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Objective To analyze the key factors affecting constant weight in the direct drying method and to optimize the experimental conditions for vacuum drying, distillation, and Karl Fischer methods as specified in the GB 5009.3—2016 National food safety standard-Determination of moisture in foods. Methods The determination of moisture content in samples was conducted according to GB 5009.3—2016. The study altered experimental conditions to explore key factors affecting constant weight in the direct drying method, optimized conditions for vacuum drying by adjusting vacuum pressure, and compared the effects of different reagents (xylene, Karl Fischer reagent) on detection results. Results In the direct drying method, sample temperature, cooling time in the desiccator and the degree of sample pulverization were identified as key factors affecting constant weight. For vacuum drying method, increasing the vacuum to -0.1 MPa and adding an effective desiccant to the drying box could rapidly evaporate moisture from the sample, improving detection efficiency. In the distillation method, the preparation and purification of analytical-grade toluene or xylene could be omitted. The Karl Fischer method could use a low-toxicity, pyridine-free Karl Fischer reagent. Conclusion The 4 detection methods in this standard are optimized separately to solve problems such as difficulty in achieving constant weight after repeated drying and the use of toxic and harmful reagents. The rationalization suggestions provide in this study have increased the operability of the standard and improved the testing efficiency of the laboratory.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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