Dielectric properties of soybean protein isolate dispersions as a function of concentration, temperature and pH

Dielectric Properties of Raw Milk as Functions of Protein Content and Temperature

“…The dielectric loss factor was improved by increased ionic conductivity. The increased ε″ with protein content was also reported for soybean protein isolate dispersions over the frequency range of 200-2500 MHz at a protein concentration range of 0-15 g/100 g water (Ahmed et al 2008) and for milk-water solution below about 1000 MHz with a milk concentration of 60-100 % in mass (Guo et al 2010a). At a given temperature and frequency, the linear relationship between dielectric properties (ε′ and ε″) and protein content could be described by the following equations:…”

“…Increasing temperature results in increased Brownian motion, which in turn reduces the static dielectric constant ε s . The decreased ε′ with temperature was also reported on nonfat milk at 25-55°C and 1000 and 3000 MHz (Mudgett et al 1974), on milk with different fat contents at 10-90°C and 915 MHz (Coronel et al 2003), and on other liquid foods or foods with high moisture content, such as fruit tissues and juices at 15 to 95°C (Nelson 2003;Zhu et al 2012), and soybean protein isolate dispersions at 20-85°C (Ahmed et al 2008) but was not found on powder materials where Brownian motion does not exhibit, such as macadamia nut kernel powder with moisture content less than 24 % wet basis ) and red pepper powder with moisture content lower than 30.8 % wet basis . Figure 4b expresses that at 40.68 MHz, when the temperature increased from 25 to 45°C, the ε″ had a little decrease, i.e., from 193.47 to 190.35, then increased to 211.04 when the temperature increased to 75°C.…”

Dielectric properties of myofibrillar protein dispersions from Alaska Pollock (Theragra chalcogramma) as a function of concentration, temperature, and NaCl concentration

“…The change in loss factor has been generally attributed to the ionic conductivity at lower frequencies while it is attributed to bound water relaxation as well as free water relaxation near the top of the frequency range (Nelson and Datta, 2001;Wang et al, 2008). The effect of the frequency is in agreement with the data reported by others (Ahmed and Luciano, 2009;Ahmed et al, 2008;Basaran et al, 2010). Fig.…”

“…Currently, a very limited amount of published information related to the dielectric properties of fish protein at microwave frequencies is available. The dielectric properties of food materials have been considered to be the major factors contributing to the interactions between microwaves and food (Ahmed et al, 2008). Furthermore, the dielectric properties are important criteria for selecting proper model foods for microwave heating because they determine how the microwave energy is absorbed, transmitted, reflected, or concentrated inside a food material (Datta, 2001).…”

Dielectric Properties of Fish Flesh at Microwave Frequency

“…Figure 4 shows the frequency-(915 and 2450 MHz) and temperature-dependent penetration depth for the three fish species. The penetration depth showed a similar trend with increasing temperature between the different species; it decreased with an increase in frequency at the same temperature, which is attributed to the effect of wavelength (λ 0 ) (Ahmed et al, 2008). At a lower frequency, the quick increase in εʺ with increasing temperature that resulted in decreased penetration depth is probably in response to the increased degree of dielectric dispersion due to ionic conductivity as the temperature increased (Nelson and Bartley, 2001.).…”