Non-enzymatic browning and ascorbic acid degradation of orange juice subjected to electroreduction and electro-oxidation treatments Patrick Fustier ⁎, François St-Germain, François Lamarche, Martin Mondor Food Research and Development Center, Agriculture and Agri-Food Canada, 3600 Casavant Blvd. West, Saint-Hyacinthe, Québec, Canada, J2S 8E3 abstract article info Article history: Received 1 April 2011 Accepted 28 July 2011 Editor Proof Receive Date 7 September 2011 Keywords: Juice Electroreduction Electro-oxidation Redox potential Ascorbic acid Non-enzymatic browning Orange juice was submitted to electroreduction and electro-oxidation treatments prior to pasteurization and compared to a control juice for oxido-reduction potential (ORP), dissolved oxygen and ascorbic acid contents. Evolution of non-enzymatic browning reactions and ascorbic acid degradation was evaluated at 4, 21 and 37 °C storage temperatures. Electroreduction treatment of the juice at 6 V (cell length of 1.58 cm) created a substantial reducing reservoir as ORP decreased from + 161 to -406 mV and it decreased dissolved oxygen by more than 90% of its initial content while the ascorbic acid content was not altered. In contrast, the electro- oxidation treatment raised the final ORP of the juice by 15 to 20 mV, increased substantially the dissolved oxygen content and decreased significantly the ascorbic acid retention. Electro-oxidation treatment resulted in an increase of non-enzymatic browning reactions during storage. Both the control and electroreduced juice showed very similar trends in ascorbic acid degradation over the 3 months storage period whereas the anions, cations and amino acids profiles of the juice remain unchanged. Contrary to the control and electroreduced juices, the electro-oxidation process decreased severely the orange flavor intensity and character being characterized as musty with sour-bitter aftertaste. Industrial relevance of electrolytic treatment to modulate the oxidation-reduction potential of comestible food systems: The limitation of shelf life imposed on comestible beverage systems (juice, beer, milk, wine, etc.) is an important and common issue for food manufactures and consumers. The shelf life is shortened by the time- dependent development of off-flavors, browning, change of colors, and deterioration of nutrients, caused by the oxidative reactions of chemical and nutrient components in the food systems. Consequently, the food is becoming unattractive to consumers. The electrochemical technique by means of an electrochemical cell has the potential in inhibiting or accelerating these deterioration reactions through reduction or oxidation of organic and inorganic compounds inherent to the products, as well as effectively controlling the oxygen content in the products. This technique can be used as an alternative to the deliberate addition of chemical compounds (sulfite and others reducing substances) to inhibit the deterioration reactions (electroreduction) as well as to accelerate the aging process of the comestible products via accelerated oxidation process (electro-oxidation). Crown Copyright © 2011 Published by Elsevier Ltd. All rights reserved. 1. Introduction Non-enzymatic browning of citrus beverages is a major quality deterioration factor. More than one type of mechanism may be involved in the formation of brown pigments: the reactions between amino acids and reducing sugars (Maillard reactions), the aerobic and anaerobic degradation of the ascorbic acid (Azandouz & Puigserver, 1999; Johnson, Braddock, & Chen, 1995; Kacem, Cornell, Marshall, Shiereman, & Matthews, 1987; Sakai, Watanebe, Takai, & Hasagawa, 1987) and further reactions of the carbonyl compounds via aldol condensation or reactions with the amino acids to yield brown pigments. Sugar solution at appropriate pH or with a low concentra- tion of amino acids and the phenolic compounds can also undergo oxidation to yield brown pigments (Ciliers & Singleton, 1989). These undesirable and complex reactions lead to the formation of a wide variety of end-products including organic acids, furans, ketones, pyrroles, and others compounds. Some of these compounds contrib- ute to off-flavors of juice (Nagy, Rouseff, & Lee, 1989). Most of these reactions are correlated with the dissolved oxygen content of the product. The addition of sulfur containing amino acids and sulfite which have the ability to act as a reducing agents and/or oxygen scavengers (Molnar-Perl & Friedman, 1988; Sapers, 1993) is among the procedures that can inhibit these reactions. These compounds act by causing the chemical reduction of the pigment precursors, but this effect is temporary as they can be oxidized irreversibly in the reaction. Additionally, they are under close scrutiny by the Food and Drug Administration. Innovative Food Science and Emerging Technologies 12 (2011) 491–498 ⁎ Corresponding author. Tel.: +1 450 768 3256; fax: +1 450 773 8461. E-mail address: Patrick.fustier@agr.gc.ca (P. Fustier). 1466-8564/$ – see front matter. Crown Copyright © 2011 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ifset.2011.07.014 Contents lists available at SciVerse ScienceDirect Innovative Food Science and Emerging Technologies journal homepage: www.elsevier.com/locate/ifset