13,591
edits
Changes
Hops
,added section in Dry Hop for Dry Hop Creep
* [https://www.therarebarrel.com/index.cfm?method=blog.blogDrilldown&blogEntryID=8141D6FA-EE78-5BCE-E08E-704DB6EEA279&originalMarketingURL=blog/Dry-hopped--Changing-process-leads-to-bottling The Rare Barrel reports on an anecdote that dry hopping in a less sour beer extracts better hop aroma, and ''Brettanomyces'' preserves the character.]
* Per Buer's experiment on the effects of dry hopping on ''Lactobacillus'':
: <youtubewidth="300" height="200">J2g5P7ZlGn4</youtube> ====The Freshening Power of the Hop====Also known as "dry hop creep", it was first discovered in 1893 by Brown and Morris that dry hopping releases glycolytic enzymes that break down starches into sugars that viable yeast can then ferment. Brewers normally aim to control the final alcohol percentage in a beer through brewhouse operations rather than postfermentation dilutions with lower/higher alcohol beers or water. This approach to brewing is called "brewing to final gravity." Due to the need to have a predictable ABV for government regulatory reasons, unexpected fermentation is, therefore, a concern for many breweries <ref name="Kirkendall_2018">[https://www.tandfonline.com/doi/abs/10.1080/03610470.2018.1469081?journalCode=ujbc20 The Freshening Power of Centennial Hops. Jacob A. Kirkendall, Carter A. Mitchell & Lucas R. Chadwick. 2018. DOI: https://doi.org/10.1080/03610470.2018.1469081.]</ref>. Historically, there have been two studies published on the phenomenon of hops releasing glycolytic enzymes that break down starches during dry hopping: [http://barclayperkins.blogspot.com/2018/03/why-dry-hop.html Brown and Morris (1893)] and [https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1941.tb06070.x Janicki et al. (1941)]. More recently, several researchers and brewers have rediscovered this phenomenon. Brown and Morris (1893) discovered that hops could break down maltodextrin, but failed to extract the enzymes from the hop plant material and hypothesized (perhaps incorrectly) that tannins were inhibiting the enzymes. Janicki et al. (1941) came to similar conclusions regarding the enzymes and tannin inhibitors, and they also concluded that the enzyme activity was independent of hop variety, geography, age, storage conditions, pH values between 4.1 and 4.8, and that one or more additional unknown factors were at play <ref name="Kirkendall_2018" />. More recent studies have shown that there is a difference in this enzymatic power between different hop varieties. [https://www.asbcnet.org/publications/journal/vol/2017/Pages/ASBCJ-2017-2257-01.aspx Cibaka et al. (2017)] reported an increase in ABV when dry hopping with Amarillo and Sorachi Ace hops, but not when dry hopping with Citra or Hallertau Blanc. Interestingly, they also found that Mosaic hops resulted in the opposite effect and it was hypothesized that Mosaic hops release some sort of molecule that inhibits yeast fermentation/growth or viability <ref name="Kirkendall_2018" />. Kirkendall et al. (2018) found the hop varieties also have a varying ability to ferment dextrins. They reported the following ABV increases when dry hopped in a pale ale at one pound per barrel: Centennial hops (+0.27%), Citra (+0.12%), Simcoe (+0.33%), Cascade (+0.49%) and Amarillo (+).49%). Prolonged contact with Centennial hops (42 days) resulted in a nearly 1% increase in ABV. Rousing the hops into suspension hastened the increase in ABV compared to samples that were left still. From their results, it appears as though contact with hops during dry hopping continues the breakdown of starches and dextrins into fermentable sugars. They also concluded that dry hopping at a temperature that is too cold for the yeast strain in the beer to ferment resulted in no change in ABV. They also compared the enzymatic activity of Centennial that was stored at -20°C versus room temperature storage and found that there was no significant difference, indicating that the as of yet unidentified enzyme(s) are relatively stable. Further work needs to be done to identify the enzyme that is responsible for dry hop creep <ref name="Kirkendall_2018" />.
===Aged Hops in Lambic===