Skip Navigation Links
METHODS
Shortcuts
About
FAQ
Subscribe
Skip Navigation Links
Methods Home
All Methods
Calculators / eXtras
Tables and Tools
Identification Guides
Beer Flavor Database
Hop Flavor Database
Flavor Standard
Spiking Calculator
Training
Lab Basics


Skip Navigation Links

Safety Statement
Propose a Method
Cite a Method
Technical Sub Committees
Archived Methods
Check Sample Program
Prefaces to Earlier Editions
ASBC Methods of Analysis - Yeast-15: Differentiation of Ale and Lager Yeast Strains by Rapid X-α-GAL Analysis

ASBC Methods of Analysis

Yeast

Yeast-15
Differentiation of Ale and Lager Yeast Strains by Rapid X-α-GAL Analysis

VIEW METHOD

Summary
The melibiose analog 5-bromo-4-chloro-3-indolyl-a-D-galactopyranoside (X-α-gal) has previously been used to differentiate lager strains (Saccharomyces pastorianus) from ale strains (S. cerevisiae). Differentiation of these two types of yeast is based on the capacity of lager strains to cleave the X-α-gal molecule through the action of melibiase. This results in the release of indol, which oxidatively polymerizes to give an insoluble blue-green dye. After incubation with X-α-gal solution, a lager yeast suspension produces a blue-green coloration while the color of an ale yeast suspension remains unchanged (cream or white). This method is a variation of a previous method with modifications to the format and reagent and yields results in ≥30 min.