Analysis of particle-gun-derived dairy powder stickiness curves

Stickiness of skim milk powder using the particle gun technique

“…Massey University, in conjunction with the Fonterra Research Centre, developed the particle gun, which has been used successfully in previous work (Chatterjee, 2004;Paterson et al, 2007;Zuo, 2004;Zuo et al, 2007) to measure the initiation of stickiness for particles travelling and hitting walls at velocities, temperatures and RHs similar to those encountered in the ducting and cyclones of industrial-scale plants. Details of the apparatus and how it is used are given in those papers.…”

The influence of particle velocity on the stickiness of milk powder

“…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.…”

“…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.…”

“…By plotting the data obtained for percentage powder deposition at different air temperatures (y-axis) against (T À T g ) (x-axis), it was shown by Paterson et al (2007aPaterson et al ( , 2007b) that, for a given powder with the same water activity, tested at the same velocity, the data fall on a common line (the % deposition line). The stickiness point is defined as the point at which the line fitted to the data intercepts the x-axis and is designated (T À T g ) critical , since it is the value of (T À T g ) where the powder becomes sticky to the extent that a detectable amount sticks to the target plate.…”