Influence of Seeds’ Age and Clarification of Cold-Pressed Raspberry (Rubus idaeus L.) Oil on the DSC Oxidative Stability and Phase Transition Profiles

Abstract

After cold-pressing, small particles of seed residue remain in raspberry seed oil (RSO), even after passing it through cold filtration. The removal of the remaining seed residue is rather an alternative option to improve the visual properties of RSO. This study investigated the influence that the seeds’ age (0, 10, 20 months) and clarification process after pressing has on the oxidative stability and phase transition of RSO by means of differential scanning calorimetry (DSC). The results proved that the oil centrifugation process reduces the DPPH radical scavenging activity and oxidative stability measured by p-anisidine value (p-AnV) and DSC oxidation induction time (OIT) at 120 °C of all RSO samples, regardless of the age of the seeds (p ≤ 0.05). No significant differences were observed on the DSC melting and crystallization properties at 1 °C/min after the oil clarification by centrifugation (p > 0.05). The storage time of raspberry seeds, i.e., 10 and 20 months after expiry date, influenced the quality deterioration of RSO, as measured by higher p-AnV, lower DPPH, and OIT values (p ≤ 0.05). The results presented provide new information about oil production processing, suggesting that producers should reconsider giving up the clarification process of oil, since it lowers all quality parameters.

Special Issue: Bioactive Compounds, Nutritional Quality, and Oxidative Stability of Edible Oils and By-Products of Their Extraction

“…Many articles in this Special Issue analyze the impact of technological processes on the quality of oils. For example, one study [ 9 ] investigated the effects of seed age and clarification processes on the oxidative stability and phase transition of raspberry seed oil. Centrifugation of the oil lowered the quality parameters, which suggests that oil clarification processes should not be abandoned.…”

DSC Phase Transition Profiles Analyzed by Control Charts to Determine Markers for the Authenticity and Deterioration of Flaxseed Oil during Storage

“…Differential scanning calorimetry (DSC) is an advanced analytical instrument which has broad applications dedicated to explaining the thermal behavior of lipid compounds, and is thus able to provide significant data regarding the authenticity and stability profiles of fats and oils [16]. Several research studies have proven the effective use of the DSC technique to explore the oxidative deterioration resulting from normal or accelerated shelf-life tests [17][18][19]. Compared to conventional chemical analyses, an assessment by DSC offers a significant database, expressed as the exothermic/endothermic phase transition phenomena manifested by curve changes as a function of temperature, which is related to the lipids composition of the oil.…”