Chemical Composition and Oxidative Stability of Roasted and Cold Pressed Pumpkin Seed Oils

In the present study, the effects of three production processes (pressing of roasted pumpkin seed paste, pressing of unroasted ground pumpkin seeds and pressing of unroasted ground pumpkin seeds while cooling the press) on the properties of pumpkin seed oils produced from two seed varieties (husked and naked) were investigated. Oils produced with roasting had a higher initial peroxide value (PV), twofold higher total phenol content and better oxidative stability while cold pressed oils had higher tocopherol content. Fatty acid and triacylglycerol compositions were not significantly affected by the processing conditions. Oxidative stability of the oils positively correlated with oleic acid content and negatively correlated with linoleic and linolenic acid contents. The lack of correlation in oxidative stability with tocopherol and polyphenol contents suggests that improvement in oxidative stability of roasted oils could have been caused by antioxidative Maillard reaction products or inactivation of oil degrading enzymes. In addition, oils produced from husked seeds had significantly higher linoleic acid, triacylglycerols (TAG) containing mainly linoleic acid (LLL, OLL and PLL), tocopherol and phenol contents while oleic acid and TAG containing mainly oleic acid (LOO and OOO) contents and oxidative stability were lower. Principal component analysis (PCA) of the analytical data confirmed the observed differences between oils from two varieties and three production processes.