Zearalenone in maize: stability testing and matrix characterisation of a certified reference material

Within the certification process of a reference material for the determination of the mycotoxin zearalenone (ZON) in maize, short- and long-time stability tests of naturally contaminated maize have been performed. The short-term stability of ZON in the maize was evaluated under four different conditions (4, 25, 40 and 70 degrees C) in preliminary studies. Four storage times of 0, 1, 2 and 4 weeks were investigated using HPLC. The long-term stability study was conducted with measurements after 0, 3, 6, 12, 24 and 36 months under three storage conditions (4, 25 and 40 degrees C) in preliminary studies using HPLC. Stability data gained under two different conditions (4 and 25 degrees C) with five storage times of 0, 1, 6, 12 and 18 months were further evaluated for the contaminated maize in the certification process. Before the certification, the maize matrix had been characterized with respect to dry residue, ash content, fat content, protein content, ergosterol content and total dietary fibre, and the efficiency of gamma-irradiation on the fungal flora was investigated. The stability of the maize matrix was evaluated by monitoring UV absorption and ergosterol content under four different storage conditions (4, 25, 35 and 70 degrees C) with five storage times of 0, 1, 6, 12 and 24 months. Other possibly occurring mycotoxins (deoxynivalenol, nivalenol, 3-acetyl deoxynivalenol, 15-acetyl deoxynivalenol, fusarenon X and moniliformin) have been quantified. On the basis of the stability measurements, which showed no significant trends for both short- and long-term stabilities, it can be recommended to store the samples at temperatures < 4 degrees C and ship the samples at ambient temperatures.