More than 50 per cent of analysed apple juice and rice samples had levels of mycotoxins produced by fungi that exceeded the maximum limits laid down by law, according to researchers from the University of Granada and the University of Valencia in Spain.

They are not very well known, but mycotoxins are the most widespread natural contaminant in foodstuffs globally, according to the researchers. Mycotoxins are toxic and carcinogenic substances produced by fungi, which reach the food chain through plants and their fruit.

Mycotoxins in apple juice

Researchers from the University of Granada used their own method of ‘microextraction and capillary electrophoresis’ to analyse concentrations of a kind of mycotoxins called ‘patulin’ in 19 batches of eight brands of commercial apple juice. They differentiated between conventional juice, organic juice and juice designed specifically for children.

“The results show that more than 50 per cent of the sample analysed exceeded the maximum contents laid down by European law,” said Monsalud del Olmo, co-author of the study, which was published in the June edition of the magazine ‘Food Control’.

The maximum levels of patulin allowed by the European Union (EU) are the 50 micograms per kilogram of product (ug/kg) for fruit juices and nectars, 25 ug/kg for compotes and other solid apple products and 10 ug/kg if those food products are aimed at breast-fed babies and young children.

However, some samples of conventional apple juices had as much as 114.4 ug/kg and one batch labelled as ‘baby food’ had 162.2 ug/kg, more than 15 times the legal limit.

Patulin is produced by several species of fungi of the Penicillium, Aspergillus and Byssochylamys varieties, which are found naturally in fruit, mainly apples. They are transferred to juices during processing because of their solubility in water and stability.

The neurotoxic, immunotoxic and mutagenic effects of this substance have been confirmed in animal models, and although it is not one of the most dangerous mycotoxins for health, it is included in group 3 within the categories laid down by the International Agency for Research on Cancer (IARC).

IARC toxin classifications

The IARC, which is a World Health Organisation (WHO) agency, classifies mycotoxins and other compounds in four groups according to their carcinogenic potential for humans: 1 (carcinogenic), 2 (probably or possibly carcinogenic), 3 (not classifiable as carcinogenic, although it has not been proven that it is not) and 4 (probably not carcinogenic).

Some mycotoxins, such as aflatoxins, are in group 1 and can be found in dry fruit, such as peanuts and pistachios, and cereals. University of Granada scientists said they had also detected concentrations of this compound above the permitted levels in a sample of rice, and they had already informed the relevant authorities of this.

Other toxins from fungi, such as fumonisins and ochratoxins, are also included in group 2. They are found in maize, other cereals and even beer, according to researchers from the University of Valencia.

Mycotoxins in beer

Meanwhile, a team from the University of Valencia has used a new technique – called HLPC-LTQ-Orbitrap – to detect the presence of fumonisins and ochratoxins in samples of beer in Germany, Belgium, the Czech Republic, Italy, Ireland, Poland and Spain. The study is also published in ‘Food Control’.

“They are minute quantities, although we cannot determine whether they are important because beer is one of the drinks which is not directly included in European law on mycotoxins,” said Josep Rubert, University of Valencia researcher and co-author of the study.

“What this study does show is that merely controlling the raw material – barley, in this case – is not enough,” added Rubert, “and that these toxins are present throughout the technological process, where it has been proven that mycotoxins that are legislated for can become hidden by joining wit glucose, so this needs to be taken into account for future research”.

Mycotoxins in other cereal products

The same Valencian team also analysed 1,250 samples of cereal-based products from Spain, France and Germany to see whether there are differences between organic and conventional foodstuffs in the case of fumosins.

According to the researchers, one of the most striking findings was that samples of gofio flour, commonly used in the Canaries, had concentrations of this mycotoxin in quantities greater than 1000 μg/kg, the limit established by European law. A couple of years ago, researchers also identified a consignment of wheat flour with concentrations of ochratoxin above the permitted level.

When the limits laid down by the EU are exceeded, scientists inform the relevant authorities, especially the European Food Safety Authority (EFSA). Then the contaminated batch must be withdrawn.

Organic vs conventional

The results of the study of cereal-based foodstuffs show that almost 11% of the organic products examined contain fumosins, whereas in conventional products this percentage is reduced to around 3.5%.

“The explanation could be that organic foodstuffs do not contain fungicides or other pesticides, so fungi may have a more favourable environment and increase their toxins. However, in any case, there are other important factors such as climatic conditions – heat and humidity benefit these microorganisms – and storage conditions which also influence the production of mycotoxins,” said Mr Rubert, who said that researchers recognise that analysis must be done on a case-by-case basis.

In fact, in the study of apple juices, the opposite happened, and the organic products had fewer mycotoxins than the conventional ones. What the researchers do agree on is the need to keep defining the toxicity of each of these harmful substances, studying their effects on health and developing more and more exact methods of analysis.