Nitrogen freezer for live bacteria used in dairy products

Many dairy and food processors, as well as suppliers of probiotic products, use live bacteria as part of their production process (eg, yoghurt or cheese). Traditionally, they have kept their own strains of bacteria and transferred them from one batch to the next.

However, as more specialised strains of bacteria have emerged, so too has the need to distribute them more widely. This is typically done by freezing them to -50°C and then storing them under temperature-controlled conditions until they are required. This, however, requires a continuous cold chain.

For this reason, freeze-dried bacteria have become popular because it can be transported and stored at ambient temperature and rehydrated as required. On the other hand, freeze-drying bacteria is a long process requiring several hours to freeze, then an additional 48 to 72 hours for the lyophilisation process to be completed; this ties up expensive freeze-drying equipment and limits production.

GEA has now launched its nitrogen freezing pilot plant for bacteria which takes a different approach, freezing the bacteria in droplets using a liquid nitrogen bath outside the freeze dryer then drying the pellets via the normal procedure. By freezing bacteria into pellets before drying, food processors are said to be provided with greater flexibility, a higher active cell count and reduced costs through better use of their fermentation lines and freeze dryers.

Other benefits include: rather than freezing all of the bacteria in a single batch, it can be collected from a continuous stream; fermentation and freeze-drying are separate, so the freeze dryer does not need to be available when the product is frozen: bacteria can be stored at -50°C until it is required; the bacteria cell count resulting from this process is nearly double that of traditional freeze-drying techniques; and frozen pellets dry much quicker than bacteria in slab form, so the lyophilisation process is also faster — typically 24 to 36 hours compared to up to 72 hours.

GEA liquid nitrogen freezer pilot plant. Image credit: GEA.

“Although there is a cost for the liquid nitrogen, this is more than offset by the optimised utilisation of the freeze dryer,” explained Morten Pedersen, Area Sales Manager for GEA Process Engineering. “Freeze dryers are expensive, so we need to make sure customers are getting the best possible output from them.”

Regarding the higher cell count from this technique, Morten stated, “Bacteria that is frozen quickly via liquid nitrogen and dried in this way is retaining twice as many viable cells than other techniques. This product is more effective than other options and ultimately reduces the customer’s costs.”

The GEA nitrogen freezer pilot plant has a simple design, is easy to use and can be cleaned in place. Trials can be organised for food and dairy processors to test the technology in their own plants.

The pilot plant will be on display at the Food Ingredients Europe Exhibition in Paris from 3–5 December 2019.

Image caption: Freeze-dried bacteria using nitrogen freezing from GEA. Image credit: GEA.