This information from BeeSource.com. For the full article go to
http://www.beesource.com/pov/usda/beekpUSA82.htmHoney that has been fermented can sometimes be reclaimed by heating it to 150ºF for a short time. This stops the fermentation and expels some of the off-flavor. Fermentation in honey may be avoided by heating to kill yeasts. Minimal treatments to pasteurize honey are as follows:
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Temperature (ºF):.....................Heating time (minutes)
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128 ........................................................470
130.........................................................170
135..........................................................60
140..........................................................42
145..........................................................7.5
150..........................................................2.8
155..........................................................1.0
160....................................................... .4
The following summarize the important aspects of fermentation:
1. All honey should be considered to contain yeasts.
2. Honey is more liable to fermentation after granulation.
3. Honey of over 17 percent water may ferment and over 19 percent water will ferment.
4. Storage below 50ºF will prevent fermentation during such storage, but not later.
5. Heating honey to 150ºF for 30 minutes will destroy honey yeasts and thus prevent fermentation.
Quality loss by heating and storing - The other principal types of honey spoilage, damage by over-heating and by improper storing, are related to each other. In general, changes that take place quickly during heating also occur over a longer period during storage with the rate depending on the temperature. These include darkening, loss of fresh flavor, and formation of off-flavor (caramelization).