Re: How does the length of time an object is in a microwave oven influnece the

Hi, Anna.

The length of time a food is in a microwave oven certainly is correlated to 
moisture loss in that food, but a general relationship - other than 
saying that the longer the time, the greater the moisture loss - is 
difficult to state.  There are so many parameters, besides time. that will 
also influence the moisture loss.

You asked for some key words to head your thoughts and searches in the 
right direction.  Some ideas to pursue are: depth of food, ability to 
conduct heat, composition of food (one item or several parts to it), 
density, wattage of the MW oven, surface area, exposure (is food in a 
covered container or sitting on a paper towel), free water versus bound 
water (probably not with the result you would expect).

There are two ways to look at your question regarding the influence on the 
concentration of water in the food. Are you looking at the change in 
overall moisture content in the food before and after microwaving?  Or, are 
you looking at how the water concentration patterns change within the food 
itself? (At first microwaves drive moisture out from just under the surface 
of the food so the concentration in the center is stable for a time.  Then 
the moisture is driven from the center out.)

Special microwave ovens are often used in laboratories to quickly determine 
the moisture content in foods.  (Older methods with more traditional types 
of lab ovens could take several hours of drying time.)  A number of 
companies supply these lab microwave ovens and often provide a lot of 
useful information about the technology on their web sites.  If you are 
interested in more, try checking out 

                 http://www.cemx.com    


Carol Crouse
Food Technologist
The Food Chain Ltd.