With the helpful interference of the
lactoglobulins, the casein particles can only
bond to each other at a few spots, and so
gather not in clusters but in a fine matrix of
chains that is much better at retaining liquid
in its small interstices.
The Fermentation Once the milk has been
heated, it’s cooled down to the desired
fermentation temperature, the bacteria are
added (often in a portion of the previous
batch), and the milk kept warm until it sets.
The fermentation temperature has a strong
influence on yogurt consistency. At the
maximum temperature well tolerated by the
bacteria, 104–113ºF/40–45ºC, the bacteria
grow and produce lactic acid rapidly, and the
milk proteins gel in just two or three hours; at
86ºF/30ºC, the bacteria work far more slowly,
and the milk takes up to 18 hours to set. Rapid
gelling produces a relatively coarse protein
network whose few thick strands give it