Palmerston North, New Zealand
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Nguyen N.H.A.,Fonterra Research and Development Center | Anema S.G.,Fonterra Research and Development Center
Food Chemistry | Year: 2017

Ultrasonication (US) of whole milk at 22.5 kHz and 50 W homogenized fat globules. Extended US without temperature control (attaining >90 °C at longest times), or with control at temperatures ⩾60 °C caused denaturation of the whey proteins and aggregation of the fat globules and proteins. Acidification of US milk produced gels with increased firmness and reduced gelation times compared to untreated milk. Below 60 °C, US of milk produced acid gels with very high firmness without whey protein denaturation; the firmness was similar to gels from heated whole milk. Extensive US without temperature control or with control at ⩾60 °C decreased acid gel firmness compared to shorter times or lower temperatures. Higher acid gel firmness could be achieved by subjecting the milk to separate heat (80 °C/30 min) and US treatment (at 20 °C) before acidification when compared with either heating or US alone. This was independent of the order of heating and US treatment. © 2016 Elsevier Ltd


Abernethy G.,Fonterra Research and Development Center | Higgs K.,Fonterra Research and Development Center
Journal of Chromatography A | Year: 2013

A liquid chromatography-mass spectrometry method to detect semicarbazide and lactose semicarbazone in milk was developed as part of a programme to set up methods for detecting the economically motivated adulteration of raw milk with nitrogen-containing compounds. The detection of semicarbazide was hampered by that fact that this compound tended to give broad, poor intensity peaks in the hydrophobic interaction chromatographic method employed. When spiked into milk at levels of 20-200. ppm, semicarbazide either partially or completely reacted with the matrix, which both increased the limit of detection of the method and made the setting of a threshold by using low level spikes almost impossible. Thus using lactose semicarbazone as a marker for semicarbazide addition to milk was investigated. Lactose semicarbazone was detected in semicarbazide-spiked milk, and its identity was confirmed by fragmentation analysis and comparison with the synthesised compound. The level of lactose semicarbazone correlated with the amount of semicarbazide added to the milk, and the acidic conditions employed in the extraction method appeared to enhance the sensitivity of detection by driving the semicarbazone-forming reaction towards completion. Thus lactose semicarbazone can be used as a marker for the addition of semicarbazide to milk; however, both compounds should be monitored during surveys looking for the semicarbazide adulteration of milk. © 2013 Elsevier B.V.


Anema S.G.,Fonterra Research and Development Center | de Kruif C.G.K.,University Utrecht | de Kruif C.G.K.,NIZO Food Research
Journal of Colloid and Interface Science | Year: 2014

Hypothesis: Oppositely charged proteins should interact and form complex coacervates or precipitates at the correct mixing ratios and under defined pH conditions. Experiments: The cationic protein lactotransferrin (LF) was mixed with the anionic protein β-lactoglobulin (B-Lg) at a range of pH and mixing ratios. Complexation was monitored through turbidity and zeta potential measurements. Findings: Complexation between LF and B-Lg did occur and complex coacervates were formed. This behaviour for globular proteins is rare. The charge ratio's of LF:B-Lg varies with pH due to changing (de) protonation of the proteins. Nevertheless we found that the complexes have a constant stoichiometry LF:B-Lg=1:3 at all pH's, due to charge regularization. At the turbidity maximum the zeta potential of complexes is close to zero, indicating charge neutrality; this is required when the complexes form a new concentrated liquid phase, as this must be electrically neutral. Complexes were formed in pH region 5-7.3. On addition of salt (NaCl) complexation is diminished and disappears at a salt concentration of about 100mMol. The coacervate phase has a very viscous consistency. If we consider the proteins as colloidal particles then the formed complex coacervate phase may have a structure that resembles a molten salt comparable to, for example, AlCl3. © 2014 Elsevier Inc.


Holroyd S.E.,Fonterra Research and Development Center
Journal of Near Infrared Spectroscopy | Year: 2013

Milk and milk products are a widely produced and traded source of nutrition globally. Near infrared (NIR) spectroscopy is commonly applied to these products for the purposes of composition measurement and quality control. The last five years have seen a growing emphasis on areas such as applications of NIR spectroscopy to compositional parameters that were previously done by specialised assays. Studies on proof of origin and authenticity as well as more qualitative applications such as health benefits have also appeared in the NIR literature in increasing numbers. Both these areas are reviewed by reference to application to liquid milk and specific products produced from milk alongside a number of new approaches to the more traditional quantitative use of NIR to measure gross compositional parameters such as fat, protein and moisture. The importance of appropriate sample preparation for respective products is also emphasised and a summary of the relevant wavelengths important for NIR analysis of milk and milk products is presented.


Abernethy G.A.,Fonterra Research and Development Center
Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment | Year: 2015

This paper proposes a mechanism to explain the trace levels of natural semicarbazide occasionally observed in foods. The analytical derivative of semicarbazide, 2-nitrobenzaldehyde semicarbazone, is often measured as a metabolite marker to detect the widely banned antibiotic nitrofurazone. However, this marker is not specific as semicarbazide may be present in foods for several reasons other than exposure to nitrofurazone. In some cases, an entirely natural origin of semicarbazide is suspected, although up until now there was no explanation about how semicarbazide could occur naturally. In this work, semicarbazide is proposed as being generated from natural food compounds via an azine intermediate. Hydrazine, in the form of azines or hydrazones, may be generated in dilute aqueous solution from the natural food compounds ammonia, hydrogen peroxide and acetone, following known oxidation chemistry. When this mixture was prepared in the presence of ureas such as allantoin, urea, biuret or hydroxyurea, and then analysed by the standard method for the determination of semicarbazide, 2-nitrobenzaldehyde semicarbazone was detected. 2-Nitrobenzaldehyde aldazine was also found, and it may be a general marker for azines in foods. This proposal, that azine formation is central to semicarbazide development, provides a convergence of the published mechanisms for semicarbazide. The reaction starts with hydrogen peroxide, peracetic acid, atmospheric oxygen or hypochlorite; generates hydrazine either by an oxaziridine intermediate or via the chlorination of ammonia; and then either route may converge on azine formation, followed by reaction with a urea compound. Additionally, carbamate ion may speculatively generate semicarbazide by reaction with hydrazine, which might be a significant route in the case of the hypochlorite treatment of foods or food contact surfaces. Significantly, detection of 2-nitrobenzaldehyde semicarbazone may be somewhat artefactual because semicarbazide can form during the acid conditions of analysis, which can free hydrazine in the presence of urea compounds. © 2015 Taylor & Francis.


Rutherfurd S.M.,Riddet Institute | Fanning A.C.,Fonterra Research and Development Center | Miller B.J.,Fonterra Research and Development Center | Moughan P.J.,Riddet Institute
Journal of Nutrition | Year: 2015

Background: The FAO has recommended replacing the protein digestibility-corrected amino acid score (PDCAAS) with the digestible indispensable amino acid score (DIAAS). Objective: The objective of this study was to compare aspects underlying the calculation of the DIAAS and PDCAAS, including 1) fecal digestibility vs. ileal digestibility, 2) using a single nitrogen digestibility value for all amino acids, and 3) the effect of truncation. Truncated PDCAAS and untruncated DIAAS values calculated as formally defined were also compared and DIAAS data presented for 14 dietary protein sources. Methods: Semisynthetic wheat starch-based diets were formulated to contain the test protein (as consumed by humans) source (whey- and soy-protein isolates, milk-, whey-, rice- and pea- protein concentrates, cooked kidney beans, roasted peanuts, cooked peas, corn-based breakfast cereal, cooked rice, cooked rolled oats, and wheat bran) as the sole nitrogen source and with an indigestible marker (titanium dioxide). Growing male rats (;250 g bodyweight) were given a basal casein-based diet from day 1 to day 7 and then allocated (n = 6) to the test diets for day 8 to day 14 before ileal digesta were collected after the rats were killed. Total feces were collected from day 11 to day 14. Results: True fecal nitrogen digestibility was different (P < 0.05; 10% difference on average) from true ileal nitrogen digestibility for 11 of the 14 protein sources. True ileal nitrogen digestibility was different (P < 0.05) from true ileal amino acid digestibility for almost half of the indispensable and conditionally indispensable amino acids (differences ranged from 0.9% to 400%). DIAAS values ranged from 0.01 for a corn-based cereal to 1.18 for milk protein concentrate. Conclusion: Untruncated PDCAAS values were generally higher than a DIAAS values, especially for the poorer quality proteins; therefore, the reported differences in the scores are of potential practical importance for populations in which dietary protein intake may be marginal. © 2015 American Society for Nutrition.


Abernethy G.,Fonterra Research and Development Center | Higgs K.,Fonterra Research and Development Center
Journal of Chromatography A | Year: 2013

A method to aid in the detection of the economically driven adulteration of fresh milk with a range of small, nitrogen containing compounds, including melamine, ammeline, ammelide, cyanuric acid, allantoin, thiourea, urea, biuret, triuret, semicarbazide, aminotriazine, 3- and 4-aminotriazole, cyanamide, dicyandiamide, guanidine, choline, hydroxyproline, nitrate, and a range of amino acids, has been developed. 15N2-Urea is used as an internal standard. The adulteration of milk with exogenous urea has previously been difficult to detect because of the variation in the naturally occurring levels of urea in milk. However, by monitoring the contaminants biuret and triuret, which comprise up to 1% of synthetic urea, the adulteration of milk with urea-based fertilizer can be detected. We estimate that to be economically viable, adulteration of the order of 90-4000ppm of the above adulterants would need to be added to fresh milk. For most of the compounds, an arbitrary detection threshold of 2ppm is therefore more than sufficient. For biuret, a lower detection threshold, better than 0.5ppm, is desirable and the sensitivity for biuret and triuret can be improved by the post-column addition of lithium to create lithium adducts under electrospray ionisation. Sample handling involves a two-step solvent precipitation method that is deployed in a 96-well plate format, and the hydrophilic interaction liquid chromatography uses a rapid gradient (1.2min). Three separate injections, to detect the positively charged compounds, the negatively charged compounds and amino acids and finally the lithium adducts, are used. This rapid and qualitative survey method may be deployed as a second tier screening method to quickly reduce sample numbers indicated as irregular by an FTIR based screening system, and to direct analysis to appropriate quantification methods. © 2013 Elsevier B.V.


Abernethy G.,Fonterra Research and Development Center | Higgs K.,Fonterra Research and Development Center
Journal of Chromatography A | Year: 2013

A rapid liquid chromatography-mass spectrometry method to detect 3-amino-1,2,4-triazine (ATZ) in milk was developed as part of a programme to set up methods for detecting the economically motivated adulteration of raw milk with nitrogen-containing compounds. When ATZ was added to unpasteurised or pasteurised milk at levels of 10-1000. ppm, the levels declined over a period of a few days and in some cases declined below the limit of detection of the analytical method (1. ppm). ATZ did not degrade in deproteinised milk extracts, in aqueous standards or in aqueous (non-milk) controls, suggesting that degradation was mediated by a pasteurisation-resistant enzymatic or microbial process. An oxidation product of ATZ was detected by mass spectrometry, and a tentative structure for this compound (3-amino-1,2,4-triazin-5-one, ATZO) was determined by fragmentation analysis and high resolution mass spectrometry. The accumulation of this oxidation product correlated with the loss of ATZ in milk samples. It was concluded that the detection of ATZO could be used as a marker for the addition of ATZ and that both compounds should be monitored during surveys looking for the ATZ adulteration of milk. © 2013 Elsevier B.V.


Cakir-Fuller E.,Fonterra Research and Development Center
Food Hydrocolloids | Year: 2015

There is a desire to incorporate increasingly high concentrations of whey proteins into nutritional beverages to improve their nutritional content and amino acid profile. However, typical thermal treatments for sterility or extended shelf life cause undesirable aggregation/gelation of the whey proteins. To address this instability issue at high protein concentration, there is a need to develop new protein ingredient technologies that can provide resistance to heat-induced aggregation. In this study, the heat stability characteristics of model food emulsions containing standard or microparticulated whey protein concentrate (WPC80) were compared. Oil-in-water emulsions [10% (wt/wt) sunflower oil] containing increasing concentrations of protein (from 2 to 12wt%) were prepared at pH 7.0. The effects of retorting at 120°C for 10min on particle size distribution, rheological properties, susceptibility to heat-induced coagulation, microstructure and surface protein concentration of the standard and microparticulated WPCs were compared. Also, various levels of NaCl were added to examine the heat stability of micro-aggregated WPC in the presence of additional salts.Microparticulated WPC emulsions showed significantly enhanced heat stability compared with standard WPC emulsions. Emulsions with up to 11wt% protein and no visible aggregation or gelation after retorting were produced using microparticulated WPC. For standard WPC emulsions under the same heating conditions, large aggregates were formed and there was a change in flow behaviour to non-Newtonian at 3wt% protein. With this specific technology, high protein whey-based nutritional beverages can be produced using conventional thermal treatments. © 2015 Elsevier Ltd.


Smith G.P.S.,University of Otago | Gordon K.C.,University of Otago | Holroyd S.E.,Fonterra Research and Development Center
Vibrational Spectroscopy | Year: 2013

Raman spectroscopy was used to determine the limits of detection and quantification (LOD and LOQ, respectively) of calcite in spiked milk powder samples. Samples of milk powder spiked with 0.5-10% (weight by weight; w/w) calcite were prepared and analysed using FT-Raman spectroscopy. Using the spectra obtained from these samples, calibration models were prepared using peak intensities, analysis of peak intensity ratios, based on band integrals and peak heights, and multivariate analysis. Analysis methods using peak intensity, peak integral ratios and peak height ratios produced LOD values of 3.8, 3.3 and 1.4% (w/w) calcite and LOQ values of 13, 11 and 4.7% (w/w) calcite respectively. Multivariate analysis produced a LOD of 1.0% (w/w) calcite and a LOQ of 3.4% (w/w) calcite. © 2013 Elsevier B.V. All rights reserved.

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