Effect of Infrared Heating on the Formation of Sesamol and Quality of Defatted Flours from Sesamum indicum L.

Infrared (IR) heating offers several advantages over conventional heating in terms of heat transfer
efficiency, compactness of equipment, and quality of the products. Roasting of sesame seeds degrades the lignan
sesamolin to sesamol, which increases the oxidative stability of sesame oil synergistically with tocopherols. IR (near
infrared, 1.1 to 1.3 μm, 6 kW power) roasting conditions were optimized for the conversion of sesamolin to sesamol.
The resultant oil was evaluated for sesamol and tocopherol content as well as oxidative stability. The defatted flours
were evaluated for their nutritional content and functionality. IR roasting of sesame seeds at 200 ◦C for 30min increased
the efficiency of conversion of sesamolin to sesamol (51% to 82%) compared to conventional heating. The
γ -tocopherol content decreased by 17% and 25% in oils treated at 200 and 220 ◦C for 30min, respectively. Therewere
no significant differences in the tocopherol content and oxidative stability of the oil. Methionine and cysteine content
of the flours remained unchanged due to roasting. The functional properties of defatted flours obtained from
either IR roasted or conventionally roasted sesame seeds remained the same.
Practical Applications: Sesame oil is stable to oxidation compared to other vegetable oils. This stability can be
attributed to the presence of tocopherols and the formation of sesamol, the thermal degradation product of
sesamolin—a lignan present in sesame. Roasting of sesame seeds before oil extraction increases sesamol content
which is a more potent antioxidant than the parent molecule. The conversion efficiency of sesamolin to sesamol is
increased by 31% by infrared roasting of seeds compared to electric drum roasting. This can be used industrially to
obtain roasted oil with greater oxidative stability.