Rennet coagulation of heated milk concentrates

The high temperature heating of cheese milk is a useful tool for preventing late fermentation during cheese ripening if the renneting properties remain unchanged. The aim of the investigations was to find heating conditions which guarantee the inactivation of clostridia spores but still enable rennet coagulation of the heated milk and milk concentrates respectively. The gel strength of the rennet gels increased the more the casein content increased. The native whey proteins did not influence the gel strength. In contrast the denatured whey proteins hinder rennet coagulation and the gel became weaker. The upper limit of denatured whey proteins dependent on the casein concentration in the retentate was able to be determined in order to achieve the gel strength of pasteurized skim milk. Almost "whey protein-free" casein solutions (3.8% casein) were produced by diafiltration. The heating conditions of $100 ^\circ$C/280 s and $110 ^\circ$C/24 s were able to destroy spores from Clostridium tyrobutyricum by 4 log units while the rennet coagulation was slightly altered.