Introduction

OCCURANCE OF ALTERNARIA SPP. ON SMALL GRAINS

DETECTION METHODS OF ALTERNARIA SPECIES

ALTERNARIA TOXINS

• dibenzo-α-pyrone derivatives: alternariol (AOH), alternariol monomethyl ether (AME), altenuen (ALT), altenuisol (AS);
• tetramic acid derivates: tenuazoic acid (TEA)
• perylene derivatives: altertoxins I, II, III (ATX-I,-II,-III)

a Source: European Food Safety Authority (2011); Abbreviations: AOH:alternariol; AME: alternariol monomethyl ether; ALT:altenuen; TEA:tenuazoic acid; ATX:altertoxin I; N: number of tested samples; n: number of samples>LOQ; LOQ: limit of quantification; LOD: limit of detection, n.d: not detected
The database concerning toxicological effects of Alternaria toxins in experimental animals and/or in humans is currently too limited to be used as a basis for detection of reference points for different toxicological effects. Experiments performed in rodents with purified Alternaria toxins indicate that the acute toxicity is in the following order: ALT > TeA > AME and AOH. However, these data are not suitable for the risk assessment of Alternaria toxins since the risk for public health related to these toxins is not expected to result from acute exposures (EFSA, 2011).Mycotoxins such as AOH and AME are found to be mutagenic and genotoxic and in certain areas in China might be responsible for oesophageal cancer (Liu et al., 1992). The mycotoxingenic potential depends on species and strains of the fungus, composition of matrix and environmental factors, such as temperature and moisture, and particularly water activity (aw) (Fernandez-Cruz et al., 2010). According to Magan et al. (1984) A. alternata needs rather high water activity (aw=0.98) to produce mycotoxins on wheat grain. Knowledge of mycotoxin production under marginal or sub-optimal temperature and aw conditions for growth can be important since improper storage conditions accompanied by elevating temperature and moisture content in the grain can favor further mycotoxin production and lead to reduction in grain quality (Oviedo et al., 2011)
Several methods have been reported in the literature for the determination of Alternaria toxins from food commodities. In particular, analytical methods are largely based on procedures, involving clean up by solvent partitioning or solid phase extraction, followed by chromatographic separation techniques, in combination with ultraviolet, fluorescence electrochemical and mass spectroscopic detection (Ostry, 2008). Since none of the mentioned techniques have been validated by interlaboratory studies and because of the lack of certified reference materials or proficiency studies available for the determination of Alternaria toxins, validated analytical methods for the quantification of Alternaria toxins are needed as a prerequisite for a survey on their occurrence in feed and food (Battilani et al., 2009).

PREVENTION AND FUTURE CONCERNS

The occurrence of mycotoxins in the food chain is an unavoidable and serious problem the world is facing with. Once the foodstuffs are contaminated with toxins it is impossible to eliminate them. Certainly, the best protection against mycotoxins is monitoring their presence in feed and food (Matić et al., 2008). Prevention of fungal contamination and thereby toxin production can be achieved either during preharvest stages by good agricultural practice and the use of a HACCP plan, as well as during postharvest stages by the application of proper drying, storage, and transport procedures (FAO, 2001). Application of fungicides at field might reduce fungal infection resulting in the decrease of mycotoxins production. However the modern trends are toward environmentally friendly alternatives at the field level rather than relying on chemicals (Bhaat et al., 2010). Development of resistant cultivars with the application of modern biotechnological methods would prove to be effective way for prevention and control hazardous fungi and their mycotoxins. A proven system of storage management which includes drying, avoiding grain damages and ensuring proper storage conditions is needed. To reduce or prevent production of most mycotoxins, drying should take place as soon as possible after harvest and as rapidly as feasible. Fungi cannot grow (or mycotoxins cannot be produced) in properly dried foods, so efficient drying of commodities and maintenance of the dry state is an effective control measure against fungal growth and mycotoxin production (FAO, 1989). Damaged grain is more prone to fungal invasion and mycotoxin contamination, thus it is important to avoid damage before and during drying, as well as in storage. Insect pests and storage pests may attack grain and due to  their activities accumulated moisture provides ideal condition for fungal growth.

However, besides toxicity and occurrence, the chemical behavior of mycotoxins during food processing needs to be understood when assessing risks associated with the consumption of food made from contaminated raw materials. Siegel et al. (2010) investigated the stability of AOH, AME and ALT upon bread baking using a spiked wholemeal wheat flour. The obtained results indicated that the Alternaria mycotoxins are barely degraded during wet baking, while significant degradation occurs upon dry baking, with the stability decreasing in the following order AME >AOH > ALT.

Further studies are needed to clarify the possible tranfer of the toxins into wheat flour after milling and their fates during food processing and coocking (Li and Yoshizawa, 2000) Additionally, more work is needed towards impact of Alternaria spp. on technological quality of small grains and small-grains based products. There is relatively large number of studies on the impact of fungal infection on food safety and yield parameters (Plavšić et al., 2010), but information on the effect of mycobiota infection on technological parameters is rather scant. A significant decrease in technological wheat quality in kernels attacked by Fusarium spp. and Alternaria spp. was proved in the researches of Šarić et al. (1997). According to these authors, increased enzyme activity of field moulds in samples with severe infection has negative impact on physical dough properties which leads to a complete wheat uselessness for further processing. Bodroža et al. (2012) found out that flour obtained from wheat affected with Fusarium spp. and Alternaria spp. showed less water and less stability during mixing and higher protein weakening during heating in comparison to the flour from wheat treated with fungicide.

Research gaps include also official validated methods for Alternaria metabolites analysis in order to carry out surveys of food and obtain an estimate of human exposure to Alternaria toxins. Additional toxicological work with purified Alternaria toxins, such as subacute toxicity and cancer studies, are also required (Magan and Olsten, 2004). Since there are no specific regulations for any of the Alternaria toxins in food, surveys to check the occurrence of these metabolities in order to ensure that contamination level do not pose a significant hazard to human health are strongly suggested.

CONCLUSION

Contamination of food and agricultural commodities by various types of toxigenic molds is a serious and a widely neglected problem. Alternaria speciesare ubiquitous plant pathogens and saprobes and are often found on small grains and small-grains based products. Alternaria spp. are also well known as post-harvest pathogens causing considerable economic losses to growers and the food-processing industry. They are of particular interest because suitable conditions may lead to production of a number of mycotoxins, such as AOH, AME, TeA, which may be implicated with human and animal health disorders. Most Alternaria mycotoxins exhibit considerable cytotoxic, carcinogenic, foetotoxic, teratogenic, antitumoral, antiviral and antibacterial activity. Prevention of fungal invasion ongrains is by far the most effective method of avoiding mycotoxin problems. It should consider an integrated management program, focusing on the good agricultural practice and food quality from the field to the consumer. Since there is currently no regulations set on Alternaria toxins in food and feed in the Europe nor worldwide, more attention is needed in monitoring of production of food safety products.

АCKNOWLEDGEMENTS

This work was supported by the project III46005 “Novi proizvodi cerealija i pseudocerealija iz organske proizvodnje” (“New products based on cereals and pseudo cereals from organic production”) financed by the Ministry of Education, Science and Technological development of the Republic of Serbia.

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