Tomato by-products (skins) were formulated with a green tea (GT) extract (5 mmol flavanol per mmol of lycopene) and dehydrated to obtain powders with potential added-value as food ingredients. The aims were to evaluate product stability during storage at different water activity (a(w)) levels in the range 0.17-0.75, by assessing: (a) lycopene and flavonoid degradation rates, (b) the antiglycoxidative and antioxidant properties, and (c) color variations. Lycopene degradation rate was maximum in the control unfortified tomato skins stored at the a(w) level of 0.17, it then decreased by increasing the a(w) level to 0.75. GT addition extended lycopene stability at the lowest a(w) level. Flavonoid degradation occurred above the a(w) level of 0.32 and was accelerated by increasing the a(w) level. The radical scavenging activity and antiglycoxidative activity slowly decreased at a(w) levels >= 0.56. The trend of color variation confirmed the observed changes in phytochemical contents. (C) 2011 Elsevier Ltd. All rights reserved.