title: A custom-built controlled-rate freezer for small sample cryopreservation studies.
abstract: A custom-built controlled-rate freezing machine is described. It operates by automatically raising and lowering the sample carrier in a static column of liquid nitrogen vapour. It is controlled by a computer-assisted thermocouple feedback system that operates a stepper motor driving the sample carrier. The cooling protocol is divided into three phases: cooling from +5 to -5 C, initiation of ice nucleation, and cooling from -5 to -80 C. Experiments are described to validate the device over a range of different cooling rates. A freezing protocol is established to cool samples in plastic straws over a range of rates up to 80 C/min, with rapid and consistent absorption of the latent heat.
authors.affiliation: Department of Animal Sciences, Facultad de Estudios Superiores - Cuautitlan, National Autonomous University of Mexico 54740 Cuautitlan Izcalli, Mexico. amedrano@servidor.unam.mx
authors.forename: A
authors.initials: A
authors.lastname: Medrano
authors.forename: J
authors.initials: J
authors.lastname: Anderson
authors.forename: J D
authors.initials: JD
authors.lastname: Millar
authors.forename: W V
authors.initials: WV
authors.lastname: Holt
authors.forename: P F
authors.initials: PF
authors.lastname: Watson
mesh_terms: D000818:Animals; D015925:Cryopreservation / Q000295:instrumentation*; D004867:Equipment Design; D005615:Freezing; D008297:Male; D012662:Semen Preservation / Q000295:instrumentation; D013552:Swine