Simple Selective Sodium Ion Electrode Measure of Sodium in Cheese

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Abstract
A selective Na ion electrode method for measuring Na in cheese was evaluated for accuracy, repeatability and sensitivity. Na in blue, camembert, cheddar, processed cheddar, parmesan, mozzarella, salt-free gouda and Swiss cheeses in duplicate was measured by ion analyzer with a selective Na ion electrode. In preparation of samples 1 g of cheese was blended in an ionic strength adjustment buffer and filtered through cheese cloth to remove foam. Na was measured directly on the filtrate by the selective Na ion electrode. Cheeses ranged from 0.05-1.72% Na by a reference atomic absorption method. Correlation of the Na ion electrode method with atomic absorption was 0.99. Comparative results of the 2 methods differed by an average of 0.06 .+-. 0.04% Na. Reproducibility was evaluated on 10 replicates for each cheese. D were .ltoreq. 0.02% Na for all cheeses and coefficients of variation ranged from 0.006 for blue cheese to 0.024 for parmesan and camembert. Sensitivity of the Na ion electrode method, as determined by standard additions of 0.5-2.5 mg Na, was excellent for all cheeses. The Na ion electrode method may offer industry laboratories a practical alternative to present methods for measuring Na in cheese.