Casein produces a curd when in the stomach. It is well known that goat milk produces a very loose curd structure with a high proportion of water and is easily broken apart.1 A loose curd structure promotes the digestion of milk proteins.2 The structure of the curd is in turn influenced by the individual casein proteins.
There are 4 casein proteins – αs1-, αs2-, β- and κ-casein. In cow milk, αs1-casein makes up around 25% of the total protein.3 In goat milk from New Zealand αs1-casein makes up only 5-10% of the total protein. Similarly, around 5% of the total protein of human is αs1-casein.4Instead as1-casein, β-casein makes up 70% of casein in goat milk compared to 69% in human milk casein and 43% in cow milk.5
Low levels of αs1-casein are associated with a loose, more fragile, curd structure.6 It is probably the fragile curd of goat milk that changes how it is digested within the stomach and therefore how the infant may react during this process.
- 1Storry et al 1983; Ambrosoli et al 1988; Remeuf et al 1989; Park 2007; Mestawet et al, 2014
- 2Ye et al, 2016
- 3Martin et al. 2002; Caroli et al, 2009
- 4Martin et al, 1996; Poth et al, 2008
- 5Marletta et al, 2007; Cebellos et al, 2009; Salem et al, 2009; Ham et al, 2010
- 6Pierre et al 1995; Martin, Ollivier-Bousquet and Grosclaude 1999; Park et al, 2007