Tom Lehman on flour and humidity

[barrelli]

Several days ago I posted a question about humidity and flour. I thank everyone for their responses. I have posted a comment below  from Tom Lehman about flour and humidity. I am no longer concerned about humidity levels in the summer in my area  which is near Houston, Texas. I hope this post is useful to others. I will also be posting his advice regarding storing flour later in the day.

Lou

Louis;
The difference between 60 and 90% relative humidity will have very little effect upon the moisture content of the flour. True, high humidity, anything above 50% will cause the flour to begin picking up some moisture from the air, but this is a very slow process typically taking 45 to 60 days before the change begins to show. It is possible for the flour to begin picking up moisture before it is delivered to you, while it is in storage by the distributor, but most distributors store the flour in a temperature controlled (air conditioned) storage facility. If they didn't, there would be the possibility that the flour could get hot enough to potentially damage the protein. This would give you less than desirable results with your dough, but even more importantly, storage in a non temperature controlled ares would definately lead to infestation (insects) in the flour. Since both of these are not good for repeat flour sales, distributors, as well as manufacturers (flour millers) will always make sure the flour is properly stored before sale to provide the customer with the best quality product possible. The longest it is  recommended that a store hold the flour at room temperature (non-refrigerated temperature) is 28 days. This corresponds to the life cycle of insects commonly found in flour (cigarette beetles and confused flour beetles). If you hold the flour flr more than 28 days there is a probability that your flour will contain insect larvae (worms) which are of little health concern, but are not very appetizing to our customers. During the 28 day storage period at room temperature the moisture content of the flour will change (normally drop) by about 1% from what it was when it was received. The lowest the flour moisture content will drop when stored under room temperature conditions (air conditioned) is to about 10% moisture content. As a reference, flour, when freshly milled has a moisture content of 13.8 to 14%. As most distributors deliver it the moisture content is at about 12% (remember, it gave up some of its moisture because it has been stored in a temperature controlled or even refrigerated warehouse). So, depending upon how much flour you use in your mix, the absorption of your dough could change by roughly a pound or so of water in a 50# flour mix. In actuality, the lot to lot change in flour absorption characteristics changes considerably more than this.
I hope this has answered your question.

[Pete-zza]

Lou,

Thank you for posting the reply from Tom Lehmann on humidity. I noticed that he talked a lot about infestation of the flour. That can be a problem with flours that start out with a high amount of moisture. For example, I am a aware of one imported flour that starts out at 15.5%, which is quite a bit higher than U.S. flours and makes it a bit more vulnerable to mold and insect infestation (see, for example, Reply 4 at http://www.pizzamaking.com/forum/index.php/topic,3014.msg25563.html#msg25563).

Peter