Understanding Different Brewing Yeast

Yeast plays a very vital role in fermentation. They are single-celled or unicellular organisms which are member of the fungus family. This key ingredient has various strains, which produce unique aromas and flavor profiles characteristic to that region. It has a well-defined nucleus so it is eukaryotic cellular organism and not prokaryotic. Today microbiology and packaged yeast have made it possible to transport these wonderful biomes to our brewing vats globally. Yet, yeast is one of the little-known aspects of fermentation. In some aspects, it still continues to remain an enigma.

Dutch scientist Anton van Leeuwenhoek first spotted yeast cells in the 17th century through his microscope. Their role in fermentation was largely ignored. The common perception, at that time, was that ‘all fermentation requires a divine intervention’. There were Gods and Goddesses for brewing. They were who to be appeased for a successful batch. Fermentation has its roots from the Latin word fervere, which means to boil. The yeast is derived from a similar term gist, which means to boil.

Dry Brewer’s yeast foaming Krasen

But Microscope was not enough. It was only in 1859 that Germ Theory (by Louis Pasteur) was proposed and scientists started studying them. Today yeast is a part of active researches. It genetically modified to help brewers hone their craft. The first year of any microbiology lab is involved researching yeast, preparing its slants, and culturing them.

Major types of yeasts used in fermentation:

  1. The most common yeast species is Saccharomyces cerevisiae. It is the most omnipresent form of life in the world. Although uni-celled, these organisms are highly specialized. They yield varied results based on the conditions of the medium. During baking, one would have come across it under the trade name Active Dry Yeast. This dry yeast is produced in tons and is the most commonly used yeast. Once hydrated, they will start foaming in 10-15 minutes and they can leaven dough in a matter of hours. Since they are chosen for aerobic fermentation and leavening, they specialize in producing a lot of CO2 in a very short period. Wines and beers need an ability to have higher alcohol tolerance and not result in stressed yeast flavors when deprived of oxygen for extended periods.
  2. The second type is wine yeast and Brewer’s yeast, which is another strain of Saccharomyces cerevisiae. Unlike baker’s yeast, they are designed to flourish in adverse environments (low pH, high alcohol, high sugar, and without oxygen) and yet ferment the fruit or sugar wash (chashani).
  3. The third strain is the Ale beer yeast. They have an additional capability of being able to metabolize maltodextrins (complex soluble sugars produced during mashing). Baking yeast, may not be able to metabolize them and will result in a heavy-bodied sweet brew. Unlike the typical wine yeasts, beer yeasts have low alcohol tolerance.
  4. The fourth one is the Lager yeast- Saccharomyces pastorianus. This is a bottom-fermenting yeast that can operate at low temperatures to produce the crisp clear lagers a.k.a. bottled beers. We can’t find this yeast in nature. Its synthesis, probably, is an accident. The tree yeast from Argentina traveled on a Spanish boat to Europe and ended up mutating with the ale yeast in an ice-brewing cave in Belgium. Its cell walls are hydrophilic, while the cerevisiae’s walls are hydrophobic. As a result, it does not attach to CO2 bubbles and float at the top. The interesting aspect is that it is able to ferment at 5oC where most of the other microbes go dormant, making the much-coveted winter beers.
  5. The fifth kind that people come across is the Acetobacter. Technically, it is not a yeast (fungus) but a bacterium. It specializes in oxidizing the ethanol produced by yeast into vinegar (acetic acid) and hence the name. We can find Acetobater on all fruit surfaces and in the air. It plays an important role in vinegar production, pickling, or pro-biotic preparation.
  6. The sixth variety is Koji. Technically, it is not yeast but a fungal mold (Aspergillus orzyae). Most Asian recipes from Sake to Soy sauce to Miso use this variety. Koji has the ability to produce enzymes that can breakdown starch and proteins. Hence, we use it to ferment rice, legumes, and soybeans.
  7. The seventh variety is Lactobacillus. As the name suggests, it metabolizes milk sugar (lactose). We can find it in curd, pickling, and most pro-biotic wild fermentation. This friendly bacteria dominate our skin pores, digestive tracts, urinary system, and genitals. They are responsible to maintain acidic levels and keep the disease-causing microbes away. Most wild fermentations relies heavily on lactobacillus to ferment sugars into lactic acids.

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Although there are several trade books and literature praising the various strains, brands, and logos of the microbial culture, one should not underestimate the significance of wild fermentation. Until about 50 years ago, laboratory isolated strains were not available commercially. Food scientists were relying on the local biome (the symbiotic wild microbes co-existing in a particular farm or region) to ferment their food. Today with awareness towards Probiotics & Eco-immunology, there is a revival of using wild strains to ferment. Yeast sediment is completely edible. They are a rich source of Vitamin B-12.

Six Golden Rules: For best yeast performance

  1. Maintain proper temperature: Either most home brewers do not have a temperature controller or they get impatient. As a result, they end up with improper temperatures or give thermal shocks (steep day and night temperature differences). Usually, we prefer the lower end of the temperature scale for better (clean and crisp) sensory notes. However, at the higher range, the fermentation will complete at twice the pace and produce 5X more esters. Buying a thermostat is one of the must-have for a brewer. The seasonal variation in beers is the result of this temperature difference.
  2. Improper yeast strain: Each yeast has its characteristic profile, which when not matched will lead to a confusing beverage. Just looking at temperature range, flocculation and attenuation are not sufficient. Review the yeast’s esters, bio-chemical chemistry, phenols and another characteristic to match it with the intended product. Trying to ferment an extra-strong brew by stressing the yeast to its maximum sugar tolerance is a bad idea.
  3. Yeast Nutrients: Lack of yeast nutrients is a notable problem with fermenting honey (meads), certain fruits, and sugar wash. Inadequate nutrients yield a sugar only diet for the yeast, which is detrimental for their health. The yeast starts autolysis (metabolizing dead yeasts) and competing for nutrients leading to a variety of off-flavors.
  4. Insufficient yeast count or pitch rate: Yeast require oxygen to multiply and do not multiply in anaerobic conditions. As a result, they start dying or mutating towards the latter half of the fermentation. Not using adequate healthy yeast would yield an altered flavor profile.
  5. Improper wort aeration: This problem is more profound in industrial-scale lagers than in small-batch beer makers. Essentially, during boiling and mashing, the dissolved oxygen gets stripped away from the wort. Without this oxygen, the yeast is not able to synthesize the required precursor’s fatty acids and sterols to multiply themselves for optimal performance. Winemakers also keep their fermenters open for the first couple of days to allow some level of oxygen to seep in.
  6. Poor yeast health & infection: Using old or expired yeast without hydrating them could result in stressed yeast traits & incomplete fermentation. Wild fermentation is gaining popularity, which poses a bit of a challenge for amateurs.

We at Arishtam provide a host of beer yeasts to suit your various recipe styles with the aim to give you the best results. Please check them out at https://www.arishtam.com/product/beer-brewers-yeast/

Propagating Wild Yeast

Yeast Spec Sheet

Most commercial strains have a detailed spec sheet which can be very technical and confusing. A few of the most important parameters in them are:

1. Aroma Wheel

Aroma wheel: Depicted either through a spider diagram or through a yeast profile paragraph. It talks about the different kinds of esters, phenols, and flavors produced by the yeast. It is a good idea to match this with the kind of fermentation we are using.

Beer Aroma Wheel

2. Fermentation Temperature

Optimal temperature: This is the most important parameter for home brewers. Fermenting ales at lager temperatures (or vice versa) can result in miserable results. Also, the same yeast produces different quantities of esters, phenols, and higher alcohol at different temperatures. High-temperature brewing can produce fusel alcohols and bio-chemicals that can induce a hangover.

English stout yeast can produce clove-like flavors when fermented in winters. However one will get banana flavors when fermented in summers.

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3. Attenuation

It is a measure of malt fermentability for the respective yeast strains. This is important for beer (grain) yeasts. Most yeasts are able to completely ferment out glucose, fructose, and sucrose. In contrast, their ability to ferment maltose has its limits. Low attenuation (~70%) yeasts result in a good body and high attenuation (~85%) results in a thinner lager-like mouthfeel.

Most wine/cider/mead and sugar wash turbo yeast have 100% attenuation. So this figure is mentioned in beer yeast only. Use a hydrometer to measure the final gravity of your beer. Attenuation is your final Brix divided by original Brix

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4. Flocculation

Flocculation measures the rate at which the yeast clumps together and settles to the bottom once all the fermentable sugar/ maltose is consumed. Most American style beers and IPA need high flocculation and fast sedimentation. While Belgian White beers, wheat beers, and hazy fruit beers are best made with low flocculation yeasts.

However, some unfiltered German-style beers need a medium to low flocculation. In ciders and wines, inadequate flocculation yield bready or yeasty notes. Hence, choose the flocculation as per the recipe style. Also do read about 7 types of haze and how to clear up beer for further details.

5. Alcohol tolerance

A lot of amateurs have an obsession with the strongest wine or brew. Personally, I rarely look at this parameter. If the yeast can produce 10% (for wine) and 5-7% (for beer), it is OK. Some special styles like barley wines and sparkling wines need very high alcohol tolerance. Do read about the measure of alcohol for details. However, I focus more on taste than ABV.

Yeasts are akin to the workers in our fermentation and will create off-flavors if not treated well. We have a chapter on handling off-flavors that specifically helps to diagnose signs of improper fermentation and yeast activity. I hope that it will help you rectify some of the issues and refine your craft.

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Aerobic vs Anaerobic Yeast Fermentation

Yeast thrives when water, oxygen, and sugar are present. It is able to assimilate all necessary amino acids and multiply in aerobic conditions. When the oxygen supply diminishes, it switches to anaerobic fermentation or respiration. Here instead of producing acetic acid, it produces ethanol and CO2. However, a point to note is that in the absence of oxygen, yeast performs only basic metabolic activities. This means that it is no longer able to multiply or make necessary enzymes for complex reactions.

This is the reason why most advanced brewing science will talk about making a starter culture, yeast count, and pitch rate. Essentially it talks about how much ammunition firepower the yeast has to complete the fermentation. Yeast also are inherently cannibalistic. They will digest the dead yeast cells and use them to get the necessary enzymes, proteins, and other chemicals that they need to thrive.

Yeast is a unique hardy microorganism. It is able to survive in almost every condition. There is no pore on the human body, fruit, or plants that do not have yeast in one form of another. In fact, yeasts found in our natural biome, in a way, guide our ability to survive skin infection, maintain skin pH, and even immunity. It can go dormant at 4 degrees celsius. If some glycerine is present, it can even survive freezing and rethawing.

How to Harvest Yeast

If you have a conical fermenter, and a stir plate, it is easy to harvest yeast at a large scale. Most microbrewery in order to reduce cost harvest yeast. It has an added advantage:

  1. Liquid yeast and a healthy starter culture accelerate fermentation.
  2. Yeast harvesting leads to a better batch to batch consistency. It also allows you to successfully out-perform any micro-brewery that uses only commercial strains
  3. It is easier and faster to maintain wet yeast. Just keep feeding it with some malt extract every second day and stirring it a bit so that it can have access to fresh oxygen. If you want to dry your harvested yeast, follow any chat groups that talk about KVEIK yeast exchange.

Do remember to collect your yeast before pressure fermenting your beer. prolonged anaerobic environment coupled with high pressure mutates the yeast flavors significantly. The video would help demystify some of the yeast harvesting steps. There are ton’s of youtube video on kveik yeast drying and harvesting that can guide you on wine and beer yeast harvesting.

Wild Yeast Harvesting for Wine and Cider Making

Dry Yeast Varieties

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Angel Brewing Yeast

1Red Wine Yeast RWMaking Red Wine from grapes
2White Sparkling
Wine Yeast SY
Ideal for White Wine, Sparkling Champagne & Hard Apple Cider
3Turbo YeastAlso called Alcohol Leaven Yeast. It is celebrated for its fast action and high alcohol tolerance on sugar wash
4Lager style IPA Yeast BF16Ideal for crisp bottled beer styles, Hoppy IPA and aromatic beer. Fermentation Temperature 10-15C, 10% ABV & 80-90% attenuation.
5Stout Porter Yeast CS31For Porters, Barley wine, extra-strong stouts, and Fruit Ales. Fermentation Temperature 18-22C, 14% ABV, 80% attenuation.
6High Temperature Beer Yeast CN36Ideal for wheat beer, and craft ale beers. Temperature 14-22C, 12% ABV, 80% attenuation.
7Flavorful Dry Rice Wine YeastFor high alcohol filtered Sake and Chinese rice yeast. It is ideal for those who love clear rice wine.
8Sweet Rice Wine YeastSweet Milky Rice Wine. It can be used for Pakhala, gruel and cloudy rice wine styles.
Various types of Angel Brewing Yeast Available in India

Safale Dry Yeast

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For more details refer to the official website of Fermentis.

Lalvin Dry Yeast for Wine

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For more details refer to Lallemand website.

Red Star Dry Wine Yeast

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For more details visit the official website.

Lalvin Dry Yeast for Beer

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For more details please refer to LalBrew website

Dry Yeast vs Liquid Yeast

Arishtam Prefers dry yeasts because:

  1. They are more stable and have a longer shelf life.
  2. Easier to ship
  3. Can withstand Indian summers
  4. Are affordable. After all Arishtam Yeast are primarily for hobby brewers and making them pocket-friendly is our goal.

The advantage of liquid yeasts are that they are available in more variety. Most yeast stains don’t survive the drying process well, but in a liquid medium they can be infinitely propagated. If you want to start your own liquid yeast bank, we recommend you these two steps:

  1. Create a protocol of isolating the yeast stains from the fruits, plants, or nature.
  2. Use a conical fermenter to make a bio-reactor. This allows you to top crop and collect from the bottom in an aseptic sterile environment.

Candida: Yeast Infection

There is a common misconception that dry yeast causes Vaginal Yeast Infection. However, it is caused by Candida albicans, a totally different species of yeast. Rather, Saccharomyces cerevisiae actually is used to successfully treat this yeast infection. Our human body has several microscopic pores on it. These pores invite Saccharomyces cerevisiae and Lactobacillus bacteria to live on our skin. These single-celled organisms maintain the skin pH and health. Moreover, they keep infections away. The use of anti-bacterial soaps, broad-spectrum antibiotics, and other environmental factors can cause an imbalance of these useful microbes. If they are weakened or depleted, then the invasive or disease-causing microbes grow on our skin, mouth, and genitalia. This can cause STD and other infectious skin diseases.

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