hello! I began doing yeast starters and givjng them 24 hours on a sturplate, and removing them to let things settle at the beginning of my brew session. For the last few batches ive taken to 24 hours on the stirplate, then another 24 or so sitting out at room temp, then cooling, decanting, and pitching,
Is there a right amount of time for starters? I find that wlp002 especially seems to floc into clumps making my starter resemble eggdrop soup after about 14 hours…does this mean the starter fermentation is done at this point and ready for pitching? For other yeasts, especially abbey yeasts, the dont floc or clump like that and it does take some time for the yeast to settle out before decanting and pitching…
Usually 24-36 hrs is a good time on the stir plate to allow fermentation to finish up. After that I take it off the stir plate and cold crash it at least overnight before pulling it out of the fridge towards the end of the brew day and allowing it to slightly warm up before pitching into warmer wort.
I do think that the above time on the stir plate will vary depending on the freshness of your yeast, the strain, and its vitality (health). The more you use a stir plate, the more accustomed you will get to necessary times needed for the starter to complete.
My stir plate starters are stirred at room temperature between the 12 and 24 hours. I understood that it is better to stop stirring when the CO2 production is almost done. This to prevent exhaustion of the yeast. Then I put it direct into the fridge to cool the starter to made to rest so it can be decanted.
There is no right time for starters because there are so many variables in the process such as viability of yeast, starter volume, o2, type of yeast and temp. in general if you follow an online pitching calculator it will get you in the range within 24hrs to 36 hrs. I agree with Brewinhard the more you use your stir plate the more you will become accustomed to the “signs” that it is finished. I just did one using the same yeast at it was done in 14 hrs also (1000ml) and i placed it in the fridge and crashed for 1 day decanted and pitched within 10 degrees of wort temp.
My most recent practice (last 4 batches) has been:
-Starter on the stir-plate for about 20-24 hours,
-Removed and let sit at room temp for an hour or two
-Put it in the fridge to crash overnight for 12-18 hours.
-Remove from fridge and let sit at room temp at beginning of brew session
-Decant and pitch after wort is cool.
I’ve noticed that this process seems to yield the quickest fermentation starts and the most vigorous fermentation–as opposed to a straight 24 hour stir-plate run with a pitch directly into the wort from the stir-plate. Based on feedback here (thank you!) i think i’m on the right track!
Why do you suppose that this yields a faster fermentation than the straight pitch? (Honest question/mere curiosity, not being an ass) I would think think that warm it up and activating the yeast, crashing it, re-activating would be stressful, whereas a straight pitch would be a ramp up in activity under similar conditions.
I think you are on the right track but as for certain processes resulting in the fastest start of fermentation it could just be a quirk. Some of this will be determined by the temp you are pitching into, a warmer pitch will typically get started faster than a colder one.
IMO, there is also no need to warm up the starter from the fridge prior to pitch, in fact, it is easier to decant off the cake when the starter is cold as the yeast stays in a cake.
I simply remove my starter from the fridge once I’m ready to pitch, decant and pitch the cold yeast into the chilled wort. I like to pitch cold and allow to self rise to the desired fermentation temperature. This allows for a good steady growth/lag phase as the yeast slowly warms.
I know that it sounds counterintuitive, but one should not allow a starter to ferment to completion before pitching. One’s goal when making a starter is different than one’s goal when making a batch of beer. There’s nothing to be gained by allowing a starter to continue to ferment after maximum cell density has been reached. At that point, it’s all downhill with respect to yeast health. Maximum cell density for a 1L starter (~200 billion cells) is usually hit 12 to 18 hours after pitching a White Labs vial. If one is pitching a relatively fresh tube, many yeast strains reach maximum cell density within six hours of pitching because the cells only need to divide (cellular mitosis) two or three times at most.
As they say, a picture is worth a thousand words.
Ideally, one wants to pitch just as the curve starts to flatten out during the deceleration phase. While it may look like one is growing more cells beyond that point, all reproduction is for replacement only. **The only cell count that matters when propagating yeast is the viable cell count. **
Additionally, the ergosterol and unsaturated fatty acid (UFA) reserves that are synthesized at the beginning of fermentation are shared by the mother cells with all of their daughter cells after the dissolved oxygen has been consumed. Allowing a starter to ferment to completion results in one pitching yeast cells with depleted ergosterol and UFA reserves, resulting in higher dissolved oxygen demand upon pitching. Ergosterol and UFAs make yeast cell membranes more pliable, which, in turn, allows for the passage of nutrients and waste products.
S Cerv - that makes a lot of sense to me for ale starters where the starter volume is relatively small compared to the batch size and you’re pitching the whole thing. But what about lagers? My lager starters are maybe 25% (or more) of my total batch size. I don’t want to pitch the whole thing; I just want to pitch a thick slurry.
Is there any alternative to letting it ferment out and cold crashing it? I’d love to hit the best of both worlds and be able to pitch a thick slurry of healthy yeast. Plus, I’d love to be able to make a starter on short notice the night before.
There’s nothing wrong with cold crashing the culture after 12 to 18 hours if you want to decant most or all of the supernatant. The difference in propagation time between a 1L starter and a 2L starter is roughly 90 minutes.
So how would this plan be for a generic ale brew? Start the starter 24 hrs before pitching time, at 18 hrs pop it in the fridge, decant and pitch 6 hrs later (24 hrs total)
Commensurate with this practice I’ve also begun using a small amount of yeast nutrient in the starter as well as in the wort, which may be a bigger factor (makes more sense as well I suppose). Healthier, happier yeast with increased reserves and better cell walls in spite of the increased stress of cooling/warming perhaps?
Sure, I understand that. I’m a relatively new brewer, so much of what I’m doing in practice comes from others’ recommendations. Big fan of jamil’s show on the BN and most of what I’ve done regarding a focus on fermentation has come from the zainasheff/palmer line of thinking, and it has demonstrably improved the quality of my beer. From what z/p indicate, the issue isn’t so much the pitching temp of the yeast, but in avoiding the shock of introducing yeast at temp x to wort at temp y…the idea being to have the yeast and the wort in a similar temp range, irrespective of where that range is on an absolute basis. I concur on the pitching cooler and ramping up. makes sense.
Interesting…so you’re saying that pitching a starter earlier (before fermentation is complete) would reduce the oxygen requirement (i.e. oxygenation of wort)? So for someone who does not oxygenate, they would be better off pitching earlier rather than later?
If you want to decant the supernatant (the clear liquid that lies above the sediment), twenty-four hours should be adequate to clear all, but the most powdery yeast strains.
It’s always better to pitch at the end of the deceleration phase than it is after fermentation is complete. Nothing is gained by allowing a starter to ferment out. No net increase in yeast biomass occurs during the stationary phase, ergosterol and unsaturated fatty acid reserves are depleted, and the cells are subjected to increasing amounts of fermentation byproducts, including ethanol. Allowing a starter ferment out also results in the cells being in the yeast equivalent of hibernation.
At the end of fermentation, yeast cells go into survival mode where their cell walls thicken and they store carbohydrate as glycogen. In effect, the cells are preparing for hard times. It takes longer to exit this state than its does when the yeast cells are still in active growth mode; hence, lag times in addition to oxygen demands are also increased.
There are only two scenarios that I come to mind where it is okay not to aerate a batch of wort. The first scenario is when pitching a quantity of yeast that is large enough that the cells do not have to undergo much in the way of multiplication. The second scenario is when pitching dry yeast.
Dry yeast is propagated using a continuous process that is very different than that that is used to propagate liquid yeast. Dry is yeast is propagated aerobically in a device known as a bioreactor (a.k.a. chemostat) where the glucose level is kept below the Crabtree threshold via continuous injection of medium (usually molasses with supplemental nutrients) and removal of yeast. Aerobic propagation is a significantly more efficient process because no ethanol is produced. Aerobic propagation also leads to yeast cells that have fully charged ergosterol and unsaturated fatty acid reserves due to continuous injection of oxygen. Liquid yeast cultures are usually propagated in batches where the glucose level significantly exceeds the Crabtree threshold (the glucose levels found in beer production exceed the Crabtree threshold by a large margin).
Most of the starters that I make are in the range of 5% to 10% DME weight by volume (w/v). I tend to shoot for a 7.5% w/v solution more often than not, which is roughly equal to 7.5 degrees Plato or a specific gravity of 1.030. Degrees Plato is a weight by weight (w/w) unit of measurement. A true 7.5% weight by w/w solution is made by dissolving 75 grams of DME into 925 milliliters or water, which will be the equivalent weight of 1L of water, but will not displace 1L of volume. A 7.5% w/v 1L solution displaces 1L of volume. I usually start with slightly more than a liter of water and boil down to 1L.
As I ferment mostly 3.5 gallons batches, my standard starter volume is 600 milliliters. I start with at most a 4mm nichrome loop of yeast taken from a slant on Tuesday night, and I have ready to pitch culture on Saturday morning. We are talking about a huge amount of cell growth compared to pitching a White Labs vial into 1L of wort.
