Effect of heating temperature on electrical properties and gel properties of carp surimi

Abstract For better application of ohmic heating technology in the food industry, it is necessary to study the variation of the electrical properties of food materials with temperature. In this paper, various initial heating temperatures were applied to investigate the impact of temperature on the electrical properties of rinsed and unrinsed carp surimi. An impedance analyzer was utilized to measure the electrical parameters of carp surimi within the frequency range of 20 ~ 120 MHz. The frequency and temperature characteristics of electrical parameters were explained based on biological and electromagnetic theories. These findings furnish theoretical references and experimental evidence for applying ohmic heating technology. The results showed that the parallel inductance ( L p ), parallel capacitance ( C p ), parallel resistance ( R p ), and impedance ( Z ) of surimi decreased as the internal temperature of the surimi increased. The greater the heating temperature of the water bath, the larger the parameter values. The L p , C p , R p , and Z values were lower for unrinsed surimi than for rinsed surimi. During the heating and cooling process, the parameter values at the same temperature point differed due to the different states of the surimi gel. As the frequency increased, the R p and Z of surimi showed different regular changes, with similar trends at the same temperature. Rinsing has been demonstrated to improve the gel properties of surimi effectively. Prolonged periods in the temperature range of 60 ~ 70°C can cause the modori phenomenon (gel degradation), leading to reduce the gel strength of surimi. Thus, it is essential to pass through this temperature zone as soon as possible during the preparation of surimi gel. The relationship between the internal microstructure of surimi gel and the electrical parameters needs to be further investigated. Practical Applications As an emerging technology for food heat treatment, ohmic heating has the characteristics of uniform heating and fast heat production. As a homogeneous material, surimi is ideal for ohmic heating. However, the heating process is not easy to control when the electrical parameters are unknown, so the purpose of this study is to explore the changes of the electrical parameters of surimi at different heating rates and temperatures, provide data reference for the heat treatment of surimi by ohmic heating, and promote the application of ohmic heating in surimi processing.