Antioxidants are substances that fight against oxidative stress and lipid peroxidation caused by different factors. In this thesis work, the effects of environmental factors and industrial processes on antioxidants will be considered. Environmental factors such as salinity, metal toxicity, not suitable nutrient supply, water imbalance, and drought have tremendous impacts on the antioxidant substances of cells. Different antioxidants (enzymatic, and non-enzymatic) are used to fight against these stress factors to save cells from cell death. Industrial processes, especially the food industry has huge effects on the antioxidant contents of plants. Thermal and non-thermal treatments during food production extend the shelf life and decrease the levels of antioxidants.