Watermelon seed oil (WSO) is distinguished by its characteristic fatty acid composition. The content of saturated fatty acids is approximately 16-25%. The content of monounsaturated fatty acids is about 15-30%. It is also characterized by about 55-65% content of polyunsaturated fatty acids. WSO is rich in vitamins A and E, as well as some minerals. It is notable for the presence of amino acids such as arginine and lysine. Furthermore, this oil is abundant in tocopherols, polyphenolic compounds, and carotenoids.
The aim of this study was to investigate the properties of WSO. The subject of this study included four commercial oils—three cold-pressed unrefined WSOs and one refined WSO. This study also included a self-obtained oil from Sugar Baby watermelon seeds, isolated using chemical extraction with hexane. The impact of oil type and storage time on the properties of the oil was determined. The degree of hydrolysis of the tested oils was determined based on the acid number and the content of primary oxidation products of the oils based on the peroxide number according to AOCS methods. Oxidative stability was determined by high-pressure differential scanning calorimetry (PDSC) and the fatty acid composition was determined by gas chromatography (GC). Tests were conducted immediately after the purchase of commercial oils and after the extraction of the oil. Subsequently, they were performed every 4 weeks and repeated over the next 3 months.
The results obtained show the varying quality of the oils. It was found that all the tested oils exhibited good hydrolytic stability—the obtained acid value results for individual oils met the requirements set by the Codex Alimentarius. The obtained peroxide value results mostly complied with the requirements contained in the Codex Alimentarius. It has been shown that WSO are a valuable source of omega-6 linoleic acid and omega-9 oleic acid.