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E-mail
mariahan@sjialab.com
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Phone
15869641262
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Building 4, Tianyi Health Industry Park, High tech Industrial Development Zone, Cixi City, Ningbo (at the northwest corner of the road)<1-3>; <1-4>
Ningbo Shuangjia Instrument Co., Ltd
Common problems and solutions for freeze-drying products
Date: 2023-09-07Read: 6
In recent years, freeze-dried products such as dried fruits, freeze-dried vegetable packs, and freeze-dried pet food have become increasingly popular in the market
Welcome, this is also thanks to the vacuum freezing technology. Vacuum freeze-drying machines, with the advantages of other drying methods, have been applied in industries such as fruits, vegetables, leisure food, and pet food. In the future, with the increasing demand for healthy and nutritious foods in the market, vacuum freeze-drying machines will see significant development, and the potential for market growth should not be underestimated.
During the freeze-drying process, some customers have also reported to us about issues with freeze-drying failure. Today we will answer each question one by one.
Common Problems&Solutions
Freeze drying failure cases
collapse
reason
This is a phenomenon that occurs in amorphous solids when the product reaches a temperature higher than the collapse temperature Tc (close to the glass transition temperature Tg). The solid amorphous phase undergoes internal motion before reaching its melting point, leading to the fragmentation or collapse of the freeze-dried cake.
solution proposal
During the initial drying stage (when there is still ice in the product), keep the product temperature below the collapse temperature. Avoid forming at the top of the surface
Huirong
reason
This situation occurs when the initial drying stage is over, but there is still ice at the bottom of some penicillin bottles. During the secondary drying process, the remaining ice cannot be removed. When this process is completed, the ice that has not been properly removed will melt and wet the dry product, forming some voids.
solution proposal
Set a longer initial drying time. Increase the safe time between initial and secondary drying.
爬壁
reason
When the initial drying begins, the unfrozen product locally boils, bursts, and sticks to the inner side wall of the penicillin bottle from the top, and the temperature of the side wall is lower than that of the product.
solution proposal
Add annealing steps for heat treatment. Use components to prevent product migration to the top level.
heterogeneous
reason
This situation occurs when the product concentration is too low or when the product undergoes a very rapid freezing step and contains low concentrations of substances such as mannitol.
solution proposal
Can increase the concentration of substances.
Penicillin bottle with broken bottom
reason
Recrystallization occurs during the freezing process, mainly in amorphous products, where the volume of freeze-dried cake increases. In addition, in concentrated solutions, if too much energy is applied to the product at the beginning of the initial drying, the vapor pressure acting on the bottom of the penicillin bottle may also increase.
solution proposal
Cool the product and slowly pre freeze it to promote the formation of larger and dendritic ice crystals, or add an annealing step for heat treatment, and finally slowly cool it before starting the initial drying, smoothly applying heat to facilitate the outflow of water vapor from the bottle. Use thicker penicillin bottles or higher quality penicillin bottles.
atrophy
reason
If the freeze-drying cycle ends but the product still has a high proportion of residual moisture, or if the bottle is filled with humid air, the freeze-dried cake may shrink due to absorbing moisture from the atmosphere in the bottle.
solution proposal
Ensure that the drying phase of the entire freeze-drying cycle has been completed correctly. Use dry nitrogen for pre venting before plugging.
Puffed Full Boiling
reason
Overheating causes natural melting of the product. The product may reach the outside of the penicillin bottle. This may also be because at the beginning of the cycle, the bottle was mistakenly pressed and closed.
solution proposal
Reduce heat input and increase step time in the first stage of initial drying. Meanwhile, control the vacuum level.
Top crust
reason
When micro boiling occurs at the top, an impermeable surface layer is formed, hindering the path of sublimation steam flow. The fundamental reason is insufficient freezing, due to the influence of freezing concentration or slow evacuation of the freeze-drying chamber during the vacuum stage, the product spontaneously concentrates at the top layer.
solution proposal
Properly apply high freezing rates. Evacuate the freeze-drying box as soon as possible. Dry once at low temperature and sublimation rate to allow water vapor to be discharged through the formed surface layer.
success cases
