Any thing that you do to your product prior to freezing to add something to your product or aid in the freeze drying process is considered " pretreatment".   This can either increase or decrease the drying time.  For example, adding a sugar to your product may reduce its freezeing point.   Salts and alcohols can have this kind of impact as well.  

For other applications,  such as when freezedrying pharmacueticals , API, probiotics etc, adding a cryo protectant may also reduce the freezing point making it critical to be able to have a machine that not only has a condenser that is below the freezing point of the product, but also have shelves that can maintain the shelf temp in negative numbers.  This cannot be done with electric heating shelves.  

The freezing, or nucleation of the product is incredibly important.  Hense the first word of the process.  Freeze. Flash freezing can be achieved with various methods.  Blast freezing, nitrogen pelletization etc, and will create smaller ice crystals which may slow down the freezedrying process, but yeild a better product.  Using a holding freezer that slowly freezes your product will create large ice crystals.   Larger ice crystals may sublimate faster, but may damage your product at the celluar level by piercing the cellular wall.  smaller ice crystals wont, but take longer to freeze dry.  Flash freezing, nitrogen pellitization will produce a quickly frozen product, and also small ice crystal size.  Allowing product to Freeze overnight in a walk in freezer may create larger ice crystals , but you may leech out vitamins, , destroy proteins, or loose your critical ingedients to your product.  

During this phase the majority of the water is sublimed out of the product.   Up to 90 , 95%.  it is critical to make sure the sublimation front of the product stays below either the Eutecti point, or the glass transition event.  this is why it is critical to use machines that offer precise control.  electric heaters dont offer this.  Be cautious when learning about your process if new, otherwise you could be stuck with an expensive machine that cant freeze dry your product, or takes much longer.  

During this phase, the remaining 5% of the bound water must be removed, through desorption.  it is common to try to enter this phase too soon, this is when you see collapse on the prodeuct, which technically, you are boiling water off the productl, not sublimation.  this is vacuum drying.  check out our section on how to avoid this.  

Any thing that you do to your product prior to freezing to add something to your product or aid in the freeze drying process is considered " pretreatment".   This can either increase or decrease the drying time.  For example, adding a sugar to your product may reduce its freezeing point.   Salts and alcohols can have this kind of impact as well.  

For other applications,  such as when freezedrying pharmacueticals , API, probiotics etc, adding a cryo protectant may also reduce the freezing point making it critical to be able to have a machine that not only has a condenser that is below the freezing point of the product, but also have shelves that can maintain the shelf temp in negative numbers.  This cannot be done with electric heating shelves.  

The freezing, or nucleation of the product is incredibly important.  Hense the first word of the process.  Freeze. Flash freezing can be achieved with various methods.  Blast freezing, nitrogen pelletization etc, and will create smaller ice crystals which may slow down the freezedrying process, but yeild a better product.  Using a holding freezer that slowly freezes your product will create large ice crystals.   Larger ice crystals may sublimate faster, but may damage your product at the celluar level by piercing the cellular wall.  smaller ice crystals wont, but take longer to freeze dry.  Flash freezing, nitrogen pellitization will produce a quickly frozen product, and also small ice crystal size.  Allowing product to Freeze overnight in a walk in freezer may create larger ice crystals , but you may leech out vitamins, , destroy proteins, or loose your critical ingedients to your product.  

During this phase the majority of the water is sublimed out of the product.   Up to 90 , 95%.  it is critical to make sure the sublimation front of the product stays below either the Eutecti point, or the glass transition event.  this is why it is critical to use machines that offer precise control.  electric heaters dont offer this.  Be cautious when learning about your process if new, otherwise you could be stuck with an expensive machine that cant freeze dry your product, or takes much longer.  

During this phase, the remaining 5% of the bound water must be removed, through desorption.  it is common to try to enter this phase too soon, this is when you see collapse on the prodeuct, which technically, you are boiling water off the productl, not sublimation.  this is vacuum drying.  check out our section on how to avoid this.