Determination of Aflatoxins and Ochratoxin A in Traditional Turkish Cereal-Based Fermented Food by Multi-Affinity Column Cleanup and LC Fluorescence Detection: Single-Laboratory Validation

Abstract

Abstract Background: Tarhana is a traditional fermented, sun-dried Turkish food containing yogurt and cereals. There are several potential sources of mycotoxins in tarhana, such as contamination of ingredients or formation during preparation, when water activity is suitable for fungal growth and may lead to mycotoxin production during fermentation or subsequent sun-drying. Objective: To optimize an immunoaffinity column method and carry out single-laboratory validation for the determination of aflatoxins B1, B2, G1, and G2 together with ochratoxin A (OTA) in tarhana. Method: A homogenized sample was extracted with methanol–acetonitrile–water (25 + 25 + 50) using a high-speed blender. The sample extract was filtered, diluted with phosphate buffered saline (PBS) solution, and applied to a multi-immunoaffinity column (AFLAOCHRA PREP®). Aflatoxins and OTA were removed with neat methanol and then directly analyzed by reverse-phase LC with fluorescence detection using post-column bromination (Kobra® Cell). Results: Test portions of blank tarhana were spiked with a mixture of total aflatoxins and OTA to give levels ranging from 2.5 to 10.0 and 1.5 to 6.0 μg/kg, respectively. Recoveries for total aflatoxins and OTA ranged from 82 to 93 and 78 to 94%, respectively, for spiked samples. Based on results for spiked tarhana (30 replicates, each at three levels), the relative standard deviation for repeatability ranged from 1.4 to 7.2 and 3.6 to 7.7% for total aflatoxins and OTA, respectively. Conclusions: The performance characteristics for recovery, repeatability, and sensitivity have demonstrated that the method meets method performance criteria for use for official purposes. The method was demonstrated as being applicable to naturally contaminated samples of tarhana of varied composition obtained from local markets in Turkey. Highlights: This is the first immunoaffinity column method for simultaneous analysis of aflatoxins and OTA in traditional Turkish food (tarhana). Suitability was demonstrated by single-laboratory validation for official purposes in Turkey. The method was demonstrated as suitable for naturally contaminated samples of tarhana of varied composition.