Effects of the vat pasteurization process and refrigerated storage on the bovine milk metabolome.

This study is the first to investigate the evolution of cow milk metabolites throughout the vat pasteurization process and storage using untargeted metabolomics based on a multiplatform approach. Nuclear magnetic resonance and ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry were used for fingerprinting water-soluble nutritional compounds, and headspace gas chromatography-mass spectrometry was used to fingerprint the volatile organic compounds. This study demonstrated that vat pasteurization was an efficient and mild means of milk preservation resulting in only minor changes to the metabolites. The pasteurized milk samples exhibited a stable metabolome during the first 8 d of refrigerated storage. However, at the latter stage of storage, the concentrations of pantothenic acid and butyrylcarnitine decreased, whereas some fatty acids, organic acids, α-AA, peptides, and ketones increased. These selected metabolites that changed during milk storage could be used as potential biomarkers to track the storage conditions of pasteurized cow milk.

Feasibility of Casein to Record Stable Isotopic Variation of Cow Milk in New Zealand.

Dairy products occupy a special place among foods in contributing to a major part of our nutritional requirements, while also being prone to fraud. Hence, the verification of the authenticity of dairy products is of prime importance. Multiple stable isotopic studies have been undertaken that demonstrate the efficacy of this approach for the authentication of foodstuffs. However, the authentication of dairy products for geographic origin has been a challenge due to the complex interactions of geological and climatic drivers. This study applies stable isotope measurements of d2H, d18O, d13C and d15N values from casein to investigate the inherent geo-climatic variation across dairy farms from the South and North Islands of New Zealand. The stable isotopic ratios were measured for casein samples which had been separated from freeze-dried whole milk samples. As uniform feeding and fertilizer practices were applied throughout the sampling period, the subtropical (North Island) and temperate (South Island) climates were reflected in the variation of d13C and d15N. However, highly correlated d2H and d18O (r = 0.62, p = 6.64 × 10-10, a = 0.05) values did not differentiate climatic variation between Islands, but rather topographical locations. The highlight was the strong influence of d15N towards explaining climatic variability, which could be important for further discussion.

A δ2H Isoscape of blackberry as an example application for determining the geographic origins of plant materials in New Zealand.

In this investigation, two previously reported precipitation δ2H isoscapes for New Zealand were used to develop a δ2H isoscape for blackberry (Rubus sp.) leaf. These isoscapes were calibrated using the measured δ2H values of 120 authentic blackberry leaf samples collected from across the country. A regression model based on environmental variables available for New Zealand was also determined to predict δ2H values measured from blackberry leaves without initially modelling the precipitation δ2H values. The three models were compared for their accuracy and precision when assigning 10 samples of blackberry leaves for their geographic location based on their measured δ2H values. One of the models based on a precipitation isoscape was similar in accuracy and precision of assignment to the model determined from the environmental variables and provides an approach for determining valid isoscapes for future plant materials.

Correlation of geographical location with stable isotope values of hydrogen and carbon of fatty acids from New Zealand milk and bulk milk powder.

The aim of this study was to investigate the correlation of δ²H and δ¹³C of bulk milk powder and milk powder fatty acids to their production region. A total of 46 milk powder samples from across New Zealand were collected and analyzed. Principal component analysis (PCA) showed that the δ²H and δ¹³C of four fatty acids (C4:0, C14:0, C16:0, C18:1) and bulk milk powder were found to be correlated with regional production area. Linear discriminant analysis (LDA) models were prepared using different combinations of bulk and fatty acid δ²H and δ¹³C. All models were effective in discriminating samples from the North and South Islands. The LDA model using just fatty acid δ²H and δ¹³C provided the best separation. Therefore, the isotopic composition of the aforementioned fatty acids can be utilized as a good biomarker in milk powder that conveys reliable isotopic information to track milk powders to their regional origin.

Modified sugar adulteration test applied to New Zealand honey.

The carbon isotope method (AOAC 998.12) compares the bulk honey carbon isotope value with that of the extracted protein; a difference greater than 1‰ suggesting that the protein and the bulk carbohydrate have different origins. New Zealand Manuka honey is a high value product and often fails this test. It has been suggested such failures are due to the pollen in the Manuka honey and an adaptation of the method to remove pollen prior to testing has been proposed. Here we test 64 authentic honey samples collected directly from the hives and find that a large proportion (37%) of Manuka honeys fail the test. Of these 60% still fail the adapted method. These honey samples were collected and processed under stringent conditions and have not been adulterated post-harvest. More work is required to ascertain the cause of these test failures.

ATR-IR spectroscopic study of antimonate adsorption to iron oxide.

Antimonate ions adsorb to iron oxides in mining contexts, but the nature of the adsorbed antimonate species has not frequently been investigated. In this study, ATR-IR spectroscopy was used to reveal that the adsorption of Sb(OH)6- ion from aqueous solutions onto an amorphous iron oxide particle film is accompanied by changes in the Sb(OH)6- spectrum and the loss of OH stretching absorptions from iron oxide surface hydroxyl groups. These spectral changes upon adsorption imply an inner-sphere surface interaction with the formation of Sb-O-Fe bonds as well as some outer-sphere adsorption. The corresponding results from solutions of antimonate in D2O confirm that chemisorption occurs. The dependence of antimonate adsorption on pH in the range from 8 to 3 follows that expected for anions on iron oxide considering its pH-dependent surface charge, with the greatest amount of adsorbed antimonate at pH 3. The study of adsorption/desorption kinetics showed a more rapid desorption of adsorbed antimonate under alkaline conditions. This trend is expected from the pH dependence of the antimonate charge and iron oxide surface charge, but it might be partly due to the fact that high pH favors hydrolysis of antimonate oligomers formed on the iron oxide surface from adsorption under acidic conditions.