Chloroxyanion Residue Quantification in Cantaloupes Treated with Chlorine Dioxide Gas

Abstract

Previous studies show that treatment of cantaloupes with chlorine dioxide (ClO2) gas at 5 mg/liter for 10 min results in a significant reduction (P < 0.05) in initial microflora, an increase in shelf life without any alteration in color, and a 4.6-and 4.3-log reduction of Escherichia coli O157:H7 and Listeria monocytogenes, respectively. However, this treatment could result in the presence of chloroxyanion residues, such as chloride (Cl–). chlorite (ClO2–), chlorate (ClO3–), and perchlorate (ClO4–), which, apart from chloride, are a toxicity concern. Radiolabeled chlorine dioxide (36ClO2) gas was used to describe the identity and distribution of chloroxyanion residues in or on cantaloupe subsequent to fumigation with ClO2 gas at a mean concentration of 5.1 ± 0.7 mg/liter for 10 min. Each treated cantaloupe was separated into rind, flesh, and mixed (rind and flesh) sections, which were blended and centrifuged to give the corresponding sera fractions. Radioactivity detected, ratio of radioactivity to mass of chlorite in initial ClO2 gas generation reaction, and distribution of chloroxyanions in serum samples were used to calculate residue concentrations in flesh, rind, and mixed samples. Anions detected on the cantaloupe were Cl– (~90%) and ClO3– (~10%), located primarily in the rind (19.3 ± 8.0 μg of Cl–/g of rind and 4.8 ± 2.3 μg of ClO3– /g of rind, n = 6). Cantaloupe flesh (~200 g) directly exposed to 36ClO2 gas treatment showed the presence of only Cl residues (8.1 ± 1.0 μg of Cl– /g of flesh, n = 3). Results indicate chloroxyanion residues Cl– and ClO3– are only present on the rind of whole cantaloupes treated with ClO2 gas. However during cutting, residues may be transferred to the fruit flesh. Because Cl– is not toxic, only ClO3– would be a toxicity concern, but the levels transferred from rind to flesh are very low. In the case of fruit flesh directly exposed to ClO2 gas, only nontoxic Cl was detected. This indicates that ClO2 gas that comes into contact with edible flesh would not pose a health concern.