1, Mixing Raw Material
Freeze dry many raw material in same time is not a good idea, there have potential risks of:
- bacteria cross contamination.
- smells/odor pollution.
- an inconstant lyophilization result, since each raw material character different cause drying time different.
So if you want a constantly and high efficiency freeze drying, please don't mix products in freeze dryer chamber.
2, Trying Dry High Sugar, High Fat Products
These products are not freeze dry well, no matter how long you take, they are still sticky because block vapor sublimation channel, not easy to clean the trays,? like pure honey, without additive or attenuation, its very hard to dry.
3, Freeze Drying Large Pieces? Products
Large volume products like large pieces meat, entire apples,pears etc. Could only cause times longer drying time than cut to pieces, and the drying protocol is hard to handle.
The most economic way to drying is slice or cut to pieces, recommend thickness <10mm, evenly put in trays, of course berry products like strawberry,blueberry could drying without cut.
4, Not Using A Liner In The Trays
Commercial and industrial large scale freeze dryer machine, plastic wrap is recommend for raw material loading, it could help a lot whether in harvest process or cleaning process.
Products direct load in trays, when harvest, they may not easy come off the trays and harvest take some time, during the period, dried products will start absorb moisture from air, as well, the trays surface leave colors and flavors, is not good for another product.
5, High Shelf Temperature Set
Expect a quick drying by set higher shelf temperature is not right, the reason because large heating energy give in a short time may cause frozen material melt(glass transition), with sugar or something together will block the vapor escape channel, freeze drying will fail. Step back,too much vapors in short time will out of condenser collect capacity, vapor go to vacuum pump will broke it.
6, Loading Too Much In Trays
The recommend loading weight is heaviest water in raw material should less than condenser capacity, otherwise they cannot complete dry. But this is not the only consideration, loading weight and drying time relation are delicate, find out the most economic drying solution(material thickness/weight in trays cause shortest drying time) could help you save energy every batch. Also remember, the each trays load volume(material evenly stacking) need similar.