Comparison of Infra-Dry and AOAC Methods for Moisture in Food Products

The Infra-Dry (IR) method was accurate, precise and faster than conventional (AOAC) procedures for moisture determinations in ten selected food products. The average percentage moisture by the IR method for 10 common food products and those by AOAC in parentheses are as follows: oatmeal 9.88 (9.87), cornmeal 10.86 (10.91), wheat flour 10.80 (10.80), grape nuts 4.73 (4.78), rice 12.39 (12.41), potato flakes 8.40 (8.36), bread crumbs 9.93 (9.99), noodles 9.58 (9.54), NFD milk 4.23 (4.24), and fresh milk 88.60 (88.71). The temperatures used for the IR method (135 to 155°C) were higher than those for the AOAC procedures (130°C for all products except NFD and fresh milk [100°C]); however, the times were considerably less (10 to 30 min) than for AOAC procedures (1 to 5 h). Standard deviations were generally <0.06%, except for cornmeal and noodles which were approximately 0.1%. Precisions were generally >97%. Upon removing the samples from the IR oven, results of good precision and accuracy were obtained by cooling the samples in a desiccator for 5 min or the built-in IR cooling chamber for 45 s. The recommended IR method uses a cooling chamber, is faster, and does not require a desiccator. Slightly lower precision and accuracy resulted when the entire IR oven was used. The best results were obtained using the back third of the oven. However, the slight difference in precision and accuracy is of little practical significance.