Occurrence of Mycotoxins in Dried Fruits Worldwide, with a Focus on Aflatoxins and Ochratoxin A: A Review

Dried fruits are popular and nutritious snacks consumed worldwide due to their long shelf life and concentrated nutrient content. However, fruits can be contaminated with various toxigenic fungal species during different stages, including cultivation, harvesting, processing, drying, and storage. Consequently, these products may contain high levels of mycotoxins. This risk is particularly pronounced in developed countries due to the impact of climate change. Several factors contribute to mycotoxin production, including the type of fruit, geographical location, climate conditions, harvest treatments, and storage management practices. The main mycotoxins in dried fruits are aflatoxins (AFs) and ochratoxin A (OTA), which can induce human health problems and economic losses. Mycotoxin contamination can vary significantly depending on the geographic origin of dried fruits (vine fruits, figs, dates, apricots, prunes, and mulberries). The aim of this review was to fill the knowledge gap by consolidating data from various regions to understand the global picture and identify regions with higher contamination risks. By consolidating research from various origins and stages of the supply chain, the review intends to shed light on potential contamination events during pre-harvest, drying, storage, and trading, while also highlighting the effects of storage conditions and climate change on mycotoxin contamination.

Contamination, Detection and Control of Mycotoxins in Fruits and Vegetables

Mycotoxins are secondary metabolites produced by pathogenic fungi that colonize fruits and vegetables either during harvesting or during storage. Mycotoxin contamination in fruits and vegetables has been a major problem worldwide, which poses a serious threat to human and animal health through the food chain. This review systematically describes the major mycotoxigenic fungi and the produced mycotoxins in fruits and vegetables, analyzes recent mycotoxin detection technologies including chromatography coupled with detector (i.e., mass, ultraviolet, fluorescence, etc.) technology, electrochemical biosensors technology and immunological techniques, as well as summarizes the degradation and detoxification technologies of mycotoxins in fruits and vegetables, including physical, chemical and biological methods. The future prospect is also proposed to provide an overview and suggestions for future mycotoxin research directions.

A preliminary study on mycobiota and ochratoxin a contamination in commercial palm dates (Phoenix dactylifera)

The occurrence of mycotoxins and mycotoxigenic fungi in palm dates has not been thoroughly documented. The aims of the present study were to identify the mycobiota present in commercial date samples (n = 19), to determine the ability of the isolated fungi to produce mycotoxins, and to determine and quantify the presence of OTA in date fruits. The majority of products originated from Tunisia (n = 14) and Algeria (n = 3). The dominant fungal species were Aspergillus niger, Aspergillus tubingensis and Aspergillus flavus which were most frequently found in premium quality and organic produce, produced without chemical preservatives. OTA was found in only one sample at a concentration of 0.75 µg/kg, as determined by HPLC with fluorescence detection. Although this preliminary study did not find elevated levels of OTA, its presence in one out of 19 samples indicates that palm dates for human consumption require continuous and stringent control, in order to prevent contaminated produce from entering the market.

Aspergillus, Penicillium and Cladosporium species associated with dried date fruits collected in the Perugia (Umbria, Central Italy) market

A total of 20 dried date samples, chosen as representative among those available on the Perugia (Umbria, Central Italy) market, were analyzed for the possible occurrence of fungal species and related contamination by fungal secondary metabolites. Twenty-six isolates, representative of the total mycobiota, were obtained and morphologically identified as belonging to the genera Aspergillus, Penicillium and Cladosporium. Inside each genus, molecular characterization (by partial sequencing of ITS region and/or β-tubulin and calmodulin regions for Aspergillus and Penicillium isolates or actin region for Cladosporium isolates) and in vitro mycotoxigenic profile characterization (by LC-MS/MS analysis) showed the presence of the following species: A. flavus, A. tubingensis, P. brevicompactum, P. chrysogenum, P. crustosum, P. glabrum, P. solitum, P. venetum, C. cladosporioides, C. limoniforme and C. halotolerans, with A. tubingensis as the prevalent species and P. crustosum, P. solitum, P. venetum and C. limoniforme first reported here on dates. Date packaging and format showed an effect on the incidence of isolated fungi, with the lowest incidence recovered from whole dates and in hermetic bag packaging. These findings can be useful both for dried dates producers and consumers, guiding them towards choices of packaging and format with a lower risk of mycotoxigenic species presence. However, no fungal metabolites were detected in the dried date samples analyzed, which were therefore regarded as safe for human consumption, underlining the absence of correspondence between fungal isolation and mycotoxin contaminations.

Occurrence of Ochratoxins, Fumonisin B2 , Aflatoxins (B1 and B2 ), and Other Secondary Fungal Metabolites in Dried Date Palm Fruits from Egypt: A Mini-Survey

This study was conducted to investigate the natural co-occurrence of 295 fungal and bacterial metabolites in 28 samples of dried date palm fruits collected from different shops distributed in Assiut Governorate, Upper Egypt in 2016. Extraction and quantification of the target analytes were done using the "dilute and shoot" approach followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. In total, 30 toxic fungal metabolites were detected. Among these metabolites, 4 types of ochratoxins including ochratoxin type A and B were quantified in 3 samples (11%) with a contamination range from 1.48 to 6070 μg/kg for ochratoxin A and from 0.28 to 692 μg/kg for ochratoxin B. In addition, fumonisin B₂ was observed in 2 (7%) samples with contamination levels ranging from 4.99 to 16.2 μg/kg. The simultaneous detection of fumonisin B₂ in the same contaminated samples with ochratoxins indicates the fungal attack by Aspergillus niger species during storage. Only 1 sample was contaminated with aflatoxin B₁ (14.4 μg/kg) and B₂ (2.44 μg/kg). The highest maximum concentration (90400 μg/kg) was for kojic acid that contaminated 43% of the samples. To the best of the authors' knowledge, this is the first report of the natural co-occurrence of fumonisin B₂ and ochratoxin A and B in addition to a wide range of other fungal metabolites in date palm fruits.

PRACTICAL APPLICATION

Mycotoxins are secondary metabolites produced by different fungi. These metabolites pose a potential risk on human health since they contaminate many food commodities. Among these, date palm fruits which are an integral part of diet in several countries. Therefore, detection of mycotoxins is a prerequisite to insure the safety of food. Here, different types of mycotoxins have been detected in levels that may have health hazard.

Aflatoxins and ochratoxin A in export quality raisins collected from different areas of Pakistan

During 2012-2014, 170 samples of export quality raisins were collected from different vendors in Pakistan. The collected samples were analysed for the presence of aflatoxins (AFs) and Ochratoxin A (OTA) contamination using high-performance liquid chromatography technique. The limit of detection and limit of quantification of AFs/OTA were 0.12/0.10 and 0.36/0.30 µg kg(-1), respectively. Only 5% of the samples were contaminated with AFs, ranging 0.15-2.58 µg kg(-1) with a mean of 0.05 ± 0.26 µg kg(-1). None of the raisin samples exhibited AFs contamination above the maximum limit (ML = 4 µg kg(-1)) as set by the European Union (EU). About 72% of the samples were contaminated with OTA, ranging 0.14-12.75 µg kg(-1) with a mean of 2.10 ± 1.9 µg kg(-1). However, in 95.3% of the tested samples, OTA level was lower than the ML of 10 µg kg(-1) as regulated by the EU. Apparently, a strict and continuous monitoring plan, including regulatory limits, improves food safety and quality for all types of commodities.

Ochratoxin A in dried grapes in Hamadan province, Iran

The occurrence of ochratoxin A (OTA) in dried grapes was surveyed in this study. Sixty-six samples of dried grapes (40 currants, 16 sultanas and 10 raisins) were collected from dried grapes factories in Hamadan province, Iran, from October 2012 to March 2013. High-performance liquid chromatography (HPLC) was used to determine OTA in these samples. OTA was detected in 23 (57.5%) currants, 10 (62.5%) sultanas and 6 (60%) raisins samples. Levels in five samples exceeded the Institute of Standards and Industrial Research of Iran (ISIRI) maximum level of 5 µg/kg. However, OTA content in none of the samples exceeded the maximum limit prescribed in the European Union (EU) regulations, which is 10 µg/kg. The obtained data contribute to information on OTA levels in Iranian dried grapes.