Abstract
This challenging study was carried out to evaluate the temporal production of ochratoxin A (OTA) by Aspergillus niger ATCC 16404 and wild type A. niger AM at different temperatures in fresh squeezed orange juice (Citrus sinensis [L.] Osbeck cv Tarocco). Each strain, inoculated into the filtered orange juice, was incubated at 4°C, 20°C, and 26°C for 28 days. In the juice, at 26°C and 20°C, the concentration of A. niger ATCC 16404 increased by more than 2 log10 up to the 21st day. At 4°C it remained constant. The microbial load of A. niger AM decreased at all temperatures. At 26°C, the maximum OTA accumulation found was 3.44 ng/mL on the 21st day for A. niger ATCC 16404 and 8. 44 ng/mL on the 7th day for A. niger AM. The OTA synthesis seemed to be an intrinsic strain-dependent mechanism. A. niger ATCC 16404 produced OTA in accordance with the higher temperatures and the biomass concentrations, whereas A. niger AM produced the toxin at all temperatures regardless of its biomass. These results showed that fresh orange juice contaminated with Aspergillus niger aggregate strains may contain OTA levels.
Highlights
The market of organic citrus fruit has increased during the last few years because of consumer demand for healthy food products [1]
Small amounts of mycotoxins remain in mould cells, as most of them are excreted in the foods
Aspergillus niger ATCC 16404 and Aspergillus niger AM aggregate strains isolated from rotted citrus fruit were inoculated on malt extract agar (MEA; Oxoid, Basingstoke, UK) at 25∘C for 7 days
Summary
The market of organic citrus fruit has increased during the last few years because of consumer demand for healthy food products [1]. If the original load is too high and/or the pasteurization process is inadequate, some microorganisms might survive and subsequently cause spoilage and possibly illness if the surviving organisms are virulent [3]. These products, especially nonpasteurized single-strength juice, are not free of microbiological spoilage problems [2, 4]. The mould growth may result in several kinds of food-spoilage: off-flavours and discoloration; if the contaminating microorganisms are pathogens, it could cause human illness [3, 5, 6]. Since most of the mycotoxins are very resistant to physical and chemical treatment, a rule of thumb exists: once the mycotoxins are in the food, they stay there during processing and storage [6, 8, 9]
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