Yoghurt powder - A review of process technology, storage and utilization

Yoghurt powders possess various nutritional and therapeutic values. Antitumour activity is associated with the cell wall of starter bacteria and so the activity remains even after drying. The primary objective of drying yoghurt is to preserve it in a shelf-stable powdered form of high quality without a need for refrigeration. Such powder can be prepared by various methods, such as freeze-drying, spray-drying, microwave-drying and vacuum-drying. Before drying, it is beneficial to concentrate yoghurt by methods including cloth bag method, mechanical, centrifugation, ultrafiltration and vacuum concentration. S. thermophilus shows less sensitivity in comparison to L. bulgaricus, during freeze- as well as spray-drying of yoghurt. Cultured products sold with any claims of health benefits should meet the criteria of suggested minimum number of more than 106 cfu g(-1) at the expiry date. Freeze-dried yoghurt can be stored for up to 1-2 years at 4degreesC. After I year of storage, the powder typically contains total bacterial counts of 10(6) cfu g(-1). Active cultures are guaranteed for I year under cool, dry conditions for spray-dried yoghurt; it can be used in the bakery and confectionary industries.