Have you ever found a yeast strain that had a great fermentation flavor, but didn’t attenuate well? Have you ever used a Belgian yeast strain that didn’t flocculate well? The solution might be blending yeasts. Historically all breweries had a blend of yeast in their fermentation. It wasn’t until the work of Louis Pasteur that breweries began using pure cultures of single yeast strains. Now you can use more than one yeast strain in a fermentation to blend fermentation flavors, to increase attenuation or increase flocculation.