Effects of dehulling and microwave treatments on physicochemical characteristics, hazardous compounds levels, and volatile substances in mechanically pressed aroma-enhanced sesame (Sesamum indicum L.) oil production

The thermal roasting process, indispensable for the development of sesame oil's characteristic organoleptic properties, is concurrently responsible for the generation of hazardous chemical compounds. Given that the influence of alternative processing techniques, specifically dehulling and microwave treatment, on this formation remains inadequately characterized, this study systematically evaluated their impacts on physicochemical properties, contaminant levels, and flavor profiles. Analytical results demonstrated that dehulling significantly increased the concentrations of hazardous compounds, specifically benzo[a]pyrene (from 6.52 μg/kg in seeds with hull to 9.56 μg/kg in dehulled seeds), 3-monochloropropane-1,2-diol esters (from 64.43 μg/kg in seeds with hull to 90.47 μg/kg in dehulled seeds), and glycidyl esters (from 9.23 μg/kg in seeds with hull to 16.07 μg/kg in dehulled seeds). Conversely, microwave treatment effectively suppressed their formation. More intensive processing parameters, for both roasting and microwave applications, correlated with a reduced acid value, decreasing from 0.78 (180 °C and 10 min) to 0.19 mg KOH/g oil (260 °C and 40 min). Furthermore, these treatments induced significant alterations in the fatty acid profile, evidenced by a reduction in unsaturated fatty acids of up to 5.5 % under extreme thermal conditions. Volatile compound analysis via electronic-nose and HS-SPME-GC-MS indicated a progressive increase in both the diversity and total concentration of volatiles (e.g., from 884.55 mg/kg at 180 °C and 10 min to 1298.42 mg/kg at 260 °C and 40 min) with treatment intensity. This study provides critical insights for mitigating contaminants while modulating oil quality, offering valuable strategies for industrial optimization and regulatory oversight.