Date of Award:

5-2010

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Committee Chair(s)

Allen J. Young

Committee

Allen J. Young

Committee

Jeffrey O. Hall

Committee

Jong-Su Eun

Committee

Kenneth L. White

Abstract

Aflatoxin M1 (AFM1) is frequently found in milk and dairy products. It is a metabolite formed in cows from aflatoxin B1 (AFB1), contained in animal feeds. In cheese production AFM1 distributes between curds and whey. In this study, cows were fed 64 µg/AFB1/d for the high treatment, and 5 µg/AFB1/d for the low treatment, to obtain milk contaminated with AFM1 over the 0.5 µg/L and under 0.05 µg/L restrictions, respectively. Cheese was manufactured with milk contaminated with AFM1 at 0.8 and 0.03 ìg/kg by the higher and lower treatment, respectively. Two commercial cheeses were elaborated: a hard-aged cheese (cheddar cheese) and soft high moisture cheese (fresco cheese) to evaluate whether the cheese type had any impact on AFM1 analysis. AFM1 was extracted from cheese using immunoaffinity columns. Analyses were carried out by using high pressure liquid chromatography (HPLC) as the reference method and fluorometry as a method of validation. Analysis was by 2-way fixed factor analyses. AFM1 was detected in all samples by both methods of analysis. There were no detectable statistical differences between cheese types (P > 0.05). AFM1 content was significantly different between the high and low concentration of AFB1 used to make the cheese type (P < 0.05). Our regression model shows a linear relationship between fluorometry and HPLC methods; R-2 = 0.9141 from cheddar cheese and R-2 = 0.9141 from fresco cheese. There were no statistical differences between methods of analysis (P > 0.05). Carryover of AFM1 in cheese detected by fluorometry in cheddar cheese was 163% and 80% for high and low treatments, respectively, and in fresco cheese was 119 and 133 for high and low treatments, respectively. These carryovers are below that reported in the literature. Results suggest that fluorometry is a simple and reliable AFM1 detection method for screening samples of complex matrices such as cheese.

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This work made publicly available electronically on August 30, 2010.

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