water phase (Figure 4.15). It has a higher fat content than milk (80%)
and uses pasteurized cream as its starting point. Typically, the cream is
pasteurized using an HTST process of 85 1 C for 15 s and held at 4–5 1 C
for a period to allow the fat globules to harden and cluster together.
In making a conventional ripened cream butter, the starter culture is
added at this stage and the cream incubated at around 20 1 C to allow
flavour production to take place. A more recent method developed at
NIZO, the Dutch Dairy Research Institute, employs a concentrated
starter added to sweet-cream butter after manufacture. Phase inversion,
the conversion from a fat-in-water emulsion to a water-in-fat emulsion, is
achieved by the process of churning. During this process fat globules
coalesce, granules of butter separate out, and considerable amounts
of water are lost from the product in the form of buttermilk. The
buttermilk phase retains most of the micro-organisms from the cream
and numbers may show an apparent increase due to the breaking of
bacterial clumps.
Traditional farmhouse buttermaking used wooden butter churns and
these were originally scaled up for the earliest commercial butter-making.
However, the impossibility of effectively cleaning and sanitizing wood
has led to its replacement by churns made of stainless steel or alumin-
ium–magnesium alloys. After the butter has formed, the buttermilk is
drained off, the butter grains washed with water and, in the case of sweet-
cream butter, salt is added usually at a level of 1–2%. The butter is then
Figure 4.15 Buttermaking
116 The Microbiology of Food Preservation