Electron Spin Resonance Study of Pumpkin Seeds, Oil and Cake Antioxidant Power

Abstract

Pumpkin (Cucurbita pepo) seed products, oil and flour, but also pumpkin seed cake as a by-product, are an important source of natural antioxidants. Antioxidants neutralize free radicals that harm human health. Radicals are products of the human metabolism, are ingested with food, smoke inhalation, and can be produced by the body's exposure to high-energy radiation (UV, X and γ). The electron spin resonance (ESR), known as an extremely sensitive spectroscopic technique in measuring the concentration of free unpaired electrons, was applied to measure the antioxidant power (AP) of pumpkin seed oil, flour and cake. 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, dissolved in ethanol, was used as a scavenging object. It was measured how the concentration of DPPH radicals decreases over time after the addition of an antioxidant (ethanol extract of oil, flour or cake). The influence of the processing temperature (40°C and 122°C) as well as of samples storage temperature (4°C and 22°C) on AP was investigated in detail. It was found that pumpkin seed cake, as a by-product, shows a significant AP. Therefore, this result additionally supports the use of the cake in the food industry in order to improve the nutritional value of products. Moreover, there is an indication that the oil production temperature and the storage temperature of oil as the final product, but also the seeds as the raw material, might have an important influence on the AP values.