SNS starter method

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Saunassa

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Ok, I had a pack of Imperial House that was 4 months old. It will be going into an oatmeal stout so was worried it would not have enough cells to properly ferment as this will be first time using liquid yeast.
First time making a starter so tried the SNS method. 1 liter starter in a 1 gallon jug. Poured in the yeast at 3am. Checked at 10am and nothing noticable, looked at 4pm and nothing noted. Left airlock in and gave it a swirl and holy crap did it blow through the airlock. Does this mean it already hit high krausen and fell?

Will brew today, and pitch approx 30 hours from when I made the starter. Anything to worry about?
 

DBhomebrew

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I've recently started doing SNS starters as well, 3 or 4 so far. I've had the same experience of wondering if fermentation came and went.

I've pitched a SNS too early and too late. All attempts have improved my beer over no starter at all. The most recent two batches had particularly early starts and aggressive fermentations.
 
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Saunassa

Saunassa

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With only 1 liter in a 1 gallon jug the airlock is good. Just surprised by the fact I thought it had not fermented at all, so gave it a swirl to see if it was complete dead and pffft blew the water out of the airlock.. I almost dropped the jug I was so surprised. If it truly fermented that quick maybe I should shake the snot out of the fermenter next time I do 5 gallons.
 
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Saunassa

Saunassa

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Oh and I think I will not worry about imperial yeast that is only 4 months old.
Oh and I now have to wait until tomorrow to brew, been recruited by swmbo to do vinyl plank in my office. Do I need to worry about the starter souring since no hops?
 
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Saunassa

Saunassa

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Well after all the delays I finally got the chance to brew a stout yesterday. Decanted a small portion to taste and see if it was ok to use. So strange to drink a one week old non-hopped beer. Even had a bit of carbonation in it.

Swirled it up and poured it into the fermenter. Approx 6 hours later I could see there was activity. Dang easy to make this starter.
Btw, the sample was like drinking a Busch minus any bitter 😂
 

CascadesBrewer

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Well after all the delays I finally got the chance to brew a stout yesterday. Decanted a small portion to taste and see if it was ok to use. So strange to drink a one week old non-hopped beer. Even had a bit of carbonation in it.
The general idea of the SNS type starters is to build up cell health and then pitch the starter during active fermentation while the yeast are at peak shape. They are really a type of a vitality starter. Where a stir plate is often used for a lager starter to build up cell counts. In this type of starter, most of the fermentation is done and the spent wort is decanted (often after cold crashing). It sounds like you did a bit of a hybrid starter. You won't get much growth in a 1L starter that is not agitated/stirred, but you will get some and it is also a good way to verify the yeast is still viable.

My inspiration: Shaken, not Stirred: The Stir Plate Myth Buster | Experimental Homebrewing
 

bagbrewer

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I don’t want to thread jack but I came across the SNS method today and did some digging. If this isn’t the place then please move this post. My understanding after doing some reading is this:

Procedure
Use a container with a 4:1 capacity to starter volume ratio (i.e. a 5L flask for a 1L starter).

Working in an aseptic manner is key. Use a 70% isopropyl alcohol-soaked cotton ball to wipe any surface that will contact yeast or wort after the boil. (Seems obvious enough if you’ve made starters before.)

Once starter wort is cooled and added to the container it is shaken for 1 minute.

Yeast is added and gently shaken to disperse and allowed to sit with the cap on for 30 minutes.

Loosen cap to vent pressure and allow yeast to reach high krausen.

Pitch entire starter contents.

The original thread I found cites stir plates as placing something called shear stress on the yeast. Being the curious homebrewer that I am I went to Google Scholar to search for any relevant papers on the topic. The abstracts from the research I’ve been able to find suggests that shear stress is indeed a concern but whether or not a stir plate has the ability to create this stress remains to be seen. I came across an article “Effect of high shear stress on microbial viability” that states in the abstract “The threshold of shear stress efficiency depended on the micro-organisms, being between 1292 Pascal and 2770 Pascal for Sach cerevisiae…” (Lange et al, 2001). It goes on to say that the rate of viability decrease is magnified by higher cell concentration. This leads me to wonder whether or not as cells divide in our starter, are we doing more and more damage as more growth occurs? This research article seems to suggest this is the case. Although admittedly I didn’t get to read the whole paper as it is behind a pay wall as were many papers that seemed to be relevant to this topic.

The original thread also suggested that this stress causes the not so pleasing smell/taste of the supernatant resulting from a stir plate starter. The second reason the shaken method is said to be preferred is it provides better oxygen saturation than the vortex of a stir plate. S. Cerevisiae states that gas permeability is greater with the foam generated in a shaken starter due to a concept call specific surface area. What I found on specific surface area relates to solids instead liquids. Gas laws however, specifically Henry and Dalton’s law, state that absorption of gas, in our case oxygen, is dependent on the pressure at which the gas is supplied, and that pressure is proportional to the component of its concentration in the mixture. In other words, the amount of oxygen is dependent on how much of it is available in the atmosphere (roughly 21%) per volume. The Food and Agriculture Organization write-up I found explains that oxygen is absorbed in water by direct diffusion and surface agitation. This leaves me to question whether the pressure build up attained by leaving the lid secured is sufficient enough to overcome the lack of continuous turnover at the starter’s surface in the SNS method.

The more I think about it the more questions arise. Ultimately the quality of the end beer is the real goal. Is the smell of the supernatant really an indicator of stressed yeast? Potentially, you may come to expect certain smells from your fermentation as you become accustomed to a given recipe/yeast and therefore learn it well enough that an off smell can tip you off to something gone wrong. Does turning the starter wort into foam really allow better uptake of oxygen into the yeast cell? It inarguably presents more surface area than a still volume of wort in a flask or container but is it in this state long enough to do the job? I’ve not had any failed fermentations with a stir plate but that doesn’t mean it creates the best environment for yeast growth/health. I’m not trying to convince anyone of adopting one method or another but would like to see more discussion on the topic.

Process Overview/Reasons - Shaken, not Stirred: The Stir Plate Myth Buster | Experimental Homebrewing

Debating the logic - Shaken, not Strirred - Page 3 - Home Brew Forum

Podcast briefly discussing it (fast forward to around 16:00 minute mark). Brew Files - Episode 49 - Starting Off Right | Experimental Homebrewing

FAO writeup on Dissolved Oxygen CHEMICAL FEATURES OF WATER

Lange, H., Taillandier, P. and Riba, J.-P. (2001), Effect of high shear stress on microbial viability. J. Chem. Technol. Biotechnol., 76: 501-505. https://www.researchgate.net/profil...obial-viability.pdf?origin=publication_detail

edit: updated study link on shear stress.
 
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