Date of Award

1999

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

First Advisor

Douglas L. Park

Abstract

Aflatoxins are the secondary metabolites of Aspergillus flavus and their presence in food and feed crops is unavoidable. This study evaluates the antimutagenic properties of phytic and linoleic acids in aflatoxin-affected food. A reduction in the number of revertants was a function of an increased concentration of phytic/linoleic acids and phosphotidylinositol in the Salmonella/microsomal mutagenicity assay (tester strains TA-100 and TA-98) with and without metabolic activation (S-9). Linoleic acid (10 and 100 mug/plate) and phosphotidylinositol (25mug/plate) were antimutagenic against most of the mutagens tested. Although a reduction in the number of revertants was observed in the phytic acid treatments, the results, however, do not suggest phytic acid as antimutagenic in this assay. The inhibition of AFB1 biosynthesis in the A. flavus inoculated Czapek-Dox liquid medium was observed as the concentration of phytic acid was increased in a 25 day study. A complete inhibition of AFB 1 production was recorded at phytic acid levels of 0.5 and 1 mg/100ml. The role of metal ions was also tested under similar conditions. In the absence of Fe++ and Zn++ ions, a complete inhibition of AFB1 production was observed; however, Cu++ and Mg++ ions did not exhibit the same response. In a 35 day storage study of corn the aflatoxin levels in the A. flavus inoculated ground and whole kernels were higher than the treatments. The reduction in the AFB1 levels was observed after 14 days of inoculation in both the treatment and controls. Phytic acid extended the most reduction among the treatments regardless of substrate type; however, not a complete inhibition in the biosynthesis of AFB1 was exhibited. The production of AFB1 and AFB2 was significantly lower (>50%) than the Aspergillus-dependent and -independent controls. The production of AFB1 in linoleic acid-treated corn was also found significantly lower (>50%) than the controls. No such observations were recorded in the combination treatment of phytic and linoleic acid. However, the production of AFB1 was like the linoleic acid treatment. Phytic acid and linoleic acid have been reported as antimutagenic in vitro. More research is warranted to evaluate their potential antimutagenic role in vivo.

ISBN

9780599548558

Pages

239

Share

COinS