Objective To establish a method for the detection of furosine in milk by microwave hydrolysis-ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Methods The optimal conditions for microwave hydrolysis were optimized by single factor experiments and response surface methodology. The hydrolysis solution obtained under the optimal hydrolysis conditions was filtered to a constant volume. The hydrolysate was diluted 10-fold with 6.0 g/L ammonium acetate solution and then analyzed. Gradient elution was performed with 0.1% formic acid aqueous solution and methanol solution as mobile phases, and the separation was carried out on a T3 liquid chromatography column (100 mm×2.1 mm, 1.8 μm). Under the positive ion mode of electrospray ion source (ESI+), multiple reaction monitoring (MRM) mode was selected for detection and external standard method was used for quantification. Results The optimal microwave hydrolysis conditions for furosine in milk were hydrolysis temperature of 160 ℃, hydrochloric acid concentration of 8.1 mol/L, and hydrolysis time of 52 min. The primary-to-secondary order of influencing factors was hydrochloric acid concentration>hydrolysis time>hydrolysis temperature. Furosine in milk showed a good linear relationship within the range of 0.005-0.500 µg/mL, with a correlation coefficient (r) of 0.9958. The limit of quantitation (LOQ) and limit of detection (LOD) were 0.20 µg/mL and 0.07 µg/mL, respectively. The average recoveries were 89.09%-97.33%, with relative standard deviations (RSDs) of 3.37%-7.02% (n=6). Conclusion This method is efficient and accurate. Compared with the traditional hydrolysis methods(12-24 hours), microwave hydrolysis shortens the hydrolysis time to 52 minutes, and there is no significant difference (P>0.05) in the detection results compared with the conventional hydrolysis methods in the industry standard NY/T 939—2016 Identification of reconstituted milk in pasteurized and UHT milk. It can provide technical reference for quality control and heat treatment process evaluation of dairy products.
| 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 |