Patulin, 4-hydroxy-4H-furo[3,2-c]pyran-2(6H)-one (Figure 13.1), is a low-molecular-weight (MW 154) a,^-unsaturated y-lactone with a melting point of 110° C. Patulin is stable under acidic conditions and resistant to thermal treatments, but it is unstable at alkaline pH . The toxin is soluble in water, ethyl acetate, methanol, acetonitrile, and acetone, and less soluble in diethyl ether and benzene. It reacts with sulfhydryl groups such as those in cysteine and glutathione, free amino groups, sulfur dioxide, and ascorbic acid [15-17]. Patulin is metabolized by yeast (Saccharomyces cerevicae) in fermenting cider into a variety of compounds including E-ascladiol and Z-ascladiol .
As more countries have passed regulatory limits for patulin in apple products, there have been increasing efforts to develop sensitive, selective, and rapid procedures for measuring patulin levels in food. Monitoring of patulin in apple juice, apple juice concentrates, and apple cider is performed to comply with regulatory limits set by the U.S. Food and Drug Administration (FDA) and regulatory agencies throughout the world . The majority of the methods currently used are based on the Association of Official Analytical Chemists (AOAC) official methods, involving liquid-liquid extraction of patulin with ethyl acetate, followed by use of high-performance liquid chromatography (HPLC) for detection and quantification. If there is need for confirmation of the amount of patulin in a product, gas chromatography/mass spectrometry (GC/MS) is performed. Shephard and Leggott  published an excellent review of the chromatographic methods used to determine patulin levels in fruit products. The following is an overview of the analytical methods used for quantifying patulin in food.
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