Influence of fluidized-bed roasting conditions of white sesame seeds on the physico-chemical properties and sensory acceptability of the cold-pressed oils

Abstract

Sesame seeds have economic interest owing to their oil content (45%–60%, dry basis). A multilevel factorial design was created in order to analyze the effects of air temperature (120, 150, and 180°C) and roasting time (20, 25, and 30 min) in a laboratory-scale fluidized-bed dryer. All treatments showed oil recovery values higher than 70%, except for roasting at 180°C for 25 and 30 min. The roasting treatment at 180°C for 20 min yielded oils with the best sensory properties and with acceptable values for chemical quality parameters: acid value (1.82 mg KOH/g oil), peroxides (not detected), oxidative stability index (11.58 hr), and antioxidants' content (total tocopherols: 410 ppm; total lignans: 9.54 g/kg oil). The combination of the seeds' roasting by fluidized-bed drying and oil extraction by screw-pressing, allowed obtaining high oil recoveries and products with high oxidative stability and sensory acceptability. Practical applications: Sesame oil is popular among healthy-food consumers given its bioactive components, mainly tocopherols and lignans, which confer a relatively high oxidative stability. Sesame seeds are roasted to change their microstructure for oil accumulation, to intensify flavor, and to increase the levels of antioxidants in the oil. Regarding the production of high-quality roasted oil, the roasting of sesame seeds in fluidized-bed dryers and the subsequent oil extraction in screw-presses have never been reported together. High oil recoveries and roasted sesame oils with a healthy physico-chemical composition, great oxidative stability, and sensory acceptability would be achieved by the oilseed industry through the use of two widely known technologies. First, fluidized-bed drying offers a high degree of mixing, and uniform heat and mass transfer over conventional direct heating methods for seed roasting. Second, screw-pressing of roasted seeds represents a green alternative to solvent extraction, mainly for specialty oils, because only mechanical power input is necessary to expel the oil.