Demystifying Active Dry Yeast

Link to article

Sponsored content from Fermentis. All images courtesy Fermentis.

Active Dry Yeast (ADY) is a topic which has always intrigued the homebrewers’  community. It does not take long to figure out that there are a lot of myths surrounding ADY and its use. One example relates to active dry yeast preparation prior to pitching – should I rehydrate or not? Information on the internet tells you that there are as many answers to this question as there are web pages! Throughout this article we will discuss several topics about Fermentis’ ADY from a manufacturer’s point of view.

A little bit of history

Brewing yeast strains have gone through a long domestication process. For those who want to dive more in science and know more about industrial yeast phylogeny, including brewing strains, we recommend reading two recent papers, both describing how this process occurred: Gallone et al. Domestication and Divergence of Saccharomyces cerevisiae Beer Yeasts. 2016. Cell 166. 1397–1410; Gonçalves et al. Distinct Domestication Trajectories in Top-Fermenting Beer Yeasts and Wine Yeasts. 2016. Current Biology 26. 2750–2761. The domestication process was driven by ancient brewmasters and contributed to generate all the diversity in this industry today. In other words, brewers have driven the evolution and diversification of these strains inside the breweries, unconsciously shaping the yeast to their needs. Nature also influenced this process, for example allowing inter and intra species hybridization, like the well-known case of Saccharomyces pastorianus (lager yeasts). This diversity is now kept safeguarded in different yeast banks, and our mission is to screen for the most representative strains available and deliver them to the industry in a convenient format to simplify brewers’ life; which is dried yeast, otherwise known as “active dry yeast (ADY)”. Although the first yeast biomass culture was dried back in the early 1970s for the baking industry, ale brewing yeast was not dried until the 1995, and lager yeast until 1996! Since the late 90’s ADY has come a long way and the industry agrees that ADY today has a state-of-the-art quality, but more about that later.

The ADY production process

Fermentis beer yeast strains are produced in plants specialized in handling multiple strains with high quality standards. The production of Fermentis ADY starts with a laboratory phase where the purity of the yeast coming from our yeasts bank located in Lille (France) is monitored before we ship a slant/slope to our industrial production site. In the plant laboratory, the culture is propagated from the slant in aerobic and constantly monitor conditions. When we have produced enough biomass, the culture is transferred to a bioreactor where industrial production takes place. Propagation is done in state-of-the-art facilities where yeast is grown in fully aerobic conditions, on a balanced nutrient base with molasses as the sugar source (which makes all of our yeasts gluten free). This production process is called fed batch fermentation. Oxygen and sugar levels are critical to control… If interested, please read about the Crabtree Effect. The idea is to produce yeast biomass from all available sugars (energy) and avoid alcoholic fermentation! In other words, we want to use sugars to produce yeast and not alcohol.

Yeast multiplication will be stopped when the desired amount of biomass is grown. At this stage, the yeast physiology is managed to prepare the cells for the next steps and resist the drying process. The yeast culture will then be centrifuged, vacuum filtered and finally dried in a fluidized air bed to reach 94-97% of dry matter. Depending on the target market segment, yeast can be vacuum-packed (500 grs bricks) or packed under inert atmosphere (soft packs, nitrogen flushed (11.5 grs, 5 grs sachets, and smaller) to protect against oxidation and moisture.

As you will guess, the details of the production process are a secret known by only a few people in this world but be assured that parameters are constantly monitored to provide you with the best yeast. What we can tell you is that each strain has its own “recipe” for the propagation and drying processes; to best grow the yeast in terms of vitality, viability, purity and fermentation re-start. It is the manufacturer knowhow which makes the difference and with over 160 years in the business, we have some experience. Also, technology is continuously improving to make the resulting product even better. These improvements allowed us to extend the shelf life to 36 months in 2016, and to launch last year the Easy-to-Use (E2UTM) concept for all our brewing yeast strains (see below). You may have been introduced to this in 2018, at the CBC in Nashville or at Homebrew Con in Portland.

Fermentis active dry yeast
Production Process of Active Dry Yeast (ADY)

Demystifying Active Dry Yeast

Through this Q&A we will answer most of the questions people have about Fermentis’ ADY and explain our Easy-to-Use (E2UTM) concept/brand.

Who are we?

Fermentis is part of the Group Lesaffre, a key global player in yeasts and fermentation. Lesaffre designs, manufactures and markets innovative solutions for Baking, Food Taste & Pleasure, Health Care and Biotechnology. Fermentis is the business unit in charge of fermented beverages (wine, cider, beer, distilled spirits, mead, etc.). In other words, we take care of the funniest part of the business. Being serious, Fermentis produces many of the most popular strains for the beer industry like SafAle™ S-04, SafAle™ US-05, SafAle™ WB-06 and SafLager™ W-34/70 to mention a few of the thirteen strains available nowadays in our range.

What is Active Dry Yeast?

Active Dry Yeast (ADY), as the name states, is dry yeast which once rehydrated will be reactivated and able to ferment the sugars that are in the wort as well as contribute with flavors and aromas. This technology has been available in the market for brewing purposes since 1995 and has been greatly improved since then. ADY are known for having numerous advantages in the brewery and when you brew at home too. The long shelf life (preservation of yeast) is one of the major advantages of ADY. In addition, when considering brewing schedule there are several other advantages of ADY: e.g. more economical, no need for propagation or starter preparation, no need for quality management equipment, increased flexibility (see E2UTM), reliability, consistent quality and time saving overall. ADY gives you the ability to be very dynamic in your strain diversification before and during the brew day. With direct pitching, you can split the batch in two, four, etc and try several strains on the fly.

What is E2UTM?

Easy-to-use (E2UTM) is a Fermentis brand used to characterize specific wine and beer yeasts & fermentation solutions which can easily be used in the beverage manufacturing process, without going through complex preparation protocols that complicate the operation. E2UTM is an innovative concept to make your life easier, to save you time, and offer more comfort and safety. In fact, the extension of this brand to our beer range was recently communicated after a study conducted by Fermentis and independent laboratories in 2017. In the study, several trials were made to measure viability, various fermentation parameters (fermentation kinetics, final ethanol production, apparent degree of fermentation, etc.) and volatile compounds production in beers made; using different media (tap water, distilled water, 7°P, 15°P, 25°P wort), different temperatures (8°C/46°F, 12°C/54°F, 16°C/61°F, 20°C/68°F, 32°C/90°F, 40°C/104°F) and different kinds of agitation (without, moderate and violent) to rehydrate yeast, in comparison with direct pitching (moderate agitation at 30°C/86°F). No significant differences were found in this study for our full range of yeasts. The study concluded that the performance of our brewing yeasts is not affected when they are rehydrated in different types of media (wort of different strengths, distilled water,tap water, etc.), at different speeds of agitation, and in a wide range of temperatures. Furthermore, it is not affected when they are inoculated directly into the wort, without previous rehydration. The range is E2UTM! You can now pitch directly, with no need to rehydrate; but if you still want to rehydrate, you can relax and use different conditions that adjust more to your process, without negative effects. But please… keep in mind that we are still talking about living microorganisms and there are some limits. Use the recommended temperature range for pitching (check the back of the sachet) and if you have always rehydrated Fermentis ADY, again, you can still do it, but do it preferably with hopped wort that will protect the yeast against microbial contamination. Last but not least, there is no need to oxygenate the wort when using E2UTM yeast by Fermentis (due to our production process) and DO NOT shake the flask extremely vigorously when you are rehydrating the yeasts. Our ADY are ready to go when you pitch them!

fermentis active dry yeast graph
Figure 4 Fermentation performance of SafAle™ S-33 (Pitching rate 50 g/hL, 15°P, 20°C) and the concentration of ethanol, residual sugars and volatiles (acetaldehyde, esters, higher alcohols and vicinal diketones) at the end of fermentation (before diacetyl rest) for 3 different rehydration procedures (in triplicate). DP: direct pitch without rehydration, W: rehydration in water at 30°C with moderate agitation, 15°P: rehydration in 15°P wort at 30°C with moderate agitation.

What is the Best Before End Date (BBE) of E2UTM by Fermentis ADY?

Best Before End Date for Fermentis yeasts is three years from production date since 2016. Study results showed that in beers made with yeast exposed to forced aging tests, and almost 4 years of natural (true) aging, the performance and sensorial profile is not affected negatively, for either ales or lagers strains. In addition, the temperatures of storage studied (-20°C/-4°F, 5°C/41°F, 25°C/77°F) do not affect the ale yeasts in any way, however there can be longer fermentation (2-3 days) for lager yeast that have been stored at ambient temperatures. So our recommendation would be to store lagers strains (SafLager™ W-34/70, SafLager™ S-189, SafLager™ S-23) at or below 10°C (50°F). Refer to the MBAA poster for more information.

Can I use E2UTM by Fermentis ADY after multiple generations?

Yeast recycling is something you can do with E2UTM by Fermentis Yeast, it is your decision. Keep in mind that yeast management requires laboratory equipment and knowledge to validate the quality of the cropped yeast as genetic drift can happen over time impacting several parameters in your beer, such as fermentation kinetics and volatile compounds produced. Our recommendation is to limit repitching to no more than 4-6 times (for any yeasts, not only Fermentis) and always check the quality of the cropped yeast. Again, the fact that you are using dry yeast does not mean you cannot recycle the culture. What is important is to check, when recycling yeast, the presence of beer spoilage microorganisms and that is something our E2UTM yeasts are controlled against from our yeasts bank and through the production process.

ADY is dry yeast biomass with almost no water (94-97% dry matter). A pitch rate in weight per volume (grams per hectoliter) is the most accurate way, for ADY, to achieve consistency in your fermentations time after time. For E2UTM by Fermentis ale strains we recommend a pitch rate of 50-80 gr/hL (2.06-3.3 oz/bbl); and 80-120 gr/hL (3.3-4.95 oz/bbl) for our lagers strains. In other words, one 11.5grs sachet (0.406 oz) is good for 5 gallons for ales and two 11.5g sachets for 5 gallons for lagers. For high gravity beers (over 18°P) it is better to pitch 2 sachets per 5 gallons brew.

For more information about our strains please check the website or download Fermentis App from the Apple Store or Google Play. You can also download our Tips and Tricks for more detail information’s of our strains from our web page.