What is Osmotolerant Yeast?
Osmotolerant yeast is capable of growing at low water activity values. High solute concentrations have been classified as “osmotolerant.” It is a special strain of instant dry yeast that performs well in high-sugar doughs, compared to other varieties of yeast.
Osmotolerant yeast can be produced by incremental addition or feeding salts such as NaCl, KCl, or CaCl2 during the later propagative stages of yeast production.1 Or, by selection from high sugar products.2
Osmotolerance in yeast is determined by the genetic constitution of the organism and by the conditions the organism is grown in.3 The exact manner in which these gene complexes interact and function is not precisely understood.
In small amounts, sugar enhances fermentation. However, when the amount of sugar exceeds about 4% of the flour weight, it creates osmotic pressure and slows fermentation by pulling water away from the yeast. This happens in sweet doughs with a sugar content of 20 to 30% by weight, such as Danish pastries, coffee cakes or doughnuts.
The osmotic pressures in sweet doughs are higher, due to increased sugar content. In such high sugar systems, either higher levels of yeast (7-10% based on a flour basis) or osmotolerant yeast is used to compensate the poor yeast activity. The use of osmotolerant yeast is more cost effective.
Dried yeast is permitted for direct addition to food for human consumption, regulated by the FDA in article 21CFR172.896.
- Chen, Shao L., and Feliks Gutmanis. “Patent US4420563 – Process for the Production of Osmotolerant Yeast.” Google Patents. Google, 13 Dec. 1983. www.google.com/patents/US4420563. Accessed 19 June 2017.
- Jermini, Marco F. G., Otto Geiges, and Wilhelm Schmidt-Lorenz. “Detection, Isolation and Identification of Osmotolerant Yeasts from High-Sugar Products.” Journal of Food Protection 50.6 (1987): 468-72.
- Panchal, Chandra J. “Yeast Strain Selection.” New York: Dekker, 1991. Print.
- “CFR – Code of Federal Regulations Title 21CFR172.896.” Accessdata.fda.gov. 1 Apr. 2016. www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfCFR/CFRSearch.cfm?fr=172.896. Accessed 19 June 2017.