An experimental study of the equilibrium for skim milk powder at elevated temperatures

Development of stickiness in amorphous lactose at constant T−Tg levels

“…The theory suggests that the rate of development of stickiness in amorphous powders should be the above function of T À T g : Stickiness tests, such as the ''stickypoint temperature'' test (Lazar et al, 1956;Downton et al, 1982;Wallack & King, 1988;Chuy & Labuza, 1994), a viscometer inserted into a small fluidised bed of powder (Brooks, 2000;Hennigs, Kockel, & Langrish, 2001;Kockel, Allen, Hennigs, & Langrish, 2002;Ozmen & Langrish, 2002), observing the end of fluidisation in the bed (Toy, 2000;Thompson, Havea, & Pearce, 2001), the ''surface caking temperature'' ðT sc Þ (Chuy & Labuza, 1994), the caking index as used by Aguilera et al (1995), the flowability as used by Aguilera et al (1995), or the angle of repose (Aguilera et al, 1995), cannot easily measure the development of stickiness with time. Peleg (1993) also used the Frenkel equation to demonstrate the time-dependent nature of stickiness development.…”

Desorption isotherm of milk powders at elevated temperatures and over a wide range of relative humidity

“…However, most milk powder sorption isotherms have been measured at around ambient temperature (Berlin, Anderson, & Pallansch, 1968;Heldman, Hall, & Hedrick, 1965;Warburton & Pixton, 1978). There have been very few reports for the temperature range 60-90°C at relative humidities of up to 40% (Kockel, Allen, Hennigs, & Langrish, 2002;Pisecky, 1992). The exhaust air from a commercial spray drier falls into this temperature and humidity range.…”

“…For isotherm measurements, samples can reach equilibrium with the moisture contained in the air by either a dynamic method (Kockel et al, 2002;Papadakis, Bahu, McKenzie, & Kemp, 1993) or a static method (Heldman et al, 1965;Warburton & Pixton, 1978). In the dynamic method, the temperature and the humidity of the air are accurately controlled and air is continuously passed through the sample.…”

An effective laboratory air humidity generator for drying research

“…Previously, especially for measuring the desorption isotherms for various foods, the majority of the experiments were carried out at relatively low temperatures or low humidities (Kockel, Allen, Hennigs, & Langrish, 2002;Berlin, Anderson, & Pallansch, 1968;Jouppila & Ross, 1994). To simulate single droplet drying kinetics, accurate desorption isotherms over a wide range of relative humidities as well as those at elevated temperatures are required.…”