Microbial decontamination and lipid quality of γ-irradiated red pepper seeds for functional oil production

Abstract Red pepper seeds are an oil-rich by-product of red pepper processing and a promising raw material for functional oils, yet they require an effective decontamination step before use. This study evaluated γ-irradiation (2.5, 5.0, 7.5 and 10.0 kGy; ⁶⁰Co source) as a non-thermal decontamination step and assessed its impact on seed microbiology and cold-pressed oil quality. Irradiation at 2.5 kGy reduced initial bacterial and fungal counts by 2.62 and 2.9 log units, respectively, while 5 kGy decreased both to below the detection limit. Oil quality indices showed dose-dependent but technologically limited changes: free fatty acids increased from 0.98% to 1.43% (as oleic acid) and peroxide value from 0.78 to 1.30 meq O₂/kg at 10.0 kGy. Antioxidant activity decreased progressively from 39.15 to 21.22 µmol Trolox/g oil with increasing dose. The fatty acid profile remained linoleic-acid–rich (C18:2 ≈ 72.5% in control vs. 72.22% at 10.0 kGy), with only minor shifts in major fatty acids. Total sterols were 8099.28 mg/kg in control oil, increased slightly up to 7.5 kGy, and declined at 10.0 kGy. Overall, γ-irradiation at 5.0–7.5 kGy achieved effective microbial decontamination with limited deterioration of oil quality, supporting its potential as a pre-treatment for safe red pepper seed valorization.