How to Preserve White Truffles  
Wrap each truffle separately in absorbent paper and store them in a closed jar. Change the paper when it becomes damp. Keep fresh truffles in the refrigerator in the vegetable tray (at 2°-3° centigrade, 35°-37° Fahrenheit). The truffles will remain fresh for a maximum of 4 to 6 days. When you are ready to use them, wash them carefully with water and a brush, and dry them with paper.
 

Preservation for a longer time
Slice the truffle and mix it with soft salted butter then put it in the deep-freezer. You can store it for 1 year.