BEST MIXING PRACTICES TO MINIMIZE THE PARTICLE SIZE IN RECONSTITUTED NONFAT DRY MILK
Source: Journal of Food Processing & Preservation, Volume 32, Number 1, February 2008 , pp. 60-74(15)
Abstract:The objective was to determine processing parameters that would minimize the particle size of reconstituted nonfat dry milk (NDM). Four mixing parameters were evaluated: equipment (blender versus recirculation), shear rate (high versus low), mixing temperature (4 versus 22C) and holding temperatures (4 versus 22C). In a second experiment, lab-scale homogenization and pH adjustment were evaluated. NDM reconstituted in a blender at 22C had the smallest particle sizes (0.133 to 0.135 µm). Shear rate did not affect particle size. Homogenization induced multimodal particle size distributions within a single dispersion, and this effect was exacerbated if the reconstituted NDM was adjusted to pH 5, 6 or 7. Changes in casein micelle structure may explain the effect of homogenization on particle size. PRACTICAL APPLICATIONS Mixing practices vary in a manufacturing setting, and this work shows that the particle size in reconstituted nonfat dry milk (NDM) was minimized using blender-style equipment and ambient temperatures (22 versus 4C). Homogenization is a process step used to manufacture beverages as it aids ingredient mixing and component interactions, and potentially extends stability. But in this work, homogenization induced aggregate formation of smaller-sized particles in reconstituted NDM. At a beverage pH of 5, the aggregates destabilized the beverage, but this was not observed in beverages from pH 6 to 7. Thus, in the formulating and processing of dairy-based beverages, homogenization should be evaluated for impact on overall stability.
Document Type: Research article
Publication date: 2008-02-01