Sterols in fresh and preserved button mushroom (Agaricus bisporus) products

Mushrooms are highly valued but also very perishable foods. As a consequence, various types of preserved mushroom products are available in retail stores. Common preservation techniques include pickling in brine and drying. Such processes might cause a partial transformation of unstable products like ergosterol, which is the most relevant sterol in mushrooms. In this study, gas chromatography with mass spectrometry (GC/MS) was used to examine the levels of ergosterol and other, lower abundant sterols in dried and pickled button mushrooms (Agaricus bisporus) from German retail. Multivariate analysis of the free sterol fraction was used to verify significantly lower ergosterol contents in the preserved products (pickled: 280 ± 30 mg/100 g dry weight, dried: 190 ± 20 mg/100 g dry weight) compared to fresh button mushrooms (610 ± 20 mg/100 g dry weight). In addition, the contribution of ergosterol to the total sterol content in dried button mushroom samples (84 ± 1%) was comparable to fresh samples (87 ± 1%) but significantly lower in the pickled products (78 ± 1%). Storage experiments with pure ergosterol standards in solution indicated a full degradation of ergosterol and the formation of seven transformation products at room temperature storage within 9 days.