Temperature stability of vitamin D₂ and color changes during drying of UVB-treated mushrooms

ABSTRACT

The study investigates the effect of drying temperature on vitamin D₂ content and color changes of UVB-treated shiitake (Lentinula edodes), oyster (Pleurotus ostreatus), and white and brown button mushrooms (Agaricus bisporus). Fresh samples were UVB treated up to 1.5 J/cm² for 20 min at 25°C and either dried in a high precision dryer (temperatures: 40, 60, 80°C, specific humidity: 10 g/kg, air velocity: 0.6 m/s) or frozen at −25°C, and then freeze-dried (pressure: 0.28 mbar). Vitamin D₂ content was not negatively affected by the increased temperatures of the drying air. The highest content of vitamin D₂ was detected in freeze-dried (171.84 µg/g) and hot-air dried shiitake at 60°C (169 µg/g), followed by oyster (121.96 µg/g), whereas the lowest amount was observed in brown button mushrooms at 40°C (34.65 µg/g). Although vitamin D₂ indicated a remarkable stability even at 80°C, the dried samples were characterized by intensive tissue darkening.

KEYWORDS:

• Button
• hot air
• HPLC
• oyster
• shiitake
• UV light
• vitamin D₂

Acknowledgments

This research has been conducted within the framework of the “Trafoon Project - Traditional Food Network to improve the transfer of knowledge for innovation.” This project has received funding from the European Union’s Seventh Framework Programme for research, technological development, and demonstration under grant agreement no. 613912. We are also grateful to Mr. Alexander Koza and Mr. Julian Wald for their technical support.