MadSci Network: Physics

Re: The melting point of chocolate

Date: Fri May 12 12:37:49 2000
Posted By: Ed O'Neill, Post-doc/Fellow, Food Science, Custom Quality Systems, Inc.
Area of science: Physics
ID: 955894393.Ph

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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