If I buy a loaf of freshly-made bread and leave it out at room temperature for a day or two, when I reach into the bag the air inside is much warmer than the rest of the room. Why?
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1$\begingroup$ Maybe there is some crystallization of organic molecules going on while the bread turns hard. This might be a chemical question after all. $\endgroup$– tobias47n9eOct 11, 2012 at 8:10
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$\begingroup$ After reading some more stuff I actually think that crystallization of starch might be the answer to this question. There is a lot of literature about this and it might very well be that it can be sufficiently exothermic to warm the small volume of air in a bag. $\endgroup$– tobias47n9eOct 11, 2012 at 18:53
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1$\begingroup$ To the above point i also want to include possible exothermic enzymatic reactions by microorganisms also $\endgroup$– EkaOct 18, 2012 at 15:31
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$\begingroup$ It could also be that inside the bag it's humid, and purely through suppressing the slow evaporative cooling of your skin it "feels" warmer. You could put on a thin nitrile glove to control for that. $\endgroup$– Nick TOct 16, 2016 at 22:48
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3$\begingroup$ Is it actually warmer or does it just feel warmer? Have you measured the temperature? $\endgroup$– matt_blackDec 30, 2016 at 11:37
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After reading some more stuff I actually think that crystallization of starch might be the answer to this question. There is a lot of literature about this and it might very well be that it can be sufficiently exothermic to warm the small volume of air in a bag.
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8$\begingroup$ I call for an experiment. Bread, digital thermometer with recording device... $\endgroup$ Oct 14, 2012 at 17:16
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1$\begingroup$ We need a controlled experiment before speculating. What sort of bread, bag, room? Moreover measure the temperature and don't rely on subjective feeling. $\endgroup$ Dec 30, 2016 at 11:39