Introduction Pengaruh iradiasi gamma (60Co) dengan berbagai laju dosis pada senyawa antigizi isoflavon dan warna kacang kedelai

2.2. Equipment A gamma source radiation facility of Natural Rubber Irradiator IRKA, was used to irradiate sample materials at 122.9 kCi activity. IRKA is at PATIR BATAN, Pasar Jumat, Jakarta. A shimadzu liquid chromatograph equipped with LC 20 AD type pump, SPD 20A type UV detector and RF 10AXL type flourescene, water-bath Napco model 220A, USA, centrifuse IEC Centra 8 Centrifuge, USA, magnetic stier Velp Scientifica type ate, Italy and the other supporting equipments. 2.3. Sample preparation Soybean was used as a sample material. The sample was weighted into 100 g, packed in polietilen plastic bag for each treatment. The samples were prepared in triplicates. 2.4. Dosimetry Radiation dose measurement was done using harwell amber 3042 and harwell red 4034 dosimeter Harwell Dosimeters Co. Ltd., Oxfordshire, UK by using spectronic spectrophotometer IAEA 2002. 2.5. Irradiation The sample was placed in the irradiation area with different locations; to get irradiation treatment with specific dose-rates. Dose-rates used were previously determined at preliminary study. Four 4 locations in irradiation area have been identified to have dose-rates of 1.30; 3.17; 5.71 and 8.82 kGyh. Irradiation treatments were done at room temperature 28 ± 2 °C for each of the samples with exposure time ranging from 0.5-55 h; depending on its dose-rate. 2.6. Determination of isoflavone Isoflavone concentration was determined according to the method of Wang et.al. 1990. The two grams of ground sample was extracted with hexane for 6 h to remove fat. The isoflavone content of non-fat sample was analyzed using a high performance liquid chromatography equipped with an UV detector at wavelength of 254 nm and each flourescene of excitation and emission wavelength was 365 nm and 418 nm. Agilent XDB-C18 column 5 μm, 4.6 x 15 cm length was used. A mobile phase was a mixture of metanol : 1 mM ammonium asetat, 6:4 at a flow rate of 1.0 mlmin.

3. Results

The initial concentration of isoflavones in soybean sample used in this study was 81.39 μgg and 367.42 μgg for free and total daidzein and 62.27 μgg and 232.55 μgg for free and total genistein, respectivelly. Wang et al. 1990 reported that free and total daidzein contents in soybean were 25.6 μgg and 330.6 μgg, and for free and total genistein were 28.4 μgg and 461.6 μgg. The difference in isoflavone concentration among soybeans used could probably due to the varieties, planting location and harvesting time Tepavcevic et al. 2011.