Defects in Butter

Defects in Butter: Their Causes and Prevention

by Claire C. Totman, Division of Agriculture, South Dakota State College & G.L. McKay and Christian Larsen, Dean of the Division of Agriculture, South Dakota State College

Formerly “Principles and Practice of Butter-Making” 1906 by G.L. McKay and Christian Larsen

Defects in Butter

A number of common defects in butter are listed as follows on the score card used by the United States Department of Agriculture, Bureau of Dairying, for students’ judging contests. It was originally prepared and adopted by the American Dairy Science Association.


Acidy. Acidy butter is made from unneutralized cream which has an acidity of 0.25 percent, or more, or it is made from butter which has been ripened too high with starter. It has a slight sharpness of flavor which tends to coarseness and indicates poor keeping quality.

Bitter. Cream which has bitter fermentation is frequently found in the fall and winter, when farm production is low and the cream is held too long on the farm. Although it has been kept too cold to sour, it may develop bitter flavors which are carried into the butter.

Bitter flavor may be caused by weeds, particularly in the fall of the year. Too much neutralizer or its improper application may be a cause. Impure neutralizers may be a factor. Certain types of bacteria thrive in cold sweet cream if held too long and produce bitterness. Lipolysis of fat may also cause a bitter flavor, particularly if milk and cream contain abnormal amounts of lipase.

Briny, Coarse. These flavor defects are frequently found together. The cause is either high salt or insufficient working, or both. The droplets of brine are large enough to give to the butter an excessively salty taste. Sometimes butter that is unpleasant in flavor, and to which no definite flavor defect can be assigned, is designated as coarse.

Burnt, Cooked, Heated. There is no great differentiation in these three terms. They all refer to excessive heat in pasteurizing cream, which may come from uncontrolled flash pasteurizers, from vat pasteurization when the vat is less than two-thirds full and the coils cook the cream, or from heating high and holding too long by any method of pasteurization. Such flavors in butter may be very prominent for a week or two and then disappear entirely. Only severe treatment of the cream will produce relative permanency of such flavors.

Cowy. This flavor is not common. It may be encountered when cows are kept in foul and unventilated barns. Usually such conditions are accompanied by careless milkers and attendants. The milk may sit uncovered in the barn for some time. It may be separated in the odors of the barn, and absorption of odors is easy. Cans stored in the barn will readily hold such odors.

Feed. Strong feeds must be given after milking to help overcome this difficulty. This permits a period of 10 hours or more under barn-feeding conditions for the cow’s digestion and metabolism to eliminate partially the odors and flavors from her system. The milk will thus be less likely to be badly affected. Pasture conditions present greater difficulties. The cows should be brought in 2 to 4 hours before milking.

Weedy Flavors. Weedy flavors are usually found in summer butter. In the early summer, French weed, also known as stinkweed, may be very troublesome. Peppergrass, as found in such abundance during the 1935 season in several extended areas in the Northwest, presented serious difficulty. Dry seasons, which encourage the development of these weeds when grass is scarce, make rather insurmountable trouble.

Butter thus flavored sells at greatly reduced prices. (Some recent unpublished work at the South Dakota Experiment Station indicates that green French weed produces offensive flavors and odors in milk, cream, and butter. Such flavors persisted for 3 months in butter stored at 0º F. Cows required starving for 48 hours or more before they ate limited quantities. Green peppergrass was readily consumed by cows. With a ration of peppergrass only, milk, cream, and butter had objectionable grassy or weedy flavors. This butter was considered marketable whereas the butter from cows on the French-weed ration was considered definitely unsalable.) An interesting angle to the peppergrass-flavored butter of 1935 was related by Mr. P.C. Betts of the Dairy and Poultry Cooperatives, Inc., Chicago. A few buyers who used this peppergrass butter at greatly reduced prices became accustomed to its high flavor and still called for it after all such butter had been sold from storage. They were willing to pay just as much for it as for high-grade butter. Old cream and fruity-flavored butter sometimes sells at unjustifiable prices when it goes to certain retail outlets.

Oily, Metallic, Tallowy, Fishy. These four flavors are considered simultaneously because they frequently represent a sequence of flavor development. Butter may be oily and not develop any of the other related flavors. Oiliness may come from high heat and lack of agitation in pasteurizing. Cream may have an oily flavor, which carries to the butter.

Metallic flavor usually comes from dissolved metals in the cream. Producer’s cans may be rusty. Cream vats may be poorly tinned, exposing bare copper, and thermometer bulbs may be bare copper. In rare instances, this flavor defect may come from bacterial action, as shown by Guthrie[1] in 1916. He stated that either good or bad cream may produce butter with this defect.

Tracy, Ramsey, and Ruehe[2] in 1933 studied tallowy flavor in milk and cream, concluding that bacteria and yeasts play a part in the control of tallowy flavor. Lowcount milk produced in the winter frequently develops a tallowy flavor when held after pasteurizing and bottling. Summer milk, sold as market milk, seldom has this flavor. Tracy, Ramsey, and Ruehe believe bacterial activity in milk, before delivery to the plant, acts as an inhibitor to this flavor. They experienced tallowiness in butter at the University creamery when good cream was held three days at 40°F. before churning. Holding such cream in glass vats for the same period and at room temperature greatly reduced the frequency of tallowy flavor in butter.

More recently Sharp, Trout, and Guthrie[3] have indicated that tallowy or oxidized flavor in milk is associated with a reduction of the ascorbic acid (vitamin C) content of milk. Pasteurization at 170° F. for 10 minutes very largely inactivated an enzyme which oxidizes ascorbic acid and in most instances prevented the development of the tallowy flavor. Pasteurization at 145° F. for 30 minutes was also quite effective in preventing tallowy flavor if every precaution was taken against solution of copper in the milk.

A.M. Swanson and H.H. Sommer (Wis. Bull. 442, 1938, Part I of Annual Report of Director of the Experiment Station) report that lecithin and cephalin, and not the true butterfat portion of milk, may be responsible for oxidized flavor. Preliminary trials are reported. The presence of dissolved metals was indicated as a contributing factor.

Metals in cream, particularly copper, are a cause of tallowy flavor. A strip of copper inserted into a pound print of butter will produce typical color fading and an old tallow taste.

Exposure of pound prints of butter to direct sunlight will produce a similar defect, which in this case travels from the surface toward the center as it develops. It is possible that metals induce tallowiness, and that limited bacterial activities help retard such flavor development.

Fishy flavor. Butter from raw cream of medium to doubtful quality often becomes fishy when stored a few months. Efficient pasteurization eliminates this consideration as one of the factors. However, some butter is made from raw cream during the flush season. Lecithin is the source of fishy flavor. It is changed by chemical reaction to trimethylamine, which is the fishy-flavored substance. The factors which favor the development of fishy flavor in butter are listed by Sommer and Smit[4] as follows:

  1. Presence of iron and copper salts.
  2. High acid in the cream.
  3. High salt in butter.
  4. Overworking.

Raw cream, also a factor, is much less frequently encountered.

Flat. Sweet-cream butter, and especially with low salt content and made during the fall and winter, may be decidedly lacking in flavor. Neutralized, unripened, low-salted butter may also be described as flat or lacking in flavor. Excessive washing, or allowing the butter to remain in the wash water for long periods, may tend to produce butter which lacks flavor.

Garlic or Onion. These flavors come from cream produced by cows’ eating these weeds in the pasture. The butter so tainted has very low marketability. Prolonged vacuum treatment of hot cream very largely removes such flavors, but the small creamery is not equipped with this expensive machinery. Recourse is had to grading very carefully. Do not accept such cream, or save it and run onion-cream churnings. The buttermaker will soon discover the need of deodorizing the vat and churn after handling such cream. The producer should be warned to avoid the use of pastures containing such weeds.

Gasoline and Kerosene. The prevention of such flavors in butter is obvious. Inexperienced men in the intake are a liability to be avoided.

Neutralizer. The improper application or excessive use of neutralizers, especially on high-acid cream, is the cause of this flavor. High-temperature pasteurization increases its intensity. Neutralization must be considered a task of major importance. It must not be hurried. Rushing neutralization and pasteurization is a frequent cause of neutralizer flavor. Exact figures and the application of both the science and art of neutralization are imperative.

Old, Stale Cream. These are very common criticisms of butter flavor. To overcome this trouble the operator must continually help his patron. He must grade cream conscientiously and pay a lower price for poor cream.

Rancid. Butter from good cream seldom becomes rancid if refrigerated properly. Cream may be rancid and the butter may have a rancid flavor even under good storage conditions. Rancidity results from the breaking down of fat into free fatty acids. Butyric acid produces a typical rancid odor and flavor.

Yeasty. Yeasty cream produces butter with this flavor defect. Unclean conditions on the farm and summer temperatures are responsible for yeasty cream. The unwashed cream separator again comes in for severe criticism. Yeasty butter will not keep well in storage and always has a sales disadvantage. Yeasty cream is recognized easily when it causes cream to foam. When the lid is removed from a can, yeasty cream is readily recognized by the same odors which accompany yeast-activated bread dough.

Surface Flavor (Putrid or Limburger). Butter stored for short periods may develop some degree of off-flavor at its surface, which may be due to one or several factors. The change which occurs at the surface may be due to chemical or microbiological processes, or may be due to mere absorption of odors from the container or from the air of the storage room.

Associated with surface flavors, but undoubtedly of different origin, are the so-called putrid or Limburger flavors, when the whole mass of butter contains a foul odor and taste. This condition is not common, and its causes are not fully understood. In Canada an outbreak of this trouble was traced to impure water used in the creameries. These flavors may also be associated with, or follow, the development of cheesy flavor in butter. Excessive curd in butter from low-grade cream which has been overneutralized may contribute to protein decomposition, with later putrid-flavor development. Relatively high storage temperatures will hasten decomposition.

Surface flavor in butter is a very serious defect. Consumers will use butter containing undesirable flavors and not be aware of their presence. No consumer, however, fails to recognize foul putrid odors on butter, and it is usually returned to the merchant. It is unlikely that over 50 pounds out of 1000 would be retained by the consumer. The reputation of an established brand of butter may be ruined promptly if such butter is sold.

The use of the removable workers in Simplex churns was discontinued because of difficulty in sterilization. It is quite possible that they were responsible for some flavor defects in butter.

Surface flavor in butter may occur when sweet cream is churned. The presence of acid in sour cream or in ripened cream butter has an inhibitory effect on organisms which cause putrid odors and flavors.

To guard against surface and putrid flavors:

  1. Keep all equipment in a sanitary condition.
  2. Grade cream carefully upon receipt.
  3. Avoid overneutralization.
  4. Pasteurize thoroughly and carefully.
  5. Check the purity of wash water for butter (overhead tanks should be clean and sanitary at all times).

Sweet Curdling of Cream. Of interest, but not known to be related to surface or putrid flavor, is the occasional sweet curdling of cream. Abbott[5] in California describes trouble in handling sweet cream which he attributes to peptonizing bacteria. Where the sweet cream is pasteurized it may contain small curd particles. Instances have been reported where about one-third of the cream in the lower part of the vat contained curd. Such instances are not common. Occasional appearances of this condition usually coincide with periods of unusually wet weather, when cows wade in muddy pools, or in hot weather, when they may stand in stale pools and fight flies. No plant-processing methods have been developed to overcome this sweet curdling. Such trouble is usually remedied by careful attention to cows, and utensils used on the farm.

While butter flavor and quality may not be lowered by the presence of peptonizing bacteria, nevertheless efforts to avoid them are necessary because of increased losses of butterfat during churning.

Ropy Milk and Cream. Of further interest in connection with a discussion of sources of bacteria which may cause putrid flavors in butter and those causing peptonization in cream is the fact that organisms which cause ropiness in milk and cream may come from similar sources. These organisms are not difficult to destroy, but careless plant methods may cause considerable contamination of equipment, floors, walls, etc., and only persistent effort will eliminate the trouble. Careful checks for sanitation must be made both in the plant and at the source of production of the milk and cream. These organisms are not known to be unhealthful but are to be guarded against on the general premise of sanitation.

Microflora of Different Regions. A discussion of these unusual fermentations suggests the fact that different regions of the same country, and different countries, may have microflora which differ greatly. The general problem of sanitation remains the same, but different methods of control and varied processing procedures may be necessary. The fact that several hundred varieties of cheese are produced throughout the world and that certain varieties can be produced only in certain regions indicates the presence of certain types of organisms capable of producing typical fermentations.

Cheesy Flavor. Cheesy flavors may develop in cream and may be found in butter, even though the cream was not cheesy. Herried, Macy and Combs[6] studied cheese-like flavors in unsalted butter. They found mixed organisms rather than single species were more frequently responsible for such flavors.

They found temperatures of 41° to 50° F. favored the development of cheesy flavors. They suggest that insanitary conditions at the farm and in the factory may be a source of trouble. Water, both at the farm and the creamery, may be the cause. Thorough sanitary measures in the creamery, efficient pasteurization of cream, particular attention to the churn, and careful cream grading may remove the causes. Storage of butter at low temperatures is effective in delaying such flavor development.


Leaky. Formerly leakiness was a rather common defect. It is due to insufficient working. Firm butter will incorporate water very thoroughly without injury to the body. A careless or inefficient operator may make leaky butter when working butter with firm body. This is quite inexcusable. When butter is soft at the time of working, the operator may not be able to incorporate the water properly without producing butter of greasy body. In an attempt to pursue a midway course, he produces leaky butter. Keep the butter firm at working time and work it until it shows no free droplets when the surface is scraped, or until a mass of the butter expels no water when pressed firmly. Adding wash water too late in the working process may be a cause of leakiness.

Mealy and Crumbly. These defects are noticeable when butter is spread on bread. The butter judge readily detects this fault. Butter is frequently short grained in the fall and winter, owing to small fat globules and to more hard fats in the butterfat. Warmer wash water has been the usual remedy. Recently the Minnesota station has shown that slightly higher churning temperatures and low wash-water temperatures are material aids.

We might list the causes of mealy, crumbly butter as follows:

  1. Small fat globules.
  2. Higher percentage of hard fats.
  3. Melting scrap butter with cream.
  4. Insufficient or neglected agitation of cream during pasteurization.
  5. Frozen cream.
  6. Use of lime as a neutralizer, particularly if improperly applied.

It is not advisable to melt too much butter with the cream in the vat during pasteurization. This is a rather common practice in disposing of printing scraps. Some creameries with retail trade have found a ready market for this butter at a reduction of 1 or 2 cents in price. Such trimmings, when of uniform color, may be allowed to soften and then be packed into jars for local sale.

Insufficient or neglected agitation of hot cream may permit some oiling off and such a condition contributes to mealy body.

Frozen cream sometimes presents a problem. Either route cream or individual deliveries of cream may be partially frozen. Freezing partly destroys the smooth natural emulsion of cream. The casein is aggregated when the water of the cream freezes. When the cream is melted, the casein remains as small lumps of curd, and may be incorporated into butter, inducing mealiness. The effects of freezing fat-globule hulls also may alter normal butter body. The extent of mealiness in the butter may be considerably reduced by slow thawing of the cream. It is best thawed at room temperature. If working conditions require faster thawing, the cans may be set in water at about 80° to 90° F. It must be remembered that the faster the thawing, the more pronounced will be the mealiness in the butter.

Lime when applied too rapidly or in too concentrated mixture may cause a partial aggregation of casein. During the winter, when conditions favor crumbly butter, lime should be used with proper judgment in order to minimize or avoid an astringent effect on the proteins in cream.

Sticky Butter. Overworking of firm butter will incorporate the water in such tiny droplets that the butter lacks spreading ability. It sticks to the knife. It will not cut well with the wire cutters used in hotels and restaurants. It sticks to the trier when bored. A plug is removed with difficulty and the fat sticks to the trier and may roll. Some larger water droplets will produce some lubrication to the trier or the knife and stickiness is greatly reduced.


Mottles or waves in butter constitute the major color defect. Different shades of butter in tubs may result from packing butter from both ends of the churn in the same tub. This condition seldom develops if the operator is efficient. If half-filled tubs from one churning are filled from the next churning, there may be butter of two colors. If this practice is followed, such tubs should be marked with two churning numbers or in such other manner as to inform the buyer.

Trimmings or scraps should not be worked in the churn with a churning of fresh butter. It is difficult to adjust the temperature of this butter to that of the butter in the churn. Uneven working results, and the butter may have yellow or light patches. This practice has the added disadvantage of introducing stale flavors. Professor Mortensen points out the possibility of having some butter passing in this way from one churning to another for months. This same possibility exists when scraps are melted with the cream in the vat.

White, Green, Yellow, and Rust Spots in Butter. White specks may be caused by casein particles passing through strainers and being subsequently incorporated in the butter. Special care must be exercised when frozen cream is processed. Strainers should not be allowed to clog and run over. Cylindrical strainers in the cream line to the churn are highly desirable.

Green spots may be caused by particles of copper or brass. These may come from the use of brass metal sponges on vat coils, from brass-fitted pumps or other surfaces which wear to the extent of giving off particles of the metal. The manner of prevention is obvious.

Rust spots or brown spots may be developed by tiny particles of iron in the butter. These may come from the use of steel wool on vat coils, from scraping metal surfaces, as in an iron pump, from rusty bolt heads and castings in churns, etc.

Yellow specks may be caused by using old butter color which has settled because of age or being stored at low temperatures. Larger yellow spots may be caused by packing small fragments of very soft butter such as may adhere to paddles, malls, etc.


Gritty butter is a result of using too much salt in proportion to the water which is incorporated in butter. Water at 58° F. will dissolve about 36 percent of salt. When the water is incorporated in butter in fine droplets it will dissolve from 15 to 20 percent of salt, depending on the purity of the salt, the manner and amount of working, the percentage of water in the butter, and the manner of salting. Work by the senior authors at the Iowa Station gave the results recorded below. The butter was worked at intervals during a period of an hour and salt was added in various amounts until a gritty condition resulted. The amount of salt that could be added without producing grittiness is given here.

Percent moisture in butterPercent salt concentration in water in butterPercent salt in butter

With wet salting it is believed that 3.0 percent of salt can be incorporated in complete solution in butter, if the moisture content is about 16 percent.

[1] Guthrie, E. S., “Metallic Flavor in Dairy Products,” Cornell Bull. 373, 1916.

[2] Tracy, P. H., R. J. Ramsey, and H. A. Ruehe, “Certain Biological Factors Related to Tallowiness in Milk and Cream,” Ill. Bull. 389, 1933.

[3] Sharp, P. F., G. M. Trout, and E. S. Guthrie, “Vitamin C, Copper and the Oxidized Flavor of Milk,” Milk Plant Monthly, Vol. 26, No. 5, 1937.

[4] Sommer, H. H., B. J. Smit, “The Fishy Flavor in Butter,” Wis. Research Bull. 57, 1923.

[5] Abbott, F. H., Personal Correspondence, 1938.

[6] Herried, E. O., H. Macy, and W. B. Combs, “The Microbiology of Cheese-like Flavors in Unsalted Butter,” Minn. Tech. Bull. 97, 1934.