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

Abstract

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 microm, 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 degrees C for 30 min increased the efficiency of conversion of sesamolin to sesamol (51% to 82%) compared to conventional heating. The gamma-tocopherol content decreased by 17% and 25% in oils treated at 200 and 220 degrees C for 30 min, respectively. There were 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.

Dietary lignans: physiology and potential for cardiovascular disease risk reduction

“…Minute amounts of the enterolignans enterodiol and enterolactone are sometimes found in animal foods (milk products) as a result of their production by bacterial metabolism in the animals' guts, but these are exceptions 36–39 . Little has been done to investigate the effects of storage and processing on lignans in most foods, 29–32,40–45 although it is known that the lignan content is apparently not changed considerably during the processing of flaxseed 46–50 and sesame seed 51–59 …”

Using Short‐Wave Infrared Radiation to Improve Aqueous Enzymatic Extraction of Peanut Oil: Evaluation of Peanut Cotyledon Microstructure and Oil Quality

“…At present, IR has been utilized to roast seeds and leads to positive results in some studies. Kumar et al reported that better quality was found in peanuts roasted by IR compared to conventional heating methods; increased oxidative stability was observed in sesame oil extracted from Near‐IR roasted sesame seeds. Lee et al roasted peanuts hulls and found higher amount of phenolics in Far‐IR roasted samples compared to heat‐treated ones.…”

A novel conversion of sesamolin to sesaminol by acidic cation exchange resin

“…Sesaminol is a naturally occurring trace compound in sesame seed and its crude oil. It is formed from sesamolin during sesame seed roasting 6, 7 and heating or refining operations (i.e., acid‐activated clay bleaching) 8–10. Among the lignans from sesame seeds, sesaminol, and its isomers were shown to have the most potent antioxidative activity in vitro experimental system, having higher antioxidative activity than α‐tocopherol and BHT 11.…”