On January 24, 1848, James W. Marshall found gold at Sutter’s Mill in Coloma, California. That discovery set into motion the 1849 California Gold Rush. Over 300,000 people migrated to California to seek their fortune, many traveling all of the way from the East Coast in covered wagons. Today, there is a different kind of gold in California. It is a type of gold that is precious to brewers, a microscopic gold. The topic of this entry is the wealth of Saccharomyces and non-Saccharomyces yeast species held by the University of California, Davis. The University of California, Davis (UC Davis) is home to two yeast collections. The larger of the two collections is the Phaff Yeast Culture Collection, which is named after Dr. Herman Jan Phaff. Dr. Phaff was born in the Netherlands in 1913. He migrated to California to attend graduate school at the University of California, Berkeley (UC Berkeley) when he was 26 years old. Dr. Phaff’s interest in enology and brewing was kindled at his family’s winery. After moving from UC Berkeley to UC Davis in 1954, Dr. Phaff went about building the existing UC Davis yeast culture collection into one of the largest in the world. Today, the Phaff collection holds 800 of the 1,600 known species, including those useful to brewers and vintners. The current curator of the Phaff Culture Collection is Dr. Kyria Boundy-Mills. Dr. Boundy-Mills was fortune enough to be able to work with Dr. Phaff before he passed away. A second yeast culture collection is held by the Department of Viticulture and Enology. While many of the strains held in this collection are also held in the Phaff Collection, it does contain a few brewing strains that were either culled from or apparently never held in the Phaff Yeast Culture Collection. The curator of this collection is C.M. Lucy Joseph, M.S. In addition to caring for the Enology Culture Collection, Ms. Joseph is a published expert on the Brettanomyces genus. With the above said, the cultures held at UC Davis are not for budget conscious brewers, nor are they for brewers who are not versed in aseptic transfer technique, which is a topic for a future blog entry. However, for amateur and professional brewers who are comfortable wielding an inoculation loop, the cultures held at UC Davis offer a unique opportunity to work with heirloom strains that have been forgotten by history. One of the first cultures in the UC Davis culture collections to capture my attention was UCDFST 40-219/UCDVEN 1219. UCDFST 40-219/UCDVEN 1219 is the production yeast culture that was used at the defunct Acme Brewing Company in San Francisco. The deposit was made in 1942, which makes the culture 73 years old. A little known fact is that the yeast currently used to ferment Anchor Steam has only been employed at Anchor since the mid-seventies. It is an old Wallerstein Laboratories strain. UCDFST 40-219/UCDVEN 1219 was used to produce lager beer in San Francisco at least 73 years ago. Since the Acme Brewing Company survived prohibition, it is not out of the realm of possibility that UCDFST 40-219/UCDVEN 1219’s use in San Francisco predates the Volstead Act. Another interesting fact is that Leopold Schmidt founded the Acme Brewing Company after founding the Olympia Brewing Company in Tumwater, Washington; therefore, it is also not out of the realm of possibility that UCDFST 40-219/UCDVEN 1219 is a descendant of the original Olympia production yeast strain. In use, I am not going to sugar coat things. UCDFST 40-219/UCDVEN 1219 is not much fun to grow on solid media. The colony-forming units on a plate are tiny enough to be mistaken for petite mutants. I had to contact Ms. Joseph when I went to subculture the slant on which the strain arrived from UC Davis because it appeared to be blank. According to Ms. Joseph, the culture is a diploid yeast strain. Most brewing strains are polyploids, which is yet another topic for a future blog entry. I wound up using the add a few milliliters of autoclaved 5% weight by volume (w/v) wort to the culture tube, suspend the cells that are available, and then pitch the liquid in the culture tube into a slightly larger amount of autoclaved 5% w/v wort technique because I was unable to harvest a significant yeast scrap from the slant. The truly strange thing about UCDFST 40-219/UCDVEN 1219 is that it does not behave like a petite isolate when pitched into wort. Attenuation proceeds at a pace that one would expect from any other production strain. The strain is very flocculent. The yeast aggregates into pea-sized flocs, resulting in rapid sedimentation at the end of fermentation. After struggling to get this strain to grow on slant, I was truly astonished to see how well it behaved after being grown into a culture large enough to pitch into a batch of wort. I have never experienced this kind of behavior with a yeast strain since plating my first brewing strain almost twenty-three years ago. The initial batch of wort used for experimentation with UCDFST 40-219/UCDVEN 1219 was a Pre-Prohibition-style Pilsner with an original gravity of 1.062 and a grist composed of 85% domestic 2-row and 15% flaked maize. The beer was hopped twice with Liberty. The boil length was 90 minutes with a hop addition at 60 minutes before the end of the boil and another hop addition at knockout. Primary fermentation was conducted at 15°C/59°F. The resulting flavor was very rich for such a well-attenuated beer. This strain quickly became a “keeper” in my bank. Another interesting culture that I obtained from UC Davis is UCDFST 40-420/UCDVEN 1420. UCDFST 40-420/UCDVEN 1420 was deposited by Dr. Catherine Roberts in 1947. This strain is from Kongen’s Bryghus (King Christian IV’s brewhouse) in Denmark. Dr. Roberts was quite a remarkable woman who was way ahead of her time. At a time when job opportunities for women were very limited, she was pioneering the field of yeast genetics with Dr. Øjvind Winge at Carlsberg Laboratory in Copenhagen, Denmark. Dr. Roberts earned her Ph.D. at UC Berkeley, which I assume is how the culture eventually wound up at UC Davis. If I had to describe UCDFST 40-420/UCDVEN 1420, I would say that it is like Wyeast 1007 with better flavor. Like Wyeast 1007, UCDFST 40-420/UCDVEN 1420 produces a huge head during fermentation. Apparent attenuation is very high (>80%), but flocculation is low, resulting in slow sedimentation. The strain is suitable for top cropping. UCDFST 40-420 is fantastic strain for those looking to produce Northern European ale styles. It is crisp and clean with a nice subtle candy-like ester profile that works very well with Pilsner malt and continental and British hop varieties. In closing, the cultures held at UC Davis offer advanced amateur and professional brewers an opportunity to work with heirloom strains that have been forgotten by time. There are many other brewing yeast strains that are not as old with respect to deposit date, but are equally intriguing, including Wallerstein strain #36C4 (better known as the yeast strain that was selected for use at New Albion) and old lager cultures from the Lucky Lager Brewery in Azusa, California and Liebmann Breweries in Brooklyn, New York. Brewers should not expect to receive much in the way of brewing data when digging deeply into the UC Davis collection. Opening up the vault is experimental brewing in the truest form because one never knows what one is going to get with culture collection strains. If any commercial yeast propagators are reading this blog, I have attempted to convince Chris White to license UCDFST 40-219/UCDVEN 1219 from UC Davis. He does not appear to be interested in licensing the culture. Here is an opportunity to propagate a true turn-of-the-century San Francisco yeast strain. I know that Dr. Boundy-Mills has shown interest in working with yeast propagators.