TEXTURAL PROPERTIES OF DEHYDRATED FOODS. RELATIONSHIPS WITH THE THERMODYNAMICS OF WATER VAPOR SORPTION

Abstract

Textural properties of pre-cooked, freeze-dried beef and of special bite-size space foods, all of which were designed for consumption without prior rehydration, were determined by instrumental and sensory methods at different relative humidity points of the moisture sorption isotherm. Supplemental instrumental measurements were also made on completely rehydrated pre-cooked, freeze-dried beef. In general, as the relative humidity increased, the mechanical properties of hardness and cohesive-ness (Szczesniak) increased, whereas the mechanical property called the crushability index (Drake) and the sensory property 'ease of biting' decreased. Close relationships were found between the heat of sorption and the sensory rating of heat evolved in the mouth during chewing of initially dry meat samples. Good correlations were also obtained between other thermodynamic functions and textural properties.