Toxin production by Alternaria alternata in tomatoes and apples stored under various conditions and quantitation of the toxins by high-performance liquid chromatography

Abstract

Alternaria alternata strain 8442-3 was inoculated into tomatoes ( Lycopersicon esculentum Mill.) and Red Delicious cultivar apples ( Malus domestica Borkh.). Half of the lots of each fruit were shrink-wrapped in high-density polyethylene film. Wrapped and unwrapped fruits were incubated under darkness at 4, 15 and 25°C for up to 5 weeks. A high-performance liquid chromatography method was developed to quantitate tenuazonic acid (TeA), alternariol (AOH), alternariol methyl ether (AME), and alternuene (ALT). Shrink-wrapping retarded, but did not completely inhibit growth in tomatoes for 3–7 days. Concentrations of up to 120.6 mg of AOH and 63.7 mg of AME per 100 g of tissue were produced in unwrapped tomatoes stored at 15°C for 4 weeks; 19.0 mg of ALT per 100 g of tomato tissue was produced after 3 weeks at 25°C. AOH, AME and ALT were also produced in unwrapped tomatoes stored at 4°C; however, no TeA was detected in decayed tomatoes, regardless of type of wrapping or storage temperature. Shrink-wrapping resulted in decreased production of AOH, AME, and ALT. Alternaria toxins were not detected in apples stored at 4 and 15°C. The highest concentration of AOH produced (48.8 mg per 100 g of tissue) was in unwrapped apples stored at 25°C for 2 weeks; 12.3 mg per 100 g of tissue of shrink-wrapped apples was detected after 5 weeks of storage at 25°C, while ALT reached 5.7 mg per 100 g after 4 weeks. TeA was not detected in apples infected with A. alternata.