Observation of Bread Yeast with Cryo-SEM

Cryo-SEM, which allows SEM imaging of a hydrated specimen in a frozen state, is used for various applications, such as biotechnology, medicines, cosmetics and foods. Cryo-SEM consists of two specimen stages. The first stage is used in a specimen preparation chamber for fracturing, etching (ice sublimation) and conductive coating. This stage can then be transferred to the second cryo-stage located in the SEM for observation. Both of the stages are cooled by liquid nitrogen and also are temperature-controlled with a heater for allowing etching.
Using Cryo-SEM,  a hydrated specimen, which is rapidly frozen by slush nitrogen in the air, can be imaged while keeping the ‘natural’ state of the specimen. This avoids dehydration of the specimen that can lead to distortion of the surface structures. It also allows imaging of oils and other components that are not observable at room temperature under vacuum. As an observation example, cryo-SEM of bread yeast is presented below.