Abstract A mixed food homogenate was prepared as a quality control material for two multi-center clinical feed- ing trials. Approximately 100 kg of homogenized human diet material was prepared under controlled conditions to maintain the stability of lipid components. More than 4800 20–25 g aliquots were prepared and stored at –60 °C in glass jars with Teflon-lined lids. The homogeneity of the composite was validated by analysis of moisture and total fat in aliquots taken throughout the dispensing se- quence. A portion of the material was reserved at the Na- tional Institute of Standards and Technology and further characterized as SRM 1544-Fatty Acids in Diet Compos- ite. Moisture, protein, ash, total lipid, fatty acids, choles- terol, sodium, potassium, calcium, and magnesium were assayed as part of routine quality-control analyses. Com- ponents were analyzed over a total time period ranging from 29 months (minerals) to 60 months (moisture), and up to 319 values per nutrient were generated. Results for all components assayed were stable over the time period studied. For example, moisture (n = 319; 60 months) ranged from 70.66 to 72.58 g/100 g with a mean, standard deviation (SD), and relative standard deviation (RSD) of 71.90, 0.27, and 0.4%, respectively. The range, mean, SD, and RSD for cholesterol (mg/100 g; n = 98; 49 months) were 13.54–17.96, 15.14, 0.64, and 4%. Introduction Accurate food composition data are required for many pur- poses, including assessment of diet-health relationships, food labeling, food safety, and the design of feeding trials. The analysis of food-based quality-control materials is critical to achieving accurate and precise measurements over time and analytical batches. A food-based quality control material (QCM) is a homogenate of food(s) simi- lar in type and having nutrient concentrations comparable with those in samples to be assayed. Analyte concentra- tions should be well-characterized and known to be stable for the duration of the study. A frozen mixed food QCM was developed to monitor the accuracy and precision of diet analyses conducted at Virginia Tech (VT) for two Na- tional Heart, Lung, and Blood Institute-sponsored multi- center feeding trials – Dietary Effects on Lipoproteins and Thrombogenesis (“DELTA”) [1], Dietary Approaches to Stop Hypertension (“DASH”) [2], and “DASH-Sodium”) [3]. A portion of this material was characterized by the National Institute of Standards and Technology (Gaithers- burg, MD, USA) to become SRM 1544 [4], and a portion of the material was used for quality-control analyses at VT. These assays took place over a cumulative total of 5 years, during which data were generated for a range of nutri- ents including total fat, moisture, protein, ash, fatty acids, cholesterol, sodium, potassium, magnesium, and calcium. There is a lack of published data on the long-term stabil- ity of proximates, cholesterol, and minerals in frozen food homogenates. Therefore, the 5-year quality-control data for these nutrients were analyzed to evaluate stability of these components in the frozen mixed food control mate- rial. Katherine M. Phillips · Amy H. Simpkins · Karen R. Amanna · Wayne Wolf · Kent K. Stewart · Seth Clark · Keun Pyo Kim · Gary R. Beecher · Joanne Holden Long-term stability of nutrients in a frozen mixed food control material Fresenius J Anal Chem (2001) 370 : 297–302 © Springer-Verlag 2001 Received: 30 September 2000 / Revised: 12 February 2001 / Accepted: 13 February 2001 SPECIAL ISSUE PAPER K. M. Phillips () · A. H. Simpkins · K. R. Amanna Department of Biochemistry, 304 Engel Hall, Virginia Tech, Blacksburg, VA 24061, USA e-mail: kmpvpi@vt.edu W. Wolf · G. R. Beecher USDA Food Composition Laboratory, Building 161, Beltsville Agricultural Research Station, Beltsville, MD 20705, USA S. Clark · K. Pyo Kim Department of Statistics, Hutcheson Hall, Virginia Tech, Blacksburg, VA 24061, USA J. Holden USDA Nutrient Data Laboratory, USDA ARS Beltsville Human Nutrition Research Center, Building 005, BARC-West, Beltsville, MD 20705–2350, USA Present address: K. K. Stewart Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 75712, USA