Tea Anti-Microbial Properties

[Doug Rice]

In article <3085719D.7065 at bu.edu> Allen Wang <alwang at bu.edu> writes:
>From: Allen Wang <alwang at bu.edu>
>Subject: Tea Anti-Microbial Properties
>Date: Wed, 18 Oct 1995 14:29:01 -0700

>Does anyone know if tea has anti-microbial properties?
>If so, which ones?

Which type of tea?
Herbal teas tend to have very high background counts of yeast, mold, and yes, 
coliforms.  This is due to the exotic origins of the diverse ingredients.  
Most herbal teas, however, have acidic ingrediets to lower the pH to an acid 
food level (<4.5).  The pH is the most important hurdle to protect herbal 
teas.  Acidic ingredients include:  hybiscus, rose hips, lemon grass, citric 
acid from orange, or lemon peel.  Some herbal teas actually have added acids 
such as citric and phosphoric.  Some of the other ingredients have volitile 
oils that are classically anti-microbial:  cinnamon and clove oil.

Black teas are naturally much lower in resident populations due to their 
production process.  All black teas go through a fermentation and aging 
process that first decreases the pH and later reduces the water activity.  
Black teas also have important "anti's" such as tannic acid that results from 
the fermentation process.

The most import anti-microbial for tea is of course boiling water.  
Considering some of the resident organisms that I have found in all types of 
tea, I would not dring unheated tea.

I hope this has been some help!!!

________________________________________________________ 
Doug Rice:  Laboratory Director; Environmental Quality Laboratory 
Microbiology of water, food, soil, and air. 
Colorado State University:  Ft Collins, Colorado. 
e-mail:  drice at vines.colostate.edu     voice:  (970) 491-6503