Effect of processing on ochratoxin A content in dried beans

Abstract

Dried pink beans naturally contaminated with ochratoxin A (OTA) and dried carioca beans artificially contaminated with OTA by inoculation with Aspergillus ochraceus (ATCC 22947) were tested for ochratoxin A levels as follows: dried beans were washed with water for 2, 60 or 120 min, soaked in water for 60, 120 min or 10 h, and cooked for 60 or 120 min. At each step, test water and beans were separated. Test water, raw beans and cooked beans were analyzed for OTA. The amount of OTA partitioned into water and in residual beans was determined by methanol–sodium bicarbonate extraction, buffer dilution, immunoaffinity column cleanup, liquid chromatographic separation and fluorescence detection. The results demonstrated that the distribution of OTA in processing water and beans depends on the method of preparation. All treatments (washing, soaking and cooking) when applied individually reduced the amounts of OTA retained in bean flour and whole beans. Higher amounts of OTA remained in whole beans than in bean flour after removing the processing water. The combination of the three treatments eliminated about 50% of the toxin from whole beans. This study provides evidence that discarding the washing, soaking and cooking water leads to a significant reduction in OTA contamination in dried beans.

Keywords:

• processing HPLC
• immunoaffinity columns
• mycotoxins
• ochratoxin A
• beans

Acknowledgements

This project was supported in part by the appointment of MH Iha to the Research Participation Program at the Center for Food Safety and Applied Nutrition administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the US Department of Energy and US Food and Drug Administration. The equipment used in part of this project was provided by Fundação de Amparo à Pesquisa do Estado de São Paulo.