Facts on Gentle Size Reduction of Freeze-Dried Bacteria Culture
Bacteria culture is used in the production of various food products such as cheese and yoghurt. The preferred bacteria are "grown" on suitable media in a controlled environment. It is later collected and prepared in a proper protective medium. These protective medium such as honey, skim milk, raffinose or glutamate are used to suspend cells to be freeze dried to protect the microorganisms against known freezing and drying damage. Freeze drying is a suitable technique for the preservation and long-term storage of a wide variety of microorganisms.
When it comes to the preservation and long-term storage of various types of microorganisms, freeze drying is a convenient application with most favorable results. Freeze drying is the process of removing water from frozen cell suspension by sublimation under reduced pressure. In a manufacturing production setting, the freeze dried bacteria culture result in "slabs" that look similar to styrofoam. These slabs of freeze dried bacteria culture vary in size and are stored in freezers until they are ready for use. The size of the slabs is reduced to a powder form so that they can be used in various manufacturing processes such as in the cheese fermentation process.
Every lab has different instruments; however, the following are key factors that should be considered in freeze drying bacteria culture:
- There is no specific that will work for all microorganisms. A method developed for one freeze dryer will not necessarily translate to a different make or model.
- Not all microbes can be successfully freeze dried. Certain strains, such as mutants with deficient membranes, may not survive the process or may die off rapidly once freeze dried.
- Lyoprotective media, such as skim milk solution, sucrose solution, or other freeze drying buffers can dramatically impact survival rates.
- Vials used for freeze drying should always be made of glass. Atmospheric water can diffuse into plastic tubes and damage freeze dried samples. Furthermore, samples are safest when flame sealed under vacuum in glass ampoules or tubes.
- Freeze drying protocols should be tested before committing to large scale projects. Evaluation can take 1-2 months and yield results that indicate cells will be stable for long durations.
- The liquid used to rehydrate freeze dried bacteria can impact viability. Culture broth, e.g., TSA or LB, is often used, as is 0.9% NaCl.
For optimum results, it is beneficial to use a gentle milling process for size reducing freeze dried bacteria culture. As well, there should be insignificant heat produced which permits maximum throughput while minimizing retention time in the mill. This helps to maximize the viability counts of the cell, That is, the number of live, unharmed cells. Using an application where the entire process directly benefits from the low heat, low energy, gentle processing, makes for a more efficient and cost effective milling process for size reducing freeze dried bacteria culture.
Today, there is now specially designed equipment and processes that effectively provides a gentle milling process for size reducing freeze dried bacteria culture that includes produces insignificant heat, allows for maximum throughput, and minimizes retention time in the mill.
