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How to produce freeze dried food? Why freeze dried food is so popular? From Freeze drying technical process and working principle, let you know why so many food & pharmaceutical industry choose and trust TOPTION freeze dryer.
1. Principle of freeze dried food freeze dried fruit & vegetables:
Freeze drying process is to dry the the moisture in food trough sublimation after the food be frozen, mainly contains freeze and sublimate these two process:
1) Sublimation: As temperature difference is too big, material through solid phase become gas phase directly, skip the liquid phase completely. Condition: quantity of heat must be supplied continuously, and vapour must be discharged continuously.
2) Eutectic point: for solid phase mixed liquid, during heating melting process, when it reach one temperature degree, will oppear liquid phase in solid, and this temperature degree is named as eutectic point.
3) Eutectic point is the lowest temperature that solid phase start appear liquid phase during product heating process. So during freeze drying process we need to avoid the food temperature reach eutectic point, or food will appear ice crystal melt.
4) Collapse temperature: When temperature is high, could reduce the solid substrate rigidity of cellular structure. After temperature reach one critical value, the solid substrate rigidity will couldn't support its cellular structure, vugular solid substrate wall will happen collapse.
2. Production process of freeze dried food freeze dried fruit & vegetables:
1) Pretreatment of freeze drying process
A. Fruit and vegetables pretreatment is same as freeze food.
B. Meat food pretreatment.
C. Liquid phase / Paste food pretreatment contains sterilization, concentration, pelletize, add antioxidant and anti-caking agent etc, process.
2) Pre-freezing of freeze drying process
Freezing speed will effect the quality and drying time of freeze dried food. If freezing speed is fast, the ice crystal which produced in food will be small and distribute uniform, food damage is little, after freeze drying could keep food original organization structure and performance. But as small ice crystal left small hole after sublimation, the vapour discharge path is straitness, resistance is big, so food freeze drying speed will be slowing.
Choose one most suitable freezing speed will help you achieve top quality freeze dried food and minimum energy expenditure.
3) Sublimation drying of freeze drying process
A. Freeze dryer's loading capacity and wet weight loading capacity are the important factors for drying time.
B. Drying temperature, temperature control principle is to avoid ice crystal melting in freeze dried food.
If you are also not clear all your doubt, please not hesitate to contact TOPTION specialist ( salesj@toptionlab.com ) directly to talk about the freeze drying process or customize vaccum freeze dryer based on your actual production needs.