Oxidative stability of roasted and unroasted pumpkin seed oils

Pumpkin is a vegetable appreciated by consumers due to its health-promoting properties that positively affect the human body. Roasting is a process that influences the nutritional value and sensory traits of seeds. This process affects resistance to oxidation and is essential to form the flavor chemical components of pumpkin seed oil. Roasting should be carried out at temperatures higher than 100°C. The aim of the research was to analyze the oxidative stability of two commercial cold-pressed oils from roasted and unroasted pumpkin seeds. Pressure differential scanning calorimetry (PDSC) under isothermal conditions was applied to measure oxidative stability of studied oils. The test was carried out at three different temperatures (120, 130, and 140 °C) and at an oxygen pressure of 1350-1400 kPa. The acid value, peroxide value, and fatty acid composition were also determined in the analyzed oils. Roasted and unroasted pumpkin seed oil contained mainly mono- and polyunsaturated fatty acids. Monosaturated fatty acids were present in roasted pumpkin seed oil (36.14%) and unroasted pumpkin seed oil (29.85%). A higher proportion of polyunsaturated fatty acids was found in unroasted pumpkin seed oil (49.55%) than in roasted pumpkin seed oil (45.26%). Roasted pumpkin seed oil was characterized by a significantly lower peroxide value and longer induction time in each temperature (from 106.61 minutes in 120˚C to 20.90 minutes in 140˚C) than unroasted pumpkin seed oil (from 83.47 minutes in 120˚C to 17.67 minutes in 140˚C). The oxidative stability of roasted pumpkin seed oil was higher than that of unroasted pumpkin seed oil.