Honey is an easy target for food fraud and adulteration with sucrose, high fructose corn syrup, molasses and other sugars are not uncommon. To quickly identify adulterants, a method using Raman spectroscopy and pattern recognition analysis was developed. To verify the method, 97 samples were tested with the new method, and the tests confirmed with HPLC, with the result that 17% of the commercial honey samples showed fraud from added sugars.
Honey is defined as “the natural sweet substance produced by honey bees” from the nectar of plants. However, there is not currently an FDA standard of identity for honey in the United States, which would further define and specify the allowed methods of producing, manufacturing and labeling honey (there is, however, a nonbinding guidance document for honey). Some of the details of honey production that a standard of identity might address include allowable timing and levels of supplemental feeding of bees with sugar syrups and the appropriate use of antibiotics for disease treatment.
In circumstances where strict regulatory standards for foods are not available, they may be created by other organizations.
What Is a Food Standard?
A food standard is “a set of criteria that a food must meet if it is to be suitable for human consumption, such as source, composition, appearance, freshness, permissible additives, and maximum bacterial content.”1
To ensure quality, facilitate trade, and reduce fraud, everyone in the supply chain must have a shared expectation of what each food or ingredient should be. Public standards set those expectations and allow them to be shared. They help ensure that stakeholders have a common definition of quality and purity, as well as the test methods and specifications used to demonstrate that quality and purity. Public standards help ensure fair trade, quality and integrity in food supply chains.
How Is a Standard Different from a Method?
A method is generally an analytical technique to assess a particular property of the content or safety of a food or food ingredient. For example, methods for detection of nitrates in meat products or baby food, coliforms in nut products, or high fructose syrups in honey. Methods are an important component of food standards.
A food standard goes a step further and provides an integrated set of components to define a substance and enable verification of that substance. Standards generally include a description of the substance and its function, one or more identification tests and assays (along with acceptance criteria) to appropriately characterize the substance and ensure its quality, a description of possible impurities and limits for those impurities (if applicable), and other information as needed (see Figure 1).
Figure 1. The Anatomy of an FCC Standard (Source: Food Science Program, Food Chemicals Codex, USP)
A standard defines both what a food or food ingredient should be and documents how to demonstrate compliance with that definition.
Public Standards and Food Fraud Prevention
Many of the foods prone to fraud are those that are not simple food ingredients, but agricultural products that can be more complex to characterize and identify (such as honey, extra virgin olive oil, spices, etc.). Milk products are an example of a commodity that is prone to fraud with a wide range of adulterants (for example, fluid cow’s milk is associated with 155 adulterants in the Food Fraud Database). Ensuring the quality and purity of a product link milk requires implementation of multiple analytical techniques or the development of non-targeted methods.
The creation of effective public standards with input by a range of stakeholders will be particularly important for ensuring the quality, safety and accurate labeling of these high value commodities in the future.
A Dictionary of Food and Nutrition 2005, Oxford University Press.
The Food Chemicals Codex is a source of public standards for foods and food ingredients. It was created by the U.S. FDA and the National Institute of Medicine in 1966 and is currently published by the nonprofit organization USP. The FCC contains 1250 standards for food ingredients, which are developed by expert volunteers and posted for public comment before publication.
The Decernis Food Fraud Database is a continuously updated collection of food fraud records curated specifically to support vulnerability assessments. Information is gathered from global sources and is searchable by ingredient, adulterant, country, and hazard classification. Decernis also partners with standards bodies to provide information about fraudulent adulterants to support standards development.
Today FDA released the results of its yearly report on pesticide residues, and the good news is that of the 6504 samples taken, most of them were below EPA tolerance levels. As part of the Pesticide Residue Monitoring Program for FY 2017, FDA tested for 761 pesticides and industrial chemicals in domestic and imported foods for animals and humans. The following are some highlights of the FDA’s findings:
Percentage of foods compliant with federal standards
96.2% of domestic human foods
89.6% of imported human foods
98.8% domestic animal foods
94.4% imported animal foods
Percentage of food samples without pesticide residues
Milk and game meat: 100%
Shell egg: 87.5%
Percentage of food samples without glyphosate or glufosinate residues
Milk and eggs: 100%
“Ensuring the safety of the American food supply is a critical part of the work of the U.S. Food and Drug Administration. Our annual efforts to test both human and animal foods for pesticide residues in foods is important as we work to limit exposure to any pesticide residues that may be unsafe,” said Susan Mayne, Ph.D., director of FDA’s CFSAN, in an agency release. “We will continue to do this important monitoring work, taking action when appropriate, to help ensure our food supply remains among the safest in the world.”
Food safety and food labeling are strictly regulated in Canada and therefore, honey adulterated with sugars labeled as genuine is considered fraudulent. The Canadian Food Inspection Agency (CFIA) investigated Canadian honey samples from various sources within the supply chain, such as importers, blenders, retailers and more. Almost 22% of imported samples were adulterated with added sugars, the domestic (Canadian) samples showed no adulterations. The CFIA will continue monitoring honey imports and take measures to avoid fraudulent products entering the Canadian market.
One of China’s most famous health brands has been banned from making honey and issued a steep fine in China after selling expired honey. For a long time, the brand’s “Premium” honey was a supposedly safe alternative in China compared to “fake” honey, mixed with sugar syrup.
Because of its high nutritional value and distinctive flavor, natural honey is a premium product with a price tag significantly higher than that of other sweeteners. As a result, honey is often the target of adulteration using low-cost invert sugar syrups. This article looks at two analytical approaches based on isotope fingerprint analysis using isotope ratio mass spectrometry (IRMS) that can be used to detect honey adulteration and safeguard product integrity.
Honey is a complex mixture of sugars, proteins and other compounds, produced in nature by honeybees from flower nectar or honeydew. The extent to which its sugars are present is heavily dependent on the floral source and differs significantly between honeys produced in different regions. Climate, processing and storage conditions can also have an effect on the amounts of these sugars.1
Fructose and glucose are the major components of honey, and account for 85–95% of the total sugars present. The remaining carbohydrates are a mixture of disaccharides, trisaccharides, and larger oligosaccharides, which give individual honeys their own characteristic taste.
These distinctive flavors, combined with honey’s renowned nutritional benefits and a growing consumer demand for natural, healthy ingredients, have contributed to a substantial increase in honey sales over the past few decades. However, this demand has also helped to raise costs, with some varieties, such as Manuka honey, reportedly selling for as much as $35 for a 250 gm jar.
Just like many other food products that have a premium price tag, intentional adulteration is a significant concern for the honey industry. The fraudulent addition of cheaper sweeteners, such as sugar derived from cane, corn and beet sources, to extend product sales, is unfortunately common within the marketplace.
Honey producers and suppliers therefore require reliable and accurate analytical techniques to profile the composition of honey to identify cases of adulteration. Using analytical data, honey adulteration and counterfeiting can be routinely identified and product integrity can be maintained.
Carbon Isotope Fingerprints of Honey
Analysis of honey is commonly undertaken using isotope ratio mass spectrometry (IRMS) for the detection of adulteration. Honey has a fingerprint, a unique chemical signature that allows it to be identified. To visualize this fingerprint, IRMS can be used to identify the botanical origin of its constituent sugars.
Two ways that carbon can be incorporated into plants by photosynthetic CO2 fixation are the Calvin cycle (also known as the C3 cycle) and Hatch-Slack cycle (the C4 cycle). The nectar used by bees to produce honey comes from plants that produce sugars via the C3 pathway, while the sugars derived from sugar cane and corn are produced by the C4 pathway.
Carbon naturally exists as two stable isotopes that behave in the same way, but possess different atomic mass numbers. Carbon-12 is the most abundant in nature (98.9%), whereas carbon-13 is far less common (1.1%). By measuring the ratio of carbon-13 to carbon-12 (13C/12C) using IRMS, the carbon isotope fingerprint of the honey can be determined. As more carbon-13 is incorporated in sugars produced by the C4 pathway, the adulteration of honey with sugar cane and fructose corn syrups, rich in C4 sugars, can be detected.
In unadulterated honey, the carbon isotope fingerprint will be similar to that of the natural protein precipitated from the honey. However, if cane sugar or high fructose corn syrup has been added, the isotope fingerprint of honey and protein will be significantly different.
Detection of Adulteration by EA-IRMS
One approach that has traditionally been used for the detection of honey adulteration is elemental analysis interfaced with IRMS (EA-IRMS).2 This highly robust, rapid and cost-effective technique is able to reliably detect the addition of C4 sugars in honey at levels down to 7%.3 The analytical approach complies with the official method for the analysis of C4 sugars in honey, AOAC method 998.12.4
In EA-IRMS, bulk honey is combusted in the presence of pure oxygen to form CO2 for analysis. The CO2 produced from the combustion of the bulk honey, including all sugars and the protein fraction, is analyzed by IRMS. Figure 1 shows carbon isotope fingerprints of four unique samples, including bulk honey and the proteins extracted from those honeys, determined using an EA-IRMS system. In each case of adulteration, shown in the grey columns, the honey δ13C value becomes more positive relative to the protein value, moving towards the carbon isotope fingerprint of C4 plants. The natural variation of δ13C in honey is shown by the red lines.5
Detection of Adulteration by LC-IRMS
While EA-IRMS can be used to identify cases of honey adulteration using the bulk sample, the analysis of low levels of added C4 sugars and C3 sugars (i.e., beet sugars) to honey reveal that a compound specific technique with more powerful separation capabilities is needed. Furthermore, as fraudsters develop more sophisticated adulteration techniques and effective ways of concealing their actions, it can be necessary to utilize other IRMS techniques.
Much lower limits of adulteration detection can be obtained from liquid chromatography interfaced with IRMS (LC-IRMS). This technique permits the analysis of very small sample amounts without the need for extensive preparation or derivatization, and can also identify C3 sugar adulteration, which EA-IRMS cannot readily achieve, and therefore serves as a strong, complimentary isotope fingerprint technique. There are IRMS portfolios available that allow for sequential automated analysis of both analytical techniques.
Using LC-IRMS, the sample is oxidized within the aqueous solvent eluting from the HPLC column. The oxidation reagent consists of two solutions: The oxidizing agent itself and phosphoric acid. Both are pumped separately and added to the mobile phase. Within this mixture, all individual organic compounds eluting from the HPLC column are oxidized quantitatively into CO2 upon passing through a heated reactor. In a downstream separation unit, the generated CO2 is then separated from the liquid phase and carried by a stream of helium gas. The individual CO2 peaks in the helium are subsequently dried in an on-line gas drying unit and admitted to the isotope ratio mass spectrometer via an open split interface.
As a result of my research, I found two fantastic resources describing the background of food fraud, the first is an excellent 3-minute podcast on our website, titled, Food Fraud by Dr. Jennifer McEntire, who at the time was VP and Chief Science Officer at The Acheson Group and is now the newly appointed VP of Science Operations at the GMA. Dr. McEntire succinctly gets to the crux of the reasons pertaining to food fraud and it is well worth a listen.
The second is a 3-minute slide deck narrated by renowned food safety expert Professor Chris Elliot, Director of the Institute of Global Food Safety at Queens University Belfast. Professor Elliot highlights the impact of various food frauds including melamine adulteration in milk, spices, meat and he specifically expands on the topic of honey laundering.
There are too many honey adulteration frauds to list here and while some have resulted in huge fines and criminal charges, there is one that will not go away is the mislabeling of Manuka honey. This premium product (and premium price) is a rare honey from New Zealand produced by bees that pollinate the manuka bush and has numerous claimed medicinal properties that can be extremely profitable for the fraudsters through substitution with a basic product. As food fraud is an international issue, various organizations likeInterpol and Europol have food fraud units and here in the UK the government has committed to, and is setting up a dedicated Food Crime Unit.
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