Dairy Sheep Symposium - the Department of Animal Sciences ...

This is often done by cheese makers with milk that does not clot (Alais 1974; Losi et al. 1982).
Cheese makers also control the temperature and the rennet concentration at which the clotting
takes place. On the other hand, cheese makers have little or no control over the composition and
quality of the milk that reaches the cheese factory. The milk received should be of high microbiological
quality, free of antibiotics and have a composition within acceptable limits. However,
this does not always occur, despite the fact that often the payment for the milk is based on its
quality (Pulina 1990). Also researchers have identified animals that produce milk that does not
clot and is therefore unsuitable for cheese making in both dairy cows (Losi et al. 1982) and sheep
(Casoli et al. 1992).
Antibiotics
Cheese
maker
Microbes
Cheese making process
(coagulation temperature,
addition of Calcium, starter cultures,
cutting time, cutting size,
cooking, salting, etc)
Milk
Somatic cells
Clotting properties
Composition
(protein, fat, total solids)
Cheese outcome
(quantity &
quality)
Figure 1. Factors affecting the outcome of sheep milk cheese at the cheese factory level. Cheese makers receive
milk with certain characteristics, and have little power to change them. These include the gross composition
of the milk (protein, fat, total solids), the presence of microbes (desirable or not), the possible
presence of antibiotics that can disturb the starter cultures and the presence of somatic cells that come
from the animals. Cheese makers can modify these characteristics only to a limited extent, but their
methods of cheese making have a great influence on cheese outcome.
High protein, fat and total solids concentrations in the milk are associated with high yields in
the resulting dairy products (Chapman 1981; Storry et al. 1983). As a consequence, the milk of
sheep has a higher yield of dairy products than the milk of cows and goats because it has higher
concentrations of protein, fat and total solids (Ucci 1945; Casu and Marcialis 1966; Anifantakis
1986, 1990).
Therefore any factor that affects the composition of the milk, will affect the yield and quality
(chemical composition, texture and flavour) of dairy products obtained from the milk.
Factors affecting the quality of sheep milk
As shown in Figure 1, the cheese maker at the cheese factory receives milk of a certain
composition and can do very little to change it. In Figure 2 the factors that affect sheep milk
quality at the farm level are shown, and it is apparent that the farmer too has little control over
some of these factors. However, the farmer has some control over the environmental factors that
affect the quality of sheep milk.