GEA, Düsseldorf, Germany, has launched a nitrogen freezing pilot plant for bacteria, giving food and dairy processors the opportunity to trial this new technology in their own plants before investing in production-scale equipment. By freezing bacteria into pellets before drying, GEA is now able to provide processors with greater flexibility, a higher active cell count and reduced costs through better utilisation of their 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 (e.g., yogurt 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 -50ºC and then storing them under temperature-controlled conditions until they are required. This, however, requires a continuous cold chain, which may be no problem in developed countries, but more challenging elsewhere.

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 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.

With its new pilot plant, GEA has taken 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. This method has many significant advantages: for example, rather than freezing all of the bacteria in a single batch, they can be collected from a continuous stream improving flexibility and equipment utilisation; 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 -50ºC until 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.

 “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 at GEA Process Engineering. “Freeze dryers are expensive so we need to make sure customers are getting the best possible output from them.” The GEA nitrogen freezing pilot plant will be on display on stand 6F141 in Hall H6 at the Food Ingredients Europe Exhibition in Paris, 3-5 December. www.gea.com

 

GEA’s liquid nitrogen freezer pilot plant

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