ARTICLE

From As to Zn - Defining Your Testing Needs for Trace and Heavy Metals in Dairy

Introduction

Milk is often described as a ‘complete food’ as it contains a wide variety of the macro and micronutrients required for a healthy human diet. As cows produce milk, the nutrients from their feed are incorporated, and so milk becomes a good source of the zinc, calcium and selenium naturally found in grass. However, if the cow’s feed is contaminated with the common pollutants lead or cadmium, this will also be incorporated into the milk and may lead to serious consequences for consumer health.

Milk is often described as a ‘complete food’ as it contains a wide variety of the macro and micronutrients required for a healthy human diet. As cows produce milk, the nutrients from their feed are incorporated, and so milk becomes a good source of the zinc, calcium and selenium naturally found in grass. However, if the cow’s feed is contaminated with the common pollutants lead or cadmium, this will also be incorporated into the milk and may lead to serious consequences for consumer health.

Lead exposure in particular can have enormous effects on a societal level; the stringent lead regulations that came into force in the 1970’s have been linked to the drastic reduction in violent crime over the last half century. Even for essential micronutrients such as selenium, there can be too much of a good thing. High dietary levels of selenium can lead to the condition selenosis, causing gastrointestinal problems, hair loss and fatigue. As the fortification of dairy products with micronutrients becomes more popular, the risk of over-exposure also increases.

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In order to maintain public health and ensure consumer confidence, it is crucial that the manufacturers of dairy products implement rigorous quality control systems for detecting and quantifying the trace and heavy metals in their goods. To aid in these efforts, PerkinElmer offers the dairy industry a range of solutions to elucidate the quantities of different metals in every product, including for complex matrices such as cheese and yogurt.

Understanding the instrumentation and methodology required for different types of products and different levels of analysis is crucial in the effort to ensure that the products consumers buy are both nutritious and safe.

Monitoring Micronutrients

Analysis of micronutrients in food has long been an important facet in the monitoring of food quality. However, recent trends in the industry have led to this analysis becoming both more important and substantially more challenging. The supplementation of dairy products with essential nutrients has become a popular means of creating added value for a business, and thus dairy products must be closely monitored to ensure that nutrient levels meet regulations.

Meanwhile, the increase in new, innovative dairy products is leading to increasingly complex matrices that may affect analysis without careful sample preparation. In addition, more stringent regulations on micronutrient levels and labelling – especially in the wake of food scandals involving infant formula – mean that accuracy is more important than ever. When deciding what instrumentation is necessary for an individual dairy testing lab, it is not only necessary to weigh up the runtimes and costs of different options, it is also vital to consider the matrices that will be handled and the regulations that must be complied with.

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While regulatory authorities demand accurate values of micronutrient contents, the methods used to obtain these values are not set in stone. Micronutrient analysis of dairy products can be performed with any of three major spectroscopy techniques: flame atomic absorption spectroscopy (FAAS), inductively coupled plasma optical emission spectroscopy (ICP-OES) or ICP mass spectrometry (ICP-MS). Deciding on which technique is most useful for a given lab depends on the number of samples and the types of dairy products being analyzed.

The standard methods (SMs) provided by industry associations such as the AOAC can help to guide these decisions. For instance, the AOAC’s SMPR 2014.004 describes the performance requirements for analysis of minerals and trace elements in infant formula and states that any analytical technique that meets these performance requirements is acceptable.

ICP-OES has emerged as a common solution for micronutrient analysis, as it provides labs with a large dynamic range, rapid multi-element throughput, and robust operating conditions. However, for smaller labs with limited space and fewer samples to run, FAAS offers an attractive and simple alternative that requires lower start-up costs and less user training.

For more advanced labs analyzing both toxic and nutritional elements at low concentrations, the cutting-edge mass spectrometry technique ICP-MS provides unparalleled sensitivity and throughput, particularly when coupled to a high-performance liquid chromatography (HPLC) instrument. However, these tools take up more space than other techniques, and require significant user training in both chromatography and mass spectrometry. Weighing up the pros and cons of different analytical techniques can be a challenging task, and it is therefore important to partner with an instrument supplier that can understand your unique needs and provide any training your users require – both on-site and in a classroom setting.

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Ac-Cu-Ra-C-Y and P-Re-C-I-Si-O-N for Speciation of Toxic Metal Contaminants

For labs analyzing toxic metals in dairy products, it is not only important to the consider the overall quantities of the constituent metals, but also their speciation, as this can have a large effect on toxicity. For instance, while organic species of arsenic are considered to be of little toxicity or even non-toxic, inorganic species of arsenic are highly toxic and present a significant danger to public health.

As regulations on toxic metals grow ever-more stringent, there is a rapidly growing market for labs offering speciation services. Labs running these analyses need instrumentation that can reliably detect different metal species at the low concentrations required to comply with regulations.

These traits are uniquely provided by an ICP-MS coupled to an HPLC, which can separate and detect a large number of different toxic metals even when multiple species are present. Compared to other spectroscopic techniques, ICP-MS offers much greater sensitivity and can also handle greater chemical interferences.

Another benefit of PerkinElmer’s ICP-MS instrumentation is the extended dynamic range that allows both major and minor metals present in dairy products to be analyzed using the same setup. This is a particularly important time-saving measure for labs analyzing fortified products that may contain relatively large concentrations of selenium while also containing low concentrations of toxic metal species. In summary, ICP-MS offers robustness and reliability, with high-throughput methods that can run a large quantity of complex samples in a short space of time.

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A High Performance Portfolio

As the consumer demand for innovative, healthy and tasty dairy products continues to increase, the need for powerful solutions to analyze the quantities of trace and heavy metals will also grow. PerkinElmer is proud to provide dairy labs with an extensive range of leading heavy metal testing technologies to safeguard consumer health and ensure consumer confidence. From the easily implementable FAAS, to advanced ICP-MS for the detection of toxic metal species at low concentrations, our suite of innovative solutions will have your metal analysis covered – today, tomorrow and in the years to come.

REFERENCES

Nevin, Rick. “Understanding International Crime Trends: The Legacy of Preschool Lead Exposure.” Environmental Research, vol. 104, no. 3, July 2007, pp. 315–36. ScienceDirect, doi:10.1016/j.envres.2007.02.008.

MacFarquhar, Jennifer K., et al. “Acute Selenium Toxicity Associated With a Dietary Supplement.” Archives of Internal Medicine, vol. 170, no. 3, Feb. 2010, pp. 256–61. jamanetwork.com, doi:10.1001/archinternmed.2009.495.

AOAC. “Standard Method Performance Requirements for Minerals and Trace Elements in Infant Formula and Adult/Pediatric Nutritional Formula.” AOAC SMPR® 2014.004. PDF available at http://www.eoma.aoac.org/SMPR/upload/35/SMPR%202014_004.pdf.