Liquid pig feed (LPF) and skimmed milk (SM) acidified to pH 4 with lactic or hydrochloric acid (HCl) were treated with 0, 2.5, 5. 12.5, 25 or 50 ppm Cu 2+ and challenged with 10 7 c.f.u ml -1 Salmonella Typhimurium DT104:30. The decimal reduction time (D) was determined by enumeration of viable Salmonellae at appropriate time intervals after inoculation. Additional SM samples, acidified to pH 2.5 with HCl were treated with 10 ppm Cu 2+ , 20 ppm Zn 2+ , 20 ppm Fe 2+ or combinations of these, and

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... challenged with Salm. Typhimurium DT104:30. In LPF and SM at pH 4.0 increasing concentrations of Cu 2+ resulted in a non-linear decrease in D for Salm. Typhimurium DT104:30. Salm. Typhimurium DT104:30 died significantly (P<0.05) faster in SM at pH 2.5 treated with Cu 2+ or Cu 2+ plus Fe 2+ compared with SM treated with HCl alone. However, Zn 2+ or Cu 2+ plus Zn 2+ had no significant effect on the death rate. Treating acidified SM with Fe 2+ alone resulted in a 3 fold increase in the survival of Salm. Typhimurium DT104:30.