Influence of Frequency on Ohmic Heating of Fish Protein Gel

Abstract

Minced fish meat (Alaska Pollack) was used to make “Kamaboko” samples containing additional NaCl (0–1 w/w%) and/or starch (0–10 w/w%), and treated with alternating current (0–20 V) at various frequency (50 Hz-10 kHz) to heat up to 90°C. The resulting products were examined for their breaking strength, color and fine structure. Heating rate was found to be dependent mainly on the frequency, and increased at 10 kHz 7.5 times as fast as that of a boiled sample. The products had similar light values (L, a, b) and always higher breaking strength whose highest value was 1.6 times as large as that of boiled one. The dielectric loss was found to be maximum at around 10 kHz, indicating that it would contribute to the quick heating and the better formation of gel. These results suggest that water is individually separated in the matrix of protein gel and that the gel has the maximum dielectric constant at specified frequency according to the gel structure and distribution of components. © 1995, Japanese Society for Food Science and Technology. All rights reserved.