Investigation of chemical properties and bioactive compounds of oils from different pumpkin seeds (Cucurbita pepo L.) during maturation

In this study, seed and oil yields, protein, and moisture ratios of seeds of four different types of pumpkin seed varieties, namely Palancı population, VD1sn8, and VD1sn6 hybrid varieties and commercial variety grown in Edirne conditions in 2014 and 2015. Also, this study aimed to determine the change of fatty acid, tocopherol, and sterol composition of mentioned pumpkin seed varieties in three different periods from seed formation to final harvest time. During the ripening period, it was obtained that the oil yield increased, the moisture content of pumpkin seeds decreased. In the last harvest period, the oil yield of pumpkin seed varieties was determined to be between 37.21% and 42.07%. Protein ratios of all pumpkin seed species were found to be very close to each other (37.94%–39.28%) and statistically similar (p > 0.05). In 2014 and 2015, the dominant fatty acids for all pumpkin seed varieties are 18:1 (39.49%–46.95%) and 18:2 (32.57%–39.26%). Except for these fatty acids, 16:0 varies between 10.65% and 13.60% in all varieties; 18:0 varies at a ratio of 5.70%–6.38%. It is seen that the dominant tocopherol isomer is γ-tocopherol for all pumpkin seed species in all harvest periods. In the last harvest period in 2014 and 2015, the amounts of γ-tocopherol constitute 99.98%–84.95% and 86.91%–89.86% of the total tocopherol, respectively. It was observed that the tocopherol composition changed during the ripening period in all pumpkin seed species (p < 0.05). In general, the amount of sterols decreased during the ripening period for all cultivars in 2014 and 2015. In order from the highest to the least, β-sitosterol, 5,24-stigmastadienol, campesterol, Δ-5 avenasterol, and stigmasterol were determined as phytosterols in pumpkin seed oils. Generally, β-sitosterol ratios in all varieties were high in the 1st harvest period, decreased slightly in the 2nd harvest period, increased again until the 3rd harvest period and reached the values in the 1st harvest period in both 2014 and 2015.