Author: Young W. Park
Agricultural Research Station, Fort Valley State University, Fort Valley, Georgia, U.S.A.
Goat milk and its products have played an important role in the economic viability in many parts of the world, especially in developing countries. A variety of manufactured products can be produced from goat milk, including fluid products (low fat, fortified, or flavored), fermented products such as cheese, yogurt or buttermilk, frozen products such as ice cream or frozen yogurt, butter, and condensed and powdered products. However, cheese is traditionally the main commercial goat milk product produced and consumed in large quantities around the world.
A successful dairy goat industry cannot be established without the highest possible levels of cooperation among goat breeders, milk producers, cheese and other dairy goat product manufacturers, distributors, and retail outlets. Producing high quality raw milk is of utmost importance for successful production and marketing of dairy goat products. The products must be safe to consume and free of pathogenic bacteria, antibiotics, insecticides, and herbicides. They should have a good taste with no objectionable flavor or odor, be free of spoilage from bacteria, and contain legal limits of all nutrients.
Through utilization of manufacturing cheeses and other products, goat milk has played an important role in the economic well-being of developing countries as well as Mediterranean, Middle East and eastern European countries. Large-scale industrialization of the dairy goat sector in many countries is limited due to the low level of milk production of goats, approximately 500 kilograms (kg) per doe, per lactation annually. Although cheese is the major commercially produced and marketed goat product, many other types of dairy goat products are available worldwide, such as beverage, fermented, frozen, condensed, and dehydrated milk products. Significant amounts of fluid, evaporated and powdered goat milk products have been marketed in the United States and New Zealand for the past several decades. In the United States, fluid dairy products are usually made from grade milk. Standardization of milk composition, especially fat content, is essential to assure the legality of the finished product as well as its uniformity. Good flavored goat milk is produced from clean, healthy, properly managed goat herds, and is essential for production and marketing of quality dairy goat products.
Production of Quality Goat Milk
Fresh goat milk is a white, opaque liquid with a slightly sweet taste and no odor. Milk drawn from the lacteal glands is highly perishable. It is adversely affected by improper practices of feeding, handling of animals and milk before, during and after milking; and by its cooling, transportation, pasteurization, processing method, packaging, and processing equipment. High-quality, pasteurized goat milk must contain no pathogens or foreign substances, such as antibiotics, antiseptics, or pesticide residues. It is similar in taste and odor to quality cow's milk. Pasteurization and protection from sunlight or UV light control oxidized and “goaty” flavors. Goaty flavor is attributable to caproic, caprylic, and capric acids, which are present at high levels in goat milk fat and subject to release from fat globule membranes by lipases if improper milking and processing are practiced.
Requirements for Grade A Goat Milk and Its Products
In the United States, the regulations for production, processing, and marketing of milk are described in the federal Food and Drug Administration (FDA) publication called the Grade A Pasteurized Milk Ordinance (PMO). Each state health department establishes minimum regulations for Grade A milk from these standards and may adopt more stringent standards than those of the PMO. Presently, the somatic cell count (SCC) standard is 750,000 cells per millimeter (ml) for cow’s milk and is 1 million per ml for goat’s milk. As goat milk contains a naturally higher SCC than cow milk, due to the natural milk secretion process, the same regulations are enforced for the milk of both species except for SCC. It is common to find a high SCC in goat milk when actual numbers of leucocytes are relatively low. The low correlation of SCC and numbers of leucocytes differs in dairy milk from dairy cows. Many states have an annotated code, wherein a permit from the state regulatory agency is required to: 1) bring, send, or receive a milk product into the state for sale; 2) offer a milk product for sale; 3) give a milk product away; or 4) store a milk product. Specific requirements differ from state to state and can be determined by contacting the regulatory agency in each state.
Milk, by FDA definition, contains a minimum of 3.25 percent fat and 8.25 percent milk solids not fat (MSNF), which is the sum of the protein, lactose, and minerals. Table 1 shows the nutrient composition of goat milk products in the United States. Notable variations in nutrient composition have been reported (Table 1.)
Processing Goat Milk and Types of Dairy Goat Products
Standardization of milk composition is essential to ensure the uniformity and legality of the finished dairy goat products. General manufacturing conditions for various cultured goat products are listed in (Table 2.)
Fluid milk includes skim or low-fat milk, whole milk, and cultured milk products, and differs depending on the method of processing. For example, a low-fat beverage milk is processed and adjusted to 2 percent fat and 10.5 percent MSNF (milk solids not fat) before it is high-temperature, short-time (HTST) pasteurized, homogenized, and packaged in 946-ml containers.
Cheeses hold the greatest economic value among all manufactured goat milk products. Agricultural Handbook No. 54 of the U.S. Department of Agriculture describes over 400 varieties of goat cheese and lists over 800 names of cheeses, many of which are made from goat milk or combinations of goat with cow, ewe, or buffalo milk. The general procedures of cheese manufacturing are: 1) standardizing the milk, 2) setting the temperature, 3) adding starter cultures, 4) adding rennet, 5) cutting curds, 6) cooking, 7) draining whey, 8) salting, 9) hooping, 10) pressing, 11) packaging, and 12) aging. Soft cheeses are made by natural draining without pressing.
Buttermilk, Yogurt and Sour Cream
Buttermilk is usually made from skim milk (less than 0.5 percent fat) using the by-product from churning butter out of sour cream. Yogurt is made from whole milk (3.25 percent fat), low-fat milk (0.5 percent to 2.5 percent fat), or skim milk. Sour cream must contain 18 percent fat in most states. Acidophilus milk can be made by the activity of L. acidophilus, which is capable of converting a greater proportion of the lactose to lactic acid (2 percent).
Kefir is an acidic, slightly foamy product made from pasteurized and fat-standardized or decreamed (partially skimmed) goat milk that has passed through a combined acidic and alcoholic fermentation of symbiotic lactic acid bacteria and yeast kefir grains. The finished product, kefir, contains 0.6 percent to 0.8 percent lactic acid and 0.5 percent to 1.0 percent alcohol.
Yogurt, one of the major cultured products, may be made from skim, low-fat, or whole milk. It is made essentially the same way as buttermilk, but a different combination of microorganisms is cultured at a higher incubation temperature. Goat yogurt is softer and less viscous and often lacks the typical flavor of cow yogurt.
Ice cream and frozen yogurt are also manufactured from goat milk. Three popular flavor formulations of goat ice cream are French vanilla, chocolate, and premium white mixes.
Evaporated and Powdered Products
Evaporated and powdered goat milk are manufactured and marketed in the United States. Evaporation is usually carried out under reduced pressure, primarily to allow boiling at a lower temperature to prevent heat damage. Powdered products available include whole milk, skim milk, whey, and infant-foods formulae.
Ghee is an Indian clarified butterfat product manufactured by fermenting whole milk into curd and churning out the butter, followed by heat clarification at 105-145°C. Additional goat milk products made in India include chhana, khoa, and paneer, a cheese. Chhana is an acid- and heat-coagulated milk product, and a chhana-based sweet is made by kneading chhana and cooking it in sugar syrup over medium heat. Khoa is a heat-desiccated indigenous milk product used for various sweets. Cajeta in Mexico and Gjetost in Norway are also popular caramelized sweet products made from goat milk. Cosmetic products such as goat milk soap and hand lotion are produced and marketed in large quantities in many countries including the United States.
Marketing Goat Milk Products and Its Challenges
The most important quality standard for goat milk is acceptable, attractive milk odor and taste. Two formidable barriers exist in marketing goat milk products: 1) negative public perception of goaty flavor, and 2) seasonal milk production, which prevents year-round uniform marketing. To overcome these barriers and develop a sustainable dairy goat industry, effective strategies have to be sought.
Technological approaches are needed to resolve the seasonal milk supply, such as ultra-filtration of milk, freezing and storage of curds, spray-drying, and production of mixed-milk cheeses. Ultra-filtration is or has been used for the production of retentate -- very high-fat and high-protein liquid -- to make the pre-cheese fraction that is subsequently made into cheese. Goat cheeses can be made during off-season using the ultra-filtered, spray-dried retentate, which can be reconstituted into cheese and stored frozen for later use.
Key factors for successful marketing of dairy goat products include: 1) consumer perception of safety and nutrition; 2) quality of flavor, body texture, and appearance; 3) availability of specialty types; 4) attractiveness of packaging; 5) relative price of products, and 6) establishment of proper distribution and marketing channels.
Various goat products, including fluid, fermented, frozen, condensed, and dehydrated milk products, are produced in many countries. Cheese is the most important goat dairy commodity, traded in large quantities among and within nations. There is high variation in nutritional, chemical, and rheological compositions between and within goat products, due to the multiplicity of manufacturing procedures, localities, animals, and management factors. Technological advances are required for a uniform supply of goat products. Consumer education, identification of proper distribution and marketing channels, and development of specialty-type goat products are crucial for development of a sustainable and profitable dairy goat industry. Although supports from government, industry and academia are crucial for the survival and sustainability of the dairy goat industry, research supports from such entities have been modest due to its relatively low level of contribution to the overall agricultural production in the United States and some other countries.
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This article by Dr. Park is published in Encyclopedia of Animal Science. W.G. Pond and N. Bell, eds. 2nd Edition. Taylor and Francis. CRC Press. Boca Raton, FL.