Food-matrix Reference Materials Research Articles

Food Matrix Reference Materials for Hydrogen, Carbon, Nitrogen, Oxygen, and Sulfur Stable Isotope-Ratio Measurements: Collagens, Flours, Honeys, and Vegetable Oils.

An international project developed, quality-tested, and measured isotope-delta values of 10 new food matrix reference materials (RMs) for hydrogen, carbon, nitrogen, oxygen, and sulfur stable isotope-ratio measurements to support food authenticity testing and food provenance verification. These new RMs, USGS82 to USGS91, will enable users to normalize measurements of samples to isotope-delta scales. The RMs include (i) two honeys from Canada and tropical Vietnam, (ii) two flours from C3 (rice) and C4 (millet) plants, (iii) four vegetable oils from C3 (olive, peanut) and C4 (corn) plants, and (iv) two collagen powders from marine fish and terrestrial mammal origins. An errors-in-variables regression model included the uncertainty associated with the measured and assigned values of the RMs, and it was applied centrally to normalize results and obtain consensus values and measurement uncertainties. Utilization of these new RMs should facilitate mutual compatibility of stable isotope data if accepted normalization procedures are applied and documented.

Feasibility studies for new food matrix-Reference Materials

This paper reports about the feasibility studies for the development of new food matrix-Reference Materials (RMs) aimed to evaluate quality, safety and traceability of selected food products, performed during the “Early Phase” (H2020 INFRADEV-02-2016 PRO-METROFOOD, G.A. 739568) of METROFOOD-RI “Infrastructure for Promoting Metrology in Food and Nutrition” (ESFRI Domain “Health & Food”), in the frame of the development of pilot services. With this purpose, batches of oyster tissue, rice grains and rice flour were prepared in lyophilized form (oyster tissue) or in their raw form (rice), homogenised, partitioned and then characterised for a very wide set of parameters, such as: contaminants, biomarkers, stable isotopes, markers of origin/authenticity. Such a wide characterisation was aimed to involve as many laboratories as possible and to go forward the development of “Multipurpose-RMs”, meaning new RMs having certified, reference or information values for several different parameters. Homogeneity studies and stability studies under thermal and luminous stress are underway.

A mixed mushroom control material to facilitate inter-laboratory harmonization of mushroom composition analyses

A wide range of nutrients and health-promoting non-nutrient components in mushrooms are a subject of international research, but specific reference materials to facilitate comparison of results among laboratories are lacking. Commercially available food matrix reference materials do not contain components unique to mushrooms (e.g., ergosterol, vitamin D2, chitin, beta-glucans, agaritine, ergothioneine). A mixed mushroom control material (CM) (homogeneous mixture of 15 types of mushrooms) was prepared and characterized for selected components, including proximates (moisture, protein, ash), total folate, folate vitamers, ergosterol, ergosterol metabolites, vitamin D2 (ergocalciferol), amino acids, total dietary fiber, agaritine, elements (sodium, potassium, phosphorous, magnesium, calcium, iron, copper, manganese, zinc), riboflavin, niacin, thiamin, vitamin B6, pantothenic acid. Subsamples of the CM are available to qualified laboratories from the Food Analysis Laboratory Control Center at Virginia Tech (Blacksburg, VA, USA), to be assayed concurrently with mushroom samples for which food composition data will be published along with results for the CM. Implementation of this CM should facilitate comparison of published data on mushroom composition and health benefit among species, and biodiversity within species by serving as common control sample that allows the separation of analytical variability from true differences in sample composition determined at different laboratories.

Quality control materials development for proximate composition determination in baby foods to enhance the Portuguese food composition database: Packaging conditions

Food matrix reference materials play an important role in the quality of data used in food composition databanks concerning the precision, trueness and accuracy of analytical values. In this work the feasibility studies according to ISO 34 ( ISO, 2000) of two commercial baby foods (ready-to-eat baby soup and milk-based powdered infant formula) were evaluated to check for their suitability as quality control materials for the analysis of moisture, protein, fat, ash and acidity. The suitability of plastic packaging materials to guarantee the reference materials’ characteristics is discussed. Official methods of analysis were used to evaluate the homogeneity and to monitor short-term and long-term stability studies. ANOVA was carried out to confirm homogeneity within and between samples. ISO 34 method was applied to monitor stability at different temperatures. The coefficients of variation obtained between sachets for milk-based powdered infant formula were less than 4.4% for moisture and 0.5% for fat. The stability data over 8.5 months storage period at 20 °C, 5 °C and −20 °C and −70 °C indicate that both materials are stable depending on the parameter studied and temperature. According to results, quality control materials (QCMs) prepared in agreement with ISO 34 requirements are a valuable tool in food composition analysis.

Improving data quality in food composition databanks: a EuroFIR contribution

Food composition databanks (FCDBs) should provide nutrient composition data comparable over time at national and international levels. However, the linkage between national database compilers and permanent structures to support the upgrading and monitoring of nutrient values in foods are far from satisfactory. This paper focuses on European efforts to improve the quality of nutrient values entered into FCDBs, emphasizing initiatives under the EU Network of Excellence: European Food Information Resource (EuroFIR – NoE). The general concept of quality assurance is described and results obtained in the project’s first year are presented. A survey among EuroFIR partners aimed at evaluating the current situation in comparability of nutrient values suggests that an integrated approach has two requirements: the implementation of a quality management system (QMS) and a harmonized data-quality assessment system (DQAS) to select values from different sources. The use of reference materials (RMs) is a key criterion in deciding on comparability and reliability of candidate nutrient values. Consequently, results of a survey on food matrix reference materials are presented. These suggest that developments in RMs for nutrient analysis in foods have a great impact on the quality of data to be included in FCDBs.

The need for reference materials when monitoring nitrate intake.

Whether dietary exposure to nitrate metabolites is detrimental or beneficial to human health has long been a matter of controversy. In spite of no consistent epidemiological evidence, nitrate metabolites are associated with the formation of carcinogenic-nitrosamines and gastric cancer. Furthermore, recent studies demonstrate that ingested nitrate plays a role in host defence against gastrointestinal pathogenic bacteria. Analytical values of nitrate content in foods are essential for estimating nitrate intake. The analytical process is of paramount importance for assessing human nitrate exposure and for establishing a link between these exposures and the current and future observed health effects. Therefore, the quality assurance of the measurement process is crucial to obtaining reliability, comparability and traceability of results. Certified Reference Materials (CRM) should play a role in the consistency of the measurement process. However, the availability of nitrate CRMs is still poor. When food monitoring is demanded, an approach could be to use In House Reference Materials (IHRM), prepared at a high metrological level, and all preparation steps should be quality driven. IHRMs were prepared, and available CRMs were used to provide traceability of the process. The homogeneity of IHRM was evaluated using an appropriate statistical design. The stability was monitored using an isochronous method. The material shelf life and storage conditions are presented. HPLC was optimised for the determination of nitrates in four vegetable categories. When a suite of IHRMs were used, the response of the HPLC system was linear over the range 1 to 8 mg L(-1). The detection limit for these compounds was 0.2 microg L(-1) and the determination limit 1.2 microg L(-1). The relationship between measurement uncertainty and critical points of the analytical process is presented. The differences in observed relative uncertainty between food categories could reflect current limitations in the food matrix reference materials.

Filling the AOAC triangle with food-matrix standard reference materials.

Well-characterized reference materials are needed by laboratories in the food testing and nutrition communities to facilitate compliance with nutritional labeling laws, to provide traceability for food exports needed for acceptance in many foreign markets, and to improve the accuracy of nutrition information that is provided to assist consumers in making sound dietary choices. As a result of the enactment of the Nutrition Labeling and Education Act of 1990 and the Infant Formula Act of 1980, the National Institute of Standards and Technology (NIST) has developed a suite of food-matrix Standard Reference Materials (SRMs) characterized for nutrient concentrations. These include SRM 1544 Fatty Acids and Cholesterol in a Frozen Diet Composite, SRM 1546 Meat Homogenate, SRM 1548a Typical Diet, SRM 1566b Oyster Tissue, SRM 1846 Infant Formula, SRM 1946 Lake Superior Fish Tissue, SRM 2383 Baby Food Composite, SRM 2384 Baking Chocolate, SRM 2385 Spinach, and SRM 2387 Peanut Butter. Many of these materials were developed at the request of the food industry to populate a nine-sectored fat-protein-carbohydrate triangle developed by AOAC International. With the completion of SRM 2387, SRMs representing each sector of the triangle are now available. These food-matrix reference materials are intended primarily for validation of analytical methods for the measurement of proximates, fatty acids, vitamins, minerals, and so on in foods of similar composition. They may also be used as "primary control materials" in the value-assignment of in-house, secondary, control materials to confirm accuracy as well as to establish traceability to NIST.

Recent developments in food-matrix Reference Materials at NIST.

Since 1996, the National Institute of Standards and Technology (NIST) has developed several food-matrix Standard Reference Materials (SRMs) characterized for nutrient concentrations. These include SRM 1544 Fatty Acids and Cholesterol in a Frozen Diet Composite, SRM 1546 Meat Homogenate, SRM 1548a Typical Diet, SRM 1566b Oyster Tissue, SRM 1846 Infant Formula, and SRM 2383 Baby Food Composite. Three additional materials--SRM 1946 Lake Superior Fish Tissue, SRM 2384 Baking Chocolate, and SRM 2385 Spinach--are in preparation. NIST also recently assigned values for proximate (fat, protein, etc.), individual fatty acid, and total dietary fiber concentrations in a number of existing SRMs and reference materials (RMs) that previously had values assigned for their elemental composition. NIST has used several modes for assignment of analyte concentrations in the food-matrix RMs, including the use of data provided by collaborating laboratories, alone and in combination with NIST data. The use of data provided by collaborating food industry and contract laboratories for the analysis of food-matrix RMs has enabled NIST to provide assigned values for many analytes that NIST does not have the resources or analytical expertise to measure.

Value Assignment of Nutrient Concentrations in Five Standard Reference Materials and Six Reference Materials

A number of food-matrix reference materials (RMs) are available from the National Institute of Standards and Technology (NIST) and from Agriculture Canada through NIST. Most of these materials were originally value-assigned for their elemental composition (major, minor, and trace elements), but no additional nutritional information was provided. Two of the materials were certified for selected organic constituents. Ten of these materials (Standard Reference Material [SRM] 1,563 Cholesterol and Fat-Soluble Vitamins in Coconut Oil [Natural and Fortified], SRM 1,566b Oyster Tissue, SRM 1,570a Spinach Leaves, SRM 1,974a Organics in Mussel Tissue (Mytilus edulis), RM 8,415 Whole Egg Powder, RM 8,418 Wheat Gluten, RM 8,432 Corn Starch, RM 8,433 Corn Bran, RM 8,435 Whole Milk Powder, and RM 8,436 Durum Wheat Flour) were recently distributed by NIST to 4 laboratories with expertise in food analysis for the measurement of proximates (solids, fat, protein, etc.), calories, and total dietary fiber, as appropriate. SRM 1846 Infant Formula was distributed as a quality control sample for the proximates and for analysis for individual fatty acids. Two of the materials (Whole Egg Powder and Whole Milk Powder) were distributed in an earlier interlaboratory comparison exercise in which they were analyzed for several vitamins. Value assignment of analyte concentrations in these 11 SRMs and RMs, based on analyses by the collaborating laboratories, is described in this paper. These materials are intended primarily for validation of analytical methods for the measurement of nutrients in foods of similar composition (based on AOAC INTERNATIONAL's fat-protein-carbohydrate triangle). They may also be used as "primary control materials" in the value assignment of in-house control materials of similar composition. The addition of proximate information for 10 existing reference materials means that RMs are now available from NIST with assigned values for proximates in 6 of the 9 sectors of the AOAC triangle. Five of these materials have values assigned for total dietary fiber-the first such information provided for materials available from NIST.