A38 is a top cropping yeast strain with high oxygen requirements and may require additional attention and care to achieve successful results.  Below are some helpful tips to consider when fermenting with A38.

• Know your pitch.  Pitch healthy viable yeast at a rate of 0.75 million cells/mL/ºP.  Use our Online Pitch Rate Calculator to determine the right pitch size for your batch.  
• Perform cell counts and viability tests between batches to ensure consistent healthy viable cell counts with every pitch.  Use our  Online Repitching Calculator to calculate the proper pitch weight for repitching subsequent batches.  
• Provide adequate oxygen.  A38 requires 20-25ppm of DO during knockout for proper sterol and unsaturated fatty acid synthesis during membrane development.  Cell growth will stall when oxygen is limited.  Use our  Online Dissolved Oxygen Calculator to estimate oxygen flow rates. 
• Track fermentation kinetics.  Perform a  Forced Fermentation Test at the beginning of fermentation to verify terminal gravity.  Record temperature, gravity, and pH daily to monitor fermentation performance.  The fermenter pH should drop rapidly within the first 48 hours before stabilizing.  The pH will then rise slightly as fermentation nears terminal gravity.
• Keep yeast in the tank during fermentation.  A38 is a chain forming yeast strain that floats to the top of the tank during fermentation.  A38 will overflow out of the tank when headspace is low leading to slurry loss and poor harvests.  Adding a small amount of antifoam (like Fermcap S) will help to keep yeast in the tank with minimal to no impact on head retention, flavor and aroma. 
• Break up floating yeast.  Twenty-four hours before harvesting, inject a small amount of CO2 through the racking arm positioned at 2 o’clock to help break up floating yeast. 
• Harvest as close to terminal gravity as possible.  Do not wait until VDK's are fully Reduced to harvest yeast.  Harvesting in two parts may help to increase slurry cell density. 
• Store and repitch yeast as soon as possible.  Terminal gravity is day one of storage time.  Store yeast cold in a clean sanitized food grade vessel with ≤2psi head pressure.  Repitch within five days or less from terminal gravity.
• Maintaining stable colloidal haze 
  • Healthy viable A38 yeast may indirectly aid long term colloidal haze stability.
  • Colloidal haze is primarily formed by protein-polyphenol complexes.
  • Raw white wheat provides increased colloidal haze stability over malted white wheat.  
  • Keep high protein adjuncts to ≤20% of the grist.  
  • Avoid using kettle coagulants.
  • Hop variety impacts colloidal haze stability.
  • Avoid active fermentation and double dry-hopping.  
  • Dry hopping between days 7-9 of fermentation is best.