A Focus on Chlorine Dioxide: The Promising Food Preservative
Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA
- *Corresponding Author:
- Zhao Chen
Department of Biological Sciences, Clemson University
Clemson, SC 29634, USA
E-mail: [email protected]
Received date: February 20, 2017; Accepted date: February 21, 2017; Published date: February 27, 2017
Citation: Chen Z (2017) A Focus on Chlorine Dioxide: The Promising Food Preservative. J Exp Food Chem 3:e107. doi: 10.4172/2472-0542.1000e107
Copyright: © 22017 Chen Z. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Chlorine dioxide (ClO2) is an unstable green-yellowish gas with an irritating odor . In water, ClO2 exists as free radicals and as a powerful oxidizing agent, it reacts easily with reducing agents. The end products of ClO2 reactions are chloride (Cl-), chlorite (ClO-), and chlorate (ClO3-) . Chlorine dioxide is a promising food preservative as a substitute for chlorine (Cl2) because unlike Cl2, it does not react with organic matters in foods to form harmful organohalogen byproducts . Chlorine dioxide can be used in aqueous and gaseous phases. Studies have demonstrated that both aqueous and gaseous ClO2 are effective sanitizing agents which can inactivate a broad spectrum of microorganisms, such as bacteria, fungi, viruses, protozoa, and algae .
The US Environmental Protection Agency (EPA) has approved the use of ClO2 as a disinfectant for potable water with a monitoring requirement of 1 ppm ClO- in the treated water . The US Food and Drug Administration (FDA) has also allowed the use of ClO2 as a bactericidal agent in poultry processing water at a level of 3 ppm residual ClO2 . Meanwhile, aqueous ClO2 has been approved by the US FDA for sanitizing fruits and vegetables at concentrations not exceeding 3 ppm residual ClO2 .
Studies have proved the effectiveness of ClO2 treatment on prolonging the shelf-life and maintaining the storage quality of a wide variety of foods. Chlorine dioxide has been reported to inhibit the activities of some browning-related enzymes to retain the stability of foods. It has been found to be able to inhibit polyphenol oxidase (PPO) activity in Golden Delicious apple , lotus root , and asparagus lettuce , and peroxidase (POD) activity in asparagus lettuce . However, there are some conflicts among findings of different authors. Browning caused by ClO2 treatment has also been observed in various foods, including shredded lettuce, peach, and apple [11-14]. To inhibit the browning of white cabbage, Gómez-López et al.  applied cysteine solution prior to ClO2 treatment.
Chlorine dioxide can possibly react with carbohydrates, lipids, and proteins in foods . It is also known that ClO2 can react with phenols . As some phytochemicals in foods are categorized as phenolic compounds, ClO2 is supposed to have an impact on these compounds. Similarly, since ClO2 is a strong oxidant, some reducing components as human nutrients (e.g. ascorbic acid) in foods could be readily oxidized. However, published scientific literatures have shown limited negative effect of ClO2 on these nutrients in various foods, such as salmon, red grouper, green bell pepper, iceberg lettuce, white cabbage, plum, and mulberry [18-23].
Several authors have reported the bleaching or white blushing in lettuce, green bell pepper, tomato, strawberry, blueberry, and mulberry as a consequence of ClO2 treatment [12,19,24-27]. Nonetheless, sufficient evidence has demonstrated that ClO2 generally has no deleterious effect on the sensory quality of foods .
Studies have been carried out to investigate the levels of chemical residues in foods after ClO2 treatment. The application of aqueous ClO2 followed by a water rinse did not leave any residues of ClO2, ClO-, or ClO3- in mulberry . For ClO2 in gaseous phase, Tsai et al.  could not detect residues of ClO2, ClO-, or ClO3- in potatoes stored with ClO2 gas. Trinetta et al.  also reported that after ClO2 gas treatment, there was minimal to no detectable chemical residues in selected fruits and vegetables. In the study of Kim et al. , low levels of ClO3- were detected in ClO2-treated sea scallop, mahimahi, and shrimp, which is not expected to pose any health risks to consumers after its conversion to Cl- during cooking. And ClO- residue was not found in any of the ClO2-treated seafoods.
Regarding toxicity, ClO2 is not classified as a carcinogen to human by the International Agency for Research on Cancer . No formation of toxic chlorinated byproducts is one significant advantage of ClO2 as food preservative over Cl2. It has been reported by López- Gálvez et al.  that washing lettuce with 3.7 mg/L aqueous ClO2 for 30 min did not produce detectable levels (<5 mg/L) of trihalomethanes (THMs), whereas the formation of THMs could be detected in process water and lettuce in which sodium hypochlorite (NaClO) was applied under some conditions.
In conclusion, as a strong oxidizing agent, ClO2 has the potential to be an alternative to Cl2 to maintain the postharvest storage quality and enhance the microbiological safety of foods, without posing any health risks to consumers.
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