Date of Award


Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)


Food Science and Human Nutrition


Beth L. Calder

Second Committee Member

Vivian Chi-Hua Wu

Third Committee Member

Jason Bolton


Fiddleheads, a wild edible green, have been associated with foodborne illnesses possibly from improper cook methods. Cooking recommendations are available, but are currently based on historical and not scientific data. The purposes of these studies were to investigate natural microbial characteristics of raw fiddleheads, to determine if microbial levels and heavy metal concentrations vary depending on location and to determine thermal processing effects on microbial load and quality of fiddleheads.

Fiddleheads were harvested from the flood zones of four rivers and streams and woodland sites in Maine. Two separate studies were conducted, fresh and cooked, and all samples were analyzed for E. co/i/coliforms, aerobic plate counts (APCs), Staphylococcus aureus and yeast/molds utilizing 3M Pertrifilms®. In the cook study, flood zone samples were combined to create a composite sample. Fiddleheads were either steamed or boiled (100°C) for 0 (control) 2, 5, 10 and 15 minutes. Texture and color analyses were also performed on all cooked fiddlehead samples. Heavy metal analyses (ICP MS) were conducted on both raw and 10-minute cooked samples. Data were analyzed utilizing one and multi-way ANOVA (p<0.05).

Fresh fiddlehead APCs ranged from 5.2-6.9 log cfu/g. Fresh fiddleheads from the Wesserunsett Stream and Kennebec River samples were significantly (p<0.05) lower than the other samples. No E. coli or yeast colonies were detected in fiddlehead samples. Mold counts varied from 3.9-5.8 log cfu/g, but no significant differences between samples were observed. Coliforms ranged from 0.3-5.6 log cfu/g and the Penobscot River fiddlehead samples had significantly higher coliform levels than other sample sites. Staphylococcus aureus counts ranged from 0.4-2.6 log cfu/g, but the Penobscot River fiddlehead sample had significantly lower Staphylococcus aureus counts than all other samples.

The cook study showed substantial reductions of all microorganisms (reduced to 1-2 log cfu/g or less for most treatments) after the 2 minute cook treatments (boil and steam). Overall, boiling and steaming appeared effective in reducing microbes; therefore, the recommendations outlined in the University of Maine Cooperative Extension Bulletin #4198, appear to be adequate. Sauteing and microwaving fiddleheads would still not be recommended cook methods due to the high microbial load of fiddleheads.

As expected, shear force (N) significantly decreased as cook time increased, as fiddleheads softened over cook time. However, the fiddleheads cooked at the 10 minute boil and steam and 5 minute boil had similar texture results. The 10 minute boil resulted in significantly less green and more yellow color attributes versus the control. The 2, 5 and 10 minute boiled fiddleheads were significantly lighter in color than control.