Influence of Treatments with Heat, Chlorine Dioxide, or Ethylene Oxide on Microbiological Load and Parthenolide Content in Feverfew Leaves

Abstract

Studies were conducted to determine the effects of heat treatments or fumigation with either chlorine dioxide (ClO₂) or ethylene oxide (EO) gas on microbiological load and parthenolide content in feverfew (Tanacetum parthenium L. Schultz Bip) leaves. Treatments were applied postharvest in three separate studies. Heat treatments included dry heat (60°C for 48 h), steam heat (121°C for 20 min), or microwave heat (100%, 1200 W, 3 min). The ClO₂ study included three concentrations: 2.2, 5, or 50 mg ClO₂ L⁻¹. The EO study included two concentrations: 4% or 12% v/v. Before and after each treatment, leaf powder was used to enumerate aerobic, coliform, and Escherichia coli counts using 3M Petrifilm count plates. Steam heat effectively eliminated microbiological contamination but reduced parthenolide content by 50%. Dry heat and microwave heat treatments both reduced microbiological load by 40%. Parthenolide content was reduced 10% by dry heat but was not affected by the microwave heat treatment. The ClO₂ gas concentrations up to 5 mg ClO₂ L⁻¹ had no effect on microbial or parthenolide contents compared to the control. The 50 mg ClO₂ L⁻¹ concentration reduced the microbial content by 60% but also lowered the parthenolide content by 30%. Though 4% EO gas concentration had no effect on microbial load or parthenolide content, 12% gas concentration killed all the microbes present without affecting parthenolide content. These results suggest that fumigation with EO and microwave heat both have potential for use as sterilants for feverfew without affecting apparent medicinal quality.

KEYWORDS:

• postharvest storage
• microbial safety
• sesquiterpene lactone
• medicinal herb

We thank Dr. Bob Dufault and Brian Ward for providing fresh feverfew materials and for Brian's support.