ELECTRICAL CONDUCTIVITY OF OAT FLOUR AS INFLUENCED BY OHMIC HEATING NIMRATBIR KAUR 1 , A. K. SINGH 2 & SANGEETA CHOPRA 3 1 Research Scholar, Department of Processing and Food Engineering, Punjab Agricultural University, Ludhiana, Punjab, India 2 Senior Research Engineer, Department of Processing and Food Engineering, Punjab Agricultural University, Ludhiana, Punjab, India 3 KAB-I, PUSA, New Delhi, India ABSTRACT The most important parameter in ohmic heating modelling is electrical conductivity. Oat flour of three particle sizes ( 0.6 mm, 1.0 mm and 1.4 mm) at different moisture contents (40%, 35% and 30%) were evaluated for electrical conductivity at varying applied voltage gradient (55V/cm, 45V/cm, 35V/cm and 25V/cm). The samples were heated for 90 seconds. In general, oat flour at 40% moisture content demonstrated greater electrical conduction than samples prepared with 35%, 30% and 25% moisture content. Moreover, significant effect of applied voltages was observed at all the four moisture contents. At 40% moisture content, the highest conductivity was observed for 55V/cm and minimum for 25V/cm. The effects of applied voltage were considerable for samples with 35% and 30% moisture content but for 25% the effect was least significant. Samples with smaller particle size were more conductive than larger particle size flour at all the voltage and moisture content combinations. In all cases, electrical conductivities exhibited linear increment with temperature, till the gelatinization temperature was attained. KEYWORDS: Electrical Conductivity, Oat Flour, Voltage Gradient, Moisture Content INTRODUCTION Ohmic heating (also referred to as Joule heating, electroheating, and electroconductive heating) is defined as a process wherein the food material is heated by passing alternating electric current (Vicente et al., 2006). When materials contain sufficient water and electrolytes to allow the passage of electric current, ohmic heating can be used to generate heat within the product (Imai et al, 1995). The heating occurs in the form of internal energy transformation (from electric to thermal) within the material (Sastry and Barach, 2000). Ohmic heating can volumetrically heat the entire mass of a food system, resulting in faster heating, better quality and less energy consumption than conventional heating or processing system. Due to the faster and uniform heating minimum structural, nutritional or organoleptic changes occur in ohmically heated food (Rahman, 1999). Ohmic heating includes other advantages like enhancing drying rates (Lima and Sastry, 1999; Wang and Sastry, 2000; Zhong and Lima, 2003) and extraction yields (Lima and Sastry, 1999; Wang and Sastry, 2002; Halden et al, 1990) in certain fruits and vegetables and preparation of pre-gelatinized starches (Fernando et al, 2005) The electrical conductivity of foods is a key parameter of ohmic heating system. The design of an effective ohmic heating system depends on the electrical conductivities of foods (Sarang et al, 2008). Electrical conductivity; particle type, size, concentration, shape and moisture content are some of factors affecting the heating rate in ohmic system (Legrand et al, 2007; Marcotte, 1999; McKenna et al, 2006; Roberts et al, 1998). Experiments have been conduct on the electrical conductivity of liquid fruit products like juices and purees (Palaniappan and Sastry, 1991; Icer and Ilicali, 2005; Castro et International Journal of Agricultural Science and Research (IJASR) ISSN 2250-0057 Vol. 3, Issue 4, Oct 2013, 57-64 © TJPRC Pvt. Ltd.