[Laboratory analysis and its variety for protein in prepackaged foods]

To observe the variety of protein analysis of prepackaged foods from different labs of China.

Fourteen foods from seven kinds (cereal products, bean products, meat products, dairy products, beverages, nuts, and snacks) were selected as food samples, according to national prepackaged foods consumption survey results in 2000. These samples protein were parallelly analyzed for three times by national standard methods in seven labs from all the country.

The 89.7% of results were up to grade by Grubbs, Cochran and Dixon screening methods. The accuracy of protein analysis was expressed by variety coefficiency (CV). The CV of inner labs and inter labs were from 0.36% to 2.79% and from 1.79% to 10.10%, the total and average CV level of inner labs and inter labs were from 2.33% to 10.47% and 4.52%. The relative expanded uncertainty of protein detection was from 4.46% to 19.60% (average 8.65%).

Protein analysis level in all labs from the country could be fit for national standards, the variety and uncertainty of protein analysis in all labs from the country could be no more than 20%.