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While blue is the most popular color around the world, not all blues are created equal and or belong into the food supply. The Rapid Alert System for Food and Feed in Europe mentioned a case of unauthorized food dye Sudan Blue II in a roasted corn snack food. Sudan Blue II, also known under the name Solvent Blue 35, is used to dye oils, solvents, alcohols, esters, hydrocarbon derivatives and other industrial chemicals, and is classified as carcinogenic and harmful to humans and the environment.
N-nitroso compounds (NOCs), or nitrosamines, have once again made headline news as their occurrence in some pharmaceuticals has led to high profile product recalls in the United States.1 Nitrosamines can be carcinogenic and genotoxic and, in the food industry, can compromise a food product’s quality and safety. One nitrosamine in particular, N-nitrosodimethylamine (NDMA), is a highly potent carcinogen, traces of which are commonly detected in foods and may be used as an indicator compound for the presence of nitrosamines.2
NOCs can potentially make their way into the food chain in a number of ways, including (but not limited to): Via the crop protection products used to maximize agricultural yields; via the sodium and/or potassium salt added to preserve certain meats from bacterial contamination; as a result of the direct-fire drying process in certain foods; and via consumption of nitrates in the diet (present in many vegetables due to natural mineral deposits in the soil), which react with bacteria and acids in the stomach to form nitrosamines.3
The crop protection and food manufacturing industries are focused on ensuring that levels of nitrosamines present in foods are minimal and safe. Detection technology for quantitating the amount of nitrosamines (ppm levels) in a sample had not advanced in nearly 40 years—until recently. Now, a thermal energy analyzer (TEA) —a sensitive and specific detector—is being relied on to provide fast and sensitive analysis for players throughout the food supply chain.
Regulatory Landscape
Both NDMA and the nitrosamine N-nitrososodiethylamine (NDEA) have been classified by national and international regulatory authorities as ‘probable human carcinogens’.3 NDMA in particular is by far the most commonly encountered member of this group of compounds.7
In the United States there are limits for NDMA or total nitrosamines in bacon, barley malt, ham and malt beverages, yet there are currently no regulatory limits for N-nitroso compounds (NOC) in foods in the EU.7
Developers of crop protection products are required to verify the absence of nitrosamines or quantify the amount at ppm levels to ensure they are within the accepted guidelines.
Crop Protection
The presence of nitrosamines must be traced and risk-managed along the food’s journey from farm to fork. The issue affects testing from the very beginning – particularly at the crop protection stage, which is one of the most highly regulated industries in the world. Without crop protection, food and drink expenditures could increase by up to £70 million per year and 40% of the world’s food would not exist.7
Development of a new crop protection product (herbicide, fungicide, insecticide or seed treatment) involves several steps: Discovery and formulation of the product, trials and field development, toxicology, environmental impacts and final registration. New product registration requires demonstration of safety for all aspects of the environment, the workers, the crops that are being protected and the food that is consumed. This involves comprehensive risk assessments being carried out, based on data from numerous safety studies and an understanding of Good Agricultural Practice (GAP).
One global producer of agrochemicals uses a custom version of the TEA to verify the absence of nitrosamines or quantitate the amount of nitrosamines (ppm levels) in its active ingredients. The LC-TEA enables high selectivity for nitro, nitroso and nitrogen (when operating in nitrogen mode), which allows only the compounds of interest to be seen. Additionally, it provides very high sensitivity (<2pg N/sec Signal to Noise 3:1), meaning it is able to detect compounds of interest at extremely low levels. To gain this high sensitivity and specificity, it relies on a selective thermal cleavage of N-NO bond and detection of the liberated NO radical by the chemiluminescent signal generated by its reaction with ozone.
The customized system also uses a different interface with a furnace, rather than the standard pyrolyser, to allow for the additional energy required and larger diameter tubing for working with a liquid sample rather than gas.
The system allows a company to run five to six times more samples with increased automation. As a direct result, significant productivity gains, reduced maintenance costs and more accurate results can be realized.
Food Analysis
Since nitrite was introduced in food preservation in the 1960s, its safety has been debated. The debate continues today, largely because of the benefits of nitrite in food products, particularly processed meats.6 In pork products, such as bacon and cured ham, nitrite is mostly present in the sodium and/or potassium salt added to preserve the meat from bacterial contamination. Although the meat curing process was designed to support preservation without refrigeration, a number of other benefits, such as enhancing color and taste, have since been recognized.
Analytical methods for the determination of N-nitrosamines in foods can differ between volatile and non-volatile compounds. Following extraction, volatile N-nitrosamines can be readily separated by GC using a capillary column and then detected by a TEA detector. The introduction of the TEA offered a new way to determine nitrosamine levels at a time when GC-MS could do so only with difficulty.
To identify and determine constituent amounts of NOCs in foods formed as a direct result of manufacturing and processing, the Food Standards Agency (FSA) approached Premier Analytical Services (PAS) to develop a screening method to identify and determine constituent amounts of NOCs in foods formed as a direct result of manufacturing and processing.
A rapid and selective apparent total nitrosamine content (ATNC) food screening method has been developed with a TEA. This has also been validated for the known dietary NOCs of concern. This method, however, is reliant on semi-selective chemical denitrosation reactions and can give false positives. The results can only be considered as a potential indicator rather than definitive proof of NOC presence.
In tests, approximately half (36 out of 63) samples returned a positive ATNC result. Further analysis of these samples by GC-MS/MS detected volatile nitrosamine contamination in two of 25 samples.
A key role of the TEA in this study was to validate the alternative analytical method of GC-MS/MS. After validation of the technique by TEA, GC-MS/MS has been proven to be highly sensitive and selective for this type of testing.
The Future of Nitrosamine Testing
Many countries have published data showing that toxicological risk from preformed NOCs was no longer considered an area for concern. Possible risks may come from the unintentional addition or contamination of foods with NOCs precursors such as nitrite and from endogenous formation of NOCs and more research is being done in this area.
Research and innovation are the foundations of a competitive food industry. Research in the plant protection industry is driven by farming and the food chain’s demand for greater efficiency and safer products. Because the amount of nitrosamines in food that results in health effects in humans is still unknown, there is scope for research into the chemical formation and transportation of nitrosamines, their occurrence and their impact on our health. Newer chromatographic techniques are only just being applied in this area and could greatly benefit the quantification of nitrosamines. It is essential that these new approaches to quality and validation are applied throughout the food chain.
Hamlet, C, Liang, L. (2017). An investigation to establish the types and levels of N-nitroso compounds (NOC) in UK consumed foods. Premier Analytical Services, 1-79.
Park, E. (2015). Distribution of Seven N-nitrosamines in Food. Toxicological research, 31(3) 279-288, doi: 10.5487/TR.2015.31.3.279.
Crews, C. (2019). The determination of N-nitrosamines in food. Quality Assurance and Safety of Crops & Foods, 1-11, doi: 10.1111/j.1757-837X.2010.00049.x
In the following article, the author reports finding Sudan dye in spices in New York State, making the argument for Class I recalls.
In New York State (NYS), Department of Agriculture and Markets food inspectors routinely sample domestic and imported food from retail markets for food dye determination. For decades, the NYS Food Lab has examined both domestic and imported food for undeclared allowed food dyes and unallowed food dyes utilizing a paper chromatography method. This method works well with water-soluble acid dyes, of which food dyes are a subset.
The NYS Food Lab has participated in four sets of the FAPAS proficiency tests: Artificial Colours in Soft Drinks and Artificial Colours in Sugar Confectionary (Boiled Sweets). The qualitative analysis was by paper, thin layer silica and thin layer cellulose chromatography. Satisfactory results were obtained.
The paper/thin layer chromatography method is a qualitative non-targeted method and has a limit of detection of approximately 1 to 5 ppm (parts per million) depending on the dye. If an unallowed dye is detected, the food product is violated as adulterated and results are forwarded to the FDA.
Some countries have a maximum concentration of allowed food dye in a food product. For example India has a 100 ppm to 200 ppm maximum for their allowed food dyes, in some food, singly or in combination.1
Early 2011, sesame seeds were found to contain Rhodamine B.
In early 2011, a food sample of pink colored sugar coated sesame seed from Pakistan was sent to the lab for color determination. The paper chromatography method could not determine any dyes. (As found out later, the unknown pink dye was not an acid dye.) From research it was found that Rhodamine B was a pink water soluble basic dye commonly used as a food adulterant. A standard was ordered and then a qualitative high performance Liquid chromatography-tandem mass spectrometry (HPLC/MS/MS) method was developed (Waters UPLC Aquity w/Waters Premier XE triple quadrapole) to determine Rhodamine B. After utilizing this new method, Rhodamine B was found in the sugar coated sesame seed.
Rhodamine B is an industrial dye and is not allowed in food anywhere in the world. Industrial dyes are not allowed in food because they are toxic; in fact, some industrial dyes are used for suicide.2,3,4 In addition, industrial dyes are not made to “food grade” specifications with regard to dye purity, heavy metal (i.e., arsenic and lead) concentrations, subsidiary dye concentrations and concentrations of unreacted precursors. From additional research of news articles and research papers, more industrial dyes were identified as common food adulterants; more dye standards were ordered and incorporated into the HPLC/MS/MS method. The NYS Food Lab’s current HPLC/MS/MS surveillance method includes 36 compounds: Water soluble “acid dyes” and “basic dyes”, organic solvent soluble “solvent dyes”, and several pigments.
The HPLC/MS/MS method has a limit of detection in the ppb (parts per billion) range for some dyes and parts per trillion for other dyes. The FDA has an action level of 1 ppb for certain water-soluble basic dyes (such as Malachite Green) when used as a fish antibiotic. However, due to concern that unallowed dyes might be present due to contamination from packaging, the food lab subsequently set an action level of 1 ppm for unallowed dyes determined by the HPLC/MS/MS method. At levels over 1 ppm, detection of dyes in food would indicate intentional dye usage for coloring food.
The food lab has participated in three rounds of the FAPAS proficiency test, “Illegal Dyes found in Hot Pepper Sauce”. The qualitative analysis was by LC/MS/MS. Satisfactory results were obtained.
Sudan Dyes Considered to be Carcinogenic
“Sudan dyes are not allowed to be added to food. There has been worldwide concern about the contamination of chili powder, other spices, and baked foods with Sudan dyes since they may have genotoxic and carcinogenic effects (according to the International Agency for Research on Cancer)”.5
“There have been several documented cases of spices being contaminated with carcinogenic dyes such as Sudan I or lead oxide. We therefore assume that the presence of these chemicals in spice ingredients will be considered a reasonably foreseeable hazard under this rule.”6
“Sudan red dyes have been used to color paprika, chili powders, and curries, but are also known carcinogens and are banned for use in foods.” 7
Sudan Dyes are a family of more than 10 synthetic industrial “solvent dyes”. Solvent dyes are typically used to color oils and waxes, including shoe polish. Sudan dyes that the food lab has found in spices include Sudan 1 (Sudan I), and Sudan 4 (Sudan IV). Sudan 1, also known as Solvent Yellow 14, is an orange colored dye. Sudan 4, also known as Solvent Red 24, is a blue shade red colored dye.
Positive identification of Sudan 4 is often hindered by the existence of a positional isomer, Sudan Red B (Solvent Red 25). This problem was addressed by using the HPLC/MS/MS method with a transition unique to Sudan 4 (381.2 > 276.0). This information was obtained from one of the two corroborating labs. The food lab has recently identified a transition unique to Sudan Red B (381.2 > 366.1).
Sudan Dyes Found in Spices in Europe
In March 2001, Europe began discovering Sudan dyes in spices. A February 2017 search of Europe’s Rapid Alert System for Food and Feed (RASFF) for “unauthorised colour” and “sudan” in the “herbs and spices” food category resulted in 429 notifications.
The 429 RASFF notifications arranged by year and by maximum concentration reported of Sudan 1 and Sudan 4 during that year are listed in Table I.
Table I.
In a search of the FDA’s Import Alert 45-02 (Detention Without Physical Examination and Guidance of Foods Containing Illegal and/or Undeclared Colors) the author could find no record of spices violated for Sudan dye adulteration.
In a search of the FDA’s Enforcement Reports the author could find no record of spices violated for Sudan dye adulteration.
Industrial Dyes in Food: Class II or Class I Recall?
The NYS Food Lab and the FDA routinely find imported food containing unallowed food dyes such as Ponceau 4R, Amaranth and Carmoisine. These unallowed food dyes are allowed for use in food in other parts of the world, while not allowed in the USA. Foods containing unallowed food dyes are violated as adulterated and a Class II recall will occur. Sudan dyes are not allowed as food dyes anywhere in the world. They are industrial dyes, used in coloring oils and waxes, such as shoe polish.
“Class I recall: A situation in which there is a reasonable probability that the use of or exposure to a violative product will cause serious adverse health consequences or death.
Class II recall: A situation in which use of or exposure to a violative product may cause temporary or medically reversible adverse health consequences or where the probability of serious adverse health consequences is remote.”8
With a Class II recall, there is no consumer notification. In contrast, as part of a Class I recall, a press release is issued. Consumers who have purchased the product might be informed and may discard the product or return it for a refund.
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