The effect of dipping pretreatment on ochratoxin A accumulation in sultanas and currants

Abstract

The dipping pretreatment on the occurrence of ochratoxin A (OTA) in sultanas and currants was investigated. Grape samples were divided into two groups before a drying process. One group was dipped with potassium carbonate-ethyl oleate, and the other group was left without treatment (the control). OTA were detected using solid-phase extraction clean-up and a high-performance liquid chromatography fluorescence detector. Results showed that OTA content was below the limit of detection in the fresh grapes of both varieties. OTA were not detected in dried vine fruits before storage. However, a real naturally environmental storage revealed that the dipping pretreated samples were contaminated with OTA earlier and to a greater extent than the control. The OTA concentration in the treated and control samples after one-year storage was 0.22 and 0.19 μg/kg for sultanas and 0.34 and 0.21 μg/kg for currants, respectively. These results indicated that dipping pretreatment might increase the toxin contamination and safety risk.

Environmental Conditions Affecting Ochratoxin A during Solar Drying of Grapes: The Case of Tunnel and Open Air-Drying

“…To enhance the water transport through grape skin and reduce the respective drying time, the chemical pre-treatment of grapes is suggested. On the other hand, the chemical pre-treatment in grapes has been reported to increase the potential hazard of OTA development especially in dried grapes stored unpackaged after drying [19]. The drying temperatures in the present solar drying experiments were lower compared to artificial drying temperatures (>50 • C) normally employed in drying of agricultural products.…”

“…Some of the previous factors cause localized hardening of the skin, which may increase the susceptibility of the fruit to splitting [14]. Zhang et al [19] investigated the effect of dipping pre-treatment on OTA accumulation in sultanas (white grapes) and currants (red grapes) and concluded that in the untreated samples OTA accumulation was more serious in red grapes than in white grapes, and that in particular this behavior was attributed to the components of red dried grapes that may favor fungal growth, which lead to a faster and higher accumulation of OTA.…”

“…The type of drying influences the drying rate due to higher achieved drying temperatures and consequently the reduced drying duration, which has been found to affect the CFU/mL and OTA production. The grape variety has been also found to favor OTA accumulation in red grape arieties compared to white varieties probably due to the components (i.e., Brix, acidity) of red dried grapes [16,19]. Based on these results, the CFU/mL cannot be used as a standalone criterion for OTA estimation.…”