Comparison between different sun drying methods for dried vine production in relation to Aspergillus section Nigri presence and ochratoxin A accumulation

Abstract

This study provides a comprehensive evaluation of three sun drying methods, gravel drying yard (GDY), dryingon structure (DS), and drying on vine (DOV), in relation to the occurrence of Aspergillus section Nigri species andochratoxin A (OTA) accumulation in dried vine fruits from San Juan, Argentina. Aspergillus section Nigri wasdetected in all samples in different percentages. Molecular identification revealed that Aspergillus section Nigriisolates were dominated by A. tubingensis within the A. niger aggregate, while all isolates of the A. carbonariusgroup were confirmed as A. carbonarius, with uniseriate species detected only rarely. Drying methods showedmarked differences in fungal incidence and OTA accumulation. GDY exhibited the lowest incidence ofA. carbonarius and minimal OTA levels, while DOV showed the highest OTA accumulation. A strong associationbetween A. carbonarius incidence and OTA levels was observed across all methods. These differences were mainlyexplained by variations in maximum temperature and drying duration. GDY and DS reached higher temperaturesand shorter drying times, limiting fungal growth, whereas DOV maintained temperatures within rangesfavourable for OTA production over extended periods. Ochratoxin A was detected in 33% of samples at the end ofstorage. Although contamination frequency was lower than that reported in other countries, concentrationsvaried widely. Notably, the highest OTA levels were observed during the storage stage, indicating that this phaserepresents a critical point for toxin accumulation. These findings emphasise the critical role of storage conditionsin OTA risk and inform improved safety management of dried vine fruit production.