SummaryChanges in heat stability and Ca2+ activity of recombined concentrated milk (18% solids non-fat:8% fat) induced by the additions of 0·011–0·217 mol phosphate/kg skim milk solids (SMS), 0·022–0·217 mol citrate/kg SMS, 0·011–0·022 mol Ca/kg SMS and 0·016–0·067 mol EDTA/kg SMS were evaluated. Heat stability was assessed using an objective method which involved determination of viscosity after heating under controlled conditions. Low levels of added phosphate and citrate generally effected an acid shift of the viscosity–pH profile, while higher levels caused a broadening of the profile. Addition of CaCl2 at a level of 0·011 mol/kg SMS resulted in a narrowing of the viscosity–pH curve; additions of higher levels resulted in a non-heat stable recombined milk concentrate. EDTA also caused a narrowing of the viscosity–pH curve. The results highlight the importance of pH control for effective stabilization of recombined milk concentrates by additions of phosphate and citrate.

-The effects of citrate addition to milks on the stability of milk foams formed by two aeration processes, whipping at room temperature and by steam-frothing, were examined. Citrate addition (0.1-0.5 mol added citrate·kg −1 milk solids non-fat) improved the whipping properties of milks reconstituted from conventional low-heat (72 • C for 30 s) and high-heat (85 • C for 30 min) powders. This effect was attributed to the role of citrate in dissociating casein micelles. However, while citrate addition (0.1-0.2 mol added citrate·kg −1 milk solids non-fat) improved the steamfrothing properties of milks reconstituted from conventional low-heat milk powder it did not improve those of milks made from corresponding high-heat milk powders. Similar effects of citrate addition on foaming and stream-frothing properties were obtained when the salts were added to skim milk concentrate prior to drying. The citrated milk powders are alternatives to physical blends of conventional skim milk powders and citrate salts for enhancing the foaming properties of milks at both low and high application temperatures. milk powder / foaming / stream-frothing / casein micelle / citrate

The effects of ultrasonic standing waves on palm oil separation of ex-screw press feed from the mesocarp of the palm oil fruit, oil recovery and oil quality were determined. The ex-screw press feed at 85°C was pumped simultaneously into two identical vessels. One vessel was the control (non-ultrasound) and the other vessel (ultrasound) was fitted with two 400 kHz transducer plates operating at 13.4 kJ/kg, which were placed in direct contact with the feed. Oiling-off by gravity settling occurred at faster rates after sonication. The total recoverable oil after 30 min gravity settling and upon centrifuging the underflow sludge (remaining colloidal fraction) at 10009g was higher after sonication. Total recoverable oil was 30.7 ± 2.9 % and 43.5 ± 8.6 % (w/w original feed basis) for the non-sonicated and sonicated samples respectively. Sonication reduced the oil content of the sludge ex-centrifuge, demonstrating that higher recovery of palm oil was obtained with ultrasound application. Sonication did not affect the DOBI (deterioration of bleachability index) value, and vitamin E and free fatty acid contents of the separated oil. High-frequency ultrasound enhances the separation rate of palm oil and increases oil recovery without compromising oil quality.

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