Effect of Roasting Condition on the Antioxidative Activity of the Methanolic Extract from Defatted Sesame Meal

YUNG-SHIN SHYU¹, JEAN-YU HWANG² AND LUCY-SUN HWANG^3*

1. Department of Baking Technology and Management, National Kaohsiung Hospitality College,
1 Sung-Ho Rd., Hsiao-Kang, Kaohsiung 812, Taiwan (R.O.C.)
2. Department of Food Science and Technology, Chung-Hwa University of Medical Technology,
89, Wenhwa 1st St., Rende Shiang, Tainan 717, Taiwan (R.O.C.)
3. Graduate Institute of Food Science and Technology, National Taiwan University,
1, Sec. 4, Roosevelt Rd., Da-an District, Taipei 106, Taiwan (R.O.C.)

(Received: October 23, 2008 ; Accepted: June 6, 2009)

ABSTRACT

   Sesame seeds are usually roasted prior to expelling oil. The defatted sesame meal contains lignan glycosides in its methanolic extract. The objective of this study was to investigate the antioxidative activity of methanolic extract from defatted black sesame meal roasted at three different temperatures (180, 200, 220°C) for different durations (5-30 min). The antioxidative activities were evaluated by the 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) radical scavenging ability and the inhibition of Cu²⁺ induced oxidation of human low-density lipoprotein (LDL). The effects of roasting condition on the browning index of sesame meal and the total phenolic content of the methanolic extract were also investigated. Results showed that as roasting temperature and time increased, the DPPH radical scavenging ability and the inhibition of Cu²⁺ induced oxidation of human LDL also increased. Meanwhile, the total phenolic content in the methanolic extract from defatted sesame meal and the browning level of sesame meal also increased with roasting temperature and time. These results suggested that the enhancement of antioxidative activity would probably be due to total phenolic compounds and Maillard reaction products formed during roasting process.

Key words: antioxidant, LDL-oxidation, lignan glycoside, sesame roasting