Paul Wehling

Exploring Authentic Skim and Nonfat Dry Milk Powder Variance for the Development of Nontargeted Adulterant Detection Methods Using Near-Infrared Spectroscopy and Chemometrics

A multinational collaborative team led by the U.S. Pharmacopeial Convention is currently investigating the potential of near-infrared (NIR) spectroscopy for nontargeted detection of adulterants in skim and nonfat dry milk powder. The development of a compendial method is challenged by the range of authentic or nonadulterated milk powders available worldwide. This paper investigates the sources of variance in 41 authentic bovine skim and nonfat milk powders as detected by NIR diffuse reflectance spectroscopy and chemometrics. Exploratory analysis by principal component analysis and varimax factor rotation revealed significant variance in authentic samples and highlighted outliers from a single manufacturer. Spectral preprocessing and outlier removal methods reduced ambient and measurement sources of variance, most likely linked to changes in moisture together with sampling, preparation, and presentation factors. Results indicate that significant chemical variance exists in different skim and nonfat milk powders that will likely affect the performance of adulterant detection methods by NIR spectroscopy.

AACCI Approved Methods Technical Committee Report: Collaborative Study on the Immunochemical Determination of Intact Gluten Using an R5 Sandwich ELISA

In 2008, the AACC International Protein Technical Committee (now the Protein and Enzymes Technical Committee) initiated a collaborative study of a method for determining gluten in selected foods using an R5 antibody sandwich ELISA system. The method has been approved as AACCI Approved Method 38-50.01. The new method has been validated for testing foods to determine that they conform to the newly defined Codex threshold of 20 mg of gluten/kg in total for gluten-free products.

AACCI Approved Methods Technical Committee Report: Collaborative Study on the Immunochemical Determination of Partially Hydrolyzed Gluten Using an R5 Competitive ELISA

In 2008, the AACC International Protein Technical Committee (now the Protein and Enzymes Technical Committee) initiated a collaborative study of a method for determining gluten in fermented products using an R5 competitive ELISA system. The method has been approved as AACCI Approved Method 38-55.01. The new method has been validated for testing fermented foods and beverages to determine whether they conform to the newly defined Codex threshold of 20 mg of gluten/kg in total for gluten-free products.

Characterization of Near-Infrared Spectral Variance in the Authentication of Skim and Nonfat Dry Milk Powder Collection Using ANOVA-PCA, Pooled-ANOVA, and Partial Least-Squares Regression

Forty-one samples of skim milk powder (SMP) and nonfat dry milk (NFDM) from 8 suppliers, 13 production sites, and 3 processing temperatures were analyzed by NIR diffuse reflectance spectrometry over a period of 3 days. NIR reflectance spectra (1700–2500 nm) were converted to pseudoabsorbance and examined using (a) analysis of variance-principal component analysis (ANOVA-PCA), (b) pooled-ANOVA based on data submatrices, and (c) partial least-squares regression (PLSR) coupled with pooled-ANOVA. ANOVA-PCA score plots showed clear separation of the samples with respect to milk class (SMP or NFDM), day of analysis, production site, processing temperature, and individual samples. Pooled-ANOVA provided statistical levels of significance for the separation of the averages, some of which were many orders of magnitude below 10–3. PLSR showed that the correlation with Certificate of Analysis (COA) concentrations varied from a weak coefficient of determination (R2) of 0.32 for moisture to moderate R2 values of 0.61 for fat and 0.78 for protein for this multinational study. In this study, pooled-ANOVA was applied for the first time to PLS modeling and demonstrated that even though the calibration models may not be precise, the contribution of the protein peaks in the NIR spectra accounted for the largest proportion of the variation despite the inherent imprecision of the COA values.

Detection and Antigenic Profiling of Undeclared Peanut in Imported Garlic Using an xMAP Multiplex Immunoassay for Food Allergens

A shipment of imported garlic powder was suspected of containing peanut. Samples (subs) collected from the shipment displayed considerable variability in peanut antigenicity when analyzed by enzyme-linked immunosorbent assay (ELISA). This raised questions regarding whether peanut was actually present, the amount present, and the basis for the variability in antigenic content. Analyses that used an xMAP multiplex assay for the detection of peanut and additional food allergens generated responses that were characteristic of peanut. Specifically, the relative intensities of two different peanut-specific antibodies coupled to beads (peanut-37 and -38) and the antigen profiles were identical to garlic controls spiked with peanut. In addition, the xMAP data did not indicate the presence of other allergens. Quantitative analyses indicated an approximately fivefold variation in peanut concentration among different subs. In contrast, within a sub, the apparent peanut concentration appeared constant. Particle size analyses of the garlic powder subs indicated a single distribution profile, with a peak at 380 μm. ELISA analysis of sieve-fractionated garlic powder from one of the subs indicated that slightly less than half of the detectable peanut was smaller than 212 μm, with the remainder almost evenly split between 212 and 300 μm and >300 μm. Modeling to predict possible oral exposure levels of peanut other than those directly measured requires additional research on the physicochemical properties of peanut and garlic, along with information on the production of the garlic powder.

Exploring the variance of authentic skim and non-fat dry milk powder spectra

investigated by the Unites States Pharmacopeia (USP) in an effort to develop a successful non-targeted solution for milk powder. A significant challenge to be faced in this study is the normal physicochemical variability of pure milk powders. The existence of these variations will have the effect of widening the boundaries for any potential non-targeted method which may have the effect of decreasing the method’s ability to detect adulterants present at low concentrations. This problem is especially true for NIR diffuse reflectance spectroscopy, with its inherent limitations in the accurate detection of chemical components which are present below approximately 0.1% w /w in a sample matrix. In this report, the variance of NIR spectra from 41 different bovine skim milk powders and non-fat dry milk powders was explored. Spectral data were examined to identify influential sources of variance using princi pal component score trends and spectral signatures in rotated principal component loadings. Chemical analysis of samples of interest was also used to support the interpretations of the rotated principal components.