|MadSci Network: Physics|
Chocolate can have a variety of melting points, depending largely on how its cooled. The chocolate fat can form different types of structures. However, none of them melt at 150 F. The range I'm familiar with is 60 F to 97 F. My guess is that technique is playing a role. Different products may vary from the 60 - 97 if they are extended with other fats that have a high melting point. Coating chocolates may have been treated this way, but its highly unlikely that you saw this with 14 different chocolate products. There are many reasons why you may have seen the high readings: 1. If a fairly large amount of chocolate was melted you could have read artificially high temperatures in a section of the pan resulting from overheating the bottom portion in order to melt the stuff floating on top. 2. If a double boiler wasn't used you could have been reading abnormally high temperatures radiating from the pan surface. 3. If a double boiler was used you may have had the thermometer in contact with, or very close to, the pan wall and read heat from the pan. 4. The thermometer may not have been working properly. A way to read melting points requires use of capillary tubes, very small diameter glass tubes. The tube is pushed into the product, forcing a sample into the center of the tube. The tube is attached to or held in close proximity to a thermometer stem in the area where the temperature reading is taking place. Slowly heat the water, preferably in a double boiler and ideally in a glass container like a beaker. Carefully watch the material in the tube, when it changes appearance you have hit the melting point where it transforms from solid to liquid. Sometimes its good to do some dry runs first so you know what this phase transition looks like.
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