The effect of concentration on the heat stability of skim-milk

Abstract

SummaryA progressive change takes place in the heat stability of skim-milk during concentration. At the maximum in the coagulation time (CT)–pH profile of milk concentrated to over 20% of total solids (TS) the total N depletion curve changed from single- to 2-stage and CT became insensitive to the addition of urea. Furthermore, addition of β-lactoglobulin to skim-milk concentrates destabilized the heated milk whilst the opposite effect was observed in the presence of sulphydryl-group blocking agents. As a result of these observations, it has been suggested that the mechanism of coagulation in concentrated milk is similar to that which occurs within the minimum of the CT–pH profile of skim-milk at normal levels of TS.