Bread is a common medium for mold growth.


What is Mold?

Molds are multicellular fungi which are morphologically more complex than bacteria or yeast (single-celled fungi). In foods, they are one of the main causes of food spoilage and foodborne diseases.

  • Molds are non-motile, filamentous, and branched microorganisms.
  • Their cell walls are composed of cellulose, chitin or a combination of both.
  • They typically grow in the form of fine branching filaments called hyphae which can aggregate to form a mycelium.1


Molds are opportunistic living microorganisms that feed on organic matter, therefore their ability to  reproduce in foods. However, they can live in virtually any ecosystem or environment.

In the food industry, these microorganisms are usually seen as enemies. Yet similar to some bacteria, they can be beneficial for certain applications and are used to produce food ingredients and pharmaceutical products.

Mold in the bakery industry

In the bakery industry, along with staling, they are considered the main limiting factors for controlling products shelf-life. Molds that cause spoilage in bread include:

Mold Appearance or defect
Aspergillus niger Black
Aspergillus glaucus Green, grey-green
Aspergillus flavus Olive green
Penicillium sp. Blue-green
Rhizopus nigricans Grey-black
Mucor sp. Grey
Neurospora sitophila Pink

High-speed bakeries strive to keep mold away from their operations and products, especially in high water activity baked goods such as bread and buns. The following table highlights some of the strategies used in bakeries to prevent mold growth (or avoid their development):

Control factors Comments Best control levels / Strategies
Water availability (aw) Lower water activity can effectively slow down mold growth. Formulate bread to water activity levels below 0.95

Ingredients that help lower aw:

  • Polyols, glycerol
  • Small proteins (hydrolyzed proteins)
  • Sugars
  • Salt
pH Low pH or acidic environments can limit mold growth. Acidic conditions can also impact the performance of mold inhibitors. Lower the product pH to below 5.6

Low pHs can be achieved through:

  • Long fermentations
  • Use of lactic acid bacteria (LAB) (added or from sourdough)
  • Acidulants (weak organic acids, acid salts)
  • Fermented / cultured...

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