Heavy coagulum formation in lactic casein manufacture results in
high
casein concentration, high starter bacteria concentration and low pH on
the base of
the coagulation vessel. No heavy coagulum was formed during slow coagulation
of
skim milk with glucono-δ-lactone, indicating that
starter bacteria were necessary.
Skim milk preheat treatments severe enough to cause denaturation of the
more heat-
stable whey proteins, α-lactalbumin and β-lactoglobulin,
also caused a reduction in
heavy coagulum formation, suggesting the heat inactivation of a co-factor
involved
in the process. These results suggest a mechanism for heavy coagulum formation
similar to that for minor sludge formation in cottage cheese manufacture.
Starter
bacteria would clump together, probably assisted by a co-factor. These
starter
clumps would generate a region of low pH causing isoelectric precipitation
of casein
in and around the clumps. The clumps would then settle forming a layer
on the base
of the coagulation vessel which might become further compressed by gravity.