Characterization of NIST food-matrix Standard Reference Materials for their vitamin C content

Energy value measurement of milk powder using laser-induced breakdown spectroscopy (LIBS) combined with long short-term memory (LSTM)

Milk powder can provide the necessary nutrients for the growth of infants, and the level of its energy value is an important factor in the measurement of its nutritional value. Therefore, the measurement of the energy value in milk powder is of great significance for the nutritional health of infants. In this study, samples of 32 different brands of milk powder were selected for spectral analysis, and laser-induced breakdown spectroscopy (LIBS) combined with deep belief network (DBN), back propagation (BP) neural network, and long short-term memory (LSTM) models was used to achieve quantitative analysis of the energy value of the milk powder. The experimental results revealed that the LSTM model outperformed the DBN and BP models in terms of accuracy, with a mean relative error (MREP) of 1.0029%, which was 73.03% lower than that of DBN (3.7186%) and 69.53% lower than that of BP (3.2914%). Moreover, the determination coefficient (RP2) value improved significantly from 0.9341 for DBN and 0.9766 for BP to 0.9984. In addition, the root mean square error (RMSEP) decreased to 0.2140 from 0.7042 for DBN and 0.9051 for BP. These results demonstrate that the LSTM model has superior predictive performance compared to the other models. Therefore, the combination of LIBS and LSTM can accurately measure the energy value of milk powder and provide an effective and feasible means for its commercial measurement.

Evolution of reference materials for the determination of organic nutrients in food and dietary supplements-a critical review

For over 40 years, food-matrix certified reference materials (CRMs) have been available for determination of trace element content, and a wide variety of materials are available from most producers of CRMs. However, the availability of food-matrix CRMs for organic nutrients has been more limited. The European Commission (EC) Bureau Communautaire de Référence (BCR) and the National Institute of Standards and Technology (NIST) introduced food-matrix CRMs with values assigned for vitamins and other organic nutrients such as fatty acids and carotenoids in the 1990s. The number of organic nutrients for which values were assigned has increased significantly in the past decade, and the approach and analytical methods used for assignment of the certified values have also evolved. Recently, dietary supplement-matrix CRMs such as multivitamin tablets with values assigned for vitamins and carotenoids, and fish and plant oils with values assigned for fatty acids have appeared. The development, evolution, and improvement of food- and dietary supplement-matrix CRMs for determination of vitamins, carotenoids, and fatty acids are described, with emphasis on CRMs made available in the past 10 years. Recent food and dietary supplement CRMs for the determination of organic nutrients include infant formula, multivitamin tablets, milk and egg powders, breakfast cereal, meat homogenate, blueberries, soy flour, fish and plant oils, dry cat food, and protein drink powder. Many of these food- and supplement-matrix CRMs have values assigned for over 80 organic and inorganic nutrients, toxic elements, proximates, and contaminants. The review provides a critical assessment of the challenges and evolving improvements in the production and the analytical methods used for value assignment of these CRMs. The current status and future needs for additional food- and dietary supplement-matrix CRMs for organic nutrients are also discussed. Graphical abstract Food Composition Triangle with currently-available food-matrix certified reference materials (CRMs) for the determination of organic nutrients positioned according to fat, protein, and carbohydrate composition.

Determination of vitamin C in foods: current state of method validation

Vitamin C is one of the most important vitamins, so reliable information about its content in foodstuffs is a concern to both consumers and quality control agencies. However, the heterogeneity of food matrixes and the potential degradation of this vitamin during its analysis create enormous challenges. This review addresses the development and validation of high-performance liquid chromatography methods for vitamin C analysis in food commodities, during the period 2000-2014. The main characteristics of vitamin C are mentioned, along with the strategies adopted by most authors during sample preparation (freezing and acidification) to avoid vitamin oxidation. After that, the advantages and handicaps of different analytical methods are discussed. Finally, the main aspects concerning method validation for vitamin C analysis are critically discussed. Parameters such as selectivity, linearity, limit of quantification, and accuracy were studied by most authors. Recovery experiments during accuracy evaluation were in general satisfactory, with usual values between 81 and 109%. However, few methods considered vitamin C stability during the analytical process, and the study of the precision was not always clear or complete. Potential future improvements regarding proper method validation are indicated to conclude this review.