Introduction
Mycotoxins are metabolic substances produced by fungi and molds contaminating grains, fruits, forages, feed, human food, and the environment (Gonçalves et al., 2017). They differ in chemical structure, biosynthetic origins, and biological effects (Bellio et al., 2016). Aflatoxins (AFs) are a subset of mycotoxins produced by molds. Several of them are categorized into a larger family of toxic compounds, i.e., di-furanocoumarins, four of which are common food contaminants (Bellio et al., 2016).
These are designated as B1, B2, G1, and G2. Aflatoxin B1 (AFB1) – the most potent aflatoxin – is produced by the mold of the genus Aspergillus, especially species A. parasiticus, A. flavus, and A. nomius that grow in various agricultural products causing food and feed contamination, and subsequently, human health risks and economic losses in crop/animal production. Because of the many economic importance of aflatoxins, it is important to scrutinize the existing literature to understand the standard methods of testing for aflatoxin poisoning.
The investigation can also help find out the national and international requirements about milk safety and gauge on the documented evidence to make an informed decision on whether mycotoxin testing in agricultural processing should be voluntary or mandatory.
Methodology
The sources of information for the project are peer-reviewed journals, scientific papers, and reports from government institutions, NAAS, FDA, and USDA. These sources are a cornucopia of information on mycotoxins, their effects on various agricultural commodities, and the many quality control programs initiated by the government to handle the same. However, this paper confines itself to the pros and cons of aflatoxins testing in the agricultural production and milk processing industry. Relevant information and statistics as pertains to mandating or not mandating AFs testing in dairy and other agricultural products are garnered and incorporated within it.
Background Information
Usually, there is a public health concern when humans and livestock consume food contaminated with high concentrations of aflatoxins. That is because AFs induce many negative physiologic processes in human beings and dairy animals. Some of the effects include the induction of carcinogenesis, mutagenesis, teratogenesis, immunosuppression, and hepatotoxicity. Ingested AFB1 undergoes biotransformation in the liver of the dairy animal to yield a monohydroxylated metabolite –aflatoxin M1 (AFM1) –that is excreted in the milk (Gonçalves et al., 2017).
AFM2 may also be produced. These secondary metabolites also have profound toxic and carcinogenic effects in the body. In lactating cows, primary manifestations of aflatoxicosis comprise a decrease in feed intake, a decline in milk production, weight loss, signs of fatty degeneration, liver fibrosis, hepatocellular carcinomas, laminitis, decreased immunity, and alteration in milk fat and protein composition (Gonçalves et al., 2017).
When dairy animals consume feed that is soiled with AFB1, the milk produced is contaminated with AFM1. This metabolite is detectable in milk even with the ingestion of sublethal doses of AFB1. The standard rate of conversion of AFB1 from feed to AFM1 in milk in lactating cows is ~ 1-2% (Gonçalves et al., 2017). However, extremely high excretion rates of AFM1 have been observed in cows of a specific genetic pool, implicating genetics in the determination of liver biotransformation rates and differential organismal sensitivity to xenobiotics (Gonçalves et al., 2017). The amount of AFM1 excreted is affected by the concentration of AFB1 ingested, milk production, stage of lactation, mammary gland health status, and the animal sensitivity to aflatoxins (Gonçalves et al., 2017).
Origins of Testing
As a result of hostile weather conditions and insect damage, the 1977 maize crop grown in the Southeastern USA was adversely affected by the growth of the Aspergillus molds (Food and Drug Administration, 2005). The surveys conducted by the FDA revealed potentially harmful levels of aflatoxins in milk. It was from that incident that the agency established the 0.5µg/L threshold for AFM1 contamination of fluid milk products (Food and Drug Administration, 2005).
Since then, the FDA routinely monitors dairy products for aflatoxins contamination. On suspicion of the probable aflatoxicosis, samples of fluid milk products are collected randomly, mixed, and analyzed by one of the protocols for AFM1 testing. The agency obtains milk samples from dairy farms, milk tankers, milk processing plants, and finished milk products. The level of testing performed is dependent upon the extent of mycotoxin contamination on animal feed.
Also, confirmation of the identity of the aflatoxin is done by the chemical derivative test. If the analysis reveals that the sample contains > 0.5µg AFM1, appropriate legal action is taken against the source of the specimen. In addition, that milk is diverted to non-edible uses, and the milk products already supplied in the market are removed from the shelf.
Methods for Testing Aflatoxins
The analytical process chosen to assay for aflatoxins depends on the type of the target molecule, chemical characteristics, complex matrix, timing of testing, and the expected limits of quantification (Bellio et al., 2016). The methods are either chromatographic or immunochemical in nature. Immunochemical tools are helpful in the speedy screening of AFM1 in diverse samples. Enzyme-linked immunosorbent assay (ELISA), used alongside sodium citrate solvent, is suitable for quantifying AFM1 in milk and milk products.
It has excellent sensitivity, excellent optimal recovery, and high precision. Alternative immunochemical methods include immunoaffinity column assay (ICA), radioimmunoassay (RIA), and sequential injection immunoassay (SILA) (Bellio et al., 2016).
Usually, chromatographic methods are valuable for either verification of the results obtained from rapid screening tests or for the precise quantitative determination of aflatoxins (Bellio et al., 2016). That is because these analytical techniques require elaborate sample preparation steps and trained personnel. These methods include TLC, HPLC/fluorometric detection, and liquid chromatography-tandem mass spectroscopy (LM-MS/MS). The use of Elisa and HPLC tests concurrently permits high-volume analysis of samples, thus saving time and money without compromising analytical accuracy and quality.
The Need for Testing
Milk is a common foodstuff in most communities and contributes remarkably to the nourishment of people of all ages. Therefore, to ensure public health and safety, it is imperative that any milk provided for human use is not contaminated above the limits established by the international and national regulatory bodies (Gonçalves et al., 2017). Factors such as geographic location, the development level of a nation, and climatic conditions determine the concentration of AFM1 in milk. Since international trade has created a global village, it implies that dairy products from one part of the world may be accessed by consumers from the other parts of the world far away.
Thus, it is necessary to assay the levels of aflatoxins in milk produced from various locations to protect consumers from its harmful effects. Many countries have set maximum residue levels (MRL) of AFM1 allowed in milk, and the tolerance limit for AFB1 in dairy cows feed (Gonçalves et al., 2017). These limits vary between countries depending on economic considerations and risk assessment. For instance, in the United States, the MRL for AFM1 is 0.5µg/L, while the European Commission adopted a significantly lower figure (0.05µg/L) (Gonçalves et al., 2017).
Because AFM1 has a high hepatocarcinogenic potential, the permissible levels of AF in dairy products are under strict regulation in the Western world (Gonçalves et al., 2017). The regulatory limits for the US and Europe areas mentioned above. Moreover, since the metabolism of carcinogens is normally slower in children than in adults, a stricter AFM1 limit (0.025µg/L) is imposed on milk processed for infants and children use (Pennington, 2012).
The US government has invested heavily in a mycotoxin research program whose objectives are to devise ways of preventing fungus and toxin production in crops, methodology development, study the effects of processing, and toxicological analysis. These are accomplished via institutions like the USDA’s Agricultural Research Service (ARS), the Cooperative State Research Education and Extension Service (CSREES), and FDA’s Center for Food Safety and Applied Nutrition (Pennington, 2012).
The monetary provision caters to scientists’ salaries, laboratory costs, agency administrative costs as well as infrastructural costs. Due to the huge fiscal and intellectual resources invested in the program, it is reasonable that the testing of aflatoxins is made mandatory. That explains why the US and other governments enforce mandatory AFM1 guidelines despite the additional costs of acquiring testing kits incurred.
The FDA has put a maximum level of contamination of 20ppb for dairy feed, and once this level is exceeded, the feed cannot be given to milking dairy cattle for consumption (Food and Drug Administration, 2005). If the feed has aflatoxins levels in the range of 20 – 300ppb, it is used as a consumption material for hogs and beef cattle. When the feed has greater AFB1 levels than 300ppb, then it is discarded. It has been outlawed to sell feed with “AFB1 levels greater than 20ppb for lactating dairy cows, and the seller of the feed is responsible for damages resulting from the sale of such feed” (Pennington, 2012, para. 4).
The mandatory testing of aflatoxins in dairy products is necessary since several studies have associated AFM1 contamination with changes in seasons, with the colder seasons reporting more cases (Pennington, 2012). Thus, the challenges of aflatoxin contamination of dairy products oscillate between high and low incidents dependent on the prevailing climatic conditions, and one cannot assume that it is wholly solved. Similarly, aflatoxins naturally contaminate various agricultural produce, whether they are in the field or store.
Reasons against Testing
Aflatoxin toxicities have been demonstrated in model animals and revealed mixed susceptibilities in these animals (Bellio et al., 2016). However, the impact of AFs on humans has not been determined. Also, the acute toxicity of AFs in humans has not been detected quite often. The argument is that various incidences in which several people are alleged to have died due to consumption of foodstuff with lethal doses of aflatoxins are speculations and not substantiated (Bellio et al., 2016).
Also, the information available on AFs as human carcinogens is not entirely consistent. Several studies have associated liver cancer occurrence with AFs consumption in the diet (Pennington, 2012). However, in each of the cases, the positive results for hepatitis B virus infection, a well-known risk factor for hepatocellular carcinomas, confounds the various epidemiological studies.
Cases of aflatoxins presence in milk and other agricultural produce cause substantial losses to dairy farmers as they often lead to consumer reluctance to purchase dairy products. The cattle growers also incur losses as the milk processors use such a context to bargain for a drop in milk-acquisition price (Pennington, 2012).
In developed nations, stringent procedures that monitor mycotoxin levels in food shield the populations from ingesting high doses of aflatoxins. Nevertheless, in developing countries where communities struggle with starvation, these regulations may be nonexistent or enforced leniently. In such a scenario, strict control of aflatoxin-infested food is not possible. Such measures may lead to a lack of food and heightened food prices. Populations in these parts of the world consume food with significant amounts of aflatoxins and survive. Observations of this nature are in line with anecdotal evidence in which several persons are reported to have consumed foodstuff containing lethal doses of aflatoxins and yet remained healthy.
Analyzing food for the probable aflatoxin contamination adds substantial costs to the industry and to the government regulatory and action authorities. These prices skyrocket in the years when contamination of the commodities is high. It has been estimated that the US spends roughly $10 million and $30 – $50 million on the annual acquisition of test kits and sample testing, respectively (Pennington, 2012).
The best way of regulating AFM1 levels is to monitor feed for AFB1 through improved production practices and the use of proper storage conditions. Also, the potential health hazards of aflatoxins may be minimized by enhancing awareness of farmers, dairy producers, and consumers on the same. Once these measures are in place, aflatoxins would be eliminated in the food chain, rendering testing unnecessary.
Conclusion
The effects of aflatoxins on livestock and human health are significant and cannot be ignored. Cognizant of this fact, many governments have implemented various quality control mechanisms and also made it mandatory for dairy farmers and milk processors to test for AFs in their milk products before availing it to both the local and international markets. Scientific research provides objective evidence that supports the need for mandating AFs testing in foodstuff.
References
Bellio, A., Bianchi, D. M., Gramaglia, M., Loria, A., Nucera, D., Gallina, S.,…Decastelli, L. (2016). Aflatoxin M1 in cow’s milk: method validation for milk sampled in Northern Italy. Toxins (Basel), 8(3), 57-65. Web.
Gonçalves, B. L., Gonçalves, J. L., Rosim, R. E., Cappato, L. P., Cruz, A. G., Oliveira, C. A. F., & Corassin, C. H. (2017). Effects of different sources of Saccharomyces cerevisiae biomass on milk production, composition, and aflatoxin M1 excretion in milk from dairy cows fed aflatoxin B1. Journal of Dairy Science, 100(1), 5701–5708. Web.
Pennington, J. A. (2012). Aflatoxin M1 in milk. Web.
U. S. Food and Drug Administration. (2005). CPG sec. 527.400 whole milk, lowfat milk, skim milk – aflatoxin M1. Web.