What is false about the freeze drying method?

The statement that is identified as false pertains to the control of pore size during the freeze drying process. In freeze drying, commonly used in tissue engineering to preserve biological materials, the rate at which freezing occurs and the pH can significantly influence the characteristics of the resulting structure, including pore size.

A slow freezing rate allows for larger ice crystals to form, which can then lead to larger pores once the ice is sublimated. Conversely, a fast freezing rate results in smaller ice crystals, subsequently leading to a finer pore structure after the drying process. Controlling the pH during freeze drying can also affect the interactions between the polymers and any stabilizers or additives used, further impacting the final structure.

Therefore, the assertion that pore size cannot be controlled by the freezing rate and pH is incorrect, as both factors are critical in determining the microstructure and porosity of the final dried material. This capability to manipulate pore size is one of the reasons freeze drying is a valuable method in tissue engineering.