Heat stability of concentrated skim milk on pilot scale
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Direct steam injection heat treatment on pilot scale as an alternative to lab scale indirect heat treatment was applied to investigate heat stability of concentrated skim milk across a broad range of temperatures from 117 °C to 153 °C and from 0.5 to 13 s holding time, assessing options for heat treat treatment of concentrated skim milk without a significant amount of protein sediment formation. The relationship between total solids content of concentrated skim milk and temperature-time combinations of heat treatment could be established using minimal heat-induced coagulation as a criterion. Coagulation of destabilized casein micelles was shown to proceed non-linear over heating temperature. Transition of critical temperature-time combinations resulted in a marked increase in sediment formation indicating that preceding reactions, noticeable as the formation of dissociated material, need to take place to some extent to induce coagulum formation. UHT preheat treatment of skim milk prior to concentration was shown to increase heat stability in terms of possible temperature-time combinations without coagulation.
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