With an estimated 76 million illnesses attributable to food per year in the US, rinsing produce with washwater containing high doses of chlorine disinfectant is becoming increasingly important. However, chlorine can react with biomolecules in the produce to form chlorinated byproducts that are potentially cancer-causing. This research will identify these chlorinated byproducts, focusing on those that remain in the produce until eaten by consumers. The research will quantify byproducts formed when lettuce, carrots, tomatoes, apples and chicken are treated with chlorine-containing washwater under conditions used in produce packing facilities. Successful completion of this research will produce results that can be used to develop guidelines for chlorine doses that control foodborne illness while minimizing cancer risk. The results will also help maintain produce exports to countries concerned about these potentially cancer-causing byproducts in food.
Foodborne outbreaks linked to contaminated produce have heightened the importance of food disinfection in processing facilities. However, chlorine is known to react with organic matter to produce halogenated disinfection byproducts (DBPs) that are often toxic and even carcinogenic. Chlorinated DBP formation during food processing may be more significant than in drinking water, because food processing can involve 100-fold higher levels of both chlorine (~300 mg/L) and organic precursors. While food safety currently focuses on pathogens, this benefit must be balanced with the potential health impacts of DBP formation. The goal of this research is to characterize DBPs produced in foods from reactions of chlorine with the amino acids tyrosine and tryptophan, and unsaturated fatty acids; two of the four major biomolecular groups in food which are highly reactive with chlorine. The central hypothesis of this research is that chlorination will initially form halogenated tyrosines, tryptophans, and fatty acid halohydrin biomolecules, and soluble byproducts can be released during prolonged chlorination. The shorter chlorine contact times of food washing (~15 min) compared to drinking water chlorination (days) will favor higher yields of these initial biomolecule-based byproducts relative to the soluble byproducts. The corollary to the central hypothesis is that biomolecule-based byproducts will remain in food while soluble byproducts will partition to the washwater. These will be tested by comparing the yields of soluble byproducts and initial biomolecule-based chlorination byproducts in various systems including: 1) model proteins and triglycerides, 2) lettuce, carrots, tomatoes, apples, and chickens treated under conditions relevant to food disinfection, and 3) samples collected from food washing facilities. The cytotoxic potencies of the amino acid- and fatty acid-based byproducts will be determined and used to normalize measured concentrations of these byproducts in foods for comparison to previous evaluations of DBP toxicity in drinking water. Benefits to society resulting from this research include broadening participation in STEM through support of the dissertation research of an African American graduate student, engagement of under-represented minority undergraduates through an REU program, and the involvement of a high school science teacher and underrepresented high school students in summer research.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
