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​​​Serial Repitching Method for New England IPAs with Midfermentation Dry Hopping

The production of New England IPAs (NEIPAs) introduces several hurdles that can lead to increased costs. Hop creep is one example of a common issue with this style, and one in which the solution can lead to other issues. For example, midfermentation dry hopping allows hop creep to coincide with primary fermentation and results in a more predictable final gravity. However, the high hop load results in lower viability in harvested yeast. Unfortunately, using fresh pitches of yeast for each brew has cost implications that can negate the benefits of midfermentation dry hopping. Repitching yeast in NEIPAs is difficult for several reasons. Not only are the high hop loads required of NEIPAs stressful for yeast, but additionally, the harvested yeast slurry contains substantial amounts of spent hop material. The yeast becomes unusable with negative organoleptic characteristics of spent hops being carried to subsequent fermentations. This paper describes a technique for harvesting midfermentation and storing the highly active yeast, while still allowing for dry hopping midfermentation. This method of midfermentation yeast harvesting is a modified version of top cropping from a cylindroconical fermenter. Yeast viability counts, detailed fermentation tracking, and microbiological checks have all confirmed this method to be useful for repitching certain yeast strains used in NEIPAs.

Keywords: harvest, repitch, New England IPA, hazy IPA, hop creep, dry hop​