Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

Подождите немного. Документ загружается.

simply as goat kid in English, as chevreau in French,

and as boklam in South African Afrikaans.

Production

0006 The value of the goat lies in its flesh, milk, hair, and

skin. However, meat production has remained the

primary reason for goat-keeping. Meat goats there-

fore constitute the major proportion of the world’s

goat population and comprise many different breeds.

Of these, the Boer goat breed is regarded as exhibiting

the most desirable meat production characteristics.

A recent study in Botswana concluded that a small

ruminant enterprise is profitable and economically

viable. Small-scale ruminant enterprises could pro-

vide a return of 34% on capital invested. In Zim-

babwe, goats are often the only dependable and

perennial agricultural output. Many rural farmers

now regard goats as an easy income-generating

venture since very little investment is required.

0007 Goats’ meat is derived from different categories of

goat. Of the meat goats, kids, does, and male cas-

trates are the preferred commercial commodities.

The main sources of meat from the milch breeds are

male kids and older culls. In New Zealand and Aus-

tralia, dairy-type feral goats are cropped for export.

Mohair-producing Angora goats are slaughtered as

culls, or marketed when the price of mohair is

down. Other goat products, notably milk and cheese

(e.g., feta, che

vre, and Gorgonzola), hair, mohair, and

cashmere, have important influences on goat popula-

tions of specific regions and the related economic

value of goats. Goat hides also yield fine leather,

which is used for wineskins, water containers, rugs,

and clothing of high quality.

0008 Goats generally feed on the leaves and shoots of

shrubs, which enables them to thrive in semiarid

scrublands and mountains. Traditionally, goats in

the developing regions are free-range or are herded

communally with little management care, including

veterinary care, nutrition, and breeding. Household/

personal herds may contain as few as three breeding

does, with an average of between five and eight in

tropical and subtropical Africa. Commercial herds

in Namibia and other regions of southern Africa

may number several hundred breeding does in a

ratio of one buck to 25 does.

Meat Production Characteristics

0009 General characteristics of goats favoring meat pro-

duction are:

0010 Females are early-maturing, highly prolific, and

have good fecundity and mothering ability.

0011An extended breeding season is usual among goats

in the tropics, and this is particularly advanta-

geous to meat production.

0012Foraging preferences of goats cause them to graze

a wider spectrum of plants than other small stock,

which accounts for their ability to thrive in adverse

conditions.

0013Foraging may account for relatively low parasite

infestation.

0014Goats exploit available feed resources selectively,

consuming material with sufficient digestible or-

ganic matter at or exceeding their maintenance

needs, and their small size enables goats to utilize

tropical shrub and shrub pastures more efficiently

than cattle.

0015Goats are generally well adapted to hot environ-

ments, tolerating the extremes of desert condi-

tions and high-temperature/humidity conditions

of the tropics, because of their small size, large

surface area to body weight ratio, an ability to

conserve water, limited subcutaneous fat cover,

and the particular nature of their coats.

Breeding and Performance Testing

0016Goats can be bred for carcass and meat characteristics

by exploiting quantitative and qualitative gene

effects. Performance testing as a means of improving

productivity of meat goats was introduced in South

Africa in 1970. The scheme provides for the perform-

ance testing and selection of goats specifically for

meat production, according to five phases:

0017characteristics of the dam, her milk production

and preweaning growth rate of her progeny

0018postweaning growth rate of progeny at various

ages

0019feed conversion efficiency and body weight of

male progeny under standardized conditions at a

central testing station

0020postweaning growth rate of male progeny under

standardized conditions:

0021on a farm under direction of the Department of

Agriculture and

0022at a central location of a cooperative institu-

tion, also under the auspices of the department

0023qualitative and quantitative evaluation of the

progeny of a buck

Nutrition and Growth

0024Well-nourished livestock have a high tolerance to

parasites and disease, exhibit good fecundity with

low mortalities, grow well, and generally thrive.

Nutrient requirements of goats are determined by

their physiological state. Specific information can be

2938 GOAT/Meat

obtained from the recommendations of the US Na-

tional Research Council on the nutrient requirements

of goats. Growth rate is an important criterion for

efficiency in commercial meat production and is

determined by the animal’s genetic growth potential,

nutrition, and health. Generally, goats do not have a

high growth rate, compared with lambs. West African

dwarf goats have growth rates of 10–30 g day

1

variable-quality tropical grasses. Poor-quality trop-

ical grasses (e.g., Gliricidia sepium) supplemented

with a legume (Leucaena leucocephala) would im-

prove the growth rate up to 46 g day

1

; a concentrate

supplement could improve growth further to 70 g

day

1

. Goat kids, adequately supplemented with

small quantities of essential nutrients, will perform

equally well on feeds with a low digestibility com-

pared to other animals on forages with higher digest-

ibility. Under favorable conditions, Boer goats may

gain weight at more than 200 g day

1

. When protein

intake is increased above that required for mainten-

ance and growth, puberty and fertility can be

achieved at an earlier age in young growing male kids.

Fertility

0025 The good fertility, mothering ability, and extended

breeding season of does in the tropics and subtropics

permits mating twice per year or three times per 2

years. Thus, the number of kids per doe can be

increased dramatically. Twins are more the rule than

the exception. Sexual activity of bucks is greatest

from sunset to midday. An apparent decline in male

libido in spring and summer needs to be taken into

account when twice-yearly breeding is practiced.

0026 Angora goats and goats originating from the

tropics have limited breeding seasons. In general,

small ruminants in Africa are year-round breeders

and, as a result, lamb or kid all year round except

where a specific management system so dictates. The

techniques of caprine embryo transfer, embryo freez-

ing, embryo splitting, sex determination, in vitro, and

caprine nuclear transfer have all been successful.

Goat Management

0027 Animal productivity is improved by applying even

the most basic management practices: herding as

opposed to free-ranging, penning at night, removing

unproductive animals from the herd, and controlled

breeding. More sophisticated management practices,

including nutrition supplementation and veterinary

care, although yielding high dividends, require add-

itional expenses that may be beyond the reach of

subsistence farmers. In these instances, subsidies and

state services should be considered.

Carcass and Meat Quality Characteristics

0028Goats have carcass characteristics slightly different

from those of sheep. Goat carcasses are generally

lean in appearance, less compact than sheep, and of

differing carcass proportions with less total tissue

distributed to the hind leg than in sheep. Goats’

meat is also different, being coarser-grained, with a

detectable different flavor and aroma. Studies on

chemical composition and meat quality have sug-

gested that goat meat is not inferior to lamb, but

may be darker red in color than lamb. Color of goat

meat is important, especially in the case of Capretto

carcasses, where flesh should be pale or pink.

Grading

0029Communicating the expected quality of meat to con-

sumers in a reliable and effective way is important in

merchandising meat. This is achieved by grouping

carcasses within a series of like quality characteristics

into distinct categories, taking into account:

0030physiological age differences due to young animals

having more tender meat because of the greater

solubility of the collagen in the connective tissue

and older animals having a stronger flavor;

0031sex differences due to the coarser grain of males

and the strong flavor of the buck’s meat;

0032fat differences due to the quality and palatability

fat imparts to the meat and the association

between fat and meat yield;

0033conformational differences due to its commercial

value in some markets and its predictive value,

although limited, in determining yield.

0034Age has an influence on palatability, with the meat

from older goats regarded as being juicier. Muscle

color may be darker and fat color more yellow with

increasing animal age.

0035Carcass quality generally refers to lean/fat content,

conformation, and the extent of damage (bruising,

abscesses, and parasite infection). Meat quality in-

cludes appearance, composition in terms of lean, fat,

and connective tissue and, in commercially displayed

cuts, bone content, pH, drip, palatability, nutritive

values, ease of processing, and shelf-life.

Dressing Percentage

0036Carcass yield is an important production criterion

and is expressed as the dressing percentage ([dressed

carcass weight/live weight]  100). However, since it

expresses a ratio of live weight to carcass weight and

many factors influence these fractions (e.g., alimen-

tary tract size and fill, slaughtering procedures, fleece

or skin mass, distribution of body fat, and secondary

sex characteristics), the dressing percentage must be

GOAT/Meat 2939

interpreted carefully and comparisons made within

species, within breed types, and within slaughtering

procedures. The dressing percentage of goats varies

between 40% in very young animals and 56% in

entire mature males. In regions where body compon-

ents (head, organs, intestine, and skin) are prized and

regarded as part of the carcass, the dressing percent-

age ranges between 66 and 82%. The dressing per-

centage increases with age, mass, and fatness, and is a

consequence of increasing metabolizable energy per

kilogram dry matter (ME kg

1

DM) in the ration.

Muscle

0037 Muscle-to-bone ratio Goat carcasses have a higher

muscle-to-bone ratio than is apparent from their con-

formation. A greater carcass and leg length results in

a less compact carcass, which may be interpreted

erroneously as signifying poor muscling. In addition,

goats have less total muscle distributed to the leg and

more to the forequarter than sheep. This is illustrated

by the muscle distribution of castrated male Boer

goats and South African Mutton Merino wether

lambs, respectively: forelimb 17.3 and 16.2%; neck

9.3 and 8.3%; ventral trunk 25.8 and 20.9%; dorsal

trunk 19.3 and 20.6% and hindlimb 28.4 and 34.1%.

(See Meat: Structure.)

0038 pH Goat muscle contains both aerobic (red) and

anaerobic (white) muscle fibers and undergoes the

same postmortem biochemical changes as beef and

mutton. The decline of goat muscle pH follows a pat-

tern typical of red meat carcasses to stabilize at around

pH 5.4. Variations occur due to differences between

muscles, sexes, and premortem stress. Exhaustive pre-

mortem stress yields dark, firm, and dry meat with a

high ultimate pH (pH > 6.0). Postmortem biochemical

changes are associated with the loss of water-binding

capacity as the pH reaches the isoelectric point of the

muscle proteins, the onset of rigor mortis, and the

release and activation of proteolytic enzymes, notably

cathepsins, responsible for the ripening of meat.

0039 Collagen Goat muscle fibers are thicker and the

fiber bundles larger than those of sheep, giving

goats’ meat a characteristic coarser grain. The attrib-

uted toughness of goat has been ascribed to the

marketing of mature animals, in which the collagen

in the connective tissue has a decreased ability to

gelatinize under the influence of heat and moisture.

Several studies have indicated that goats’ meat is

inherently less tender than that of sheep. Muscles of

male Boer goat kids have a higher collagen content

with lower collagen solubility than those of male

lambs of four sheep breeds. Lambs and mutton are

more tender with less fibrous tissue residue and a

more intense aroma than Angora and Boer goat

meat. The species’ flavor is also more pronounced.

Goat breeds may also differ in their meat quality:

meat of Angora goats has a more acceptable flavor

and is more tender with less residue than meat of Boer

goats, which could be explained by the lower collagen

content and slightly better collagen solubility. Evalu-

ation of collagen alone, however, would be insuffi-

cient for conclusions on differences in tenderness.

Other factors may be involved, especially muscle

fiber size, the type of matrix formed by collagen,

and the state of muscle contraction.

0040Electrical stimulation Goat carcasses, having a

poor insulating subcutaneous fat cover, are suscep-

tible to muscle toughening through the effects of cold

shortening. Cold shortening can be countered by elec-

trically stimulating the carcasses immediately after

slaughter. Electrical stimulation increases the rate

of postmortem glycolysis, depleting the adenosine

triphosphate (ATP) energy source for muscle contrac-

tion due to the anaerobic state. The residual contract-

ile properties of muscle are reduced, rigor mortis is

advanced, and the enzymes associated with the con-

ditioning of meat are activated. Electrical stimulation

of goat carcasses, as with beef, can improve meat

tenderness and facilitate accelerated processing of

carcasses by hot boning, preferably after a 2-h condi-

tioning period, with no detrimental effect on total

bacterial count, tenderness, or cooking loss. Advan-

tages of hot boning are a reduced mass loss in chillers,

less carcass chiller space required, and faster through-

put and packaging of the meat. (See Meat: Slaughter.)

0041Nutrient value Muscle contains the most important

quality parameters and nutrient value of meat. Goat

muscle is highly nutritious with a high biological

value. The percentage moisture in raw, lean tissue

ranges between 74 and 76%. Protein, fat, and ash

contents are, respectively, 20.6–22.3, 0.6–2.6, and

1.0–1.1%. The essential amino acids determined in

the proteins (mg g

1

) are arginine (74), histidine (21),

isoleucine (51), leucine (84), lysine (75), methionine

(27), phenylalanine (35), threonine (48), tryptophan

(15), and valine (54). (See Amino Acids: Metabolism.)

0042The most important minerals in the muscle and

organs of male cross-bred goats are shown in Table 1.

Red meat is an excellent source of iron: heme iron is 5–

10% as available as nonheme iron. A value of around

2.1 mg g

1

reported for lean goat meat from Malaysia

compares favorably with values for separable lean beef

(2.72 mg g

1

), lamb (1.74 mg g

1

), and veal (1.11 mg

1

). Refer to individual minerals.

0043The contents of the vitamins thiamin, riboflavin,

and niacin in lean goats’ meat compare well with

2940 GOAT/Meat

those of lean beef and lamb, as shown in Table 2.(See

Niacin: Physiology; Riboflavin: Physiology; Thiamin:

Physiology.)

0044 The average biological value of goats’ meat, based

on feeding trials with rats fed a 10% level of protein,

is 60.4 and beef 68.6. The digestibility coefficient of

meat protein is 97%, giving ingested meat a heat

combustion of 17.87 J g

1

. The effect of cooking on

muscle is method-, time-, and temperature-dependent

and the response of muscles to heat treatment varies

between muscles and according to pre- and postmor-

tem influences. Generally, temperatures below 100



affect palatability, but do not reduce the nutritive

value of meat severely. (See Protein: Quality.)

Fat

0045 Goat carcasses characteristically have a low propor-

tion of subcutaneous fat and a high proportion of

intermuscular fat, giving goat carcasses a lean appear-

ance. In terms of total body fat, goats are not neces-

sarily leaner than sheep. At the same degree of total

body fatness (21% of empty body weight), dressed

Boer goat carcasses recorded 22% carcass fat with

6.7% in the subcutaneous fat depot, while Dorper

and South African Mutton Merino carcasses were

both 24% fat, with 12.7% and 10.4% subcutaneous

fat, respectively. The comparatively poor fat covering

of goat carcasses means that the criterion of subcuta-

neous fatness, which is a reliable predictor of yield in

lamb and mutton carcasses, is not suitable for classi-

fying and grading goat carcasses. Lipogenesis occurs

in a preferential order between the adipose depots.

Visceral fat (omental, mesenteric, kidney, and pericar-

dial) is the earlier-developing depot followed by inter-

muscular, subcutaneous, and intramuscular fat.

0046Carcass fat is highly variable and easily influenced

by:

0047Sex – males are leaner than females and castrated

males.

0048Nutrition – the greater the metabolizable energy

intake (ME kg

1

DM), the fatter the carcass.

0049Age – increasing fatness to maturity is a phenom-

enon of normal growth in all sexes.

0050Physiological condition – lactating does will

catabolize body fat reserves and become leaner;

disease and stressful conditions reduce appetite,

causing body reserves to be drawn upon.

0051Physical activity – physical activity, such as

foraging or when determining social ranking,

increases energy usage, yielding leaner carcasses;

penned animals fatten more easily, yielding fatter

carcasses.

0052Fat quality Fat remains an important quality deter-

minant of carcasses and meat. The chemical and

physical properties of fat have no direct effect on the

commercial value of carcasses, as does fatness, but

do influence the organoleptic properties and keep-

ing quality of meat. The degree of saturation of

fat, expressed as the iodine number and determined

by the number of double bonds in the component

fatty acids, is one of the most important characteris-

tics affecting these quality parameters. Saturated

fats containing long-chain fatty acids with no or

very few double bonds solidify easily upon cooling,

thus affecting the palatability of the meat. The less

tbl0001 Table 1 Mean mineral concentrations (mg 100 g

1

) in muscle and selected organs of cross-bred goats

Mineral Muscle Liver Kidney Heart Spleen Brain

Ca 11 10.06 13.58 7.7 11.47 46.99

P 155.5 263.9 168.1 111.71 214.03 245.64

Mg 19.7 15.08 10.19 9.63 15.28 12.82

K 350 188.55 122.26 100.15 194.9 277.68

Na 64.48 58.18 148.68 38.52 59.38 136.92

Cu 0.30 8.28 0.52 0.53 0.41 0.40

Zn 3.51 2.99 2.61 1.41 2.19 1.40

Fe 4.37 7.82 9.78 4.40 34.79 3.07

Mn 0.087 0.66 0.19 0.098 0.159 0.122

Dry matter (%) 21.90 25.14 16.98 19.26 19.11 21.36

tbl0002 Table 2 Thiamin, riboflavin, and niacin contents (mg 100 g

1

)of

goats’ meat, lean beef, veal, and lamb

Species Thiamin Riboflavin Niacin

Goat

0.1 0.56 3.6

Beef

0.082 0.218 3.6

Lamb

0.088 0.234 5.33

Veal

0.06 0.3 7.6

From:

Abdon I, Del Rosario IF and Olga LG (1980) Food Composition

Tables Recommended for Use in the Philippines. Handbook 1, 5th edn. Manila:

Food and Nutrition Research Institute,

USDA (1986) Composition of Foods:

Beef Products ^ Fresh Processed Prepared. USDA, Human Nutrition

Information Service, Agricultural Handbook No. 8–13. Washington, DC: US

Government Printing Office,

Ono K, Berry B and Johnson HK et al. (1984)

Nutrient composition of lamb of two age groups. Journal of Food Science

49:1233,

Ono K, Berry B and Douglas L (1986) Nutrient composition of

some fresh and retail cuts of veal. Journal of Food Science 51:1352.

GOAT/Meat 2941

saturated fats containing a greater number of fatty

acids with double bonds are easily oxidized, either by

direct chemical action or through intermediary activ-

ity of lipolytic enzymes. Direct chemical oxidation is

less important in meat than the action of lipases that

split fatty acids from triacylglycerols. The rate of

autoxidation increases with the number of double

bonds, increasing the probability of affecting the

flavor and odor of the meat. Chemical oxidation

releases peroxides with free radicals (ROO



—,



—,OH



—) which may react to damage proteins,

enzymes, other lipids, and vitamins. In goat meat, as

with other red meat with low lipid- to heme ratios,

heme compounds can stabilize peroxides of free rad-

icals and exert an antioxidant effect.

0053 The profile of the long-chain acids of goat meat

show oleic acid (C

18:1

) to be the most abundant, with

palmitic (C

14.0

) and stearic acids (C

18.0

) being rela-

tively high. Nutritional influences on the fatty acid

profile of ruminants are less than on monogastric

animals, owing to the biohydrogenation and synthe-

sis of fatty acids in the rumen. It would appear, how-

ever, that nutrition could cause subtle changes in

ruminants, including goats. The high variance of

each fatty acid in kids could be ascribed to the mono-

gastric characteristic of suckling animals, which

would be sensitive to nutritional influences.

0054 Visceral fats are more saturated than subcutaneous

fats, as is illustrated in the differences between the

fatty acids of the subcutaneous and kidney depots.

The unsaturated-to-saturated ratio in the subcutane-

ous fat of goats was 1.11 and of sheep 0.67. Fat

from the triceps brachii, biceps femoris, and obliquus

internus abdominus muscles of Korean goats con-

tained 55.2–59.6% C

18:1

and 24.5–25.6% C

16:0

Unsaturated fatty acids predominated, ranging from

68.5 to 72.3%. Oleic acid levels were slightly higher

in the subcutaneous, intermuscular, and kidney fats

of Sudanese goats than sheep. Comparing iodine

numbers within and between species could be mis-

leading owing to the range of fatty acids occurring in

the fat and the exogenous and endogenous influences

on the fatty acid profiles. Fatty acids, particularly

and C

18:3

, influence the flavor of lamb and

both 4-methyloctanoic and 4-methylnonanoic acids

appear to contribute to the odor of mutton and

goats’ meat.

0055 Nutrient value Lipids, although recommended to

constitute a smaller proportion of the western diet,

are an essential nutrient source component in all

human foods. In dispute is not whether lipids, includ-

ing animal fat (triacylglycerols), are a health threat,

but the extent to which specific fatty acids, the

amount ingested as a proportion of total energy

intake or cholesterol, constitute a health threat, in

general. Energy-dense triacylglycerols provide readily

metabolizable energy. Excessive energy consumption

beyond the body’s needs for a given physiological

state leads to obesity and related health risks. Linoleic

18:2

), linolenic (C

18:3

) and arachidonic acid (C

20:4

)

acids, constituents of cell walls, mitochondria, and

other active metabolic sites, are regarded as essential

in the diet since the body cannot synthesize these

long-chain polyunsaturates. (See Fatty Acids: Dietary

Importance.)

0056Fatty acids appear to be closely associated with the

body’s immune response system. Excessive consump-

tion of dietary fats rich in o-6 polyunsaturated fatty

acids have been shown to possess immunosuppressive

properties, influencing immune function in disease,

whereas o-3 polyunsaturated fatty acids have both

an antiinflammatory effect and reduce immunosup-

pressive properties. Goat fats have low o-6 and o-9

polyunsaturated fatty acids.

0057Cooking Normal cooking changes the composition

of animal fat and increases the concentration as an

energy source. Mass reduction can be 20–35%,

of which 70–80% is lipid cookout. Fatty tissue of

cooked meat is typically about three times as concen-

trated a source of energy as is cooked lean tissue, with

variances between cuts. Prolonged cooking leads to

rendering in which a very high percentage of fat cook-

out is obtained.

Processing

0058Traditionally, meat processing is a means of

extending shelf-life (preserving) and producing a con-

venient item for use later and elsewhere. Processing

is aimed at reducing the enzyme activity in the

meat, retarding oxidation of the fat, and preventing

spoilage by microorganisms. These aims have been

achieved through drying, curing with salts, or

smoking meat. Sausage manufacturing, for which

meat is ground to varying degrees, is another form

of processing, in principle for the same purpose.

Either one or a combination of these procedures in

various regions of the world has preserved goats’

meat. (See Meat: Preservation.)

0059In modern times, meat is processed not only as a

means of preserving, but also for producing con-

sumer-acceptable products compatible with modern

lifestyles and philosophy of a health-related quality

of life. In order to achieve this the processor has to

define clearly the image and commercial appeal of the

envisaged product. The decision-making process of

the consumer needs to be defined in terms of real

and perceived value, the convenience the product

offers, and its palatability.

2942 GOAT/Meat

0060 Goat meat, regardless of breed, can be used to manu-

facture processed products of acceptable sensory qual-

ity, particularly when a spicy formulation is used. The

low appeal of goat meat to some consumers may be due

to its lack of tenderness, particularly in meat from older

animals. Tenderness should not be a problem for com-

minuted meat products (e.g., patties) or products that

undergo slow cooking or pressure cooking/retorting

(e.g., curries and stews). Although goat meat has a less

desirable flavor, aroma, tenderness, and juiciness than

beef or pork to western taste panelists, a panel found up

to 40% substitution of beef by Angora goat meat to be

quite acceptable in frankfurters. The goat frankfurters

had good physical attributes, being firm, resilient, and

springy under forefinger pressure with a firm ‘bite’–a

desirable textural attribute in quality emulsified saus-

ages. Such frankfurters would maintain their form

and shape during peeling, indexing, and packaging op-

erations. (See Meat: Sausages and Comminuted Prod-

ucts.)

0061 Vienna sausages manufactured from meat of

mature does (six teeth) had detectable different palat-

ability characteristics compared with viennas manu-

factured from beef. The goat viennas also recorded

higher shear force values (P < 0.0002). Differences in

both physical and textural attributes could be related

back to the characteristics of the raw meat. Cured and

smoked buttocks of mature does (six teeth), com-

pared with cured and smoked beef silverside (two

teeth), received higher ratings (P < 0.01) in terms of

aroma, tenderness, juiciness, and tastiness. No differ-

ence in residue could be detected.

0062 Overall, the goat was rated 3.54 with a standard

deviation of 0.6 on a scale of 0–5, as opposed to the

2.96 + 0.97 rating of beef. The results suggest that

smoked and cured goat buttock or leg of goat has the

potential of being a delicacy and could compete com-

fortably with other products such as smoked beef and

pork gammon.

0063 Processing hot muscle holds decided advantages.

Prerigor muscle has a higher water-holding capacity,

better fat-emulsifying properties, and produces saus-

ages with less moisture loss and rendering out when

cooked. Patties manufactured from hot goat meat

(3–4 h postmortem), not electrically stimulated, had

lower cooking yields (P < 0.05) than patties prepared

from chilled meat (24 h postmortem). However, redu-

cing the postmortem time lapse to processing to 1–2h

improved the yield. The organoleptic scores of patties

broiled in an oven at 190



C for 15 min to an internal

temperature of 72 + 2



C were similar for hot and

chilled meat. Reheating precooked, frozen patties

reduced sensory scores significantly (P< 0.05).

The fat content of patties has a significant influence

on cooking loss and flavor, texture, and overall

acceptability. According to sensory scores a 20% fat

content would be the optimum. The quality of warm

minced goat meat (3 h postmortem) could be im-

proved by addition of 2.5% sodium chloride and

1% tetrasodium pyrophosphate. These salts resulted

in a significant increase in pH, water-holding cap-

acity, and water-soluble proteins, and a decrease in

cooking loss and improved redness and overall ap-

pearance. The effects on the emulsifying capacity and

salt-soluble protein concentration were also signifi-

cant. Indications are that bacterial growth can be

inhibited by treatment with ammonia added at a

concentration of 0.402–0.67 mol l

1

. The effect was

more pronounced on Gram-positive bacteria. (See

Sensory Evaluation: Texture; Taste.)

See also: Amino Acids: Metabolism; Fatty Acids: Dietary

Importance; Meat: Structure; Slaughter; Preservation;

Sausages and Comminuted Products; Niacin: Physiology;

Protein: Quality; Riboflavin: Physiology; Sensory

Evaluation: Texture; Taste; Thiamin: Physiology

Further Reading

Abdon I, Del Rosario IF and Olga LG (1980) Food

Composition Tables Recommended for Use in the

Philippines. Handbook 1, 5th edn. Manila: Food and

Nutrition Research Institute.

Breuking HR and Casy NH (1989) Assessing the accept-

ability of processed goat meat. South African Journal of

Animal Science 19: 76–80.

Casey NH and Paterson CP (1990) Quality of hot and cold

boned, prepacked beef following electrical stimulation.

South African Journal of Food Science and Nutrition

2: 99–102.

Casey NH and Van Niekerk WA (1985) Fatty acid com-

position of sub-cutaneous and kidney fat depots of

Boer goats and the response to varying levels of maize

meal. South African Journal of Animal Science 15:

60–62.

Gaili ES and Ali AE (1985) Meat from Sudan desert sheep

and goats. II. Composition of the muscular and fatty

tissues. Meat Science 13: 220–236.

Gime

nez MS, Baudini PM, Ojeda MS, Molins de Pedernera

M and Gime

nez LA (1985) Some physicochemical prop-

erties and composition of adipose tissue of goats fed with

different diets. Nutrition Reports International 32:

389–397.

Kondaiah N, Anjaneyulu ASR, Sharma N and Joshi HB

(1985) Effect of salt and phosphate on quality of buffalo

and goat meats. Meat Science 15: 183–192.

Lawrie RA (1985) Meat Science, 4th edn. Oxford: Perga-

mon Press.

National Research Council, National Academy of Sciences

(1981) Nutrient Requirements of Goats: Angora, Dairy

and Meat Goats in Temperate and Tropical Countries.

Washington, DC: National Academy Press.

GOAT/Meat 2943

Ono K, Berry B, Johnson HK et al. (1984) Nutrient com-

position of lamb of two age groups. Journal of Food

Science 49: 1233.

Ono K, Berry B and Douglas L (1986) Nutrient compos-

ition of some fresh and retail cuts of veal. Journal of

Food Science 51: 1352.

Padda GS, Keshri RC, Sharma N, Sharma BD and Murthy

TRK (1988) Physico-chemical and organoleptic proper-

ties of patties from hot, chilled and frozen goat meat.

Meat Science 22: 245–253.

Panin A and Mahabile M (1997) Profitability and house-

hold income contribution of small ruminants to small-

scale farmers in Botswana. Small Ruminants Research

25: 9–15.

Srinivasan KS and Moorjani MN (1974) Essential amino

acid content of goat meat in comparison with other

meats. Journal of Food Science and Technology 11:

123–124.

USDA (1986) Composition of Foods: Beef Products – Fresh

Processed Prepared. USDA, Human Nutrition Informa-

tion Service, Agricultural Handbook No. 8–13. Wash-

ington, DC: US Government Printing Office.

Wan Zahari WM and Wahid SA (1985) Mineral concen-

trations in the blood plasma and various tissue of local

crossbred goats. MARDSI Research Bulletin 14: 333–

340.

Webb EC, Cronje

PB and Donkin EF (1998) Research and

training strategies for goat production systems in South

Africa. In: Proceedings of a Workshop held on 22–26

November 1998 at Kings Lodge, Hogsback, Eastern

Cape, South Africa. Available online at: http://

www2.fao.org/agris.

Milk

M Guo, University of Vermont, Burlington, VT, USA

Introduction

0001 More people drink goats’ milk than the milk of any

other species on this planet, although goats’ milk pro-

duction ranks third after bovine and buffalo milk.

Dairy goat farming plays an important role in the diet

and economy of many developing countries. Goats’

milk provides one of the principal sources of animal

protein, calcium, and phosphorus in many regions,

such as the Middle East, southern Asia, and some

tropical countries. It also serves as an appropriate sub-

stitute for cows’ milk and is often recommended by

medical professionals in situations where bovine milk

may cause allergic responses in consumers. Neverthe-

less, goats’ milk products are considered specialty

foods but becoming more popular in the USA and

other developed countries. The goats’ milk industry

will continue to grow during the next decade.

0002The major breeds of dairy goats in Europe and North

America are Saanen, Toggenburg, Alpine, La Mancha,

Nubian, Oberhasli, and Angora. In the Middle East,

Asia, and other regions, various native goats, cross-

breeds, and pure imported goats are used for milk

production. In this article, chemical, physiochemical,

and nutritional properties of goats’ milk and goats’

milk product technology will be briefly discussed.

Gross Composition

0003Gross composition includes total solids (TS), fat,

crude protein, lactose, and ash. The gross com-

position of goats’ milk in comparison with cows’ and

human milk is shown in Table 1. The levels of TS, fat,

crude protein, and ash in goats’ milk are, on average,

higher than those in cows’ milk. The lactose content

of goat’s milk is 4.5%, i.e., slightly lower than cow’s

milk (* 4.7%). The gross composition of milk is

affected by many factors, including breed, individual

animal, diet, yield, season, stage of lactation, environ-

ment, and management. Fat content is the most vari-

able component in goats’ milk, ranging from 2 to 8%.

There is an inverse relationship between milk yield

and the concentrations of fat, protein, nonfat solids,

and ash in the milk. Fat, protein, and ash contents are

high in the early stage of lactation, fall sharply to

reach the lowest levels during summer months, and

then increase gradually towards late lactation.

Lactose content does not show considerable changes

during lactation. The ash content of both goats’ and

cows’ milk are three to four times higher than that of

human milk in general, the ash content of milk is

closely related to the growth rate of the species for

which it was designed. An inverse relationship

between lactose and ash is essential and exists to

maintain the osmotic pressure of the milk.

Lipids

0004The lipids in goats’ milk consist mainly of triacylgly-

cerols (98% of total lipids), phospholipids (1%), and

cholesterol and its esters (1%). The cream or butter of

goats’ milk is white in color as there is very little

tbl0001Table 1 Gross composition of goats’, cows’, and human milk

(g 100 ml

1

)

Nutrients Milk

Goat Cow Human

Total solids 12.90 12.50 12.50

Fat 4.10 3.50 4.40

Crude protein 3.50 3.30 1.00

Lactose 4.50 5.00 6.90

Ash 0.80 0.70 0.20

2944 GOAT/Milk

b-carotene in the milk. Like cows’ milk, goats’ milk

lipids also exist in the form of globules. The average

size of the fat globules in goats’ milk (2 mm in diam-

eter) is smaller than the globules in cows’ milk (3 mm)

and buffalo milk (5 mm). Goats’ milk has a poor

creaming ability at cooler temperatures due to its

small fat globules and lack of agglutinin, a clustering

agent which causes fat globules in milk to cluster

upon cooling.

0005 Goats’ milk has a higher level of short-chain fatty

acids (C

–C

) than cows’ milk (Table 2): 15% of

total fatty acid in goats’ milk compared to 9% in

cows’ milk. Most of the short-chain fatty acids are

esterified at the 3-position of glycerol while the longer

chains are at 1 or 2 position. Lipases attack ester

linkages of short-chain fatty acids more easily than

those of longer ones. The level of free fatty acids in

goats’ milk is also higher than that in cows’ milk. The

short-chain free fatty acids, especially C

and C

, are

responsible for the specific ‘goaty’ flavor of goats’

milk products. There is a strong positive correlation

(r ¼0.83) between the amount of free fatty acids and

the goaty flavor score of the cheese made from goats’

milk. Fatty acid composition is strongly affected by

diet and stage of lactation. The fatty acid profile can

be manipulated by feeding different fats. The concen-

tration of essential fatty acids and conjugated linoleic

acid (CLA) in goats’ milk can be increased by feeding

them with canola oil. The proportion of short-chain

fatty acids (C

–C

) in goats’ milk is lower, while that

of C

18:0

and C

18:1

is higher due to does drawing

on their body fat at the beginning of the lactation.

The long-chain fatty acid profile of goats’ milk is

similar to that of cows’ milk. The lipids of both

goats’ and cows’ milk contain an adequate amount

of essential fatty acids for human consumption. (See

Fats: Classification.)

0006 Goats’ milk contains 30–40 mg phospholipids per

100 g milk or 8–10 mg g

1

fat. About 40% of total

phospholipids in goats’ milk is in the skim milk, with

the remainder in the fat globule membrane. The

cholesterol content of goats’ milk is in the range of

10–20 mg 100 ml

1

. The cholesterol content in the

colostrum of goats’ milk is much greater (40 mg

100 ml

1

). Most of the cholesterol in goats’ milk is in

the free form, with only a small fraction in the form of

esters.

Proteins

0007Goats’ milk contains more crude protein, ranging

from 3.0 to 3.8%, than cows’ milk. In general, the

protein profile of goats’ milk is similar to that of

cows’ milk. However, goats’ milk has a lower level

of casein nitrogen and a higher level of nonprotein

nitrogen than cows’ milk. This is responsible for a

low cheese yield and a weak yogurt structure/texture.

The concentrations of amino acids in goats’ milk are

compared with those of cows’ and human milks in

Table 3.(See Protein: Food Sources.)

0008The five major proteins of goats’ milk are

-casein, b-casein, k-casein, b-lactoglobulin, and

a-lactalbumin. Sodium dodecyl sulfate-polyacryl-

amide gel electrophoretograms of goats’ milk show

that a

-casein is the slowest-moving of the three

major casein bands, b-casein the major protein in

the middle, and k-casein migrates the fastest of the

caseins (Figure 1, lanes 3 and 4). The amino acid

compositions of these proteins is shown in Table 4.

It was previously believed that goats’ milk lacked a

protein homologous to bovine a

-casein. However,

recent studies have shown that this protein does exist

in the milk of some goat’s milk. The level of a

-casein

affects the coagulation properties of the milk. b-

Lactoglobulin (b-lg) and a-lactalbumin (a-la) are the

tbl0002 Table 2 Fatty acid profiles of goats’, cows’, and human milk

fat (%)

Fatty acids Goat Cow Human

0.7 1.4 0.1

2.4 2.2 0.2

3.2 1.8 0.3

8.7 3.6 2.1

4.7 4.0 7.2

10.7 13.0 10.9

28.5 30.2 29.6

13.0 13.7 7.3

18:1

25.2 27.1 35.3

18:2

2.9 3.0 6.7

tbl0003Table 3 Amino acid composition of goats’, cows’, and human

milks (mg 100 g

1

)

Amino acid Goat Cow Human

Typtophan 44 46 17

Threonine 163 148 46

Isoleucine 207 198 56

Leucine 314 321 95

Lysine 290 260 68

Methionine 80 82 21

Cystine 46 30 19

Phenylalanine 155 158 46

Tyrosine 179 158 53

Valine 240 220 63

Arginine 119 119 43

Histidine 89 89 23

Alanine 118 113 36

Aspartic acid 210 249 82

Glutamic acid 626 687 168

Glycine 50 69 26

Proline 368 318 82

Serine 181 178 43

GOAT/Milk 2945

two major whey proteins of goats’ milk (Figure 1,

lanes 3 and 4).

0009 b-Casein is quantitatively the major component in

the casein fraction of goats’ milk. It consists of 213

amino acid residues, compared to 209 amino acid

residues in bovine b-casein. Goats’ k-casein is a chain

of 171 amino acid residues instead of 169 for its

bovine counterpart due to valine and histidine being

inserted at positions 132 and 133. Like the bovine

homolog, goats’ k-casein has phenylalanine at pos-

ition 105 and methionine in 106. Therefore, chymo-

sin can hydrolyze the molecule between these two

residues producing, para-k-casein and caseinomacro-

peptides. This process leads to rennet-induced coagu-

lation during cheese-making. Goat a

-casein differs

from its bovine counterpart in that it contains a chain

of 217 amino acid residues instead of 207.

0010Goat b-lg, like its bovine homolog, consists of a

polypeptide chain of 162 amino acid residues. Like

bovine milk, goats’ a-la is a chain of 123 amino

acid residues. (See Amino Acids: Properties and

Occurrence.)

0011Like bovine milk, the casein in goats’ milk exists as

micelles. The majority of goat casein micelles are less

than 80 nm in diameter, which is smaller than the

casein micelles (120 nm in diameter) in cows’ milk.

The proportions of small micelles is much greater

than in cows’ milk. The stability, especially alcohol

stability, of casein micelles in goats’ milk appears to

be lower than those in cows’ milk.

Carbohydrates

0012Lactose is the major carbohydrate in goats’ milk. The

content of lactose in normal goats’ milk is about 130

mmol l

1

, or in the range of 4.2–4.8%. This is slightly

lower than the level in cows’ milk. Other minor

carbohydrates in goats’ milk include inositol (7 mg

100 ml

1

), and trace amounts of galactose and sialic

acid. (See Lactose.)

Minerals

0013The mineral contents of goats’ milk is compared with

that in cows’ and human milk in Table 5. Goats’ milk

contains about 133 mg calcium and 100 mg phos-

phorus per 100 ml. Human milk contains only about

16–25% of these concentrations. Goats’ milk has a

higher content of calcium, phosphorus, potassium,

magnesium, and chlorine and a lower level of sodium

than cows’ milk. Unlike the major minerals, the

concentrations of trace elements in goats’ milk are

affected by diet, breed, individual animals, and stage

of lactation. Goat colostrum has two to four times as

much iron (Fe), copper (Cu), manganese (Mn), and

zinc (Zn) than mature milk. Most milks, including

human milk, are deficient in Fe. Mature fresh goats’

milk has about 0.07 mg Fe per 100 ml (Table 4) and

the zinc content is the highest among the trace elem-

ents, at 0.56 mg per 100 ml. Goats’ milk generally

contains more Mg, and lower or comparable levels

of iodine (I) and Cu than cows’ milk. (See Minerals –

Dietary Importance.)

Vitamins

0014Goats’ milk contains a higher level of vitamin A than

cows’ milk due to the fact that goats convert all

tbl0004 Table 4 Amino acid composition of individual goats’ milk

proteins (residues per mole)

Amino acid a

-Casein b-Casein k-Casein b-lg a-la

Alanine 10 5 16 16 5

Arginine 6 3 5 3 1

Aspartic acid 17 9 16 14 22

Cystine 2 0 3 5 8

Glutamic acid 45 43 26 24 13

Glycine 4 6 1 5 5

Histidine 5 5 4 2 3

Isoleucine 11 9 11 10 8

Leucine 12 20 8 21 13

Lysine 22 12 8 16 13

Methionine 4 6 1 4 0

Phenylalanine 8 9 4 4 4

Proline 18 33 19 8 2

Serine 14 15 13 6 6

Threonine 14 12 15 8 6

Tryptophan 2 1 1 2 4

Tyrosine 11 4 9 4 4

Valine 12 21 11 10 6

Total 217 213 171 162 123

-CN

β-CN

β-LG

α-LA

κ-CN

12 34

fig0001 Figure 1 ‘Sodium dodecyl sulfate polyacrylamide gel electro-

phoretogram (SDS-PAGE) of samples of goats’ milk (lanes 3 and

4), cows’ milk (lane 2), and standard b-lactoglobulin (lane 1).

2946 GOAT/Milk

carotenes into vitamin A, which gives the milk a

whitish color. Goats’ milk supplies adequate amounts

of vitamin A and niacin, and excesses of thiamin,

riboflavin, and pantothenate for human infants

(Table 6). Both goats’ and cows’ milk are equally

deficient in vitamin C and D; therefore, these

vitamins must be supplemented with other food

sources. Goats’ milk contains only 20% as much

folic acid as cows’ milk. The bioavailability of folic

acid in goats’ milk is also lower than that in cows’ or

human milk, so goats’ milk must be fortified with

folic acid for infant feeding in order to prevent infants

from getting anemia. (See Vitamins: Overview.)

Physiochemical Properties

0015 The pH of goats’ milk is somewhat lower than that of

cows’ milk, with values ranging from 6.3 to 6.7. The

average pH of goats’ milk is about 6.5, compared with

6.7 for cows’ milk. The titratable acidity of goats’ milk

is 0.15%, expressed as a lactic acid, which is slightly

lower than that of cows’ milk (0.16%).

0016 The osmolality of goats’ milk is about 295

mosmol kg

1

O. The freezing point of goats’ milk

is 0.580, compared with 0.540 for cows’ milk,

indicating that the former contains a higher level of

solute constituents, such as salts, than the latter.

0017The average electrical conductivity of goats’ milk is

0.0052 O cm

1

, which is slightly greater than that of

cows’ milk (0.0048 O cm

1

). The refractive index of

goats’ milk lies midway between those of cows’ and

buffalos’ milk, in a range of 1.3454–1.3492 at 40



0018The surface tension of goats’ milk is similar to that

of cows’ milk, with values ranging from 40 to 55 dyn

1

, which is much less than water (72 dyn cm

1

The viscosity of goats’ milk is about 13 mPa, which is

slightly lower than that of cows’ milk (15 mPa).

0019Like milk from other species, goats’ milk has a

rather wide range of specific gravity – 1.026–1.042.

The relationship between percentage of TS and spe-

cific gravity (SG) and fat (F) content for goats’ milk

has been reported by the author’s research group as

follows:

TS ¼ 0:13SG þ 1:41F þ 4:28ðr

¼ 0:94; P < 0:01Þ

Nutritional Properties

0020In general, there is little difference in nutritional value

between goats’ and cows’ milk since the chemical

composition of both milks is very similar. A random-

ized double-blind clinical study on the growth of

undernourished children using goats’ milk as a sub-

stitute for cows’ milk showed that goats’ milk has a

nutritional value similar to that of cows’ milk.

0021Goat’s, cows’, and human milk provide approxi-

mately the same amount of energy: each furnishes

about 3135 kJ of energy per liter. The outstanding

difference is in the proportions of energy derived

from lactose and protein. In goats’ and cows’ milk,

fat, protein, and lactose account for about 50, 25, and

25% of the energy, respectively, but in human milk

they furnish 55, 7, and 38%, respectively.

0022A human infant fed solely on goats’ milk is over-

supplied with protein in relation to calories. In terms

of protein quality, profiles for human and cows’ milk

proteins are similar to those of goats’ milk. The three

milks differ in the proportions and kind of proteins,

but the overall amino acid composition of the mixture

of proteins is similar in all three. All three have a

satisfactory balance of essential amino acids, meeting

or exceeding the Food and Agriculture Organization

– World Health Organization requirements for each

amino acid.

0023Both goats’ and cows’ milk contain adequate con-

centrations of essential fatty acids (e.g., linoleic acid)

for human infants. In either of these milks, linoleic

acid provides about 1% of the total calories. The fat

in goats’ milk has been reported to be more easily

tbl0005 Table 5 Mineral concentrations in goats’, cows’, and human

milks (per 100 ml)

Minerals Goat Cow Human

Ca (mg) 133 119 32

P (mg) 100 93 14

K (mg) 190 151 51

Na (mg) 44 49 17

Cl (mg) 165 104 43

Mg (mg) 16 12 4

Citrate (mg) 130 156 60

Zn (mg) 0.56 0.53 0.38

Fe (mg) 0.07 0.08 0.12

Cu (mg) 50 60 40

Mn (mg) 0.8 3.0 1.2

I(mg) 22 26 7

tbl0006 Table 6 Vitamin content of goats’, cows’, and human milk

(per 100 g)

Vitamins Goat Cow Human

Vitamin A (IU) 185 126 190

Vitamin D (IU) 2.1 2.0 2.2

Thiamin (mg) 0.068 0.045 0.017

Riboflavin (mg) 0.21 0.16 0.04

Niacin (mg) 0.27 0.08 0.17

Pantothenic acid (mg) 0.31 0.32 0.20

Vitamin B

(mg) 0.046 0.042 0.011

Folic acid (mg) 1.0 5.0 5.5

Biotin (mg) 1.5 2.0 0.4

Vitamin B

0.07 0.4 0.03

Vitamin C (mg) 1.5 2.1 4.3

Choline (mg) 15 14 9

GOAT/Milk 2947