MadSci Network: Biochemistry
Query:

Re: What is it about egg yolks that remove coffe stain??

Date: Sat Apr 22 19:35:46 2000
Posted By: Dian Dooley, , Associate Professor, Food Science and Human Nutrition, University of Hawaii at Manoa
Area of science: Biochemistry
ID: 954342713.Bc
Message:

Aloha, Violet,

     I'm not sure if egg yolks remove coffee stains or not.  However, if 
they do, it would be most likely be due to the fat and fat-like compounds 
(especially lethicin, a phospholipid) in egg yolks that would dissolve the 
fat-soluble components (oils/fats) that make up the color of coffee.
     With regards to the tea stain/vinegar connection:  The most probable 
answer would be that the colored phytochemical compounds (chemicals found 
in plants), such as polyphenols/tannins, that provide the color to tea are 
broken down by the vinegar (which is a weak acid) and become more soluble 
and can be washed away.
     These were my 'best guesses,' but I also checked with one of my food 
science/chemistry colleagues, Dr. Alvin Huang on the University of Hawai`i 
faculty, and he concurred with my answers.  Since my training is in 
nutition sciences, it's always good to have someone confirm my answers to 
more food-related questions, especially when they are related to food 
chemistry.
     



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