|MadSci Network: Biochemistry|
The ice or moisture inside the wrap is neither good nor bad; it is a symptom. Ordinarily, bread contains some free moisture or water that is not bound to the starch and protein in the bread. The free moisture can vaporize and condense within the bread but, some of the vapor will escape and the bread becomes harder and "stale". If you cover bread in a moisture resistant wrap, then the free moisture is trapped inside the wrap. The water vapor bounces off the wrap and back into the bread. To see how much moisture is hitting the wrapper, put an ice cube on the wrapper. The condensed water you see is how much water vapor was hitting that spot. In other words, as the water vapor atoms hit the cold spot, the ice absorbs their energy, and the vapor turns back to liquid. Thus, the ice crystals you see on the inside of a wrapper originated from free moisture inside the bread that condensed on the cooling wrapper. The fresher the bread, the more moisture within it. But some breads have more free moisture that others. Take a stick of fresh bread that has a hard crust, such as French bread and divide it. Put half in a plastic bag, leave the other half open or in a paper bag. Check the sticks after 8-24 hours. You'll see the half in the plastic bag has become softer than before; this is because the free moisture has equilibrated between the soft interior and the formerly dry crust. The half left open will have become harder (unless it's a rainy or very humid day) because some of the free moisture has escaped. Dry bread is hard bread; unbuttered toast is another example of hard dry bread. Keeping the moisture in is not necessarily a good thing. If you kept the two sticks of bread for several days, you would notice that the open bread would get harder and crustier. The bread in the plastic bag would remain soft but grow mold. Wrapping the bread and putting it in a freezer keeps the moisture in and prevents mold growth.
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