DYNAMIC EVALUATION OF THE DEHYDRATION RESPONSE CURVES OF FOODS CHARACTERIZED BY A POULTICE-UP PROCESS USING A FISH-PASTE SAUSAGE. I. DETERMINATION OF THE MECHANISMS FOR MOISTURE TRANSFER

Abstract

In order to discern the mechanism for the transfer of moisture in foods as they are drying, the pore structure of food and the distribution of moisture in food matrices were studied in detail by using a fish-paste sausage that was prepared with various contents ofmo isture (W ₀). A uniform distribution ofmois ture was achieved with a poultice-up process. The void fractions (V_f ) that occurred as a result ofchanges in the pore structure of the food were evaluated from a graphical analysis of SEM photographs on a cross-sectional observation ofthe sausage. The V_f -values obtained changed drastically depending on the W₀ and were classified into two regions: I (W ₀ > 100%-d.b.), which gave V_f = 0.10 ± 0.08, and II (W ₀ < 100%-d.b.), which gave V_f = 0.24 ± 0.05 at a drying temperature of 35°C. For the analysis ofmois ture state, the temperature-programmed desorption (TPD) profiles and the correlation time ofwater protons evaluated from nuclear magnetic resonance (NMR) were effectively used. The results produced three states ofmois ture: weakly and strongly restricted water at Region I and gaseous water at Region II.

Keywords:

• Moisture State in the Food Matrix
• Pore Structure of Solid Food
• Proton-NMR
• TPD

ACKNOWLEDGMENTS

The authors express their appreciation to Mr. S. Nagai for measuring the proton-NMR and to Dr. I. Simono for taking the SEM photographs of the fish-paste sausage.