MadSci Network: Microbiology

Re: Bread mold experiment acceleration

Date: Thu Jan 7 10:04:37 1999
Posted By: Charlene Wolf-Hall, Faculty, Food Science, North Dakota State University
Area of science: Microbiology
ID: 915468099.Mi

Wow, 4 week old bread with no mold - that's pretty well preserved I would 
say.  One of the most widely used preservatives in breads is propionic 
acid.  This is usually used in a calcium or sodium salt form to improve the 
solubility in the food system.  Propionic acid is an organic acid that 
shows antifungal properties, but does not affect the growth of yeast.  This 
is why it is used in bread - it will inhibit mold growth but allow the 
yeast fermentation to go unabated.  Propionic acid has its best antifungal 
activity at low pHs, so that may be why you see some growth on your "high 
pH" bread.  Molds, in general, will grow over a wide range of pHs.  In 
fact, to isolate mold from a food sample the medium we grow it on may be 
have the pH lowered to inhibit bacterial growth and allow mold growth.  I 
would suggest that you retry this experiment with some fresh bakery or 
home-made bread that does not contain preservatives.  It should only take 
about a week before you see good mold growth on these.  I would also 
suggest that you dust the surface very lightly with some soil to make sure 
you are incoulating the bread with mold spores.  Also, keep the bread moist 
by putting each slice in a container along with a damp piece of paper 
towel - molds need some water to grow.  Hope that helps and good luck in 
the science fair.

Reference:  Modern Food Microbiology. 1996.  James M. Jay.  5th Edition.  
Chapman & Hall.  New York. 

Current Queue | Current Queue for Microbiology | Microbiology archives

Try the links in the MadSci Library for more information on Microbiology.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-1998. All rights reserved.