Product characteristics and storage stability

The dried cell concentrate is typically produced by specialized suppliers and distributed worldwide. As the producers of fermented foods want to build up some stock, the cultures should be stable for at least one year. As the activity of the cultures after drying depends on the previous fermentation step (see Section 11.3), and the storage stability depends on the drying process as we will show in this section, the starter cnlture preparation process must be looked at in a holistic approach. This 

In general, the storage stability of dried cultures for a given strain depends on the moisture content, the storage temperature, the presence of protectants, the presence of oxygen, and the physical state of the sample. 

With regard to moisture, the stability increases with decreasing moisture content down to a certain moisture level. Below this level the stability becomes less. The maximum stability is found for a moisture level of 3-4% (wet basis) (Pehkonen et al., 2008 Scott, 1958 Zayed Roos, 2004). The impact of moisture on stability is temperature dependent. At higher storage temperatures, the moisture has a higher impact on stability (Aschenbrenner et al 2012 Higl et al 2007). 

Reprinted from Aschenbrenner et al. (2012), copyright 2012, with permission from Elsevier. 

With regard to temperature, storage temperature has a large impact on stability. The temperature dependence of the inactivation constant is described by the Arrhenius function  

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