Whey separation, which refers to the appearance of
liquid (whey) on the surface of a milk gel, is a common
defect in fermented milk products. Whey separation can
occur if the gel network is damaged or if the gel undergoes
substantial structural rearrangement. Syneresis is
defined as shrinkage of a gel and this occurs concomitantly
with expulsion of liquid or whey separation.
Spontaneous syneresis is contraction of a gel without
the application of any external forces (e.g. centrifugation)
and is related to instability of the gel network (i.e.
large scale rearrangements) resulting in the loss of the
ability to entrap all the serum phase (Walstra, 1993).
Yoghurt manufacturers try to prevent whey separation
by increasing the total solids content of milk and in the
case of stirred yoghurt by adding stabilizers (