Identifier

etd-07102008-105943

Degree

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

Document Type

Dissertation

Abstract

This study assessed the efficacy of the ozonation process in degrading aflatoxin in corn, and investigated the chemical reaction between aflatoxin and gaseous ozone. Ozonation (12-13 wt%) totally degraded aflatoxin B1 in a model system. Conversion of aflatoxin into polar compounds was observed during ozonolysis of 100 µg aflatoxin B1 in an aqueous environment and in solid form. Seven intermediate reaction products were separated by two-dimensional thin layer chromatography. HPLC analysis of ozonated AFB1 revealed the presence of six major peaks. MALDI-MS analysis detected compounds that have higher molecular weights than AFB1. The dichloromethane fraction contained compounds with molecular ion peaks at 459 and 439 m/z while the water fraction contained compounds with molecular ion peaks at 475 and 494 m/z, after ozonation for 50 sec and 60 sec, respectively. Biosynthesis of [14-C]-labeled aflatoxin B1 by Aspergillus flavus (A53, C50Aa) and sodium acetate-1,2-[14C] as a precursor yielded 339 µg of [14C]-AFB1 with a specific activity of 1.06 µCi/µmol (7548 dpm/µg). Corn kernels inoculated with Aspergillus flavus (A53, C50Aa) resulted in the production of grains contaminated with aflatoxin B1 (7452 ng/g) and aflatoxin B2 (704 ng/g). Modification of AFB1 after treatment with gaseous ozone was determined using [14C]-labeled AFB1. Ozonated and non-ozonated corn spiked with [14C]-AFB1 were evaluated and compared through a series of extraction, partition, and digestion procedures. Ozonation (9-10 wt%) resulted in 74% and 44% reduction of AFB1 and AFB2 levels, respectively. Radioactivity measured by liquid scintillation counting showed an increase in the percentage of radioactivity in more polar and aqueous solvents from ozonated corn compared with non-ozonated corn. These results suggested the formation of more polar and/or water soluble aflatoxin-related compounds from the reaction of ozone with AFB1. Based on these results, it is postulated that ozone attacked the double bond in the C8-C9 position and converted aflatoxin B1 into an aldehyde.

Date

2008

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

King, Joan M.

Included in

Life Sciences Commons

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