Cereal based foods, including breakfast cereals and Asian noodles are potentially good sources of selenium. Although these are major foods consumed globally, their contribution to dietary intakes of selenium is unclear. In addition, there has been very limited research into the effect of processing steps on the analysis and apparent retention of selenium. The low levels typically present in foods and the presence of multiple chemical forms of the element provide significant analytical challenges to research in this area. Therefore, the aims of this study were firstly to evaluate and validate procedures for extraction and measurement of selenium in wheat flour. Secondly, the procedure has been applied to analysis of selenium in cereal foods. The methods employed were firstly validated using wheat-based reference materials and then samples of various breakfast cereals as well as different styles of Asian noodles were analysed. Selenium was extracted using closed- v essels by microwave digestion with a mixture of nitric acid and hydrogen peroxide, followed by determination through Inductively Coupled Plasma - Mass Spectrometry (ICP-MS). The optimum conditions for selenium determination in cereal based foods involved the digestion of 0.1 g samples using 1 mL of nitric acid and 1 mL of hydrogen peroxide. The addition of 1% (v/v) methanol was found to enhance the sensitivity of the ICP-MS system. Two particular isotopes of selenium (77 and 82) could be effectively employed in the analysis and there was no significant decrease in total selenium in the digested extracts during storage for up to twelve days under refrigeration and room temperature conditions. Good precision levels were obtained and the total selenium levels in the breakfast cereal samples ranged from 0.059 to 0.378 µg/g. For white salted noodles the values varied between 0.057 and 0.712 µg/g, for yellow alkaline noodles, 0.109 to 0.265 µg/g and 0.077 to 0.284 µg/g for fried instant noodles. There was no appar ent change observed in total selenium during the processing of fried instant noodles, indicating the effectiveness of the extraction method developed here. It is concluded that microwave digestion is an effective approach to sample extraction, the procedures validated in this study are suitable for cereal grain foods and that there is considerable variation in the selenium contents of breakfast cereal and Asian noodle products.
| Identifer | oai:union.ndltd.org:ADTP/210471 |
| Date | January 2008 |
| Creators | Elis, [forename not supplied], elis.cen@student.rmit.edu.au |
| Publisher | RMIT University. Applied Sciences |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://www.rmit.edu.au/help/disclaimer, Copyright [forename not supplied] Elis |
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