Dear Mr. Wizard,
I use iodophor to sterilize and mix it according to the directions on the bottle. Do you have to rinse after you sterilize with it? I never have and I’ve never had any off-flavors, but I wonder if it is slowly eating away my insides.
Mr. Wizard replies: Iodophor is a very effective sanitizer and, unlike bleach, can safely be used as a no-rinse sanitizer without adversely affecting the flavor of your beer. The recommended concentration of iodophor is 25 parts per million. Most iodophors are diluted so that the typical use rate is somewhere around 0.1 ounce per gallon (7.8 mL per liter). They are always labeled with instructions giving suggested usage rates. If you use it at this concentration and allow your equipment to properly drain, you will be in good shape. Iodophor does have a flavor and, when used at higher-than-recommended strengths, it can impart an iodine flavor to beer — especially if it is not drained from the equipment surface.
Excessive iodine intake (extended consumption of about 0.75 milligrams per day) can cause iodine goiter, a condition characterized by enlargement of the thyroid gland. One ounce of a 25 ppm iodophor solution contains 0.75 milligrams of iodine. To leave that much sanitizer on your equipment would correspond to very careless technique. In addition, your beer would taste objectionable and the off-flavor would be a good warning sign to pay attention to your sanitation procedures. I suppose the flip side is that if you had 1/10th of an ounce (which is still a pretty fair volume) of residual on beer bottles and drank 10 beers per day you could have the same effect.
For more information on cleaning and sanitizing, see Steve Bader’s article, “Beer Minus Bacteria,” in the Janiary-February 2003 issue.
For more of Mr. Wizard's wit and wisdom please pick up the latest issue of Brew Your own, now available at better homebrew shops and newsstand locations.