Mycotoxins & Coffee Beans (Green, Roasted, Instant): Dark Roast May Reduce Exposure

by

Coffee is one of the most popular beverages globally, with billions of cups consumed every day.

However, coffee beans are prone to fungal infections that can produce harmful toxins known as mycotoxins.

Key findings:

  • Ochratoxin A (OTA) and aflatoxins were detected in commercial green, roasted, and instant coffee samples from Qatar.
  • Higher mycotoxin levels were found in instant coffee compared to roasted and green beans.
  • Traditional Arabic roasting and brewing methods significantly reduced OTA and aflatoxins in naturally contaminated beans. High roast coffee had the biggest mycotoxin reductions.
  • Volatile compounds from the bacterium Bacillus simplex strongly inhibited fungal growth and mycotoxin production in infected coffee beans.

Source: PLOS One 2021

Mycotoxins in Green, Roasted, and Instant Coffee

Researchers tested for the mycotoxins ochratoxin A (OTA) and aflatoxins in three forms of commercial coffee – green beans, roasted beans, and instant (soluble) powder.

  • All coffee types contained detectable levels of OTA, with instant coffee having the highest average concentration at 8.95 μg/kg.
  • 25% of roasted coffee exceeded the EU limit of 5 μg/kg OTA.
  • Aflatoxins were also found in all samples. Levels were highest in instant coffee (average 90.58 μg/kg) followed by roasted beans (33.61 μg/kg) and green beans (9.07 μg/kg).
  • The toxigenic fungi Aspergillus niger, A. flavus, and A. carbonarius were isolated from the green coffee samples.

These results indicate consumers may be exposed to significant amounts of mycotoxins from coffee, especially soluble instant types.

Processing methods that reduce mycotoxins in the final product are needed.

Traditional Coffee Roasting Reduces Mycotoxins

Researchers tested three traditional Arabic roasting methods ranging from light to dark roast on green coffee beans naturally contaminated with OTA or aflatoxins.

  • Roasting reduced OTA levels by 15-57% depending on roast intensity. Brewing provided additional reductions up to 43%.
  • High-temperature dark roasting had the biggest impact, lowering OTA by 64%.
  • Aflatoxins declined 32-62% after roasting, with darker roasts again showing greater reductions. Brewing further lowered aflatoxins by up to 10%.
  • In total, high roast plus brewing lowered OTA by 65% and aflatoxins by 62%.

These results demonstrate that traditional coffee processing, especially darker roasting, can significantly decrease mycotoxin levels in contaminated beans.

See also  Low Doses of Caffeine: One Cup of Coffee Alters Brain Waves to Enhance Cognition

Choosing dark roast coffee may lower consumer exposures.

However, roasting may not completely eliminate risks as substantial amounts can remain.

Volatile Bacterial Compounds Inhibit Fungi and Mycotoxins

As an alternative to roasting, researchers tested if volatile compounds from the bacterium Bacillus simplex could control fungal growth and mycotoxin production in infected coffee beans.

  • When placed near infected beans, B. simplex completely inhibited the growth of toxin-producing fungi including Aspergillus ochraceus and A. flavus.
  • Beans exposed to the bacterial volatiles contained up to 58% less aflatoxin and 54% less OTA than infected beans alone.
  • The researchers identified three antifungal volatile compounds produced by B. simplex – quinoline, benzenemethanamine, and 1-octadecene.

This demonstrates the potential for bacterial volatiles to biologically control mycotoxigenic fungi and lower mycotoxin contamination during coffee production and storage.

The compounds could provide an alternative to synthetic fungicides.

Further research is needed to test these under real-world conditions.

Mycotoxins & Coffee: Major Takeaways

Mycotoxins were detected in green, roasted, and instant coffee indicating a need to mitigate consumer exposures.

Traditional high-temperature roasting reduced ochratoxin A and aflatoxins in contaminated beans by over 60%.

Darker roasts appear to be more effective than lighter roasts.

Volatile compounds from Bacillus simplex strongly inhibited fungal growth and mycotoxin production when applied to infected coffee beans.

Further study is needed to optimize roasting and biocontrol conditions and confirm reductions under large-scale real-world coffee processing.

Research should also examine the effects of mycotoxin reduction on coffee flavor to ensure quality.

Regulatory limits may be needed for certain mycotoxins in coffee as they can reach concerning levels.

In conclusion, this research demonstrates that while mycotoxin contamination in coffee is common, traditional processing methods like roasting and emerging biological controls can potentially reduce levels and make coffee safer for consumers.

References