Physical and Microbiological Approach in Proving the Identity of Gamma-irradiated Different Teas

  • Kausar, Tusneem (Department of Food Science and Technology, Kyungpook National University) ;
  • Kim, Byeong-Keun (Department of Food Irradiation, Korean Atomic Energy Research Institute) ;
  • Kim, Dong-Ho (Department of Food Irradiation, Korean Atomic Energy Research Institute) ;
  • Kwon, Joong-Ho (Department of Food Science and Technology, Kyungpook National University)
  • Published : 2005.02.28


Photostimulated luminescence (PSL), thermoluminescence (TL), electron spin resonance (ESR), and direct epiflourescent filter technique/aerobic plate count (DEFT/APC) were applied to detect dried green, black, and oolong teas irradiated between 0-10 kGy. Teas irradiated at 2.5 kGy and higher showed over 5000 photon counts/60 sec, while non-irradiated teas yielded 650-1000 photon counts/60 sec. TL glow curves for minerals separated from teas were detected at about $300^{\circ}C$ with low intensity in non-irradiated samples, whereas around $150^{\circ}C$ with high intensity in all irradiated samples. Ratio of $TL_1/TL_2$ based on re-irradiation step, showing lower than 0.1 and higher than 1.44 for non-irradiated and irradiated samples, respectively, enhanced reliability of TL results. ESR measurements for irradiated teas showed signals specific to irradiation. Log DEFT/APC ratio increased with irradiation dose; this result could be applied to identify irradiated tea samples.


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