ChBE Seminar Series: Keisha Wilson McDowell
Tuesday, December 9, 2014
11:00 a.m.-12:15 p.m.
Room 2108, Chemical and Nuclear Engineering Bldg.
Professor Jeffery Klauda
Effect of Dehydration Particle-Formation Processes on the Water Vapor Sorption Characteristics of Skim Milk Powders
Keisha Wilson McDowell, Ph.D.
Principal Investigator & Internal Consultant
DuPont Engineering Research and Technology
Skim milk powders were produced via laboratory spray-drying and freeze-drying processes, and water sorption isotherms were determined at various temperatures using a high-resolution dynamic vapor sorption method. Equilibrium relative humidity environments from 1–95% were generated via mixtures of wet and dry gas streams fed to an isothermal sample chamber containing a sensitive microbalance. The isotherms showed the type II sigmoid-shape, according to the BDDT classification, very typical of food materials; and equilibrium moisture contents decreased with increasing temperature. The dynamic sorption data were compared with equilibrium measurements obtained using saturated salt solutions, static water activity measurements using a portable meter, and sorption isotherms of commercial granulated skim milk powders. Two-parameter BET and three-parameter GAB equations were used to model the moisture sorption behaviors. The models showed good fit to the data, and differences in the fitting parameters could be related to the structure generated via the dehydration process used. These data are useful in determining optimal storage stability conditions and packaging selections for dried products.