Effect of water activity on lycopene and flavonoid degradation in dehydrated tomato skins fortified with green tea extract

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 (aw) 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 aw level of 0.17, it then decreased by increasing the aw level to 0.75. GT addition extended lycopene stability at the lowest aw level. Flavonoid degradation occurred above the aw level of 0.32 and was accelerated by increasing the aw level. The radical scavenging activity and antiglycoxidative activity slowly decreased at aw levels ⩾ 0.56. The trend of color variation confirmed the observed changes in phytochemical contents.

► Tomato skins were fortified with a green tea extract and dehydrated.
► A model for product stability was devised in the range 0.17 ⩽ aw ⩽ 0.75.
► GT addition enhanced lycopene stability at the lowest aw level.
► Flavonoids, antioxidant and antiglycation activities were stable up to aw 0.32.
► Colour variations confirmed the observed changes in phytochemical contents.