Most of what decides a freeze drying cycle happens before the chamber door closes.
Vapour has to travel out of the product. Shorter distance, faster cycle.
Slicing thinner shortens the path the sublimation front has to travel and increases surface area. Uniformity matters as much as thickness — a tray of mixed piece sizes finishes at mixed times, and the cycle has to run until the slowest piece is done.
A deeper tray holds more and takes disproportionately longer.
The dried layer above the sublimation front insulates and impedes vapour flow, so doubling depth more than doubles the time for the bottom of the load. Shallower, uniform loading usually produces more finished product per day than deep loading does, even though it looks like less per batch.
The one pretreatment step that is genuinely a trade-off rather than an optimisation.
Slow freezing grows large crystals: wide vapour channels, faster drying, more cell damage. Fast freezing gives small crystals: structure preserved, narrower channels, slower drying. Which you want depends on whether structure or speed is the product.
Pre-freezing outside the dryer is usually better practice than freezing in the chamber — it frees the machine for drying and gives you control over the rate.
Borrowed from dehydration practice, and not always appropriate here.
Blanching deactivates enzymes that cause browning and off-flavours, at the cost of some heat-labile nutrients and added moisture. Acid dips limit oxidative browning in fruit. Neither is automatic — freeze drying is gentle enough that many products do not need what a hot-air process would require.
Sometimes. Blanching deactivates browning enzymes but costs heat-labile nutrients and adds moisture. Because freeze drying is gentle, many products that need blanching before hot-air drying do not need it here.
Thinner and uniform is faster and more even. The specific answer depends on the product, but uniformity matters as much as thickness — a tray of mixed sizes runs until the slowest piece finishes.