Brief Brewing Background
I have been homebrewing for 9 years (8 of that all grain). I brew 24-26 times a year (every other weekend) and I usually make 5-6 gallon batches. For the last 3 years I have been top cropping ale yeast with various different procedures.
Top Cropping Procedures
My current top cropping method isn't very technical and I recently lost a batch of beer so I want to hear from the yeast wizards out there if there is anything they would change.
Typically 48 hours after pitching my yeast, I use a sanitized (starsan) measuring cup and lift the lid of my brewbucket and carefully scoop the yeast on top of the beer and put it in a re-purposed 8 pound size PBW plastic jug (sanitized with starsan). I always put the plastic jug on a scale (set to measure grams) and I try to collect 100 grams of the foam from the beer, but sometimes I fall short because I pulled all of the foam already. Then, I sanitize the valve on the brewbucket and pour in about a pint of beer on top of the yeast I collected. The lid to the plastic jug is fitted with an air lock and I screw this on and let the beer ferment in the small jug for 2 days, then refrigerate. About 1-3 days in advance of a brew day, I make a 1 quart starter and pour this into the jug and to wake the yeast up and have some (although who knows how much) cell growth.
Now to the beer I lost... I had been top cropping WLP001 since July 2014 and the 15th batch went bad. All previous batches of beer were good, but I did notice a house flavor developing. I am not sure if I had bad cleaning and sanitation that led to the bad batch or I slowly picked more contaminates in the yeast that finally took over the pitch. At any rate, I think going that many generations might be to many so I will start buying a new pitch sooner.
Let me know if you have any questions and thanks in advance for any advice you may have.