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Comparison of Methods of Measuring Potassium in Pork and Lamb and Prediction of Their Composition from Sodium and Potassium¹

Michigan Agricultural Experiment Station, East Lansing^,3

Abstract

The present investigation was conducted to ascertain some possible sources of error in measuring the composition of animals and meat from their K⁴⁰ content. Flame photometry was used as an alternative method for measuring the potassium content and the accuracy of the method is discussed and also compared with the K⁴⁰ approach. In addition, the sodium content was measured by flame photometry.

In the first experiment the potassium content of 10 lamb carcasses was measured from the K⁴⁰ content and by means of flame photometry. The potassium content when measured by flame photometry (but not from K⁴⁰ content) was significantly related to carcass composition. On the average, both methods agreed on the potassium content of separable lean and separable fat. The sodium content was also significantly related to carcass composition.

In the second experiment, the potassium content of 20 lots of ground pork and 15 lots of ground lamb were determined from K⁴⁰ content and by means of flame photometry. Both methods gave approximately the same estimate of the potassium content of the samples. The flame photometrically determined potassium content was more closely related to the chemical composition of the samples in terms of % water, % fat and % protein than was their natural gamma activity. The data suggest that such relationships are closer for pork than for lamb. Furthermore, the potassium content on a fat-free basis was higher for pork than for lamb. The sodium content was also very closely related to the composition of the samples, but the relationship was not as good as that observed for potassium.

Results of the potassium analysis using flame photometry demonstrated the close relationships between potassium content and composition. However, a degree of precision at least comparable to that obtained by flame photometry is needed for a non-destructive method (such as K⁴⁰) before the accuracy is great enough to be useful.

¹ Journal Article 3015, Michigan Agricultural Experiment Station.

² Department of Food Science.

³ This study was supported in part by funds provided by research grant No. AMO4172–03 provided by the National Institutes of Health.