Dried fruits marketed in Russian: toxigenic mold contamination

Introduction. Dried fruits are a valuable source of dietary fibre, many vitamins and minerals in the population’s diet. However, the high content of readily available carbohydrates makes this type of product vulnerable to mould contamination. The greatest danger among which are toxigenic species. But there is practically no scientific information about the contamination presented on the Russian market dried fruits with moulds producing mycotoxins. That does not allow judging about this aspect of food safety. 

Materials and methods. Contamination with moulds and bacteria of 57 samples of dried fruits of 7 species popular in Russia was studied using cultural methods of analysis. Monospore isolates of moulds were isolated from dried fruits; in vitro mycotoxins production studied; by UHPLC-MS / MS analyzed mycotoxins in the multidetection mode.

Results and discussion. In general, the microbial contamination of dried fruits was low: 87.7% of the samples met the established microbiological standards, in most cases, moulds caused it. At the same time, the highest frequency and levels of contamination were found in dates. Aspergillus sp. dominated in the micoflora of all types of dried fruits. Among the isolated 33 strains of moulds, 45.5% turned out to be toxigenic and, in vitro, were capable of biosynthesis of significant amounts of several types of mycotoxins, including emergent mycotoxins. Fumonisin- and ochratoxin-producing activities have been found in Aspergillus strains of the Nigri section. In model experiments, the accumulation of mycotoxins in individual strains exceeded the level normalized in grain products, including (in μg/kg): for aflatoxins B1 - more than 32000 and B2 - 3230; fumonisin B2 - more than 3100; ochratoxin A up to 4.3; for emergent accumulation reached: sterigmatocystin up to 6218220 and citreoviridine - 153. 

Conclusion. Moulds are the main type of microflora that contaminates dried fruits. The ability of mould isolates from dried fruits to form mycotoxins has been established, among which highly toxigenic strains have been identified. This indicates the presence of a potential risk of contamination of this type of food with unregulated mycotoxins and a possible increase in their content in the diets of consumers. The results obtained substantiate the need for extensive monitoring of mycotoxin producers in dried fruits. This is important for predicting the risk of toxin formation and identifying the relationship of specific mycotoxins with certain types of dried fruits. The presence of toxigenic activity of moulds isolated from dried fruits has been shown in Russia for the first time.

Contribution:

Minaeva L.P. — concept and design of the study, collection and processing of material of microbiological studies, writing and editing of the manuscript, responsibility for the integrity of all parts of the article;

Polyanina A.S., Efimochkina N.R. — collection and processing of material of microbiological studies;

Kiseleva M.G., Chalyy Z.A. — collection and processing of material UHPLC-MS/MS research results;

Sheveleva S.A. — editing.

All authors — approval of the final version of the article.

Conflict of interest. The authors declare no conflict of interest.

Acknowledgement. The study was supported by Russian Science Foundation (grant No 18‐16‐00077).