Associate professor University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, Romania
Cold-pressed pumpkin seed oil is well known as a valuable source of bioactive molecules, including phenolic compounds. Besides their ability to totally or partially replace trans and saturated fats, oleogels are considered efficient tools for the protection and delivery of bioactives. Consequently, the present work aimed to assess individual phenolic compounds dynamics and infrared fingerprints during the ambient storage of pumpkin seed oil and thereof oleogel. For oleogels production, a 5% waxes ternary mixture was used (1% rice-bran, 1% sunflower, and 3% beeswax). Aliquots (30g) of liquid and gelled oil were sampled fresh (T0), after one (T1), and five months (T5), respectively. Phenolic compounds were extracted by traditional liquid-liquid extraction, followed by HPLC-MS quantification. FTIR (400-4000cm-1) was used for the evaluation of intermolecular forces between oleogelators mixture and oil, as well as for characterizing and monitoring the oxidative stability of oleogel and reference oil samples. Specific wavenumbers indicated oxidative processes in stored sample sets; storage time and sample clustering patterns were revealed by chemometrics. Isolariciresinol, vanillin, and caffeic and syringic acids were quantified. The main changes were determined for isolariciresinol, which decreased in liquid pumpkin seed oil samples from 0.77 (T0) to 0.37mg/100g (T5), while for oleogel samples from 0.64 (T0) to 0.41mg/100g (T5). A slight decrease of phenolic compounds was noticed initially, most probably caused by oleogelation thermal treatment. However, during the storage at room temperature, it was concluded that oleogelation technique used might show potential protection of phenolic compounds, higher phenolic contents being registered in oleogel samples.