Evaluation of Alternaria toxins in fruits, vegetables and their derivatives marketed in China using a QuEChERS method coupled with ultra-high performance liquid chromatography-tandem mass spectrometry: Analytical methods and occurrence

Alternaria species are invasive fungi that infect fruits and vegetables and produce Alternaria toxins resulting in loss of commodity values and harmful effects on human health. To establish a reliable analytical method for Alternaria toxins in fruits, vegetables and their derivatives (e.g., fruit and vegetable juices, purees and jams; dried fruit and vegetables; fruit and vegetable powders), a QuEChERS extraction method was developed and validated for the determination of most reported Alternaria toxins (alternariol monomethyl ether [AME], alternariol [AOH], tentoxin [TEN], tenuazonic acid [TeA], and altenuene [ALT]). The limits of quantitation (LOQ) of the target analytes in food matrices were 1.0–5.0 μg/kg. The extraction recoveries were 73.0%–120%, with good repeatability (<12.9%) and within-laboratory repeatability (<14.7%). The developed method was applied to 270 fruits, vegetables, and their derivatives randomly collected from the market in China. Approximately 45.2% of the samples were contaminated with varying levels of Alternaria toxins. The lowest incidence of contamination by Alternaria toxins was detected in fruits and vegetables (3.6%), and the highest incidence was found in fruit and vegetable powders (60.6%). TeA exhibited the highest detection frequency (22.6%) and the highest level of occurrence level (639 μg/kg) among the tested samples, followed by AOH (14.1%), ALT (11.9%), AME (4.4%), and TEN (3.3%). Furthermore, the simultaneous co-presence of two to five Alternaria toxins was detected in 13.7% of the analyzed samples. The combination of AOH + TeA was the most predominant, accounting for 4.8% of samples. This study developed a reliable and sensitive analytical method and provided representative occurrence data to support the assessment of emerging mycotoxins, especially Alternaria toxins, in fruit and vegetable products.