Characteristic innovation of a food drying process revealed by the physicochemical analysis of dehydration dynamics

Abstract

A typical food drying process was characteristically innovated by using a water tank model derived from the physicochemical analysis of dehydration dynamics. A fish paste sausage was effectively used, as a model food, to evaluate five characteristic parameters for water movement; effective diffusion coefficient ( De), diffusion activation energy ( E D), void fraction of dried sausage ( V f), and proportion of weakly restricted water ( f w), and strongly restricted water ( f s). The dehydration curves obtained were clearly classified into two regions that were divided at a 100%-d.b. of water content ( W 0); region I ( W 0 larger than 100%-d.b.) and II ( W 0 smaller than 100%-d.b.). The molecular states of moisture in the sausage structure were characterized, using the Temperature Programmed Desorption (TPD) and proton-NMR methods, as liquid water in region I and as gaseous water in region II. A mathematical model based on the water tank model was developed as a function of E D, V f, f w and f s. Using a computer simulation technique, a significant enhancement of the drying process, 2.0–3.5 times acceleration of drying rate and 1.18–1.11 times shortening of drying time, was proposed by use of the poultice up operation in region II rather than in region I.