Biochemical characteristics and quality of goat milk
1997
Jaubert, G. (Institut Technique des Produits Laitiers Caprins, Surgeres (France))
Goat milk quality depends on a large number of factors which are related to both the animal (breed, number and stage of lactation, health status) and the conditions of production (region, diet, rearing system), and has a predominant influence on the quality of subsequent goat milk products. A significant relationship between flavour and milk composition stressed the effect of animal-related factors (age, stage of lactation and yield) and, to a lesser extent, the type of feeding. Lipase activity and spontaneous lipolysis play a major role in the development of flavour in goat milk. The volatile fatty acids, and particularly branched-chain fatty acids (4-methyloctanoic and 4-ethyloctanoic), have been found the most important compounds for the characteristic goat flavour. Appreciable amounts of 4-methyloctanoic acid have also been found following the action of natural lipase on goat milk fat. The technological behaviour of milk (coagulation, acidification and drainage abilities; heat stability) is primarily affected by the state of the casein micelles and the changes they undergo during treatment of the milk for the purposes of storage or processing. The genetic polymorphism of goat k- and alpha s2-caseins has also been demonstrated and accounts for the existence of 2 variants of k-casein (Di Luccia et al. 1990) and 3 variants of alpha s2-casein. The most important work carried out in the last few years has concerned the genetic polymorphism of alpha s1-casein characterised by marked qualitative heterogeneity resulting in 6 classes of variants, and associated with different levels of protein synthesis. Nowadays, it is possible to determine the genotype of animals at birth, using the tools of molecular biology and analytical techniques. Such advances open up interesting prospects in terms of improved control of the technological quality of goat milk.
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