Production of freeze-dried kefir culture using whey

• Published in: International dairy journal 2008-03, Vol.18 (3), p.247-254
• Main Authors: Papavasiliou, G., Kourkoutas, Y., Rapti, A., Sipsas, V., Soupioni, M., Koutinas, A.A.
• Format: Article
• Language: English
• Subjects: batch fermentation; Biological and medical sciences; cryoprotectants; cultured milk starters; Fermentation; Food engineering; Food industries; food processing; food processing quality; Freeze-drying; Fundamental and applied biological sciences. Psychology; General aspects; Kefir; kefir culture; microbiological quality; milk analysis; Milk and cheese industries. Ice creams; milk composition; Whey
• ISSN: 0958-6946; 1879-0143
• DOI: 10.1016/j.idairyj.2007.09.005

A freeze-dried kefir culture produced using whey as raw material was studied in three steps. The first step examined the effect of air flow rate and agitation in a bioreactor for the production of biomass. The highest daily biomass productivity of 14.1 g dry weight L −1 was obtained when 8.3 vvm air flow rate was used, where vvm is volume of air per unit volume of medium min −1 and is defined as the ratio of air volume fed to the volume of ungassed broth in the fermenter min −1. In the second step, production of freeze-dried cultures was studied testing various cryoprotective agents and cooling rates. Fermented whey proved to be a suitable cryoprotective medium, providing 86% survival of the kefir culture and showing satisfactory metabolic activity of freeze-dried cultures. The third step involved evaluation of the freeze-dried product in carbohydrate fermentations, showing a high operational stability during repeated batch fermentations. The use of freeze-dried kefir culture in food production as a value-added starter culture thus appears possible.