Results obtained showed clearly that EGCG is very susceptible to degradation under elevated temperature and humidity. This is in agreement with the previously reported (Li et al., 2011) theoretical understanding of the chemical features of EGCG (Fig. 1). It is a polyphenolic compound containing an ester group. Under such conditions, EGCG can degrade into epigallocatechin or EGCG dimers in addition to formation of autoxidation products (Friedman et al., 2009). Results confirmed also that neither the formula nor the final packaging of this product conferred the required protection to the active ingredient. Thorough investigation of the effects of the studied stress conditions on the total polyphenol content and the antioxidant activity is not under the scope of this work and is being investigated by our research group.