Preservation of Lactic Acid Bacteria by Freeze-Drying

Lactic acid bacteria are widely used in the manufacture of fermented milk products, such as cheeses, sour cream butter, yoghurt and fermented milk beverages. These microorganisms may also be applied to the production of fermented meat products and silage. We may easily cultivate lactic acid bacteria in milk. However, it is a laborious work to preserve the organisms in liquid state because viability of the conventional milk culture is often lost within one or two weeks even at 4 to 7°C. Freezing is useful for extended storage of lactic acid bacteria. Recently, in the United States and some European countries, frozen concentrated cultures of lactic acid bacteria can be supplied in an active form which eliminates the need of regular transfer in plant. Frozen cultures are highly promising but their shipment is troublesome. Freeze-drying is applied successfully to the preservation of microorganisms and it has been employed in the distribution of lactic acid bacteria. This article gives an outline of the author's study intended to establish the preparation method of active freeze-dried culture of lactic acid bacteria.