Infant milk formulae processing: effect of wet-mix total solids and heat treatment temperature on rheological, emulsifying and nutritional properties

This study investigated the effects of total solids (TS) in the wet-mix and pasteurisation temperature on the whey protein (WP) denaturation, rheological behaviour, emulsifying properties and available lysine content of a model infant milk formula (IMF). IMF with 50% or 60% (w/w) TS were produced by wet-mix process and pasteurised at 75 °C or 100 °C for 18 s. Measurements were taken after dispersion, pasteurisation, homogenisation and spray-drying of wet-mix. Pasteurisation at 100 °C caused extensive WP denaturation (above 80%) and increased the viscosity. Available lysine content was 52% higher in powdered IMF obtained from wet-mixes pasteurised at 75 °C compared to 100 °C. A significant reduction in energy consumption could be achieved by producing IMF from 60% TS wet-mixes pasteurised at 75 °C, while obtaining powders with less than 7% WP denaturation, no loss of available lysine during processing and post-reconstitution stability for 2 h.