engleski

Colour and keeping quality of pumpkin seed oil, pure and blended with other vegetable oils

The addition of refined and unrefined rapeseed and sunflower seed oil and their influence on colour and oxidative stability of two samples of commercial pumpkin seed oil was investigated on "salad oil" as the model system, which was a blend consisiting of 20% pumpkin seed oil and 80% other vegetable oil. During 17-week storage at room temperature in the light and darkness, the colour index was determined and visible absorption curves were recorded; oxidative stability was studied by peroxide value (PV) determination. The accelerated deterioration in an oven at 98oC (during 24 hours) and under UV lamp of 365 nanometers (during 8 hours) was also carried out. Colour loss in all investigated ois is much greater during storage in light than in darkness, especially in blended oils, more for the addition of sunflower see- than rapeseed oils; both refined oils expressed greater influence than unrefined ones. During the storage either in the light or darkness, blended oils deteriorated faster than initial pumpkin seed oils, what was especially expressed for the addition of both sunflower seed oils. In the conditions of oven test at 98 oC, the PV increase was especially evident for blends with sunflower seed oils, while the changes with rapeseed oils were insignificant. On the contrary, by expression to the UV-light both pure pumpkin seed oils deteriorated most quickly.

pumpkin seed oil; blended oils; storage; accelerated deterioration; colour index; shelf life

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