Pomegranate (Punica granatum L.) seed: A comparative study on biochemical composition and oil physicochemical characteristics

The pomegranate seeds of four Iranian commercial varieties  (Abanmahi (AB), Malas (MS), Pust Sefid (PS) and Shahvar (SH)) were evaluated in terms of some quality properties including protein, oil, dietary fiber, mineral contents and fatty acid composition. Physicochemical properties and antioxidant activity of pomegranate seed oils (PSOs) were also determined. The oil antioxidant activity was measured by ۱,۱-diphenyl-۲-picrylhydrazyl (DPPH) radical scavenging capacity. Results showed that PS had the highest oil (۱۶.۹%) and crude fiber (۴۲.۴%), and nutritional value (۴۶۰.۷Kcal/۱۰۰g) among selected varieties. PS had the highest level of phosphorus (۲۷۶۶.۳ mg/kg) and magnesium (۲۰۵۲.۰mg/kg), while the highest calcium (۶۷۵.۳mg/kg) and potassium (۳۷۲۴.۶mg/kg) were related to SH. The main fatty acid identified by gas chromatography was punicic acid ranged from ۷۲.۰۷% for SH to ۷۳.۳۱% for MS (p<۰.۰۵). The ratios of polyunsaturated/saturated and unsaturated/saturated fatty acids of PSOs were found to be between ۹.۱۷۴ and ۹.۴۵۰, and ۱۰.۳۲۵ and ۱۰.۸۶۱, respectively (p<۰.۰۵). PSOs obtained presented acid (۳.۷۸-۸.۳۶% punicic acid), peroxide (۰.۳۹-۰.۴۸meq O۲/kg), iodine (۲۱۶.۹-۲۲۰.۳g I۲/۱۰۰g) and saponification (۱۷۹.۳-۱۸۲.۵mg KOH/g) values. Also, refractive index at ۲۵°C, viscosity and density of PSOs varied from ۱.۴۶۱-۱.۵۲۷, ۰.۰۳۶-۰.۰۶۳Pa.s and ۰.۹۲۰۲-۰.۹۳۱۱g/cm۳, respectively. The oil obtained from MS showed the lowest level of ortho-diphenols (ODC) and DPPH radical scavenging capability. The relationship between percentage of remaining DPPH and ODC of PSOs also illustrated high correlation among all varieties (R۲ = ۰.۹۸, p<۰.۰۱).

Keywords:

Pomegranate seed , Fatty acid profile , Oil characterization , Ortho-diphenols , DPPH radical scavanging