Freeze drying, of starter cultures

Inhibition of Starter Cultures. The primary cause of antibiotic residues in milk and milk products is the failure of producers to withhold milk from the market for a sufficient time period following veterinary therapy for mastitis or other diseases in dairy cattle. Consumption of antibiotic-supplemented feed may also lead to residues in the milk. These antibiotics are quite stable and remain in the milk even after manufacturing pro-cessses including pasteurization, drying or freezing. Marth and Ellickson (22), Marth (23) and Mol (17) have reviewed extensively problems in the dairy industry associated with antibiotic residues in the fluid milk supply. 

The propagation and production of starter cultures must be economically feasible. The starter culture can be preserved by freezing or freeze drying with little practical loss of activity. Essential properties of starter cultures such as fermentative ability are stable under defined storage conditions for several months. 

Growth and Harvesting of Microaloae. Skeletonema costatum starter cultures were obtained from Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, Maine. The culture conditions are described by Polak (11). The cells were harvested when they were 2 or 3 weeks old by continuous centrifugation. The biomass obtained was immediately frozen at -28°C, freeze-dried, flushed with and stored at -28°C in darkness. A total of four batches were grown and used in experiments. 

In the case of salami, starter cultures can be cultivated on meat substrate and freeze-dried, where they remain active at a large rate. The storable culture substrate is added to the salami raw mixture to start the desired ripening process. Depending on process course, it can already contain flavour or flavour-precursors which contribute to accelerating the ripening process. 

Starter cultures are mainly applied as liquid cultures with about 10 to 10 ° microorganisms per ml. They are also available in a freeze-dried or deep frozen preparation with the advantage of very simple application. 

Commercial starter cultures are available in both frozen and freeze-dried formats and can be used to directly inoculate the material to be fermented. The use of these types of cultures, referred to as direct vat set (DVS) cultures, has many advantages over the... 

Freeze drying for the production of dried starter cultures... 

In their nationwide survey of over 100 wineries, Fugelsang and Zoeck-lein (1993) report that 43% of respondents used freeze-dried preparations, with an additional 8% using frozen concentrates. Already reactivated liquid cultures were being used by 34% of the winemakers and only 5% developed starters from their own cultures. Since that time, additional producers of freeze-dried cultures have emerged and the numbers of winemakers availing themselves of these more user-friendly sources of inocula has most likely increased. 

One commercial LAB starter (Vinflora LP, available through Chris Hansen Laboratory) is marketed as a freeze-dried culture for prefermentation addition to juice/must. In this case, MLF is initiated and partially carried out in advance of alcoholic fermentation by the addition of a high-titer inoculum of the homofermenter Lactobacillus plantarum. Being homofermentative, any utilization of glucose at this stage yields lactic acid solely. However, the strain is relatively susceptible to alcohol thus, activity... 

Starter cultures and probiotics are produced and distributed world wide by specialised companies. Therefore, stabilization of the bacteria is essential. Drying is a common stabilization method as it leads to an increased storage stability and facilitated transport compared to freezing. However, drying leads to an inactivation of the cells. The dehydration damage is especially pronounced at low Water content where structural water is removed from the biomolecules such as proteins and hydrophilic surfaces of biomembranes. 

Costello, P. 1988. The conduct of malolactic fermentation under commercial conditions. II. Use of commercial freeze-dried and frozen starter cultures of Leuconostoc oenos. Tech. Rev. Aust. Wine Res. Inst. 51 9-12. 

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