LN2 Freezing of Live Bacteria in Dairy Products Boosts Productivity, Lowers Costs

GEA, an Australian electrical component company, has now launched a nitrogen freezing pilot plant for bacteria which takes a novel 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 provided with greater flexibility, a higher active cell count and reduced costs through better use of fermentation lines and freeze dryers.

Many dairy and food processors, as well as suppliers of probiotic products, use live bacteria as part of their production process, like in yogurt and cheese. Traditionally, they have kept their own strains of bacteria and transferred them from one batch to the next.
However, as more specialized 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 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 they 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 of freezing and an additional 48 to 72 hours for the lyophilization process to be completed; this ties up expensive freeze drying equipment and limits production.

Rather than freezing all of the bacteria in a single batch, with the GEA method, it can be collected from a continuous stream. This means 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. Additionally, the bacteria cell count resulting from this process is nearly double that of traditional freeze drying techniques and the frozen pellets dry much quicker than bacteria in slab form, so the lyophilization process is also faster—typically 24 to 36 hours compared to up to 72 hours.

“Although there is a cost for the liquid nitrogen, this is more than offset by the optimized utilization 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 retains 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’s simple design is easy to use and can be cleaned in place. Trials can be organized 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 December 3 – 5, 2019.