It took a little longer than expected to finish the second part of my summaries of the presentations at the 5th International Young Scientists Symposium on Malting, Brewing and Distilling, but here they are. You can find the first part here. I will hopefully have time to post the final part next week. I will also be posting a summary of my own presentation on new lager yeast hybrids.

• Screening for the brewing ability of non-Saccharomyces yeasts by Maximilian Michel

Maximilian talked about the use of non-conventional yeasts for beer production and he had screened a range of non-Saccharomyces yeasts for brewing potential. Yeast isolates were first identified with genetic fingerprinting and RT-qPCR, and then sent through an initial screening test, which included growth on various carbon sources (glucose, fructose, sucrose, maltose, maltotriose and melibiose), hop resistance (various concentrations of iso-alpha acids), ethanol tolerance (various concentrations of ethanol) and phenolic off-flavour production. Promising strains were then chosen for 2L fermentations. He had focused especially on Torulaspora delbrueckii (but he had also looked at Schizosaccharomyces pombe, Pichia anomala, Hanseniaspora uvarum, Kluyveromyces lactis and Kluyveromyces marxianus), and out of the ten strains he had fermented with at ‘larger’ scale, only one was able to use maltose (and maltotriose). That strain also produced a fruity and berry-like flavour profile. So there are definitely gems to be found in the vast range of wild yeast that are available in nature.

• Lachancea thermotolerans in primary beer fermentations by Jen House

Jen continued on the topic of using wild yeast in beer fermentations. Her research was on the use of Lachancea thermotolerans, which is an interesting species because of its ability to produce lactic acid. Hence, there is potential to use it in pure culture fermentations for the production of sour beer. Jen had tested three different strains of various origins in wort fermentations, and found that all three were able to use maltose, but not maltotriose. The three strains also produced more lactic acid and glycerol than the S. cerevisiae control. They also seemed to have quite low O2 requirements and were resistant to iso-alpha acids up to at least 60 IBU, which makes them interesting for brewing use. The pH only dropped to around 4.2 in her experimental fermentations, which means that they will only produce a mildly tart beer and may not be suitable for sour beers (as the only microbe). Lachancea yeasts have been isolated from the bark of oak trees, so that may be a good place to start looking in case you are interested in trying to isolate your own!

• Biodiversity of yeast and lab population isolated from Beninese African Sorghum Beer Starter by Sedjro Emile Tokpohozin

Emile has been looking at the biodiversity of Beninese sorghum beers by isolating yeasts and lactic acid bacteria from starter cultures brought from Benin. These starter cultures aren’t made from pure yeast cultures, rather a small amount of beer from the previous batch is used as a starter culture for the next. Emile had isolated (identification by ITS-PCR and MALDI-TOF-MS) a range of yeasts (e.g. Saccharomyces cerevisiae, Candida krusei, Candida ethanolica and Debaryomyces hansenii) and lactic acid bacteria (Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus helveticus, Lactobacillus brevis and Lactobacillus paracasei) from a starter culture, and he further screened these for the ability to use various carbon and nitrogen sources, as well as beta-glucosidase ability (in order to break down the cyanogenic compound dhurrin that is found in sorghum). Several possible candidate isolates were identified and these are to be used in some pilot-scale fermentations next. Again shows how much ‘wild’ microbes are out there that are potentially useful in brewing!

• Invited Speaker: Yeast culture collections by Kyria Boundy-Mills

This talk was a bit different, as Kyria talked about the Phaff yeast culture collection (of which she is the curator of). The Phaff collection is the fourth largest in the world, and contains thousands of yeasts. Many of the deposited yeasts have not been characterized very well, so Kyria talked about the possibility of finding ‘hidden gems’ in the collection. These could have some very interesting properties and phenotypes, relevant not only to the brewing industry, but also e.g. the biofuel industry (oleaginous yeast).

• Relationships between the speed of fermentation and levels of flavor compounds post-fermentation by Maria Josey

Maria had examined the beer aroma compounds and modelled the fermentation kinetics (using a logistic model) of 10 successive fermentations using serially repitched yeast. The 10 fermentations all behaved quite similarly, with only minor differences in fermentation rate. There also didn’t seem to be any relationship between fermentation rate and number of times the yeast was repitched. This shows that you can easily reuse your yeast for over 10 generations without any significant effects on your fermentation (as long as your hygiene practices are good). Positive linear correlations were found though between the concentrations of several aroma compounds and the maximum fermentation rate (the B parameter in the model). Faster fermentation leads to more isoamyl acetate, isobutyl acetate, ethyl hexanoate and ethyl octanoate, which of course is something that seems logical as these compounds are synthesized from metabolic intermediates.

• Omics analysis revealed multiple stress responses of lager yeast in the process of autolysis by Jinjing Wang

Jinjing had studied the yeast responses associated with autolysis by performing proteomic and transcriptomic analysis on yeast strains with different tendencies to autolyse. She also presented various methods for the quantification of autolysis, including measuring total protein in beer, the stability of the redox potential and nucleic acid release. Using microarray analysis they had identified a range of genes that were down- and upregulated in yeast strains that showed high tendency for autolysis (e.g. RLM1 and UBC4). To confirm the roles of RLM1 and UBC4 in the autolysis process, these genes were both knocked out and overexpressed in a production strain. Overexpression of RLM1 and knocking out UBC4 led to increased autolysis. However, one must keep in mind that autolysis is a complex process that is influenced by a range of cell functions and genes.

• Energy state model for bottling plants by Isabel Osterroth

Isabel held the only presentation in the ‘Packaging’ topic, and she talked about an energy state model which she had developed for bottling plants. Sustainability and reducing energy use, combined with the fact that bottling plant models haven’t been made before, was the driving force for creating the model. The model described the energy use of various machines in the bottling plant depending on their operational state (machines use energy even when idle). A model that was able to predict the energy use of all the separate functions in the bottling plant was successfully created, and future work will include the use of the model for optimization purposes.

• Impact of ascorbic acid additions in mashes by Joe Williams

Joe talked about his research on supplementing ascorbic acid to the mash, and gave a virtual tour of the pilot brewery at UC Davis. The motivation for adding ascorbic acid to the mash was to increase thiol and polyphenol formation and to decrease color development in the wort. The study was very preliminary at the moment, and it will be interesting to see the final results. The pilot brewery at UC Davis was quite impressive, featuring a six-vessel 170L brewhouse and four 20L nano-breweries. I am quite jealous.

• Optimizing hop aroma in beer dry hopped with cascade utilizing glycosidic enzymes by Kaylyn Kirkpatrick

Kaylyn talked about the use of various glycosidic enzymes in dry hopped beer in order to release glycosidically bound aroma compounds. She had tested a range of commercial Rapidase enzymes and what effect they had on the concentrations of various hop aroma compounds in a beer dry hopped with Cascade. The addition of these enzymes seems to have had quite little effect on linalool concentrations, but the concentration of geranyl acetate seems to have been enhanced with the ‘Rapidase Hoptimase’ enzyme. Their sensory panel also noticed an increase in ‘tropical fruit’-like aroma, which could be attributed to several compounds that weren’t quantified in this experiment. It seems like an interesting idea though; using e.g. Cascade in combination with a glycosidic enzyme to replicate the aroma profile of some of the modern aroma hops (e.g. Citra). Not sure how economical such a solution is though?

• Investigating sources of variation during dry-hopping by Daniel Vollmer

Daniel talked about methods to reduce the amount of variability between replicates in dry hopping experiments. Daniel had noticed in earlier experiments that there was quite large variation between his replicates during dry hopping experiments at pilot-scale, and thus attempted to locate sources for this variation. One of the key findings was that oxygen pickup has a large (negative) effect on hop aroma intensity, and this seemed to have been one of the largest sources of variation. Other sources was the raw material (i.e. the hops cones), which for future experiments will be ground. Another interesting observation, which I mentioned already in the summary of Tom Shellhammer’s keynote lecture, was that there is huge variability in oil content within the same hop cultivar (e.g. Cascade) from different farms. Also very interesting, as I mentioned, was that there seemed to have been no correlation between oil content and aroma intensity. So there are clearly other factors that affect hop aroma intensity as well.

I apologize again for the inactivity on the blog. I haven’t been brewing much the last half a year. The wife and I bought a house in the end of last year and we’ve been renovating it since. We finally moved in a couple of weeks ago, and have started settling in. So soon I’ll be able to return to brewing again! Anyways, last week I attended the 5th International Young Scientists Symposium on Malting, Brewing and Distilling, which was arranged at Sierra Nevada’s brewery from April 21-23, 2016 in Chico, California, USA. First of all I want to thank Ken Grossman, Sierra Nevada, Charlie Bamforth and all the other organizers for a fantastic conference (especially Sierra Nevada for their generosity)! The conference featured great scientific and social program, awesome food, a relaxed atmosphere, amazing people and delicious beer! I myself presented some of the recent research we’ve been conducting on lager yeast hybrids at VTT the past year (I’ll post a link to the presentation slides soon!). To sum up, we’ve been looking at how the ploidy of new lager yeasts affect their phenotypical properties. I’ll be writing up a more detailed post on this particular research soon, as we just had a manuscript on this work accepted.

As I mentioned, there were a lot of interesting presentations during the conference! I thought I’d write some short notes / summaries of all the presentations in case you are interested. Since there were a lot of presentations, I’m splitting this post into three parts. Anyways, here is the first third of the summaries:

• Keynote: How Craft Brewing is Transforming the Way We Think About Hops and Hop Flavor by Tom Shellhammer

Tom opened the conference with an interesting talk on the current situation of hop use in the craft industry and hop research at OSU. Craft brewers are using more and more of the global hop production, which also has shifted from being ‘bitter hop’-dominated to being ‘aroma hop’-dominated. Tom also reminded the audience that 1 IBU is not the same as 1 ppm iso-alpha acid. This is particularly relevant with heavily dry hopped beers, where oxidized alpha acids (which are bitter, but not as bitter as iso-alpha acids) can influence the IBU value. In some commercial (dry hopped) beers that had been analysed at OSU, they had observed very high levels of oxidized alpha acids. Another point that was brought up, was that the perceived bitterness gets saturated at high IBU levels (i.e. very little sensorial difference between a 80 IBU beer and a 100 IBU beer). Tom also showed a very interesting figure (which Daniel Vollmer showed again later in his presentation), showing the relationship between hop oil content in Cascade hops sourced from different farms and the hop aroma intensity in beers brewed with these hops (determined by a sensory panel). What was extremely interesting was that there seemed to be no correlation what so ever. The beer brewed with the Cascade hops with lowest oil content actually seemed to have one of the highest aroma intensities. Furthermore, many of the Cascade hops that had the highest oil contents produced beers with the lowest aroma intensities. This just shows that blindly looking at hop oil contents in hops doesn’t actually tell very much about what kind of hop aroma it will give to the beer. If I remember correctly, Tom also suggested that there was no correlation between linalool or myrcene concentrations and the hop aroma intensity either, meaning that there are other key aroma compounds responsible for hop aroma out there that still need to be identified.

• Towards the release of a 2-row barley variety for California craft malting and brewing by Joshua Hegarty

Joshua talked about how they have attempted to breed a 2-row barley variety that would be suitable for the ‘harsh’ growing conditions in California. These include an abundance of plant pathogens and dry conditions. They had crossed different parent strains, and selected superior varieties which they had then tested in the field. The new breeding lines had shown good yields and malting quality in the field trials. Using gene mapping they had also found several regions associated with disease tolerance in barley.

• Impact of barley varieties on malt and beer flavor by Lindsay Barr

Lindsay presented some research on the influence of barley varieties on malt and beer flavour that had been carried out at the New Belgium Brewing. Barley variety seems to have quite a big influence on both wort and beer flavour (at least according to their sensory panel). However, there didn’t seem to be any correlation between the flavours that were observed in the wort and the beer. Beer age seemed to have had a bigger impact on the beer flavour than the barley variety.

• Selective pressurized liquid extraction of hop oil from hop cones by Katy Orr

Katy talked about some of the hop-related research that had been done at Sierra Nevada Brewing. Her background was in environmental chemistry, where she had used different extraction methods to quantify hydrocarbons from environmental samples. Here, she talked about how they had tested two different extraction methods, selective pressurized liquid extraction and Likens Nickerson distillation, to test the efficiency of their hop torpedo. Both methods seemed to have yielded quite similar results for some of the compounds that were analysed. However, the main points that were brought up were that the extracted amount does not equal the actual contents and subsequently the importance of good internal standards (that behave chemically and physically as similarly as the compound of interest as possible).

• Pro-oxidative effects on the storage stability of German Perle and Czech Saaz pellet hops by Mark Zunkel

Mark had compared the stability of Perle and Saaz hops exposed to oxygen at room temperature during a 9 month period. The hop storage index (HSI; which measures the loss of alpha and beta acids spectrophotometrically) of Perle remained quite stable for around 4 months, after which there was a more rapid loss of the hop acids. Saaz seemed to have remained slightly more stable than Perle, but also experienced a more rapid loss in the latter half of the experiment. Unsurprisingly, both hop varieties suffered a rapid loss of hop oil in the pro-oxidative environment (50% loss of hop oil in a week). This just shows that aroma hops should be stored cold and without the presence of oxygen!

• The effect of hopping regime, cultivar and yeast ß-glucosidase activity on terpene alcohol levels in beer by Daniel Sharp

Daniel talked about the research he had been doing on the release of hop terpenes into beer from hop glycosides. This is an interesting topic for brewers interested in hop aroma, as aroma-active compounds can potentially be released during fermentation through the hydrolysis of hop-derived glycosides in the beer. He had tested the beta-glucosidase activity of a wide range of brewing yeast strains, and then selected strains with high and low activity. Surprisingly, beta-glucosidase activity didn’t seemed to affect the maximum hydrolysis level that was achieved during fermentation (and this level was much lower than the positive control where purified enzyme was added to wort). It just took a slightly longer time to reach this level with the low activity strain. Daniel didn’t seem to see any correlation between beta-glucosidase activity and the amount of aglycones in the beer. Higher glycoside extraction was achieved with whirlpool and dry hopping compared to kettle hopping. Some varieties that seemed to be high in glycosides were Columbus, Centennial, Simcoe and Summit.

• Creating a gin utilizing novel Scottish Botanicals: A University-Industry collaboration by Margaux Huismann

Margaux talked about her MSc project, which was carried out as a collaboration between Edinburgh Gin and ICBD. During the project, she and 3 other students had developed a gin featuring Scottish (coastal) botanicals. They went to the Scottish coast to forage for interesting botanicals, and then distilled them in lab scale to develop a recipe. The recipe was then used at larger scale at the distillery to produce a commercial product. One botanical in particular, Bladderwrack, seemed to have given off a strong ‘fishy’ aroma during distillation, and its volatile aroma compounds were analysed in more detail. We later got to try the actual gin, and it was really nice (not at all as salty or ‘fishy’ as I first was expecting). Thanks Margaux!

• Keynote: Impact of brewing practice on yeast performance by Katherine Smart

Katherine talked about some of the research she has been doing the last 15 years. This research has been focused mainly on repitching, yeast viability, stress tolerance and petite mutants. Most interesting to me was the work on why ‘1st Generation’ yeast (i.e. yeast that have already undergone one fermentation) seem to start fermentation faster than ‘0 Generation’ yeast (i.e. yeast that come straight out of the propagator). One cause, is that G1 yeast bud faster than G0 yeast (i.e. enter the replication cycle faster) and (if I remember correctly) are able to use glucose faster from the wort. G1 yeast also seem to use less FAN from the wort, which I found interesting (less nitrogen demand or more biosynthesis?). They had also used high-throughput screening systems to isolate osmo- and ethanol tolerant strains. A quite interesting remark was that strains are seldom good at both, i.e. an osmotolerant strain is rarely ethanol tolerant as well. One good point that was made regarding these high-throughput systems is that you find what you are looking for. These isolates may have high tolerance, but may otherwise perform badly in wort or produce off-flavours.

• Cambridge Prize Lecture: The Influence of Yeast Handling on Petite Mutant Formation by Stephen Lawrence

Congratulations to Stephen for winning the Cambridge Prize! Stephen talked about the research he had carried out, which won him the Cambridge Prize. His research was focused on petite (or respiratory-deficient) mutants in brewing, and during his presentation he also talked about various stresses the yeast are subjected to during fermentation. Petite mutants (i.e. cells with damaged mitochondrial DNA) form during fermentation as a result of fermentation stresses, and these can accumulate when yeast is repitched for several generations. These petites perform worse in several regards compared to wild type cells, so their accumulation is not desirable from a brewer’s point of view. Some interesting points that were brought up, were that older cells (i.e. cells with more budding scars) were more susceptible to petite formation and that lower mtDNA copy numbers actually didn’t increase the likelihood of petite formation (e.g. older cells tend to have more mtDNA copy numbers). This seems to suggest that the accumulation of mtDNA damage has a higher impact on petite formation than the copy numbers of mtDNA. This was a very interesting talk, and the topic still seems to be quite poorly understood. It will be interesting to follow the topic in the future.

Parts two and three will be posted during next week!