Oxidative stability assessment of industrial and laboratory-pressed fresh raspberry seed oil (Rubus idaeus L.) by differential scanning calorimetry

Abstract

Quality variation in oxidative stability between raspberry seed oils produced by industry and manually-pressed in laboratory was investigated. Oxidation induction time measured by differential scanning calorimetry (DSC) at 120 and 140 °C for industrial oils ranged from 60 to 100 min and 14 to 26 min, respectively, while for laboratory-pressed oils, ranged from 96 to 106 min and from 23 to 28 min, respectively. Both groups of oils contained a high amount of tocopherols, ranging from 95 to 256 mg/100 g, where γ-tocopherol dominated up to 70% of the total tocopherols. Significant correlations were stated between all DSC thermo-oxidative parameters and total tocopherols content (p ≤ 0.05). All oils of industrial group had significantly lower DPPH radical scavenging activity (p ≤ 0.05) than laboratory-pressed oils. Principal component analysis differentiated all oils samples into three clusters based on the parameters tested. First cluster consisted of all laboratory pressed oils (L1, L2, L3), the second of commercial samples (I1, I3), and the third separate cluster with one commercial oil (I2).

Keywords

• Raspberry (Rubus idaeus L)
• Differential scanning calorimetry (DSC)
• Oxidation induction time
• Oxidation induction temperature
• Tocochromanols