Trends in Food Science & Technology 46 (2015) 110e119
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Review
Aflatoxin M1 in milk and dairy products, occurrence and recent challenges: A review S.Z. Iqbal a, S. Jinap a, b, *, A.A. Pirouz a, b, A.R. Ahmad Faizal a a b
Food Safety Research Centre (FOSREC), Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia
a r t i c l e i n f o
a b s t r a c t
Article history: Received 14 November 2014 Received in revised form 18 August 2015 Accepted 22 August 2015 Available online 28 August 2015
Background: Milk is a highly nutritious food, and it is a source of necessary macro- and micronutrients for the growth, development and maintenance of human health. However, it may also be a source of natural food contaminants that may cause disease. The presence of aflatoxin M1 (AFM1) in milk and dairy products throughout the world has been known since twenty to thirty ago. Milk and dairy products contamination with aflatoxin M1 is important problem worldwide especially for developing countries for the last ten to twenty years. Scope and Approach: The presence of this mycotoxin in these products is important issue, especially for children and infants, who are more susceptible than adults. This review provides information regarding the occurrence of AFM1 in milk and dairy products in many regions of the world, its stability during processing and some reduction strategies. In this review the toxicity, occurrence of AFM1 in milk and dairy products (preferably for the last 5 years), regulations, strategies for its reduction, latest developments in detection methodologies and future challenges are described. Key Findings and Conclusions: Strict regulations and adapting good storage practices in developed countries have minimized the contamination of AFM1 in milk and dairy products. The current advancements in analytical techniques have helped the law enforcement agencies to implement strict regulations. Furthermore, the improvement in analytical facility and increasing the awareness related to the health effects of AFM1 in milk and dairy products could minimize its occurrence level in developing countries. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Aflatoxin M1 Milk and dairy products Occurrence Analytical techniques Future challenges
1. Introduction Milk is a highly nutritious food containing many macro- and micronutrients that are essential for the growth and maintenance of human health. The health of human populations is often reflected in the condition of their food-producing ecosystems. Moreover, the implementation of food regulations may be directly linked with the quantity and quality of available food. Therefore, consumers from developing countries, especially from rural areas, face issues related to food security and food safety because they depend on locally produced foods (Marroquín-Cardona, Johnson, Phillips, & Hayes, 2014). The presence of aflatoxin M1 (AFM1) in
* Corresponding author. Food Safety Research Centre (FOSREC), Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia. E-mail address:
[email protected] (S. Jinap). http://dx.doi.org/10.1016/j.tifs.2015.08.005 0924-2244/© 2015 Elsevier Ltd. All rights reserved.
milk and dairy products is an important issue, especially for developing countries (Prandini et al., 2009). 2. Aflatoxins Aflatoxins (AFs) are a major class of mycotoxins produced primarily by Aspergillus species including Aspergillus flavus, Aspergillus parasiticus and Aspergillus nomius (Creppy, 2002). Aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1) and aflatoxin G2 (AFG2) are the major classes of AFs (Sweeney & Dobson, 1998). Factors such as prolonged drought, high temperatures, substrate composition, storage time and storage conditions play an important role in fungal growth and the synthesis of AFs (Stack & Carlson, 2003, p. 43). Aflatoxin B1 is the most toxic, carcinogenic, teratogenic and mutagenic class of AFs (Iqbal, Paterson, Bhatti, & Asi, 2010) and is listed as a group I carcinogen by the International Agency for Research on Cancer (IARC, 2002; Iqbal, Asi, & Jinap, 2014a). Shortly
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after the discovery of AFs, researchers suggested that its residue might occur in milk and other animal products from animal that ingested contaminated feedstuff (Van Egmond, 1993). 3. Aflatoxin M1 and its toxicity Aflatoxin M1 is a hydroxylated metabolite of AFB1, as shown in ~ o, & Hussain, 2012), that is excreted in milk in Fig. 1 (Asi, Iqbal, Arin the mammary glands of both humans and lactating animals (Fallah, Jafari, Fallah, & Rahnama, 2009). Approximately 0.3e6.2% of AFB1 is converted into metabolized AFM1 and excreted in milk, depending on factors such as the genetics of the animals, seasonal variation, the milking process and the environmental conditions (Unusan, 2006). International Agency for Research on Cancer (IARC) has placed it with AFB1 as a Group 1 carcinogen (IARC, 2002). Studies have shown that the presence of AFM1 in milk and milk products is a health issue because in many countries, every age group regularly consumed these products in their daily diet (Fallah et al., 2009). Furthermore, it may subsequently contaminate other dairy products, such as cheese, yoghurt, and may generate health concerns for consumers. Aflatoxin B1, is the most toxic subtype, considered from the viewpoint of both toxicity and occurrence, most attention was given to its metabolite aflatoxin M1 (Van Egmond, 1993). The conversion of AFB1 to the AFM1 is typically considered a detoxification process because the in vivo carcinogenicity of AFM1 is approximately only 10% of that for AFB1. Furthermore, using in vitro metabolic activation, AFM1 only has 10% of the mutagenicity of AFB1 (Wogan & Paglialunga, 1974). The relative carcinogenicity of AFB1 and AFM1 correlate with the relative metabolic activation rates observed in vitro using rat hepatic microsomes (Neal & Colley, 1979). However, the acute toxicities of the two toxins in ducklings and rats are very similar quantitatively as well as qualitatively. The symptoms of acute aflatoxicosis that are normally observed in mammals include lethargy, lack of appetite, rough and/or pale coat hair, ataxia, and enlarged, fatty livers. Meanwhile, the symptoms of chronic AF exposure typically include jaundice, decreased feeding efficiency and milk production, and loss of appetite. AFs may lower resistance to diseases and interrupt vaccine-induced
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immunity (Diekman & Green, 1992). Furthermore, weight gain and intake diets containing 700 mg/kg AFs have an effect on beef cattle. However, if the increase in liver weight was employed as the criterion for toxicity, 100 mg/kg would be deemed toxic to beef cattle. The health and productivity of dairy herds may be influenced at dietary AFs levels higher than 100 mg/kg, which is significantly more than the amount that produces illegal milk residues (Patterson & Anderson, 1982). Guthrie (1979) has reported that when lactating dairy cattle in a farm situation were fed a diet containing 120 mg/kg of AFs, their reproductive efficiency decreased, and when these cattle were fed with non AFs contaminated feed, their milk production increased by 25%. Milk production decreased in cows consuming AFs produced by culture, however if pure AFs was ingested their production was not markedly affected (Applebaum, Brackett, Wiseman, & Marth, 1982). 4. Stability and reduction of AFM1 in milk and dairy products AFM1 is very stable at high temperatures. Several studies have investigated the distribution/stability of AFM1 from milk to milk products. Oruc, Cibik, Yikmaz, and Kalkanli (2006) found that AFM1 was stabile in kashar cheese for over 60 days and in traditional white pickled cheese for over 90 days. Their results showed that the toxin was stable during cheese storage and ripening. In another study, Govaris, Roussi, Koidis, and Botsoglou (2002) studied the stability of AFM1 in yoghurt artificially contaminated with concentrations of 0.050 and 0.100 mg/L during storage for 4 weeks at 4 C and at pH values of 4.0 and 4.6. Their results show that at pH 4.6, the AFM1 levels did not significantly change (p > 0.01); however, in the yoghurt at pH 4.0, AFM1 decreased significantly (p < 0.01) after the third and fourth weeks of storage at both concentrations. Therefore, this decrease in AFM1 may be a function of low pH. In a similar study, during the fermentation of yoghurt, the AFM1 levels decreased significantly (p < 0.01) from the initial levels present in milk. The authors concluded that this decrease in AFM1 levels may be attributed to factors such as low pH, the formation of organic acids or other fermentation byproducts, and even the presence of Lactobacillus sp. (Govaris et al., 2002). However, Bakirci (2001) has found 13% higher level of AFM1 in yogurt
Fig. 1. Aflatoxin B1 metabolism in liver.
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samples as compared to bulk-tank milk samples, but the difference of AFM1 level was not statistically significant. Cattaneo, Marinoni, Iametti, and Monti (2013) observed the stability of AFM1-contaminated whey and deproteinized whey subjected to different technological treatments. During ricotta cheese production, the majority of AFM1, 94% on average, was removed in the discarded whey, so only 6% remained in the curd. Then, the use of ultrafiltration and diafiltration removed more than 90% of the toxin remaining in the whey or deproteinised whey discarded from ricotta cheese production. The spray-drying was efficient in reducing AFM1 contamination in whey, where toxin retention was approximately 60%, while in deproteinized whey, the AFM1 retention was approximately 39%. During the processing of milk and liquid milk products, Ultrahigh treatment (UHT), typically in range 135e150 C, is used to commercially sterilize milk and liquid milk products (FAO & WHO, 2009). Some reports e.g. Purchase (1967) and Kabak (2012) have indicated reductions of up to 32% in AFM1 during heat treatments, while others e.g. Galvano, Galofaro, and Galvano (1996) have indicated that AFM1 is heat stable. In another report, depending on the conditions employed to heat the milk, 12e35% decrease in the AFM1 content of the milk was observed. In general, however, aflatoxins are stable during heat treatment (Prandini et al., 2009). There are several reports of attempts to reduce the level of AFM1 in milk or dairy products (Carraro et al., 2014; Elsanhoty, ~ o et al., 2013). Salam, Ramadan, & Badr, 2014; Serrano-Nin Carraro et al. (2014) used clays to remove or attenuate AFM1 contamination in bovine milk. This study showed that bentonites were very efficient, and contaminated bovine milk (up to approximately 80 ng/L) was purified to safe levels (50 ng/L for adults and 25 ng/L for lactants) with only a slight alteration of the nutritional properties of the milk. Elsanhoty et al. (2014) used different strains of lactic acid bacteria in yogurt to reduce the AFM1 level. The yoghurt fermented by 50% yoghurt culture (S. thermophilus and L. bulgaricus) and 50% L. plantrium attained the highest reduction in the AFM1 level at the end of the storage ~ o et al. (2013) used five period. In another study, Serrano-Nin strains of probiotic bacteria for the reduction of AFM1 in milk in an in vitro digestive model. These results revealed that all assessed strains exhibited different degrees of aflatoxin binding in PBS, ranging from 19.95 to 25.43%. Furthermore, the bioaccessibility of AFM1 in the in vitro digestive model was reduced from 23 to 45%, depending on the probiotic strain assessed. Therefore, more studies on the detoxification of AFM1 are necessary to completely destroy this lethal toxin. Therefore, to minimize the health risks associated with these toxins, most countries have implemented regulations (Iqbal, Asi, & Jinap, 2013). 5. Regulations on aflatoxin M1 in milk and dairy products The international regulations for the maximum limit for AFM1 in milk and dairy products range from 0 to 1.0 mg/kg are shown (Table 1). The EU limits the total AF levels to no more than 20 mg/kg in lactating dairy feeds and 0.05 mg/kg in milk. Practically, the regulatory limit is defined as the concentration of AFM1 in milk equivalent to 1.7% (range from 0.8 to 2.0%) of the concentration of total AFs in dry matter. Cattle consuming a diet containing 30 mg/kg AFs will excrete milk containing AF residues above the 0.5 mg/kg level (EFSA, 2004). The United States Food and Drug Administration established action levels for AF concentrations of 20 and 0.5 mg/kg for human food and milk, respectively (Chase, Brown, Bergstrom, & Murphy, 2013). The regulatory limits for AFs in food vary from 0 to 50 mg/ kg (FAO, 2009). According to the United States regulations, the
Table 1 Regulation on aflatoxin M1 in milk and milk products in different countries. Country
Milk (mg/kg)
Dairy products (mg/kg)
USA EUa Austria
0.50 0.05 0.05, 0.01 (pasteurized infant milk)
France Switzerland
0.05, 0.03 (for children
