Contribution of tocopherols and squalene to the oxidative stability of cold-pressed pumkin seed oil (Cucurbita pepo L.)

Consumption of cold-pressed pumpkin seed oil (CPSO) is gaining ground due to increasing interest in natural products. The present study aimed at the examination of the contribution of two important classes of antioxidant compounds, tocopherols and squalene, in the course of autoxidation and photooxidation of this oil. Roasted pumpkin seed oil (RPSO) was used for comparison. During autoxidation studies, CPSOs were more vulnerable to oxidation than the RPSOs. The respective losses in alpha- (24-69% and 21-59%) and gamma- (13-21% and 18-20%) tocopherols, and squalene (12-27% and 22-28%) contents, indicated their strong participation to oil resistance. Squalene exhibited a weak antioxidant activity at the early stages of autoxidation whereas tocopherols showed their antioxidant effect after 3 weeks of storage. After that period, the content of squalene remained stable whereas loss in tocopherol content continued. The contribution of tocopherols and squalene to the stability of CPSOs oils under light exposure was also important, higher than that reported for virgin olive oil under the same conditions. Overall, CPSO is more prone to oxidation than RPSO, a finding that is important in its packing and distribution line. Practical applications: Pumpkin seed oil comes to the market in two types. Little is known for the stability of the cold-pressed one, which does not contain the strong antioxidants formed during seed roasting. The examination of the evolution of alpha- and gamma-tocopherols as well as squalene in the course of autoxidation and photo-oxidation of cold-pressed and roasted pumpkin seed oils is of scientific interest regarding their contribution to oil oxidation and of practical application in view of reducing loss in nutrients and other bioactive ingredients upon packing and distribution line.