Starter cultures are used to assist the fermentation process in preparation of various foods and fermented drinks. A starter culture is a microbiological culture which actually performs fermentation. Freeze drying is an effective way to preserve starter cultures.
Freeze Drying Process
The freeze drying process was developed during the Second World War for preserving medical supplies that required refrigeration. Since then freeze drying has been applied to the food industry and is now a standard process used to increase the shelf-life of many products that would otherwise spoil.
Freeze drying uses a process called lyophilization to gently freeze the specimen and extract the water in the form of vapour using a high-pressure vacuum. The vapour collects on a condenser, turns back into ice and is removed. A gradual temperature rise extracts all remaining 'bound' moisture from the specimen. This process retains the physical structure of the product and preserves it for storage and/or transport. The product can easily be re-hydrated using water and in some cases can be used directly in its freeze-dried form.
Advantages of Freeze Drying Starter Cultures
With freeze drying, both solids and liquids can be preserved without damaging their basic chemical structure. The natural size, composition and consistency of the sample are retained.
Regular drying methods have a major disadvantage as the high temperatures used can cause chemical or physical changes to the product. For biological cultures, this could render them ineffective or affect the taste or quality of the end product.
Applications of Freeze Dried Starter Cultures
- Cultured Milk (widely used in African countries)
- Sour Cream
- Sourdough bread
Cuddon designs and manufactures freeze drying machines for sale worldwide.