Effect of radiation-sterilization on free radicals content in dry beverages

anglais. This study was done to determine free radicals content in several dry beverages, namely instant coffee, milk powder, cane sugar, nutrisari, tea, and cacao powder after radiation-sterilization at 25 kGy and stored at room (24 deg. C.) and freezing (-13 deg. C.) temperatures. Each sample was vacuum-packed in Al foil laminate pouches, then irradiated at 25 kGy in dry ice temperature. Free radicals contents in some samples after being dissolved on soaked in hot water (73 degree C.) then freeze-dried were also measured. The free radicals content was measured using Electron Spin Resonance (ESR), Spectroscopy and expressed in spectrum area/g in arbitrary unit. The results showed that free radicals content increased after irradiation, but it decreased immediately after storage especially at room temperature. After about 5 months of storage either at room or freezing temperatures, free radicals contents of irradiated coffee, milk powder and cacao powder were similar to those of the unirradiated control, while in tea sample stored at freezing temperature, the free radicals was still a little bit higher than that stored at room temperature which was already similar to the content. Free radicals content of irradiated sugar as well as nutrisari was higher than the other samples, and the radicals were relatively stable either at room or freezing temperatures. However, after dissolving or soaking the samples in water, the ESR spectra or free radicals contents of the irradiated samples were found to be identical to the control. The indicates that free radicals formed by irradiation in the samples disappear because of termination

indonésien. Penelitian ini dilakukan untuk mengetahui kandungan radikal bebas dalam beberapa jenis bahan minuman kering, yaitu kopi bubuk instan, susu bubuk, gula pasir, nutrisari, teh celup, dan kakao bubuk setelah disterilkan dengan iradiasi (25 kGy) dan disimpan pada suhu kamar (24 derajat Celsius) dan suhu beku (-13 derajat Celsius). Masing-masing sampel dikemas vakum dalam kantong Al foil laminasi, lalu diiradiasi 25 kGy oada suhu CO2 padat (es kering). Dalam penelitian ini diukur pula jumlah radikal bebas dalam beberapa sampel setelah diseduh dalam air panas (73 derajat Celsius), lalu dikeringkan dalam freeze drier. Kandungan radikal diukur dengan spektrometer Electron Spin Resonance (ESR) yang dinyatakan dalam luas spektrum ESR/g tanpa satuan (arbitraty unit). Hasil menunjukkan bahwa kandungan radikal bebas meningkat setelah iradiasi, tetapi cepat menurun setelah penyimpanan terutama pada suhu kamar. Setelah sekitar 5 bulan penyimpanan pada suhu kamar maupun suhu beku, kandungan radikal bebas sampel kopi susu dan kakao bubuk iradiasi sudah sama dengan kontrol yang tidak diiradiasi, sedang pada teh celup, kandungan radikal bebas sampel yang disimpan pada suhu beku masih sedikit lebih tinggi daripada kontrol. Kandungan radikal bebas sampel gula pasir dan nutrisari yang disterilkan dengan iradiasi lebih tinggi daripada sampel yang lain, dan relatif stabil baik pada penyimpanan suhu kamar maupun suhu beku. Akan tetapi, setelah penyeduhan dalam air panas ternyata spektrum ESR atau kandungan radikal bebas sampel iradiasi sama dengan kontrol. Hal ini membuktikan bahwa radikal bebas yang terbentuk akibat iradiasi lebih cepat terminasi