Distribution and chemical fate of chlorine dioxide gas during sanitation of tomatoes and cantaloupe

Authors: Smith, David; Giddings, John; Herges, Grant; ERNST, WILLIAM - Ica Tri-Nova Corporation, Llc

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/22/2015
Publication Date: 11/3/2015
Citation: Smith, D.J., Giddings, J.M., Herges, G.R., Ernst, W.E. 2015. Distribution and chemical fate of chlorine dioxide gas during sanitation of tomatoes and cantaloupe [abstract]. Recent Advances in Food Analysis. p. 140.

Interpretive Summary: Bacteria that cause human disease may be present on fresh produce after harvest. Although washing is sometimes effective at removing these bacteria from produce, especially those having smooth surfaces, washing is ineffective at removing bacteria from rough, scarred, or damaged produce surfaces. Chlorine dioxide gas is highly effective at eliminating pathogens and rot organisms on smooth or rough surfaced fruits and vegetables without the use of copious amounts of water. The purpose of this study was to describe the fate and residues deposited on tomatoes and cantaloupe after chlorine dioxide sanitation. Data generated by the study clearly demonstrate that under the proper sanitation conditions chlorine dioxide is transformed to chloride ion and does not leave undesirable residues in edible portion of produce.

Technical Abstract: A series of studies was conducted to establish the 1) distribution and chemical fate of 36-ClO2 on tomatoes and cantaloupe; and 2) the magnitude of residues in kilogram quantities of tomatoes and cantaloupe sanitized with a slow-release chlorine dioxide formulation. Tomatoes and cantaloupe were respectively treated with 50 and 100 mg 36-ClO2 per kg of mass for 2-h durations in sealed glass containers exposed to light. Radioactive residues were concentrated on reaction vessel walls and on the stem-scar area of tomatoes, representing 25-36% of the total 36-ClO2 generated; cantaloupe rind contained 52% of the total 36ClO2 produced. Edible flesh of cantaloupe did not contain detectable radioactive residues. Radioactivity in tomato tank rinses was composed of 36Cl-chloride, 36Cl-chlorate, and 36Cl-perchlorate with the same ions occurring in tomato serum, but with 36Cl-chloride predominating (>80%). In cantaloupe, radioactive residues were not detectable in edible flesh and insufficient residue was present in seed bed for speciation. Cantaloupe rind contained mostly chloride ion, with lesser amounts of chlorate and with perchlorate occurring just above detection levels. Chlorite ion was not present in rinse fractions, or in tomato or cantaloupe homogenates. 36Cl-Chlorite added to tomatoes at high levels (131 µg/g) was completely transformed to 36Cl-chloride (98.3%) and 36Cl-chlorate (1.7%). Subsequent studies with unlabeled ClO2 gas unequivocally demonstrated that the major variable influencing the formation of perchlorate and chlorate during ClO2 generation was the presence of light. Therefore kilogram quantities of tomatoes and cantaloupes were sanitized with 50 and 100 mg ClO2, respectively, and residues determined in edible and inedible fractions using a slow-release ClO2 formulation. Sanitation experiments were conducted in the dark and residues in homogenates were quantified using LC-MS-MS methods. Chlorate residues were not quantifiable (LOQ, 60 ng/g) in control or treated tomatoes and perchlorate residues (9 ng/g) were similar (P > 0.05) in control and treated groups. In cantaloupe edible flesh, chlorate residues were not detectable (LOD 30 ng/g) and perchlorate residues were below the LOQ (1.5 ng/g); cantaloupe rind + edible flesh, however contained 1300 ± 250 ng/g of chlorate with perchlorate residues (2.2 ± 0.2 ng/g) being similar (P > 0.05) to control cantaloupe (1.9 ± 0.03). Collectively these results suggest that slow-release ClO2 gas could be a safe and effective tool to prevent the contamination of produce with pathogenic bacteria.