A brass block., 3 .7 mm high and 10 mm in diameter, which has three openings to accommodate rivet-type or plain tubular specimen holders for scanning electron microscopy at low temperature, has been designed to fit the Hexland Cryotrans CT 1000 assembly in place of the original aluminum disc. Viscous food samples are placed in two-piece tubular holders (0.9 mm inner diameter, 1.2 mm outer diameter) made from sterling silver, and rapidly frozen. The holders are inserted into the brass block under 1 iquid nitrogen and tightened with individual setscrews. A handle screwed into the central hole of the block facilitates manipulation of the block. The samples are fractured inside the Cryotrans CT 1000 assembly by knocking off the part of the sample located in the upper tube. The subsequent operations are the same as those suggested by Hexland.
A second simple type of holder has been developed for low-moisture foods, such as cheese, which are resistant to ice crystal formation during freezing . This holder consists of a Hexland aluminum sample disc drilled with a single opening (4.0 mm in diameter) temporarily closed at the bottom with sticky tape. The food is sampled with a cork borer and the sample plug is then inserted into the 4.0 rrm opening, with a rivet covering the part of the sample protruding from the disc. Thermal contact between the sample, the disc, and a rivet that is used to cover the part of the sample protruding from the disc, is provided by Tissue Tek. The sample with the disc is rapidly frozen in nitrogen slush, mounted in the Hexland Cryotrans CT 1000 assembly, and inserted into the prechamber of the cold stage attachment where the rivet is knocked off. From that point on, the regular procedure recommended by Hexland is followed.
Kalab, Miloslav; Allan-Wojtas, Paula; and Yang, Ann Fook
"Sample Holders for Solid and Viscous Foods Compatible with the Hexland Cryotrans CT 1000 Assembly,"
Food Structure: Vol. 7
, Article 13.
Available at: http://digitalcommons.usu.edu/foodmicrostructure/vol7/iss1/13