Electrical Conductivities of Hydrocolloid Solutions

Abstract

Ohmic heating was applied to solutions of 5 hydrocolloids (carrageenan, 1–3% w/w; xanthan, 1–3% w/w; pectin, 1–5% w/w; gelatin, 2–4% w/w and starch, 4–6% w/w) in a static cell to study the effect of concentration and temperature on electrical conductivities. For each experiment, the sample was poured into the cell and heated at a constant voltage gradient of 7.24 V/cm. Voltage, current, time and temperature were logged at time intervals and used to calculate electrical conductivities as a function of temperature. Of the thickening agents examined, carrageenan gave the highest value for electrical conductivity (0.2 S/m at 25C and 1% and 1.4 S/m at 100C and 3%) followed by xanthan (0.14 S/m at 25C and 1% to 1.1 S/m at 100C and 3%). Pectin and gelatin samples were found to exhibit lower, but similar electrical conductivities (0.06 S/m at 25C at the lowest concentration to 0.37 S/m at 100C at the highest concentration). Starch samples had the lowest electrical conductivity varying from 0.05 S/m at 25C and 4% to 0.21 S/m at 100C and 6%. Regression equations were established for each type of hydrocolloid solutions revealing a strong interaction between the concentration and the temperature and the electrical conductivity values. Major differences were observed between hydrocolloid types on electrical conductivities that were mainly attributed to their ash content.

Pulsed Electric Field-Induced Structural Modification of Whey Protein Isolate

“…The effects of PEF treatments on the RIFI values for 5% WPI were similar to the effects of PEF treatments on the RIFI values for 3% WPI. The higher protein concentration led to a higher electric conductivity or lower resistance than the lower protein concentration (Marcotte et al 1998). Since 5% WPI showed low resistance and its pulse width was narrow, the treatment time for 5% WPI was shorter than that of 3% WPI.…”

Physical, mechanical, thermal and electrical properties of cooked red bean (Phaseolus vulgaris L.) for continuous ohmic heating process

“…For example, the maximum temperature deviation between two thermocouples can reach 10°C whatever the particle concentration. Marcotte et al (1998) also found major differences between temperatures at different positions within the static ohmic heating cell for hydrocolloid samples. Fryer et al (1993) reported that the issue of non-uniformities arises in static heating systems where there is a lack of convection in high viscosity solutions.…”

“…Several authors have reported the electrical conductivities of various liquid foods (El-Hajal, 1997;Marcotte, Piette, & Ramaswamy, 1998;Palaniappan & Sastry, 1991a) and a global equation was proposed by Fillaudeau (2004). A set of electrical conductivity parameters was obtained for particles (Halden, de Alwis, & Fryer, 1990;Marcotte, 1999;Palaniappan & Sastry, 1991b;Wang & Sastry, 1997).…”

“…A set of electrical conductivity parameters was obtained for particles (Halden, de Alwis, & Fryer, 1990;Marcotte, 1999;Palaniappan & Sastry, 1991b;Wang & Sastry, 1997). Generally, solid vegetable particles have lower electrical conductivities than liquids but many factors affect the electrical conductivity: electrolyte concentration (Wang & Sastry, 1993), particle orientation and shape (de Alwis, Halden, & Fryer, 1989), particle concentration (Zareifard, Ramaswamy, Trigui, & Marcotte, 2003), food composition changes and heating effects (Halden et al, 1990), the specific heat (Zoltai & Swearingen, 1996), the viscosity (Khalaf & Sastry, 1996), the temperature (Marcotte et al, 1998;Wang & Sastry, 1997), the liquid/solid electrical conductivity ratio (Sastry & Palaniappan, 1992). Several authors have proposed correlations according to these experimental parameters (Fryer, de Alwis, Koury, Stapley, & Zhang, 1993;Palaniappan & Sastry, 1991b;Yongsawatdigul, Park, & Kolbe, 1995) but never a single relationship for all products.…”

A method for detecting in real time structure changes of food products during a heat transfer process

“…This might be explained by the difficulty to detect structure modifications based on the simple follow-up of the delivered electrical conductivity signal. Indeed, for numerous food manufacturing operations involving heating, it can be observed that electrical conductivity values are influenced both by temperature (one may mention papers of G€ oft, Dethlefsen, Prediger, & Worstorff, 1994;Marcotte, Piette, & Ramaswamy, 1998;Palaniappan & Sastry, 1991, which have all observed this fact respectively for vegetables, milk and texturant agents) and by structure modifications (Tsouli, Ville, & Valla, 1976). Due to these coupled Journal of Food Engineering 64 (2004) [289][290][291][292][293][294][295][296] www.elsevier.com/locate/jfoodeng effects, a simple follow-up of the electrical conductivity signal is not enough sensitive to alert a human operator that significant structure changes of food products are happening in the batch reactor.…”