MadSci Network: General Biology

Re: I like to bake bread and of course I use no preservatives, if I use more ye

Date: Thu Jan 17 17:26:09 2002
Posted By: Charlene Wolf-Hall, Faculty, Food Science
Area of science: General Biology
ID: 1011290191.Gb

Hi Lyn,

The answer depends on what you mean by "fresh".  Bread usually goes bad 
either by staling, which involves the starch in the bread, or by spoilage 
from microorganisms like molds.  

The yeast is added to bread dough because it produces carbon dioxide, which 
forms bubbles in the stretchy wheat proteins in the bread dough, making the 
dough rise and giving desired "loaf volume".   The yeast also adds aroma 
and flavor to the bread.  In commercial production, yeast can be one of the 
most expensive ingredients to use, so a lot of research involves looking at 
ways to make good bread with less yeast.

Preservatives are added to both prevent microbial spoilage and staling.  
Interestingly, some yeast strains may produce  "natural preservatives", 
which aren't all that different from "artificial preservatives".

By increasing the yeast concentration in your bread, you may get some 
preservative effect due to byproducts of the yeast metabolism.  However, 
you may also get a lot more carbon dioxide, which could over expand your 
bread dough.  A couple of limiting factors will be the amount of food 
(sugar) for the yeast and the amount of time that the dough is allowed to 

So, do some mad scientist experimentation and try it.  At least now, you 
might have some idea of what is happening either way it turns out.

I hope this helped.

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