Hi vinesh..dry the powdered sample completely pack in zipper pouch and keep that in airtight containers..u can add moisture absorbents to the container..
Flash freezing is used widely in food processing as it gives little opportunity for ice crystal expansion to cause significant damage to the product. In a lab environment immersing the sealed specimens in liquid nitrogen to flash freeze and later store in a sub 0°C environment is a good way to have a control to evaluate which manner of traditional preparation is most efficient.