Complexing of Calcium by Hexametaphosphate, Oxalate, Citrate, and Edta in Milk. I. Effects of Complexing Agents on Turbidity and Rennet Coagulation

Abstract

The effects of Ca-complexing agents on turbidity and rennet coagulation in milk were studied, employing hexametaphosphate (HMP), oxalate, citrate and ethylenedi-amine tetraacetate (EDTA). Turbidity was decreased by these agents, and increased by Ca. To determine the equivalent amount of Ca bound by each, neutralized CaCl2 solution was added to milk containing these agents until normal turbidity was restored. Mole numbers of Ca to offset 1 M quantities of the Ca-complexing agents were 6 M for HMP and approximately 1 M for oxalate, citrate and EDTA. Coagulation time was prolonged in logarithmic proportion to the amount of complexing agent added, but was restored to normal by the addition of Ca. Mole ratios of HMP, oxalate, citrate and EDTA to Ca were, respectively, 1:5.8, 1:1, 1:1 and 1:1. Coagulation time was shortened when the milk solids content was increased. As the solids were increased in the milk, HMP became less effective in retarding rennet coagulation.