Plastic microcentrifuge tubes (~3 cm long) whose lower section
were sawed off and covered by 5 layers of cheese cloth, were used
for transferring samples (~1 g) that were excised from approximately 3 cm below the surface of the yogurt variations. The upper
part of the centrifuge tubes was also covered with cheese cloth, and
the tubes were left to stand for 2 h at 4±0.5
C to allow drainage of
excess water, while theflocs were retained on top of the lower
cheese cloth plug without suffering structure breakdown. The
adapted centrifuge tubes were placed vertically and immersed into
glass recipients containing 2 g 100 m L
1
glutaraldehyde solution in
phosphate buffer (0.1 mol L
1
, pH 7.2) forfixing the proteins