Abstract
The effect of solvent polarity, polar and non-polar solvents, on pumpkin (Cucurbita maxima) seed oil yield and quality based on selected physicochemical properties was investigated. Five different solvents, like petroleum ether, hexane, cyclohexane, acetone and ethanol were used on a laboratory scale in this study. Results showed that both physicochemical properties and oil yield extracted from the pumpkin seed were influenced by solvent polarity. Oil yield ranged from 4.12 to 27.93%, with higher yield registered in petroleum ether and lowest in ethanol. Results on the physicochemical properties were as follows: Refractive index ranged from 1.437 (cyclohexane) to 1.466 (hexane), acid value, in mg KOH/g oil, ranged from 1.80 (cyclohexane) to 43.54 (ethanol), Peroxide value ranged, in meq O2/kg, from 6.70 (hexane) to 58.11 (ethanol), Iodine value, in g I2/g, ranged from 1.20 (petroleum ether) to 36.73 (ethanol), Saponification value, in mg KOH/kg, ranged from 30.54 (hexane) to 121.14 (acetone). The findings have demonstrated that solvent polarity significantly influenced physicochemical properties and oil yield extracted from pumpkin seed and therefore can assist in selecting solvents required in oil extraction to maximize yield and enhance or maintain oil quality. Key words: Cucurbita maxima, dielectric constant, oil, polarity, phytochemical properties, soxhlet extraction.  
Highlights
Plant seeds contain nutrients and energy rendering them significant in humans’ and animals’ diet
The highest free fatty acids (FFAs) values obtained using polar solvents such as ethanol suggest that solvent polarity influences oil quality and non-polar solvents produce oil with high quality based on FFAs
The high FFA value in ethanol extracted oil is in agreement with what has been previously reported that ethanol extracts more FFAs than non-polar and dipolar aprotic solvents (Johnson and Lusas, 1983)
Summary
Plant seeds contain nutrients and energy rendering them significant in humans’ and animals’ diet. Seeds are sources of edible oil and fats providing energy twice more than a unit carbohydrate and protein (Ali et al, 2001). Pumpkin (Cucurbita maxima) seeds have significant nutritional content providing high quality oil and proteins (Mahasneh and El-Oqlah, 1999; Montesano et al, 2018). The oil content in pumpkin seeds has been reported to be 37.8-45.4% (Lazos, 1986) and 47.03% with some variations based on species and genetic diversity (Younis et al, 2000). C. maxima seeds produce good quality oil and are excellent sources of proteins in the range of 25.2-37% (Lazos, 1986; Kim et al, 2012).
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