ASCORBIC ACID DEGRADATION KINETICS DURING CONVENTIONAL and OHMIC HIEATING

Abstract

Ascorbic acid (vitamin C) degradation during electrical and conventional heating was studied to determine if the presence of an electric field altered the rate of degradation. Experiments were peiformed using a static ohmic heating apparatus, and heating histories were matched using applied voltage in the electrical case and hot oil in the conventional case. A statistical analysis showed that electric field has no significant effect on ascorbic acid degradation. Pseudo first order degradation kinetics were observed for both conventional and ohmic cases. the activation energy and frequency factor for the conventional case was 12.6 kcal/mol and 19.95 × 105 min‐1, respectively; for the ohmic case, values were 12.5 kcal/mol and 19.59 × 1O5 min‐1. the effect of electrolysis on ascorbic acid degradation was also examined. Gas production and dissolution appeared

Temperature dependent electrical conductivities of fruit purees during ohmic heating

“…H 2 or O 2 gas). Lima, Heskitt, Burianek, Nokes, and Sastry (1999) and Assiry, Sastry, and Samaranayake (2003) concluded that electrolytic reactions were not evident with specially coated electrodes or in the use of high frequency power. zFurthermore, Castro et al (2004) explained that in an un-pressurized heater, if air is occluded in the sample, the air bubbles will expand with temperature, with the pressure remaining constant.…”

Thermal degradation kinetics of nutrients in orange juice heated by electromagnetic and conventional methods

“…With reference to kinetics of destruction of vitamin C in food systems, different buffer systems and real products with different processing methods have been examined (Frias, Oliveira, Cunha, & Oliveira, 1998;Hussein et al, 2000;Lathrop & Leung, 1980;Lee & Nagy, 1988;Lima, 1997;Lima, Heskitt, Burianek, Nokes, & Sastry, 1999;Rao, Lee, Katz, & Cooley, 1981;Robertson & Samaniego, 1986;van den Broeck, Ludikhuyze, Weemaes, Loey, & Hendrickx, 1998). Many of these studies are related to the storage of pasteurized juices or higher temperatures of processing.…”

Non-enzymatic browning and ascorbic acid degradation of orange juice subjected to electroreduction and electro-oxidation treatments

“…The relationship between browning, oxygen content and Lascorbic acid has been discussed by other researchers (Lee & Nagy, 1988;Lima, Heskitt, Burianek, Nokes, & Sastry, 1999). Increasing the levels of dissolved oxygen in the juice by electrolysis caused a substantial increase in the development of browning reactions, due to the additional incorporation of dissolved oxygen in the juice.…”