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Objective Study why nicotinamide is transformed tonicotinic acid occurred when detect vitamin ${\mathrm{B}}_{3}$ in milk powdercontaining lactic acid bacteria by GB 5009.89-2016 high performanceliquid chromatography method, and its mechanism was discussed. MethodsThe samples were pretreated according to standard procedures, and theeffects of the placement time of the sample extraction solution, theplacement time of the sample solution before acid hydrolysis and the $\mathrm{{pH}}$ value of acidhydrolysis were investigated by single factor test. Results Thetransformation of nicotinamide to nicotinic acid occurred in theplacement step after the sample was dissolved and before acidhydrolysis, but after adjusting the pH value to 1.7 specified in thestandard for acid hydrolysis, the transformation was completelyinhibited. Conclusion If you want to detect the content of nicotinicacid or nicotinamide separately in samples containing lactic acidbacteria, you need to adjust the $\mathrm{{pH}}$ value to 1.7 when thesample is dissolved to inhibit the transformation of nicotinamide tonicotinic acid.
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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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