Fate of pyrrolizidine alkaloids during dairy processing of naturally and artificially contaminated sheep and goat milk

Toxic pyrrolizidine alkaloids (PA) and their <i>N</i>-oxides (PANO) are produced by various plants and can be transferred into the milk of ruminants <i>via</i> contaminated feed. Data on the behavior of PA/PANO during dairy processing and their occurrence in dairy products are sparse. Within this work, naturally and artificially contaminated sheep and goat milk was used to manufacture Manchego and Feta type cheese (sheep) or Picodon type cheese and yogurt (goat). Samples taken along the production processes were analyzed using LC-MS/MS. PA/PANO contents remained constant or slightly decreased during heat-treatment of naturally contaminated raw milk. PANO levels were reduced partially or entirely due to microbial fermentation, whereas PA appeared stable. Transfer factors for cheese manufactured from naturally contaminated milk ranged from 0.28 ± 0.06 (Feta type cheese) to 0.68 ± 0.06 (Manchego type cheese). Experiments with artificially contaminated milk confirmed the results and indicated a reduction of PANO to the corresponding free base form due to microbial fermentation. The data imply that yogurt, whey, and cheese, except for Feta type cheese, are contaminated with PA in a similar range as the initial milk used for manufacture.