Reliable detection and quantification of flow-aid concentrations in grated cheese is warranted for both quality assurance and to prevent fraud, yet no official method exists. This study evaluated enzymatic-gravimetric methods that quantify insoluble dietary fiber, as well as near-infrared spectroscopy (NIR), for their suitability to measure cellulose and flow-aid concentrations in ground Parmesan with known amounts of commercial flow-aid preparations. The range of flow-aid concentrations spanned 0 to 5.01 g/100 g of cheese, corresponding to 0 to 1.39 g/100 g of cellulose. Use of the total dietary fiber assay, with or without modifications, consistently overestimated flow-aid concentrations by formation of aggregates that were presumably difficult to digest. Increasing protease amounts reduced but did not eliminate this issue. In contrast, the integrated dietary fiber assay and NIR spectroscopy were suitable methods for quantification of cellulose and flow aid. However, analyzing control cheeses without flow aid proved difficult with both methods. For these samples, the integrated dietary fiber assay and NIR spectroscopy calibrated for cellulose gave higher than actual values with poor precision (0.50 ± 0.36 and 0.38 ± 0.22 g/100 g, respectively). However, NIR calibrations for flow aid (which also contained starch), instead of cellulose, specifically yielded more accurate results for samples with 0 g/100 g of flow aid (0.06 ± 0.14 g/100 g). In general, prediction of higher concentrations of flow aid via NIR spectroscopy had lower accuracy than with the integrated dietary fiber assay; however, results obtained via NIR spectroscopy had lower variability. The total dietary fiber assay always overestimated cellulose in ground Parmesan, and further modifications are necessary to obtain accurate results. Differences between the pH at which protein digestion occurs (lower for the integrated dietary fiber assay than the total dietary fiber assay) may have contributed to differences in results.
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