Reconstituted undenatured whey protein concentrates (WPC) at pH values below 7.3 were unstable to direct UHT [ultra-heat-treated] processing, with plant blockage and/or sedimentation in the product being observed. Heat treatment of reconstituted WPC (3.5% protein) improved stability slightly. Addition of 0.25% disodium hydrogen orthophosphate di-hydrate to reconstituted WPC before pre-heat treatment at 85.degree. C for 5 min improved stability to UHT processing, with no blockage of the plant or sedimentation being encountered down to pH 6.6. Addition of Pi to reconstituted WPC, after pre-heat treatment or without pre-heat treatment, did not improve stability. Incorporation of the Pi/pre-heat treatment steps during normal WPC manufacture improved stability of the product to UHT processing.
