Structures of Degradation Products and Degradation Pathways of Aflatoxin B₁ by High-Voltage Atmospheric Cold Plasma (HVACP) Treatment

Abstract

High-voltage atmospheric cold plasma (HVACP) is a novel nonthermal decontamination technology that has potential for use in the food industry. In this study, HVACP was applied to treat pure aflatoxin B₁ (AFB₁) powder on a glass slide. AFB₁ was degraded by 76% using a 5 min HVACP treatment in air having 40% relative humidity. The degradation products of AFB₁ were separated, and their molecular formulas were elucidated using liquid-chromatography time-of-flight mass spectrometry (HPLC-TOF-MS). Six main degradation products were observed. The structures of the degradation products were further clarified via orbitrap mass spectrometry by means of fragmentation of the parental ions. Two degradation pathways were proposed on the basis of the structure of the degradation products. Among the six degradation products, two were ozonolysis products of AFB₁. The appearance of the other four degradation products indicates that AFB₁ was degraded by other reactive species besides ozone that were generated during HVACP treatment. Reactive oxygen gas species are suggested as the major agents for aflatoxin degradation during HVACP treatment. Two degradation pathways of AFB₁ by HVACP treatment were proposed. One pathway involves reactions in which H^•, OH^•, CHO^• radicals are added. The other involves epoxidation by HO₂^• radicals and oxidation of AFB₁by the combined effects of the oxidative species OH^•, H₂O₂, and O₃. According to the structure-bioactivity relationship of AFB₁, the bioactivity of the AFB₁ samples subjected to HVACP treatment is significantly reduced because of the disappearance of the C8═C9 double bond in the furofuran ring in all of the major degradation products as well as the modification of the lactone ring, cyclopentanone, and the methoxyl group.