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Best practice

It is thought-provoking that ‘best practice' for brewery yeast storage is based on a combination of common sense and practical good design. Of course, as with all aspects of yeast handling and management, hygienic design of vessels and mains together with effective clean-in-place procedures is a given. More specifically in terms of yeast storage and minimizing damage, key parameters include storage temperature (2-4°C), homogeneity through ‘gentle' mixing of yeast, time (ideally < 2 days but no more than 4 days) and yeast solids at ca 40%. Ideally, there are two further considerations that ‘add value'. As noted above, barm ale abv has an overarching impact on yeast viability during storage and ideally should be reduced with sterile water to < 5%. Further, there is benefit in avoiding any exposure to air/oxygen by the application of an inert headspace gas to the storage vessel.

Consequences of failure

As a process, yeast storage is assured through control of temperature and management of time. Should either of these parameters drift or hygienic practices fail, then yeast in storage vessel will be compromised in viability or microbial contamination. In such an event, the yeast would probably go forward without notice and any subsequent issues of fermentation performance or beer quality would possibly be flagged after the event. It is noteworthy that where viability has been compromised, traditional yeast viability measurement prior to pitching adds value in flagging deterioration. Conversely, automated pitching systems that pitch on viable cell number would correct for reduced viability and pitch more yeast biomass to achieve the desired pitching rate. However, in doing so, more dead yeast would be pitched, to the detriment of beer quality.

Acknowledgments

Thanks to the Quain family for putting up with the yeast obsession.

Sadly, as has become the way, I acknowledge Ellie the Labrador (December 2001-March 2015), who, through years of walking and companionship,

gave me time to reflect, think and conjure up the

next steps for projects like this.

 
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