Quality and safety of walnuts and walnut oil, during the storage, depend largely on the enzyme content and their activity. Lipoxidases catalyze the oxidation of unsaturated fatty acids such as linoleic, linolenic and arachidonic acids, in this way it form esters and peroxides, this process reduces the product’s quality. This article provides a bibliographic study of enzymes and their assessment methods in walnut kernels and walnut oil. There were collected and studied different types of walnuts (Juglans regia L.) from Moldova. Nuts were evaluated fresh or after being stored for 1 and 2 years at room temperature. The study presents the changes of enzymes’ activity during storage of the walnuts and oil, using titrimetric and spectrophotometric methods.