judging butter has been devised called "scoring." 3° Different items which are considered important in appraising the quality of a sample are given numerical values which are added to give the total rating or score. The method that has been used for many years of prorating the score to various factors has been abandoned in favor of the rating of the four significant factors of flavor, body, color, and salt.

The butter is first examined for its flavor quality. Each flavor level has a definite rating, as, for example, a "fine" flavor is rated as 93, a "pleasing" flavor 92, a "fairly pleasing" one 91-90, "definitely acidy" 90, and so on throughout the range of the flavors that are usually encountered. Each of these specific flavor ratings from 93 to 90 inclusive is allowed a tolerance or "defect" of 1/2 point without deducting anything from the score. Flavor scores of 89 and 88 are al-lowed defects of 1 point each, a flavor of 87 is allowed 2 points, 86 is allowed 3, and 85 is allowed 4. These defects are the factors of body, color, and salt, which are given numerical ratings according to the degree of the off-quality. The official score is made by deducting, from the flavor rating of the sample, the amount that the total rating of the defects in body, color, and salt is in excess of the rating for defects permitted in these factors for butter of the particular flavor rating. Expressed as a mathematical formula, the score is calculated as follows:

S=A— (x — y)

where S = score; A = flavor rating; x = sum of the ratings of defects of body, color, and salt; and y = rating of defects permitted for the particular flavor rating.

The new method of scoring, together with examples of its application and also a good description of the various defects and their causes, is discussed in practical detail in a booklet 31 which can be obtained without charge by writing to the U. S. Bureau of Agricultural Economics, Washington, D. C.

In spite of the apparent mathematical precision which is implied in the use of figures to indicate the score of a given piece of butter, the actual quality is not capable of being measured nearly so accurately. A procedure which depends exclusively on such abstract factors as the senses must allow a relatively wide leeway between the scores of duplicate or even split samples. Then, too, the scoring standards differ between the New York and the Chicago markets. Human frailties (such as colds and bad taste), trade conditions, and training greatly affect the judgment.

It is unusual for a butter to score above 93; most butter scores between 89 and 92. In the milk industry, quality control starts on the farm, and the rated quality of the bottled milk comprises the sum total of the sanitary measures all the way from cow to bottle. In the butter industry, quality, heretofore, has depended on the "score" of the finished butter, with no recognition of its background of sanitation. This condition is now changing.

Packing-stock butter is a trade name usually applied to miscellaneous lots of country or other butter. It is the normal source of supply of the process- or renovated-butter manufacturer, but not all packing-stock butter marketed in the United States reaches a legitimate and licensed manufacturer of process or renovated butter.

Federal statutes (Section 4, Act of May 9, 1902, 32 stat., 194) define "adulterated butter" as a grade which has been deodorized or improved in palatability by the addition of some refining chemical or other substance to cheapen it, as, for example, a foreign product or an emulsifying agent to enable it to absorb abnormal amounts of water, milk, or cream. Such butter is subject to a special tax of 10 cents a pound, and also manufacturers' and dealers' special taxes, and its production and sale are regulated by the Bureau of Internal Revenue of the U. S. Treasury Department 32

Process or renovated butter is defined by the same statute as a butter subjected to any process by which it is melted, clarified, or refined and made to resemble genuine butter. This butter is also under the control of the above department and is subject to a tax of 1/4 cent a pound. The manufacturer also pays a special tax of $50 a year.

The Bureau of Dairy Industry of the U. S. Department of Agriculture is authorized to supervise the sanitation of the operations, and to issue certificates of quality when any of this butter is offered for export.

Ladled butter is made by mixing or stirring butter to obtain uniformity of color. If it is not melted or treated with chemicals, it may be washed with water without being subject to tax.

Besides being under the above control, all these products are subject to the provisions of the Federal Food, Drug and Cosmetic Act, the same as any other foodstuff.

The Chicago market recognizes the following grades: creamery, centralized creamery, held, renovated, ladle, packing-stock, and grease butter.

Types of adulteration encountered. By far the greatest cause of regulatory action against butter is the finding of too low a content of butterfat. This may be caused by leaving too much water in the churning, by actually adding water, or by adding milk or milk powder. Sometimes a foreign fat is substituted for the milkf at. Occasionally preservatives may be found. Within the past year or two, there have been numerous condemnations for the presence of extraneous matter.

Examination for adulteration and unwholesomeness. Physical tests. Butter is sampled by withdrawing a plug with a trier. This sample is examined physically and organoleptically for scoring.

Extraneous material. The insoluble foreign matter can be strained onto sediment discs for examination as to identity and amount.

Chemical tests. SAMPLING. The sample is softened, well mixed, and weighed quickly to avoid moisture change.

MOISTURE. About 2 grams are weighed into a flat-bottom dish and dried to constant weight on a water bath.

FAT. This may be leached from the dry residue from the moisture determination by means of ether, and calculated from the difference in the weights before and after this extraction.

CASEIN. The residue in the crucible from the indirect method of determining the fat is carefully incinerated. The loss in weight is the casein.

MINERAL. The residue from the above treatment is the mineral matter, consisting mostly of sodium chloride. This can be determined directly by shaking the butter in a separatory funnel with hot water, and titrating the sodium chloride directly with standard silver nitrate solution.

COLOR. The color is extracted with ether, and identified by the methods for the separation and identification of the different dyes used in foods. These methods are based on color changes with different reagents.

FOREIGN FATS. If butter has been adulterated by the addition of oleomargarine or other fats, the effect is to increase the percentage of insoluble fatty acids and the iodine number, and to lower the Reichert-Meissl number, the specific gravity, and the saponification number. Common adulterants are lard, beef oleo oil, and coconut and cotton-seed oils..

All the above chemical procedures are presented in detail in the official methods of analysis 35 A simple routine procedure for plant use, similar to the official methods, is the modified Kohman method. This enables a plant operator with meager laboratory facilities to obtain a working knowledge of the proximate composition of his butter.

The addition of renovated butter can be detected by microscopic examination. Pure butter presents a uniform field, whereas renovated butter discloses opaque masses of curd. Under polarized light, it shows a mottled field with variegated colors. This same effect is given by oleomargarine.

The spoon test has been valuable for detecting the addition of margarine or renovated butter, but its significance has now been minimized by the use of stabilizers or emulsifiers. When a small piece of the product is heated in a spoon, the margarine and the renovated butter boil noisily, sputter, and produce no foam, whereas butter boils smoothly and foams. Also, the curd of the adulterants gathers in larger masses or lumps than the curd of butter.

The Waterhouse test 37 indicates the presence of margarine and renovated butter by distinguishing between the ease with which the warmed butterfat of butter mixes with milk, whereas that of the adulterants collects in a sticky lump or granules.

ADDED FLAVOR. The addition of diacetyl and its precursor acetylmethylcarbinol can be quantitatively determined by steam-distilling 200 grams of butter culture (or 400 grams of butter) into a solution of hydroxylamine hydrochloride-sodium acetate solution and nickelous chloride, collecting the precipitate on a Gooch crucible, and weighing. The results are expressed as milligrams of the nickel salt. Unadulterated butter may contain from 0.05 to 4.0 p.p.m. (see page 164 for discussion). If the ratio of diacetyl to acetylmethylcarbinol is greater than about 1 to 15-20, it is possible that diacetyl has been artificially added, although in the present state of our knowledge the significance of such analytical data is not established.

PASTEURIZATION. The phosphatase test has been successful in determining whether butter is made from pasteurized cream. The water serum is separated from the butter, and 1 milliliter is added to ten milliliters of the buffer substrate. The rest of the procedure is similar to that for milk.

METHYLENE BLUE REDUCTASE TEST. The reductase test for the bacteriological grading of milk has been adapted by Macy for the grading of sweet cream. The general procedure is similar to that followed for milk except that the strength of the methylene blue solution is tripled.

Microbiological tests. SAMPLING. Samples are taken from a churn, tub, or print by means of a sterile trier.

TOTAL BACTERIAL COUNT. A special beef infusion agar is used for making total plate counts by the general methods of milk analysis, except that the plates are incubated for 4 to 5 days at 21° to 25° C., and then for 2 days longer at 37° C.

Occasionally the question is raised as to the determination and significance of the presence of coliform organisms in butter, but no authoritative work has appeared in this field.

SPECIAL BACTERIOLOGICAL EXAMINATION. It has been found that proteolytic (protein-digesting) and also lipolytic (fat-splitting) bacteria are often associated with the spoilage of butter. Determination of these organisms in butter is indicative of the care taken in the proper pasteurization and handling of the stock in the plant.

YEASTS AND MOLDS. The determination of these organisms is valuable as an indication of the care taken in pasteurizing the cream, in cleaning the butter-handling equipment, in the quality and purity of the butter starters, and in the sanitation of the plant. The determination is made with a potato dextrose agar which is acidified with a sterile tartaric acid solution. The results are expressed as the sum of both the yeast and the mold colonies.

DIRECT MICROSCOPIC EXAMINATION. Fay has worked out a method for the direct microscopic examination of butter which helps the analyst to study the microbiological condition of butter somewhat as the Breed microscopic method does for milk. Hammer and Nelson's method 41 is somewhat more complicated because it involves the separation of the serum from the melted butter by centrifugation, and then the spreading of 0.01 milliliter of the serum over an area of 1 to 9 square centimeters, depending on the number of organisms present. The slides are then dried, stained, and examined under measured microscopic fields.

Supervisory practices. The butter industry is not under the super-vision of public-health officials to anywhere near the same extent as the milk and ice-cream industries. No permits are required to operate the business, and no detailed requirements for plant compliance have been promulgated. Butter-manufacturing plants are usually located in communities which are too small to supervise their milk supplies adequately, and which lack proper regulatory facilities to warrant them in assuming additional responsibilities for butter control. Likewise, the state officials have such limited budgets and personnel that they use their restricted resources for the inspection of milk supplies, and to a less extent, ice-cream plants. However, a responsibility rests on officials as well as on the industry to supervise its raw materials, its practices, and its products.

An unclean plant is a potential health hazard, as well as a handicap to the production of a high quality product. Its condition can be appraised only by a thorough inspection of the premises, the condition of the equipment, the cleanliness of the operations, the adequacy of the pasteurization, the health of the employees, the grade of the raw materials, and the quality of the finished product. There is no fundamental reason why butter plants should not be equipped and operated under sanitary conditions fully as advanced as those maintained by the ice-cream and the milk industries.

Butter control now rests almost entirely upon the examination of samples of incoming cream and the finished butter. The cream is examined organoleptically by the platform operator, and for the butterfat content. In some states, the grading of cream is enforced (see page 161). Samples of butter from the markets are examined by the regulatory officials chiefly for content of butterfat, although recently an active campaign for the improvement of cleanliness has been based on the examination of cream and butter for the presence of extraneous material. Microbiological examinations of samples of butter are used only by those persons responsible for quality production. Some regulatory control officials are now examining market samples of butter by the phosphatase test, especially those labeled to have been made from pasteurized cream. Regulatory action consists in condemning or denaturing cream that contains unclean extraneous matter, and in seizure of shipments that are substandard in content of fat or that are short in weight.

REFERENCES

1. V. C. MANHART, Purdue University Agr. Exp. Sta., Circular 193, 1932.

2. M. B. MICHAELIAN, R. S. FARMER, and B. W. HAMMER, Iowa Agr. Exp. Sta. Research Bul. 155, 1933.

3. Special Rept. Ser. 175, Med. Res. Council, 1932, p. 46, quoted from Am. J. Pub. Health, 23, 205 (1933).

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6. C. F. POE and H. A. FEHLMANN, J. Dairy Sci., 16, 559 (1933).

7. E. C. SCHROEDER and W. E. COTTON, U. S. Dept. Agr. Bur. Animal Ind. Circular 127, 1908.

8. J. R. MOHLER, H. J. WASHBURN, and L. A. RoGERS, 26th Ann. Rept., Bur. Animal Ind., U. S. Dept. Agr., 179, 1909.

9. F. W. TANNER, The Microbiology of Foods, Twin City Printing Co., Champaign, Ill., 1932, p. 290.

10. J. W. EDINCTON, Lancet, 2, 81 (1934).

11. C. P. FITcH and L. M. Blsum', Proc. Soc. Exptl. Biol. Med., 30, 1205 (1932-3).

12. C. M. CARPENTER and R. BoAK, Am. J. Pub. Health, 18, 743 (1928).

13. F. W. TANNER, Food-borne Infections and Intoxications, Twin City Printing Co., Champaign, Ill., 1933, pp. 148-151.

14. H. J. WASHBURN, 25th Ann. Rept. Bur. Animal Ind., 1908, p. 297.

15. M. F. Born, J. Am. Med. Assoc., 69, 2030 (1917).

16. A. E. BERRY, J. Prevent. Med., 1, 429 (1926-7).

17. M. J. ROSENAU, W. D. FROST, and R. BRYANT, J. Med. Research, 30, 69 (1914),

18. J. A. CRABTREE and W. LITTERER, Am. J. Pub. Health, 24, 1116 (1934).

19. J. FANNING, Brit. Med. J., 1, 583 (1935).

20. C. ARMSTRONG and T. PARRAN, JR., Supplement Pub. Health Repts. 62, 1927.

21. C. S. TRIMBLE, 25th Ann. Rept. Internat. Assoc. Milk Sanitarians, 1936, p. 311.

22. G. CAVEN, Dairy Produce, Aug. 23, 1933.

23. C. OLDENBUSCI, M. FROBISHER, JR., and J. H. SHRADER, Am. J. Pub. Health, 20, 615 (1930).

24. "Butter," Commission on Milk Standards, Pub. Health Repts., Reprint 634, 1921.

25. B. W. HAMMER, Iowa Expt. Sta. Research Bul. 156, 1914.

26. "Definitions and Standards for Food Products," S. R. A. Food and Drug 2, Fifth Revision, November, 1936.

27. Tentative U. S. Grades for Churning Cream, Bur. Agr. Economics, U. S. Dept. Agr., Feb. 15, 1935.

28. J. O. CLARKE, Dairy Produce, 41, 10 (1935), quoted from J. Dairy Sci., 19, 101 abs. (1936).

29. Report of Chief of the Food and Drug Administration, 1938, p. 8.

30. (a) J. A. NELSON and G. M. TROUT, Judging Dairy Products, Olsen Publishing Co., Milwaukee, Wis., 1934; (b) L. C. THOMSEN, National Butter and Cheese J., 27, 8 (1936).

31. Revised Tentative U. S. Standards for Quality of Creamery Butter, Bur. Agr. Economics, U. S. Dept. Agr., March, 1938. (These grades became effective on April 1, 1939.)

32. Regulations 9 relating to the taxes on oleomargarine, adulterated butter, and process or renovated butter, Bur. Internal Revenue, U. S. Treasury Dept., April, 1936.

33. Regulations for Carrying into Effect the Process or Renovated Butter Act, Bur. Dairy Industry, U. S. Dept. Agr., B.D.I. Order 1, revised, December, 1936.

34. W. S. GREENE, Mimeograph release, Food and Drug Administration, U. S. Dept. Agr., Nov. 22, 1935; Laboratory Manual, American Butter Institute, Chicago, 1937.

35. Official and Tentative Methods of Analysis, Assoc. Offic. Agr. Chemists, 4th ed., Washington, 1935.

36. "Subcommittee on Butter Analysis," J. Dairy Sci., 16, 300 (1933); revision, ibid., 20, 351 (1937).

37. A. G. WOODMAN, Food Analysis, McGraw-Hill Book Co., New York, 1931, p. 228.

38. W. L. DAvIEs, Food Manufacture, 8, 346 (1933), from Chem. Abs., 28, 835 (1934); C. R. BARNICOAT, Analyst, 60, 653 (1935), from Chem. Abs., 30, 174 (1936).

39. H. SCHARER, J. Milk Technol., 2, 16 (1939). See also J. Dairy Sci., 21, 21 (1938), and J. Milk Technol., 1 (5) 35 (1938).

40. H. MACY, Univ. Minn. Agr. Exp. Sta. Bul. 310, 1934.

41. "Subcommittee on Butter Analysis," J. Dairy Sci., 16, 289 (1933).

42. A. C. FAY, ibid., 18, 603 (1935).

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