A series of preliminary experiments were conducted where different levels of glucono-d-lactone (GDL) were added to milks at pH
6.5–7.1 and at 30 C. The milks were allowed to stand at 30 C for
12 h to hydrolyse the GDL and lower the pH’s of the milks. The pH
of the milks were measured after 12 h, and from these experiments
a series of equations were developed in order to calculate the level
of GDL required to achieve any desired pH in each of the milks
samples. In the full experiments, the required levels of GDL were
added to the milks, and the milks were held at 30 C for 12 h before
further experimentation. The pH was measured to ensure that the
desired pH had been achieved.