Adulteration is a legal term meaning a food product fails to meet legal standards. It indicates the intentional, fraudulent addition of extraneous, improper, or cheaper ingredients to a product or the dilution or removal of a valuable ingredient with the intention of increasing profits, ultimately compromising quality and resulting in the sale of substandard foods. Economically Motivated Adulteration (EMA) is estimated to cost the food and beverage industry between $10 billion to $15 billion per year. The increasingly global nature of the food supply chain as well as the massive size and scope of the food and beverage industry makes combating EMA a very daunting task. The UK Food Standards Agency (FSA) defines two main types of food fraud: the deliberate misdescription of food and the sale of food that is unfit and potentially harmful, although a combination of these can exist for certain incidents. The FSA estimates that approximately 10% of all food on UK supermarket shelves is adulterated in some form. In the United States, the Federal Food, Drug, and Cosmetic (FD&C) Act was passed in 1938 and contains criteria for food adulteration. Criteria that make food adulterated include: a poisonous or deleterious substance that makes it unsafe in the food itself or container, an unsafe pesticide chemical residue, food additive, animal drug, or color additive, and a filthy, putrid, or decomposed substance as well as being prepared, packed, or held under unsanitary conditions. Improper irradiation, dietary ingredients that present a reasonable risk of illness or injury when consumed under the conditions recommended in labeling, and improper importing are included as well. The criteria for EMA is as follows: a valuable constituent that has been omitted in whole or in part replaced with another substance, concealing damage or inferiority, or the addition of a substance that has been added to increase the bulk or weight, reduce quality or strength, or make it appear of greater value than it is worth. The FD&C has been amended numerous times and both the Federal Meat Inspection Act and Poultry Products Inspection Act contain provisions for adulteration as well. Some adulteration can be defined as incidental, meaning foreign substances can be incorporated into food from negligence or ignorance. This can occur during harvesting. Harvesting at the wrong time can also create adulteration by reducing nutritional value or having a product with an improper moisture level. Farmers may do this out of fear of theft or because they need money quickly. Intentional adulteration occurs with the intent to cause harm or create economic gain. Some forms of intentional adulteration are relatively innocuous, such as mispresenting the origin of a product. While this may entail a reduction in product quality, it does not present the potential for harm. In other cases, the intentional addition of toxic substances has resulted in illness and even death. In today’s social media environment, any reported incident of adulteration can have devastating consequences to the reputation and profits of food and beverage manufacturers and sellers, even if the adulteration was not their direct fault. One such example is the UK supermarket chain Tesco, which suffered a €300 million drop in market value in 2013 after horsemeat was discovered in burgers sold in their markets. Although no one was physically harmed, consumer anger led to the decrease in market value and a big hit to the company’s reputation. Brand confidence, company reputation, and the market economy can all suffer from publicized incidents of adulteration. New methods of adulteration are being developed all the time and present a big challenge to the food and beverage industry to detect and prevent adulteration.
History and Incidents
The documented history of food fraud and adulteration goes all the way back to Assyrian tablets and Egyptian scrolls in biblical times. In the Middle Ages, high value imported spices were often combined with nutshells, seeds, juniper berries, and even stones and dust. Even today, spices are considered one of the most economically desired targets for adulteration because of a high value unit per mass and specificity of desired flavor characteristics. During the 18th and 19th centuries in the United States, chalk and plaster were used to water down and color milk as well as to bulk up flour. Lead was added to wine and beer. Dirt, sand, and leaves were added to coffee, tea, and spices. Preserved fruit and vegetables were artificially colored with copper salts. In more recent times, adulteration methods have become more advanced and sophisticated plus the expansion of global markets and the current social media environment have made the consequences for manufacturers and sellers of food and beverage even more pronounced. Some high-profile incidents have made global news in recent years. In 1994, ground paprika in Hungary was adulterated with lead oxide, leading to several deaths and dozens of illnesses. In 2005, Sudan I dye was discovered in Worcestershire sauce contaminated with adulterated chili powder. Sudan I dye is a known rodent carcinogen and is banned as a food additive. Herbal medicines have been adulterated with the withdrawn obesity medication sibutramine. Thirty-four products marketed as herbal supplements were recalled by the FDA in 2009 for containing sibutramine. More warnings have been issued in recent years for dietary supplements marketed as “natural”, “traditional”, or “herbal medicine”. Similar incidents have occurred in other countries. China was the location for two high-profile incidents of melamine adulteration. Melamine is a plasticizer that mimics high quality protein in routine quality tests. In 2007 it was discovered in pet food, leading to the deaths of thousands of dogs and cats and raising concerns about the safety of food imported from China. In China in 2008, melamine was added to milk and infant formula. The incident led to the hospitalization of around 54,000 infants, six deaths from kidney stones, and multiple criminal prosecutions including the execution of two of the conspirators. The horsemeat in burgers incident in England had tough consequences for the market. Sometimes the statistics of food can reveal adulteration just from analysis. In 2013, harvest statistics of the expensive Manuka honey from New Zealand revealed that only 1,700 tons of it were harvested per year, yet global sales of this honey were as high as 10,000 tons per year. Obviously, widespread fraudulent selling of ordinary honey as the more expensive Manuka honey occurred for this to happen. A test of dried oregano from English and Irish supermarkets revealed that nineteen out of seventy-eight samples contained other ingredients. These ingredients include olive and myrtle leaves and were present at levels ranging from 30% to 70%. In 2015, seven of Italy’s largest olive oil producers were under investigation for selling virgin olive oil as the higher quality extra virgin olive oil. Testing of twenty brands revealed that nine of them were found to not meet standards for extra virgin olive oil. On a larger scale, Operation Option IV was coordinated by Interpol and Europol at the end of 2014 and beginning of 2015. More than 2,500 tons of counterfeit and illicit foods were seized in forty-seven countries, including mozzarella cheese, strawberries, eggs, cooking oil, and dried fruit. These documented incidents underscore the large global scale of the food adulteration problem and the need for fast, cost-effective, and evolving methods for testing and monitoring of food fraud.
Methods for food adulteration are always evolving and changing, making it difficult for testing and detection to keep up. Spices are a primary target of adulteration. They can be adulterated by adding a non-food substance, such as Sudan I dye or brick dust. Another method is to add a lower quality consumable substance. Examples of this include tomato skin in paprika, starches in onion powder, and buckwheat, millet, papaya seeds, and chili in black pepper. Black pepper is the most widely used spice in the world and thus is frequently subjected to adulteration. A substitution of a lower-quality product fits the definition of adulteration as well, such as adding Chinese Cassia cinnamon to the higher quality Ceylon cinnamon. Spent plant material added to the final product and exhaustively extracted material both qualify as adulteration. Sibutramine adulteration in herbal supplements falls under similar standards for adulteration. There have even been reports of selling road salt as food salt. Olive oil is another valuable food product that is frequently subjected to adulteration. Standards for extra virgin olive oil are strict and there are many ways to adulterate olive oil. Misrepresentation of geographical origin constitutes adulteration. A cheaper type of oil such as vegetable oil can be added. Poorer olive products such as pomace are another example. All edible oils can be subjected to adulteration but since olive oil is the most valuable, it occurs the most often in olive oil. Popular beverages have become very valuable in the market and adulteration can occur in them. Coffee is extremely popular in many parts of the world and has been adulterated by misrepresentation of geographical origin, lower quality beans, and cheaper foreign materials, such as husks and stems, chicory, grains like corn and barley, woody tissue, cocoa or soya beans, and acai berries. Alcoholic beverages are another popular beverage around the world that offer a tempting target for adulteration. Examples of adulterants in alcoholic beverages include excess water, ethanol not meant for human consumption (such as antiseptic or fuel additive) and the potentially toxic methanol in distilled beverages. Wine can be misrepresented by vintage and adulterated by adding sweetener, extra water, or other additives. Fruit juices are a valuable commercial product and can be subjected to saccharin adulteration, addition of low-quality sugars, and dilution with water. Likewise, honey is very valuable and is a target for adulteration with cheaper sugar products, such as corn syrup, sugar cane syrup, agave syrup (C4 sugars), rice, wheat, and beet syrup (C3 syrups) as well as misrepresenting higher quality honey with a lower quality brand. Sugar adulteration can occur by adding the cheaper sugar directly to the honey or feeding the bees with it, leading to lower quality honey. The dairy industry has many possibilities for adulteration. The value of milk varies depending on the animal of origin and lower value milk can be added to more valuable varieties of milk. For example, cow milk can be adulterated with buffalo, bovine, ovine, or caprine milk. Camel milk is one of the most valuable milks on the market and cow milk can be an adulterant in that case. Foreign proteins can be added as adulterants and this has proven to be dangerous, even in the case of other consumables like soy, pea, almond, wheat, and peanuts because they can cause food allergies in people. Peanut allergies are a common cause of food fatal and near-fatal allergies, making peanuts an especially dangerous adulterant if consumed by someone allergic to them. The high-profile cases of melamine adulteration in infant formula and pet food show the dangers of using a foreign toxic substance as an adulterant. Milk can be also be adulterated in its powdered form. Grains and flour are also potential targets for adulteration. In the case of cereals, the price is chiefly determined by protein content, starch content, and hardness which can vary greatly based on varieties and geographical origins. The same is true for rice. Both cheaper varieties and foreign substances like husk and sand have been added to adulterate cereals and rice. In the case of flour, durum wheat flour is considered to be superior in the manufacture of pasta products and is approximately 20% more expensive than common wheat, making durum wheat flour adulteration with common wheat flour a prime target. A more dangerous form of adulteration in flour is the addition of castor bean meal. Castor bean meal contains ricin, which is a toxic protein. Gluten free products have become a huge part of the food market in recent years and cross-contamination of gluten in products that are marketed as gluten-free is a form of adulteration. One example of this is adding the gluten source wheat flour to rice and corn-based products. The meat and seafood markets are extremely large across the globe and are likewise subjected to adulteration. Typical meat adulteration methods include the addition of water to increase weight and adding a lower quality meat to higher quality meat. The verification of a proper meat species is important for both ethical and religious concerns. Examples of meat adulteration include turkey meat in beef, lamb and beef with horsemeat, chicken, and pork, and veal with pork. In the case of seafood, the large global supply chain presents particular challenges in detecting adulteration. A cheaper product added as an adulterant is one form, such as mixing lower quality crab meat with higher quality. Crab meat is expensive and makes a prime target for adulteration. Other forms of seafood adulteration can be very difficult to detect. Freshly caught fish have a higher nutritional value than farm-bred fish, making fresh fish more valuable in the market. Representing farm fish as freshly caught constitutes adulteration. Frozen-thawed cycles are defined as the number of times a fish is thawed and frozen before consumption. Repeated frozen-thawed cycles will decrease the nutritional value of fish and thus can be constituted as a form of adulteration if a fish has lost nutritional value after being thawed and re-frozen multiple times. The multiple methods of adulteration that are continuously emerging present a tremendous challenge when it comes to testing and monitoring for adulteration.
Monitoring and Testing
Testing for food adulteration has become a big part of food quality control. Visual examination to detect adulteration is usually insufficient for multiple reasons. In most cases, the amount of adulterant added to make an economic difference in the product is small enough that it can not be visually detected. The concentration of a toxic adulterant that is enough to make a product dangerous for human consumption is usually small enough that visual detection is impossible (such as melamine in dairy products). Adding water to meat, fresh fish vs. farm-bred fish, and multiple frozen-thawed cycles are other examples where visual detection is impossible. Thus, many methods have been developed for detecting adulteration in food and beverage products. Such analysis can vary from analyzing the headspace gases around a sealed product to free flowing, turbid, and viscous liquids to intact solid products. Headspace gas analysis is done by gas chromatography (GC). It measures the volatiles emitting from the sample and can detect the presence of inappropriate compounds, indicating the possibility of adulteration. Mass spectrometry (MS) is an effective tool for identifying the composition and structure of chemicals in a compound. GC and MS are often used in combination to identify different substances in samples and separate compounds into individual components. High-Performance Liquid Chromatography (HPLC) is often used for liquid analysis and has proven to be an effective tool in detecting many forms of food adulteration. Wet chemistry tests can be used as well and these are good for determining adulteration by measuring composition of components in food. Examples of this are acid hydrolysis and solvent extraction for fat and the Kjehdahl method for protein. These tests can be inadequate for some types of adulteration, as will be shown in the analysis of melamine adulteration in dairy products and animal feed. Morphological, microscopic, and DNA tests can be used as well depending on the food or beverage being analyzed. While these methods are usually effective, they have numerous drawbacks. They are time-consuming, expensive, and require the use of both chemicals that must be carefully handled and skilled technicians. These tests are also impossible to implement on a large scale as they are far too expensive to test multiple portions of the same batch. Sample preparation can be an extensive process and the tests may not be representative of what is occurring in a large batch of food or beverages. There is a need for fast, non-invasive testing methods for food that are cost-effective and can be representative of a large batch of food or beverage. One category of methods that fit these criteria is infrared spectroscopy.In recent years, infrared spectroscopic methods such as visible (VIS), mid-infrared (Mid-IR), and near-infrared (NIR) have shown potential for the verification of the authenticity of food and beverage products. Vibrational spectroscopy has proven to be effective in determining composition analysis, product quality assessment, and production control. Spectra can provide a global fingerprint which when combined with the application of chemometric techniques can be used to extract compositional characteristics that are not easily detected by traditional chemical analysis. Work is required to interpret the complex spectra obtained but once effective calibrations are created, they can be a very powerful tool for both qualitative and quantitative analysis of a product. There are numerous advantages over traditional techniques. Spectroscopic methods are easy to use in routine operations, environmentally friendly, cost-effective, and can be used to test a large portion of any food or beverage batch in a reasonable amount of time. They also possess the advantage of being able to measure multiple constituents in products with a single acquisition of a spectrum, provided that calibration models have been created for each parameter of interest. Out of VIS, Mid-IR, and NIR, NIR has proven to be the most effective of these three methods. NIR requires minimal if any sample preparation, can test a large portion of a sample, and has light penetration deep into the sample. VIS and Mid-IR are both inferior to NIR when it comes to sample preparation time and testing a large portion of a sample. The potential savings in the form of reduced time and cost of analyses have positioned NIR spectroscopy as not only an attractive technique with a bright future in food and beverage adulteration analysis, but for analyzing all kinds of natural products as well. Application studies have proven the effectiveness of NIR spectroscopy as a technique for adulteration detection. There is a clear role for spectroscopic techniques in the production plant and at critical points in the food and supply chain that will continue to evolve with more work as the 21st century moves forward.
Summary of Published Papers, Articles, and Reference Materials
Thirty-nine research papers on using NIR spectroscopy to detect food fraud and adulteration in numerous segments of the food and beverage industries were examined and summarized. Food and beverage products examined were spices, edible oils, honey, alcoholic and non-alcoholic beverages, dairy, animal feed, flour, meat, and seafood. Some topics were research concerning well-publicized incidents, such as melamine in dairy products, sibutramine in herbal medicines, and horsemeat in beef. Others were more anticipating of potential adulteration in the future. The types of adulterants examined ranged from relatively innocuous to potentially fatal. Misrepresentation of origin or substituting a cheaper quality product (in most cases) constitute adulteration that may have market consequences but little threat to human health. Contamination with peanut products or gluten are two examples of a product substitution that could create health issues. Adulterants that can have severe consequences to human health include melamine, sibutramine, Sudan I dye, methanol, industrial gelatin, and castor bean meal. Some studies compared different sampling methods and types of instruments, with an emphasis on practical advantages and disadvantages in a real setting. The feasibility of using NIR spectroscopy to replace current expensive and time-consuming methods for detecting food adulteration and food fraud was presented in all studies and the results are summarized in the individual sections.