Effect of thermal treatment on generation of reactive oxidative species (ROS) from sugar solutions

Abstract

Thermal treatment is the most widely used method of food preservation. However, it also results in losses in some quality due to undesirable chemical reactions. Sugars such as fructose in aqueous solution have been shown to accelerate the degradation of some food components such as ascorbic acid and anthocyanin (Cao et al., 2009; Rojas & Gerschenson, 2001), possibly due to oxidation. However, the mechanism of underlying this deleterious effect of sugars during thermal treatment is unclear. Previous studies have shown that monosaccharaides such as fructose and glucose can be autoxidized and generate reactive oxidative species (ROS) under physiological condition in the presence of oxygen and metal ions (P. Thornalley, Wolff, Crabbe, & Stern, 1984). However, information on ROS generation at elevated temperature is limited. The overall hypothesis for this project is to determine that sugars generate similar oxidative compounds at elevated temperatures. The objective of this study is to identify the generation of oxidative species during thermal treatment of sugars, and to understand the mechanism of the oxidative reactivity. To achieve this purpose, I measured the levels of oxidative species such as hydrogen peroxide and singlet oxygen generated from sugar solutions during thermal treatment. The effects of various factors such as types of sugars, fructose, glucose and sucrose; temperature, pH and the presence of phosphate buffer were investigated. To study the role of oxygen in oxidative species generation during thermal treatment of sugars, the consumption of dissolved oxygen by sugar solution during thermal treatment was also investigated. Further, acids generation during thermal treatment of sugar solution were measured and confirmed by pH measurement and acid-base titration. This study demonstrated that ROS are generated from sugar solutions during thermal treatment. The results suggested that dissolved oxygen in solution is crucial for ROS generation. Elevated temperature, lower pH and the presence of phosphate buffer showed a significant promotion effect on ROS generation from sugars during thermal treatment. The results from this study indicated that ROS generation from thermal treatment of sugars shared a similar mechanism as sugar autoxidation. We believe that the results of this study will provide methods to understand better the oxidation mechanism of sugar solutions and will be useful to improve the thermal treatment of food products containing sugars.%%%%M.S., Food Science – Drexel University, 2014