1 General -- Nature of the Products Cultured goat milk products are those products made from goat milk by culturing with specific microorganisms (bacteria) so as to induce specific changes in flavor, physical, and chemical qualities. The most noticeable change is the conversion of lactose to lactic acid which results in the development of a sour flavor. The increase in acid content, measured by an increase in titratable acidity and reduction in pH, causes denaturation or coagulation of the milk protein which results in the great increase in viscosity. Other less noticeable changes include the production of other flavor compounds and changes in the physical dispersion of milk fat, protein and some minerals. As a result of the synthesis of lactic acid, there is a decrease in the lactose content of the milk so that it may be more acceptable to persons who have difficulty digesting lactose. The production of uniformly high quality cultured products depends on practicing great care in preparation of the milk, providing suitable cultures of uniform activity, and careful processing of the product.
2 The sale of cultured goat milk is dependent upon the product being uniform in flavor and body characteristics from day-to-day. Uniformity from one day to the next is more difficult to obtain in cultured products than in other items in the dairy line. This is so because conditions favorable to the growth of the cultured microorganisms also encourages the growth of organisms which produce undesirable flavors and body qualities. There is also the possibility that the desired bacterial growth will be prevented or greatly reduced by the presence of antibiotics or bactericidal chemicals in the milk. A third cause of partial or complete failure to attain in desired microbial growth is the presence of bactericidal factors known as bacteriophage. With all of these possibilities for inadequate or interrupted bacterial growth, some failures are to be expected resulting in the final products being less than desirable or outright unsaleable.
3 Manufacturing Procedures
Selection and Preparation of Milk or Cream
Only Grade A quality, fresh sweet milk, free of objectionable flavors and foreign material (antibiotics, bactericides, etc.), and of low bacteria and somatic cell content should be used to make cultured products. There is an inclination to think that because cultured products have a sour flavor they are a good dumping ground for old or off-flavored milk or cream. Such is not the case -- incubation generally amplifies objectionable flavors, rarely covers them up. Thus, the previous statement takes on greater importance.
4 The milk or cream to be made into buttermilk, yogurt, or sour cream should be standardized for fat content. It also may need to have the milk solids-not-fat content adjusted if low. Standardization of the composition is essential to assure the legality of the finished product as well as its uniformity. Consumers have as much concern about uniformity in the foods they purchase as in the suits or automobiles they buy. Buttermilk is usually made from skim milk (less than 0.5 milk fat); yogurt may be made from whole milk (3.25225683497622587700000000000 low fat milk (0.5 to 2.52256834976225877000000000000000000000000000000000018225683497622587700000000000000000000000000000000000000000000000000000000 body (viscosity) it may be due to low protein content, in which case the milk solids-not-fat may need to be increased. Such may prove to be impossible unless low-temperature vacuum evaporator equipment is available because Grade A nonfat dry goat milk may not be available commercially. Superior quality cultured milks can be made when the milk solids-not-fat content is adjusted to 10 to 11
5 Proper pasteurization of the milk or cream to be made into a cultured product is very important. If raw products are used, the normal microflora reproduce rapidly during incubation and undesirable flavors generally result. This is so critical that the heat treatment recommended for these products is 185F (85C) for 30 minutes. The high temperature not only deactivates the bacteria and enzymes but also denatures the protein which aids in developing the smooth thick body desired. Following pasteurization, the product should be cooled to the incubation temperature. Great care should be exercised in preventing recontamination of the pasteurized material.
6 Cultures: Purchase vs Propagation
It is not possible to make fine quality cultured products without having bacterial cultures of proven purity and activity. Fortunately, a number of organizations make a business of supplying such materials. Improved techniques now make it possible to supply cultures in a form ready to be added to the customers pasteurized milk or cream. Even so, many manufacturers of cultured products, including cheesemakers, prefer to maintain their own stock of ''mother cultures.'' Skilled personnel, special equipment, and facilities providing a controlled atmosphere are needed for complete success in that operation. Most small operators will have fewer failures and more uniform quality through the use of ''ready to use'' cultures.
7 Those who are using rather large quantities of bulk starter culture on an almost daily basis may find it economical to carry mother cultures. To do so successfully, the technician must have knowledge of microbiology and aseptic technique. An especially high quality milk must be used as a culture medium. Facilities must be provided for sterilizing the milk and all utensils used. Temperature controlled incubators must be provided, if several kinds of culture are to be used, it would be necessary to have an incubator operating at the temperature most favorable to each species of microorganism.
8 Setting and Incubating Cultured Products
While each kind of cultured product requires specific procedures, all have some commonality in the treatment required. After the milk or cream has been standardized as to composition and heat treated to deactivate bacteria and enzymes normally present, it should be cooled to the setting temperature. Precisely what that temperature should be depends on the kinds of organisms introduced by the culture. A summary of the kinds of micro organisms used in making various cultured products together with suggested sources of culture, rates of inoculation and incubation conditions is shown in the accompanying table. It is possible to vary these conditions and make high quality products, but a specific set of conditions should be adhered to once the desired product has been attained. To do so the operator must have equipment and supplies which permit composition control and time and temperature regulation.
9 Buttermilk, Dip, and Sour Cream
The details of manufacture of these products are discussed at the same time because the microorganisms used in all of them are similar. That is not to say that the cultures used should all be identical -- some variation in species and mixed species can be used to produce differences in the finished product.
10 There is a major difference in the several products as to their milk fat content. Buttermilk is usually made from skim milk because it originally was the by-product from churning butter out of sour cream so was essentially free of fat. Buttermilk can be made from milk of any fat content; it is thought of as a product for drinking. By increasing the fat content of the base, chip-dips and sour cream are produced. They usually have a consistency suitable for dipping or spreading. All of these products are frequently used as ingredients in baked or other prepared foods.
11 Viscosity is very important in consumer evaluation of these products. Generally, it is not possible to get the desired viscosity without adding to the milk solids-not-fat (MSNF) of the base -- this is especially true in making buttermilk. A superior product usually requires the skim milk to contain 10 to 11 percent MSNF. If Grade A nonfat dry goat milk is available, it is no problem to add a sufficient quantity (usually 1 to 2) to increase the MSNF content to the desired level. In the absence of nonfat dry goat milk, the easiest procedure is to concentrate part of the skim milk in a vacuum evaporative condensor and add that back to the remainder of the skim for buttermilk. Sour cream and dips may require added MSNF, depending on the composition of the milk from which they were obtained and the manufacturing process used.
12 The procedure followed in setting these kinds of cultured products consists of adding the desired quantity of the inoculum selected to the prepared milk base in an aseptic manner and stirring the mixture till homogeneous. This batch is then allowed to remain undisturbed, with the desired temperature maintained throughout the incubation period, until the desired degree of acidity has developed. That may be estimated by tasting, but tests for titratable acidity and/or pH give more precise control. Usually a titratable acidity in the range of 0.7 to 0.8 is desired -- it will continue to increase while the product is cooling.
13 When incubation is completed, the product should be cooled by circulating cold water around it and agitating it mildly. Development of too much acid, or too vigorous agitation may cause the protein to separate from the whey, in which case cheese has been produced instead of buttermilk.
14 Special Cultured Milks:
Kefir and Acidophilus -- Production of these types of cultured milk drinks should be undertaken only to meet special market requirements. The production procedures are not so much more specialized or difficult, but the finished products are somewhat unusual and so little known as to require special marketing.
15 True Kefir is a drink developed by utilizing both bacteria and yeast as the culture organisms. The fermentation involves the production of lactic acid, carbon dioxide, and ethyl alcohol; acid to a concentration of about 0.8, alcohol to about 1, and carbon dioxide to give slight effervescence. It is a delightful drink used extensively in some parts of the world but not made much in America. A substantial market for the product probably could be developed if one wished to make the effort.
16 Acidophilus buttermilk is also a specialized product for which no market has been developed. It utilizes the activity of a bacterium, Lactobacillus acidophilus, which is capable of converting a greater proportion of the lactose to lactic acid. The lactic acid content of the finished product approaches 2a level of sourness not generally accepted in American markets. This organism is one of very few capable of surviving the strong acid (pH +/- 2) of the human stomach, which means that when consumed, living organisms pass into the lower digestive tract where they may live and reproduce. There is some evidence that this may aid digestion and have other healthful benefits.
17 Yogurt -- Even though yogurt has been consumed for centuries by some people, it is a relatively new item in the dairy product line in the US. The products being manufactured here are not the same as the old world products. Yogurt made from goat milk provides excellent sales potential; wherever offered, it has been well received.
18 In its simplest form, yogurt is a cultured milk product, but as it is offered to the consuming public in the US, it has become more complex as to manufacture and sale. This is because a variety of different forms are being produced. There are now two basic products -- one is a viscous liquid suitable for drinking, and the other is semi-solid and eaten with a spoon. The yogurt consumers in other countries prefer is a simple cultured milk product, but in the US the major share of the market is for products with added flavoring material. Specially prepared fruits and berries are most frequently used for flavoring yogurt. The flavored yogurts have undergone diversification - there are three different methods used for flavoring material distribution. The most widely used has the flavoring distributed throughout the body of the yogurt -this is called Swiss-style yogurt. Another fairly common yogurt is called Sundae style; in it, the flavoring material is all in thebottom of thepackage. This style product is supposed to be eaten bydischarging the product from the carton onto a plate with the result having the flavoring material flow down the sides of the yogurt in the manner of an ice cream sundae. In practice, most of the yogurt is eaten directly from the package, so a third style has been developed with the flavoring material at the top of the container. Each form or style of yogurt does require some special procedures in manufacturing and special packaging equipment when made in large quantities.
19 Yogurt to be consumed as a drink is made in essentially the same way as buttermilk excepting a different combination of microorganisms are cultured which necessitates a higher incubation temperature. Skim milk is most frequently used, but either low fat or whole milk can be used for yogurt. It should have a consistent fat content, and may require added MSNF. After standardization and pasteurization, the milk should be cooled to 110 to 114F. It should then be inoculated with about 1.250f each of the two bacteria Streptococcus thermophilus and Lactobacillus bulgaricus. After thorough mixing the inoculated milk should remain undisturbed until the desired acidity is attained - usually about 0.9 The coagulum should then be broken by gentle stirring and cooled by circulating chilled water around it. If the unflavored product is desired, it can be packed when cold, if flavored, the flavoring material (fruit puree is most frequently used) should be added at a rate of 12 to 20, thoroughly distributed, and then packaged. The most frequently encountered problems with this product are separation of clear whey and settling of the flavoring material in the package. Both are associated with insufficient viscosity in the yogurt. High temperature long time heat treatment and increased MSNF content of the milk are the most effective remedies. If the fruit particles in the flavoring material are too large, they will settle out. Most fruit flavorings prepared for use in yogurt have some sweetener added, if not it may be added with the fruit if desired. Two to four percent added sweetener may make the product more acceptable.
20 The manufacture of yogurt which is intended to be spoonable and of custard-like consistency is a little more complicated. While the basic procedure is the same, some modifications must be made to provide the greatly increased viscosity. Three alternatives can be used to do so. The first, probably the most difficult for the goat dairyman, is adding MSNF to the milk. The second alternative is to prepare the milk and inoculate it in the usual way, then package it and incubate it in the package. The time and temperature of incubation would be the usual. This permits all the viscosity developed during incubation to be retained in the finished product, since it is never agitated after packaging. If alternative method number two is practiced, a level of 11 to 12 MSNF may be adequate but if alternative number two is not feasible, the level of MSNF required may be 13 to 14 The third alternative and the easiest and cheapest by far is to incorporate a water-binding agent or stabilizer (usually gelatin or a special starch) to the milk prior to pasteurization. Any desired viscosity can be attained by adjusting the amount added - less than 1 0s usually adequate.
21 Each of the three alternatives have disadvantages which must be considered. The main problem with increasing the MSNF is that in most situations it simply cannot be done because no commercial product is available or is so large that small quantities of goat milk cannot be handled. Alternative number two may require special package filling equipment and certainly requires more space for incubating the product at controlled temperature. Also, cooling of the product when incubation is complete is slow and costly and is conducive to more variability in the finished product. The third procedure offers good quality control at low cost but necessitates showing the presence of the additive on the label. Some customers find this objectionable even though some nutritive qualities may be improved by the added material.
22 Packaging Cultured Goat Milk Products
Most cultured products are packaged in 4 to 8 oz cups because they generally are consumed as snacks. Bulk packages, varying from quart to 10 lb size have also been used sucessfully. Only single serving size packages can be used for making products with the flavoring material separate from the cultured milk. Most regulatory agencies require packages to be filled mechanically. The manufacturer should check with the proper regulatory body about packaging requirements and also about proper labeling of the products. In most situations, these products must carry nutritional information on the label. If required, it must be quite definitive; and this necessitates very stringent composition and quality control in the manufacturing process.
23 Making Cultured Products for Home Consumption
No specialdirections need be given for making buttermilk, chip dips, sour cream, special cultured milk drinks, or yogurt in small quantity for home consumption. The information previously given is applicable. Modifications of the procedures described would have to be made as to equipment used, etc. But to make products which are of high quality, it will be necessary to use high quality milk or cream. A reliable source of culture should be patronized, and close control of the level of inoculation, temperature and time of incubation must be practiced. Yogurt making for home consumption can be simplified because packaging is not an important consideration. When incubation is completed and the desired flavor and body attained, it can be cooled and held in bulk. If it is to be flavored, the flavoring material can be added when served.