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Microwaves Inhibit Bread Mold

Bioeffects Seen

Carl M. Olsen · 1965

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Microwave radiation's proven ability to kill microorganisms demonstrates these frequencies have real biological effects on living systems.

Plain English Summary

Summary written for general audiences

This 1965 study investigated using microwave energy to control bread mold growth, testing whether microwaves could reduce populations of common fungi that spoil bread products. The research explored microwave radiation as an alternative to chemical preservatives like sodium propionate for extending bread shelf life.

Why This Matters

This early research reveals an important reality about microwave radiation that the food industry has long understood: these frequencies are biologically active enough to kill living organisms. While the study focused on beneficial applications for food preservation, it demonstrates that microwave energy at the frequencies used in our ovens, WiFi routers, and cell towers has measurable biological effects on living systems. The science shows that if microwaves can inhibit fungal growth and kill microorganisms, we should take seriously their potential effects on human cells and tissues. The fact that this antimicrobial property was being studied commercially in 1965 underscores how long we've known about the biological activity of these frequencies.

Finding

The numbers of viable spores of Aspergillus niger, Penicillium sp. and Rhizopus nigricans were greatly reduced by exposure to microwave energy. The numbers of colonies of Penicillium sp. from bread not treated with microwave was about 1,486 per PDA plate in the undiluted shaker suspension. Those treated with microwave had only about 0.143 colonies per plate. The numbers of colonies of Aspergillus niger from bread not treated with microwave was about 2,000 per plate. Those treated with microwave had only about 0.188 colonies per plate.

In their words

The numbers of viable spores of Aspergillus niger, Penicillium sp. and Rhizopus nigricans were greatly reduced by exposure to microwave energy. The numbers of colonies of Penicillium sp. from bread not treated with microwave was about 1,486 per PDA plate in the undiluted shaker suspension. Those treated with microwave had only about 0.143 colonies per plate. The numbers of colonies of Aspergillus niger from bread not treated with microwave was about 2,000 per plate. Those treated with microwave had only about 0.188 colonies per plate.

Figures from the Original Paper

Diagram extracted from the original research document.

diagramPage 3 - Figure 3 illustrates the survival of spores from three bread mold organisms after microwave treatment and untreated conditions.

Exposure Information

Specific exposure levels were not quantified in this study.

Cite This Study
Carl M. Olsen (1965). Microwaves Inhibit Bread Mold.
Show BibTeX
@article{microwaves_inhibit_bread_mold_g6463,
  author = {Carl M. Olsen},
  title = {Microwaves Inhibit Bread Mold},
  year = {1965},
  
  
}
No DOI on file for this study.

Quick Questions About This Study

Yes, this 1965 study specifically investigated microwave energy's ability to reduce populations of common bread molds including Penicillium, Aspergillus, and Rhizopus species. The research explored using microwaves as an antimicrobial treatment for food preservation.
The baking industry wanted alternatives to chemical preservatives like sodium propionate, which makes up 0.1% of bread dough. Consumer objection to food additives was growing, making microwave treatment an attractive preservative-free option for extending shelf life.
The three most troublesome bread mold fungi are Penicillium species, Aspergillus species, and Rhizopus nigricans. These cosmopolitan fungi are prolific spore producers that spread through airborne contamination, especially in bakery environments with abundant nutrients.
Bread contamination primarily occurs during cooling after baking and during the slicing operation. Once wrapped, the loaf creates an incubation chamber with 35% moisture content and enclosed nutrients that promote rapid fungal growth.
While sodium propionate chemically inhibits fungal growth through pH manipulation, microwave energy appears to work through direct lethal effects on microorganisms. This physical approach could eliminate the need for chemical additives in bread products.