Quality-control materials in the USDA National Food and Nutrient Analysis Program (NFNAP)

Abstract

The US Department of Agriculture (USDA) Nutrient Data Laboratory (NDL) develops and maintains the USDA National Nutrient Databank System (NDBS). Data are released from the NDBS for scientific and public use through the USDA National Nutrient Database for Standard Reference (SR) ( http://www.ars.usda.gov/ba/bhnrc/ndl ). In 1997 the NDL initiated the National Food and Nutrient Analysis Program (NFNAP) to update and expand its food-composition data. The program included: 1) nationwide probability-based sampling of foods; 2) central processing and archiving of food samples; 3) analysis of food components at commercial, government, and university laboratories; 4) incorporation of new analytical data into the NDBS; and 5) dissemination of these data to the scientific community. A key feature and strength of the NFNAP was a rigorous quality-control program that enabled independent verification of the accuracy and precision of analytical results. Custom-made food-control composites and/or commercially available certified reference materials were sent to the laboratories, blinded, with the samples. Data for these materials were essential to ongoing monitoring of analytical work, to identify and resolve suspected analytical problems, to ensure the accuracy and precision of results for the NFNAP food samples.

Nutrient composition of selected traditional United States Northern Plains Native American plant foods

“…Results for the CCs and CRMs analyzed with the samples were compared to the certified ranges (for the CRM) and to established in-house tolerance limits (for the CC) to validate the accuracy of the measurements (Phillips et al, 2006a). The limited availability of sampling locations and harvested material allowed only a single analytical value for most foods; therefore, the precision (relative standard deviation, RSD) of inter-day results for these materials analyzed at the same laboratory were used to estimate precision of a value in the case of single analysis of a given nutrient/food.…”

“…Samples of well-characterized control composites (CC) with established tolerance limits developed for the NFNAP (Phillips et al, 2006a) and/or certified reference materials (CRMs) were included in each analytical run to validate results, as described previously (Phillips et al, 2006a(Phillips et al, , 2007 …”

“…Andersson et al, 2011;Bhargava et al, 2008;Guil et al, 1997;Guil-Guerrero et al, 2003;Kuhnlein, 1990;Yildirim et al, 2001), without common control samples between studies it is impossible to compare nutrient concentrations because interlaboratory analytical uncertainty could be confused with a true difference in composition (Phillips et al, 2006a). Additionally, different growing conditions can affect the concentration of nutrients in the same plant species (Bhargava et al, 2008;Pennington, 2008).…”

Preparation and characterization of control materials for the analysis of conjugated linoleic acid and trans-vaccenic acid in beef

“…The processor was pulsed for two sets of 5 s, then run for 30 s using the lowest speed setting. Subsamples of each CC were dispensed while frozen into subsamples of 10-12 g each in 30 mL glass jars with Teflon™-lined lids (Qorpak catalog #GLC-07098; Qorpak, Bridgeville, PA), following standard methods developed in this laboratory (Phillips et al, 2006). The aliquots were sealed under residual nitrogen gas and stored at − 60°C.…”

“…Finally, even when a specifically validated method is routinely applied to a large number of different samples within the same laboratory, there is significant potential for analytical error or imprecision across assay batches due to isolated experimental errors. These issues and the need for quality control materials have been demonstrated for many foods and nutrients (Phillips, Patterson, Wolf, Sharpless, & Holden, 2007;Phillips & Stewart, 1999;Phillips et al, 2006). Because of the complex nature of CLA and TVA analysis, matrix-specific food control samples and laboratory-specific method validation are especially critical for accurate quantitation and comparison of the CLA and TVA content of foods.…”