The objective of the proposed experiment was to determine changes in the content of vitamin C in the vegetable material (fresh and processed) during a certain period of time, and to determine the optimal expiry date of a product (in terms of the vitamin C content), as well as to introduce students to common factors adversely affecting the content of vitamin C in food products (with a special emphasis on oxidizing enzymes). The research revealed that regardless of the type of cucumbers (fresh, pickled in brine or in vinegar), the content of vitamin C is rapidly dropping after the destruction of the cellular structure (grating, slicing etc.). In the case of fresh cucumbers, it is a process determined by two factors: release and activation of ascorbinase from the destroyed cellular structure and availability of oxygen. Low pH values in the remaining cases reduce the effect of ascorbinase, and a decrease in the vitamin C content is related to the process of oxidation with atmospheric oxygen.