Stickiness of skim milk powder using the particle gun technique

The influence of particle velocity on the stickiness of milk powder

“…The particle gun equipment and method, described in detail in Zuo et al (2007), were modified as described by Murti et al (2009) to reduce experimental variation. Analysis methodology was as explained in Paterson et al (2007aPaterson et al ( , 2007b.…”

“…However, when compared on similar powders, each method gives different sticky point condition measurements which is not surprising as the dynamic conditions that exist at the point of particle collisions are dramatically different in each test (Boonyai et al, 2004;Zuo, Paterson, Chatterjee, & Bronlund, 2006). The one aspect that all test methods have shown is a decrease in the sticky point temperature as either the relative humidity of the contacting air increases or the moisture content of the powder increases (Fanshawe, 2001;Jaya, Sudhagar, & Das, 2002;Murti et al, 2006aMurti et al, , 2006bOzmen & Langrish, 2002;Roos & Karel, 1991;To & Flink, 1978a, 1978b, 1978cTsourouflis, Flink, & Karel, 1976;Wallack & King, 1988). This has led to a typical sticky point curve for a powder such as those shown by Zuo et al (2006).…”

“…These include the Jenike shear cell tester as a means of testing the flowability of powders where beds of powder have their shear strength measured under different levels of compaction (Fitzpatrick et al, 2007;Jenike, 1964;Paterson & Wang, 2007;Provent, Chulia, & Cary, 1993;Purutyan, Pittenger, & Tardos, 2005;Teunou & Fitzpatrick, 2000), the blow tester where small beds of powder that have been exposed to different levels of relative humidity air have their caking strength tested by measuring the velocity of air needed to blow a channel in the bed (Paterson, Bronlund, Zuo, & Chatterjee, 2007a;Paterson, Brooks, Foster, & Bronlund, 2005;Paterson, Zuo, Bronlund, & Chatterjee, 2007b), the stirred cell sticky point temperature test where powder is placed in a cell with a stirrer inserted into the powder and the level of power needed to stir the bed is measured as the temperature of the bed is raised (Chuy & Labuza, 1994;Downton, Flores-Luna, & King, 1982;Hennigs, Kockel, & Langrish, 2001;Lazar, Brown, Smith, Wong, & Lindquist, 1956;Wallack & King, 1988), a fluid bed sticky point tester where a fluid bed of powder has the relative humidity of the air raised until such time as the fluidisation stops (Chatterjee, 2004, chaps. 3, 4;Fanshawe, 2001), a cyclone sticky point testing device where powder is circulated in a cyclone with increasing levels of humidity in the air until such time as the powder sticks to the side of the cyclone (Boonyai, Bhandari, & Howes, 2004;Boonyai, Howes, & Bhandari, 2006) and the particle gun developed in our laboratory where powder particles are fired down a tube with increasing levels of relative humidity air at a target plate and the percentage of powder that sticks is measured (Chatterjee, 2004;Murti, 2006;Murti, Paterson, Pearce, & Bronlund, 2006a, 2006b, 2009Paterson et al, 2007aPaterson et al, , 2007bZuo, 2004;…”

“…In this work, the particle gun and a fluid bed rig were used to measure the sticky curves of skim milk powder (SMP) and whole milk powder (WMP). The particle gun (Murti et al, 2009;Paterson et al, 2007aPaterson et al, , 2007b was used to measure the fraction of a powder sample that adheres to a target plate. To do this, several samples of the powder were tested, and the relative humidity (RH) at the tip of the gun was increased between each sample while the air temperature was held constant.…”

“…It should be noted that for the particle gun, the particle temperature is taken as the air temperature at the tip of the gun, as it is assumed that the surface of the particle approximates to the surrounding air temperature. Murti et al (2009) has shown that the RH of the ambient air surrounding the powder feed device also influences the (T À T g ) critical obtained from the particle gun. Earlier work by Chatterjee (2004), Paterson et al (2007aPaterson et al ( , 2007b, Zuo (2004) and Zuo et al (2007) made no attempt to control this parameter, subsequently increasing the observed scatter in their data.…”