EFFECTS OF DEHYDRATION THROUGH THE INTERMEDIATE MOISTURE RANGE ON WATER ACTIVITY, MICROBIAL GROWTH, AND TEXTURE OF SELECTED FOODS

Abstract

Various food systems were inoculated with Pseudomonas aeruginosa and Staphylococcus aureus and vacuum-dried to different moisture contents in the intermediate moisture range. Water activity (aw) values were determined instrumentally with a hygrometer indicator equipped with appropriate hygrosensors. Sorption isotherms and bacterial growth curves at the various water activities were plotted and correlated with food texture, Growth of P. aeruginosa was inhibited at aw test values below 0.98, 0.98, and 0.96 in custard, pea, and beef products, respectively, and growth of S. aureus did not occur below aw test values of 0.94 and 0.96 in custard and ham products, respectively. These results generally agree with earlier work done on model systems. With none of the foods studied could microbiologically stable intermediate moisture products of acceptable texture be produced by drying alone.