Abstract: [Objective]To optimize the detection conditions of automatic Kjeldahl method for detecting protein content in dairy products. [Method]The protein content in dairy products was detected by Kjeldahl method. By comparing the effects of different sample weights,digestion time and cooling time after digestion on the detection results,the best parameters and conditions were selected to optimize the automatic Kjeldahl method and improve the detection efficiency. [Result]For dairy products with uniform mixing,the influence of sample weight within a certain range on the results was small,and the precision met the requirements of the national standard. However,the more the sample weight of sterilized milk,prepared milk and beverage was,the better the precision was. For fermented milk,the more the sample weight was,the lower the precision was. Digest at 230 ℃ for 30 min and 420 ℃ for 80 min, which can be completely digested,and the precision can be controlled within 1%.The samples were cooled in time after digestion,and there was no significant difference in the test results within 48 hours. [Conclusion] Through this test, it is proved that when using Kjeldahl method to detect protein content in dairy products, adjusting sample weight, digestion time and cooling time has no significant impact on the test results.

Key words: Kjeldahl method, dairy, protein, optimization