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Electrical properties of hydrated collagen. I. Dielectric properties

1973; Wiley; Volume: 12; Issue: 2 Linguagem: Inglês

10.1002/bip.1973.360120212

1097-0282

V. P. Tomaselli, Morris H. Shamos,

Meat and Animal Product Quality

Abstract The effect of water on the low‐frequency (10 2 ‐10 5 H z ) complex permittivitv of native, sold‐state collagen has been investigated experimentally. Measurements at ambient temperature show that dry collagen exhibits essentially no frequency or temperature dependence. As water is absorbed, both dielectric constant and loss factor increase simultaneously and rise sharply upward at a hydration level which may be associated with the completion of the primary absorption layer as determined from independent water absorption studies. The behaviour is qualitatively identical to that observed for other proteins and related materials. Temperature‐dependent measurements made under vacuum conditions in the range −196°C to +100°C are characteristic of the dielectric properties of the water in the sample. Dehydration produced by successive temperature recycling to the maximum temperature effectively eliminates any temperature or frequency dependence. A maximum in the temperature‐dependent curves is found at about +40°C and is explained as the superposition of two processes: ( 1 ) the transition of water molecules from bound to free states, and ( 2 ) the difffusion of water molecules out of the system. The dielectric constant of dry collagen, after desorption at ambient temperature, is about 4.5. Desorption at elevated temperatures reduced the room temperature value to about 2.3 and the liquid nitrogen temperature value to a number indistinguishable from the optical value of n 2 = 2.16.