High rehydration rate is an important indicator for measuring the quality of freeze-dried food, but it cannot be simply equated with "good freeze-drying process".
Although the rehydration rate reflects one aspect of the freeze-drying process, it is not absolutely positively correlated with the overall quality of freeze-drying. To comprehensively evaluate the freeze-drying process, it is necessary to take a comprehensive view from the following dimensions:
1. The high rehydration rate does reflect some process advantages
In an ideal state, high-quality vacuum freeze-drying (FD process) can maintain the original physical structure of ingredients, forming a porous sponge like structure inside. This structure allows moisture to quickly infiltrate during rehydration, resulting in a fast rehydration speed and high rehydration rate. This usually means that the vacuum degree and refinement level of the freeze-drying equipment are high, and the raw materials are relatively fresh.
Why is high rehydration rate ≠ best process?
In actual production, the rehydration rate and the core quality of freeze-drying (such as nutrient retention) are not always completely synchronized:
Balance of nutrient retention: Some freeze-dried products may lower the freeze-drying temperature or change process parameters in order to pursue the ultimate rehydration speed, which may actually lead to mild denaturation of proteins, resulting in a decrease of 5% in core nutrients (such as protein retention rate).
The impact of dietary fiber: Some pure meat freeze-dried products have a relatively slow rehydration rate due to the rich fiber content of the meat itself, but this does not mean that their process is poor. On the contrary, the protein retention rate of such products is often extremely high.
3. The "gold standard" for evaluating freeze-drying processes
The truly top-notch freeze-drying process not only requires good rehydration, but also requires maximum locking of the nutrients of the ingredients in extremely low temperature and high vacuum environments. Therefore, in addition to rehydration rate, the following core indicators must also be considered for evaluation:
Protein retention rate: This is the core indicator for measuring freeze-drying quality. High quality high-end freeze-drying typically requires a protein retention rate of ≥ 90% and a retention rate of ≥ 95% for essential nutrients such as taurine.
Moisture content: High quality freeze-drying and dehydration are thorough, and the moisture content is usually ≤ 5% (some standards require ≤ 8%), which can extend the shelf life and prevent bacterial growth.
Process type: It must be vacuum freeze-drying (FD process), not high-temperature hot air drying (AD process). The FD process can sublime moisture in low temperature environments below -30 ℃, retaining over 95% of nutrients.
In summary, high rehydration rate is an excellent "bonus point" for freeze-drying technology, but it is not the "only standard". When selecting or evaluating, the rehydration rate should be combined with indicators such as protein retention rate and moisture content to arrive at the most objective conclusion.
 

E-mail:

sales@syguanfeng.com

Tel: 
+86 15088506234
 

Address: 

South Industrial Park of Dongguan, Shangyu District, Shaoxing City,Zhejiang Province,China.