Water activity affects the stability of dehydrated foods because it determines both chemical reaction rates and microbial activity. The limiting value of aw for the growth of any microorganism is around 0.6. Below this value, food spoilage is mainly due to enzymatic and chemical reactions, such as oxidation . The rate of oxidation may rise as water content increases since water can enhance reactant mobility and bring catalysts into solution. In relation to carotenoid stability. showed that both trans a- and b-carotene from dehydrated carrots present their maximum stability at aw values between 0.34 and 0.54. These results confirm previous findings by other authors