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Mycotoxins are secondary metabolites of filamentous fungi that contaminate food products such as fruits, vegetables, cereals, beverages, and other agricultural commodities.
Mycotoxins are naturally occurring, poisonous compounds produced from filamentous fungi or molds that can be found in foods. Mycotoxins have a huge set of chemical compounds generated by diverse mycotoxigenic fungi species [1]. Over 400 toxic metabolites are produced by more than 100 fungi species [2]. Humans are exposed to mycotoxins through the consumption of contaminated foods [3]. They can pose negative health effects, ranging from acute toxicity to chronic symptoms, such as kidney damage, liver damage, immune deficiency, and cancer [4][5].
Cereal grains and fruits can be infected by molds at various stages of production, for example, during cultivation, harvesting, and storage [6]. The contamination of mycotoxins is a worldwide problem, but it is more serious in humid and warm environmental conditions that favor the growth of fungi and production of mycotoxins. As secondary metabolites, mycotoxins are very durable chemical components that can be transmitted from raw materials to processed products such as beverages, which can pose a serious health risk to consumers (Figure 1).
Figure 1. Mycotoxin contamination of beverages and adverse effects on health (drawn using Adobe Illustrator CC software).
Over the last few years, distinguishable progress in society has driven reforms in the world beverage market. Consumers are becoming more conscious about the effect of diet on their health. Beverages are not only responsible for providing energy and hydration but also for strengthening health and preventing nutrition-related defeciencies [7]. The application of effective measures to protect consumers from the toxic effects of mycotoxins and, subsequently, to defend against public health is very significant and crucial.
Aflatoxins (AFs) are mainly produced by Aspergillus spp. In most of the cases, contamination with AFs takes place after harvesting and during storage. Inappropriate management during transportation and storage including exposure to conditions such as high humidity (˃65%) and temperatures rapidly increases the AF concentration in food.
Ochratoxins (OTs) are group of mycotoxins that are mostly generated by Aspergillus and Penicillium species. The occurrence of OTA-producing fungi and the level of OTA may vary with the climatic conditions [8]. OTA is generally found in subtropical areas and in high-temperate climate regions and can be available in various food products in these areas, for example, beer, wine, and grape products [9]. Table 1 summarizes the major mycotoxins responsible for the contamination of beverages.
Table 1. Major mycotoxins involved in the contamination of beverages.
Mycotoxins | Products Contaminated | Producing Microorganisms | References |
---|---|---|---|
Aflatoxins B1, B2, G1, G2 |
Orange, apple juice, grape juice, grapefruit peel | Aspergillus chevallieri, A. flavus, A. niger, A. oryzae, A. parasiticus, A. repens, A. ruber, A. tamarii, and A. wentii | [10][11] |
Ochratoxin A (OTA) | Grape juice, coffee, beer, and wine | A. ochraceus, A. carbonarius, A. niger, A. tubingensis, and Penicillium expansum | [10][12] |
Patulin (PAT) | Fruit juices | Penicillium expansum, P. patulum, Aspergillus clavatus, Byssochlamys fulva, and B. nivea |
[13][14] |
Fumonisins (FBs) | Beer | Fusariumproliferatum, F. verticillioides, and F. nygamai | [15][16][17] |
Trichothecenes (type B: Deoxynivalenol (DON)) |
Plant-based beverages, beer | F. graminearum, F. cerealis, and F. culmorum | [16][18][19][20] |
Trichothecenes (type A: HT-2) |
Functional vegetable milks, beer | F. sporotrichioides,and F. langsethiae | [20][21] |
Trichothecenes (type A: T-2 toxin) |
Plant-based milks, beer | F. sporotrichioides, and F. langsethiae | [19][21] |
Zearalenone (ZEN) | Beer, wine | F. graminearum, F. culmorum, F. equiseti, F. cerealis, F. verticillioides, and F. incarnatum | [16][22] |
Alternaria toxins (TeA, AOH, AME) | Fruit juices, wine, beer | Alternaria alternate, A. tenuissima, and A. arborescens | [23][24] |
Patulin (PAT) is predominantly generated from various Penicillium, Aspergillus, and Byssochlamys species and possesses various hazardous features such as toxicity, carcinogenicity, and mutagenicity. P. expansum, B. fulva, and B. nivea are significant PAT-producing microorganisms. Patulin has been identified in many foods, particularly in fruits and beverages [25].
Fumonisin (FB) mycotoxins are secondary metabolites of Fusarium spp, mostly Fusarium verticillioides and F. proliferatum. It was found to be a contaminant of wheat, corn, and barley.
Trichothecenes (TCs) belong to a large group of structurally related toxins, mainly produced by fungal species of the Fusarium genus [26]. T-2 and HT-2 toxins have been detected in barley, oat, maize, wheat, rice, beer, and plant-based milks, especially in oat- and soy-based milks and beverages [19][26][27][28]. Deoxynivalenol (DON) is synthesized by different species of the Fusarium genus, mainly by Fusarium culmorum and Fusarium graminearum in cereals [29]. It also contaminates cereal-based food products, for instance, pasta, bread, and beer.
Zearalenone (ZEN) is produced by various species of Fusarium, mainly F. graminearum, F. culmorum, and F. sporotrichioides. It infects corn, wheat, barley, oat, and rye, mainly in areas with temperate climates [30].
The main Alternaria mycotoxins are Tenuazonic acid (TeA), Alternariol (AOH), and alternariol monomethyl ether (AME). Alternaria spp., mainly Alternaria alternata, A. tenuissima, and A. arborescens produce Alternariols and are found in a large range of foods including berries, prune nectar, carrot juice, apple juice concentrate, grape juice, raspberry juice, cranberry juice, beer, and red wine [31][32].
In most cases, mycotoxin levels in contaminated food and beverages can be very low, and this necessitates the development of a suitable, rapid, and sensitive detection method. Various analytical testing procedures have been developed for mycotoxin detection and quantification due to their diverse forms [33]. Normal chromatographic procedures are usually time consuming and cost intensive; therefore, a range of methods, mostly based on immunological principles, have been developed and commercialized for quick determination [34]. Some common mycotoxin detection methods in beverages as well as beverage-producing crops are summarized in Table 2.
Table 2. Overview of common detection methods for mycotoxins in beverages as well as beverage-producing crops.
Analytical Methods | Detection Method | Toxin | Applicability | LOD | References | Advantages | Disadvantages |
---|---|---|---|---|---|---|---|
TLC | CCD | Patulin | Apple Juice | 14 µg/L | [35] | Time saving, specific fluorescence spot on UV light | Limited plate length and environmental effects on measurement |
HPLC | FD | OTA | Wheat | 23 pg | [36] | Fast, high resolution data, accurate and easily reproducible. Less training required | Expensive and method development could be challenging |
MS/MS | Wine | 0.005 ng/ml | [37] | ||||
FD | 0.09 µg/L | [38] | |||||
AFs | Food items | 1.6-5.2 mg/kg | [39] | ||||
UV and FD | Milk | 0.13–0.16 mg/L | [40] | ||||
LC | FD | OTA | Wine | 0.07 ng/ml | [41] | Several mycotoxin detections, high sensitivity, provides confirmation | Expensive, required expertise In case of MS, sensitivity depends on ionization |
ZEN | Barley, Maize, Wheat | 100 µg/Kg | [42] | ||||
AFB1 | Corn | 2–5 ng/g | [43] | ||||
MS/MS | Trichothecenes | Wheat and maize | 0.2–3.3 µg/Kg | [44] | |||
Automated microarray chip reader | Chemiluminescence | OTA | Coffee | 0.3 µg/L | [45] | High throughput, multiplexed, parallel processing method | Not so common to their variability and reproducibility, require intensive labor |
Electro-polymerization onto surface | SPR | ZEN | Corn | 0.3 ng/ml | [46] | Suitable for cereals sample, sim- plicity, portability, and ease to use, can be used in field |
Optimization and validation not reported for this method |
Immunochromatographic strip | Highly Luminescent Quantum Dot Beads | AFB1 | Maize | 0.42 pg/ml | [47] | A simple method for rapid screening, superior performance | Required expertise |
Direct, competitive magneto-immunoassay | SPR | OTA | Beverages | 0.042 µg/L | [48] | Rapid, cost effective, and sensitive | |
Electrochemical | FB | Maize | 0.33 µg/L | [49][50] | |||
Lateral flow immunoassay | Colorimetric | 199 µg/Kg | [51] | Fast, one-step assay, no washing step, low cost and simple | Qualitative or semi quantitative results, sample volume governs precision | ||
Photonics immobilization technique | Quartz-crystal microbalance (QCM) | Patulin | Apple puree | 56 ng/ml | [52] | Specific, higher sensitivity, generality, response (only requires a few minutes), flexibility, and portability |
The decrease of the signal in the presence of high analyte concentrations, in situ analysis |
Surface-enhanced Raman scattering (SERS)-based immunoassay | Silica-encapsulated hollow gold nanoparticles | AFB1 | Food | 0.1 ng/ml | [53] | Enhanced ELISA method | Hard to synthesize and expensive |
ELISA | UV absorbance | AFM1 | Milk | 4–25 ng/L | [54] | Fast, simple, economical, high sensitivity, simultaneous analysis of multiple samples, easy to screen | Lack of precision at low concentrations, matrice interference problems, possible false-positive/negative results |
ZEN | Maize | 0.02 µg/L | [55] | ||||
AFB1 and AFM1 | Food items | 0.13-0.16 mg/L | [40] | ||||
Electrochemical | FB | Corn | 5 µg/L | [56] |
Thin layer chromatography = TLC, High performance liquid chromatography = HPLC, Liquid chromatography = LC, Enzyme-linked immunosorbent assay = ELISA, FD = Fluorescence detection, Ultraviolet = UV, Charge-coupled device = CCD, Surface plasmon resonance = SPR, Mass spectrometry = MS.
Nearly all mycotoxins are thermally resistant and cannot be simply degraded by normal heat treatment methods during food processing or household cooking methods [17]. Normally, mycotoxin contamination in beverages can be controlled by preventing the contamination of agricultural raw materials used for the production of beverages [57][58].
Implementation of good manufacturing practices will help to ensure safe beverage production without mycotoxin residues. Good manufacturing practices (GMPs) include the use of proper sorting, processing, drying, cooling, and storage conditions for agricultural raw materials. Complete reduction in the number of mycotoxins, or at least a number not higher than the maximum allowable limits, can be achieved by different pre- and postharvest treatments [59] (Figure 2).
Figure 2. Scheme for reducing the mycotoxin concentration in beverages using postharvest treatments (drawn using Adobe Illustrator CC software).
Mycotoxins possess very stable chemical structures that remain unchanged after pasteurization treatment. It has been reported that proper selection, adequate cleaning and washing, and careful sorting of fruits are very crucial factors for the mitigation of mycotoxin contamination during the manufacturing of beverages [60]. As children drink more juices than wine as compared to adults, therefore, the incidence of mycotoxins in fruit juices is a matter of serious concern [61][62].
Physical methods can be applied at large and small scales for a wider range of food, but some physical methods including irradiation have negative effects on the nutritional, antioxidant, and sensorial properties of food. Chemical methods are easy to use and comparatively cheap, but their main limitation is the toxicity of residues and secondary products. Additionally, the toxicity of the mycotoxin-degraded products needs to be measured. Although the adsorption of mycotoxins by chemical adsorbents is one of the most inexpensive detoxification methods, the safety of absorbent materials and the removal of the adsorbent–mycotoxin complex from foods is still challenging. In addition, the overall sensorial quality and final quality parameters (color, clarity, brix, titratable acidity, pH, and TSS) can be adversely affected by chemical treatments. Biological control methods are healthy and environmental friendly. However, microbial approaches may deteriorate the food quality by absorbing nutrients and releasing metabolites into the food matrices. Additionally, biological control methods are more expensive than physical and chemical control measures. Another critical challenge is the commercialization of biological control methods by overcoming the limitations in translation from laboratory trials to commercial applications.