Effect of roasting process on total phenolic compounds and gamma-tocopherol contents of Iranian sesame seeds [sesamum indicum]

ABSTRACT

Sesame [Sesamum indicum L.] seed and oil have long been used widely as healthy foods to supply energy and prevent aging. Some of the main active anti-oxidative constituents in sesame seeds are y-tocopherol and phenols. The purpose of this study was to investigate the relationship between roasting temperature and time with gamma -tocopherol and total phenolic compounds [TPC] of sesame seeds when roasted in a domestic electric oven. Eight cultivars of sesame seeds in this study were Darab, Dezful, Karqj, Moghan, Naz-Branching, Naz-NonBranching, Siah and Varamin. Each cultivar was divided into ten group based on the roasting time [10, 15 and 20 min] and temperatures [180, 200 and 220 °C] andunroasted one. The high-performance liquid chromatography [HPLC] and spectrophotometeric methods were used for gamma-tocopherol [n = 80] and TPC [n = 80] analysis, respectively. The gamma -tocopherol content ranged from 329 +/- 5 mg/L in Naz-Branching sesame oil to 1114 +/- 7 mg/L in Siah sesame oil and 169 +/- 6 to 577 +/- 1 mg/kg in sesame seed respectively, gamma -tocopherol content of six cultivars increased significantly [p < 0.05] as the roasting temperature and time; until 200 °C for 10 min, but they were decreased by roasting at 220 °C in longer time. Also TPC increased significantly as the roasting temperature. The amount of TPC varied in different sesame cultivars from 20.109 +/- 3.967 microM to 129.300 +/- 3.493 in Varamin and Naz-Branching sesame seed cultivars, respectively, also TPC increased from 70.953 +/- 5.863 microM in unroasted Naz-Branching sesame seed to 129.300 +/- 3.493 microM after roasting in 200 °C for 20 min. The present study showed that Iranian sesame seed can be considered as a good source of natural antioxidant specially after roasting. The optimum temperature and time roasting to obtain the most y-tocopherol and total phenolic content was 200 °C for 10 and 20 min, respectively