273
et al. 2013). Higher levels of conjugated linoleic acid (CLA) (C18:2 cis 9, trans 11)
were found in goat and sheep milk than in cow milk (Markiewicz-Kęszycka et al.
2013). The content of CLA in milk will vary depending on the feeding regimes; for
instance, milk from animals fed on pasture was found to contain higher levels of
CLA compared to the indoor fed animals (Zervas and Tsiplakou 2011).
It is also of interest for processors of goat milk to know that the composition may
vary considerably during the lactation period and according to the feeding regime.
Brendehaug and Abrahamsen (1986) investigated the variation in the chemical composition of milk from a herd of NL goats during a lactation period including periods
of variations in feeding regime. They found, for instance, that the fat content
decreased over the first 4 months of lactation and increased again during the mountain pasture period. The protein content decreased during the first 4 months and then
increased until the end of lactation, while the lactose concentration decreased
throughout the lactation. Variation in content of the individual fatty acids and in the
mineral content was also observed.
Milk is a good carrier of minerals, essential for the growth and development of
infants. However, there is a difference in mineral contents as well as vitamins in
milk from different species (Table 2). The contents of calcium, phosphorus, magnesium and potassium are higher in goat milk compared to cow milk. On the other
hand, cow milk has higher contents of sodium and sulphur compared to goat milk
(Park 2010b). Goat milk has a higher content of vitamin A compared to cow milk
because goats are efficient converters of β-carotene (pro-vitamin A) to vitamin A
(this explains why goat milk is whiter than cow milk). However, goat milk has
lower contents of pyridoxine, vitamin B12 and folate compared to cow milk (Turck
2013). If goat milk is used as a substitute for human milk in the infant diet, the
supplementation of a folate-rich ingredient is important in order to reduce the risk
of anemia.
2.3 Goat Milk Processing
Technological Properties of Goat Milk
In dairy processing, milk is subjected to heat treatment to reduce bacterial load,
prolong shelf life and to improve the technological properties of milk. Understanding
the technological properties of milk, for example, heat stability, is important in the
manufacturing of dairy products. From a scientific point of view, there has been a
limited focus on the heat stability of goat milk (Zadow et al. 1983), probably because
it is less commercialised than cow milk. Goat milk is less stable to heat compared
to cow milk, this could be explained by a higher content of ionic calcium in goat
milk compared to cow milk (Zadow et al. 1983). Heat stability of goat milk for UHT
could be improved by pH adjustment, the addition of calcium sequestrant (2% disodium phosphate) and preheating of milk before processing (Zadow et al. 1983).
Goat Milk Quality and Possible Dairy Products from Rural Households of Tanzania…
et al. 2013). Higher levels of conjugated linoleic acid (CLA) (C18:2 cis 9, trans 11)
were found in goat and sheep milk than in cow milk (Markiewicz-Kęszycka et al.
2013). The content of CLA in milk will vary depending on the feeding regimes; for
instance, milk from animals fed on pasture was found to contain higher levels of
CLA compared to the indoor fed animals (Zervas and Tsiplakou 2011).
It is also of interest for processors of goat milk to know that the composition may
vary considerably during the lactation period and according to the feeding regime.
Brendehaug and Abrahamsen (1986) investigated the variation in the chemical composition of milk from a herd of NL goats during a lactation period including periods
of variations in feeding regime. They found, for instance, that the fat content
decreased over the first 4 months of lactation and increased again during the mountain pasture period. The protein content decreased during the first 4 months and then
increased until the end of lactation, while the lactose concentration decreased
throughout the lactation. Variation in content of the individual fatty acids and in the
mineral content was also observed.
Milk is a good carrier of minerals, essential for the growth and development of
infants. However, there is a difference in mineral contents as well as vitamins in
milk from different species (Table 2). The contents of calcium, phosphorus, magnesium and potassium are higher in goat milk compared to cow milk. On the other
hand, cow milk has higher contents of sodium and sulphur compared to goat milk
(Park 2010b). Goat milk has a higher content of vitamin A compared to cow milk
because goats are efficient converters of β-carotene (pro-vitamin A) to vitamin A
(this explains why goat milk is whiter than cow milk). However, goat milk has
lower contents of pyridoxine, vitamin B12 and folate compared to cow milk (Turck
2013). If goat milk is used as a substitute for human milk in the infant diet, the
supplementation of a folate-rich ingredient is important in order to reduce the risk
of anemia.
2.3 Goat Milk Processing
Technological Properties of Goat Milk
In dairy processing, milk is subjected to heat treatment to reduce bacterial load,
prolong shelf life and to improve the technological properties of milk. Understanding
the technological properties of milk, for example, heat stability, is important in the
manufacturing of dairy products. From a scientific point of view, there has been a
limited focus on the heat stability of goat milk (Zadow et al. 1983), probably because
it is less commercialised than cow milk. Goat milk is less stable to heat compared
to cow milk, this could be explained by a higher content of ionic calcium in goat
milk compared to cow milk (Zadow et al. 1983). Heat stability of goat milk for UHT
could be improved by pH adjustment, the addition of calcium sequestrant (2% disodium phosphate) and preheating of milk before processing (Zadow et al. 1983).
Goat Milk Quality and Possible Dairy Products from Rural Households of Tanzania…