Pitch Rates and Over Pitching

[JimInNJ]

The oft repeated advice is:
24 ºBrix or below, 1 gram of wine yeast/gallon of must.
25 ºBrix or above or otherwise stressful fermentation,1.25 grams of wine yeast/gallon of must.

What are the potential consequences of exceeding these recommend rates? Overly fast / hot fermentation? Failure of the yeast to produce certain desired characteristics? Unnecessary cost? Other? An obvious advantage would be quickly overwhelming other microbes. Are there other advantages? What effect would over (or under) pitching have on yeast nutrient requirements?

In the past I have occasionally been guilty of grossly over pitching (using full packets of dry yeast in small experimental batches) and the results were wine. In beer brewing, over pitching tends to reduce the esters that are produced during the lag phase, and which are an important part of certain styles which are expected to be consumed young. But in wine (particularly red) aren't the fermentation esters expected to age out?

 

[Johnd]

The oft repeated advice is:
24 ºBrix or below, 1 gram of wine yeast/gallon of must.
25 ºBrix or above or otherwise stressful fermentation,1.25 grams of wine yeast/gallon of must.

What are the potential consequences of exceeding these recommend rates? Overly fast / hot fermentation? Failure of the yeast to produce certain desired characteristics? Unnecessary cost? Other? An obvious advantage would be quickly overwhelming other microbes. Are there other advantages? What effect would over (or under) pitching have on yeast nutrient requirements?

In the past I have occasionally been guilty of grossly over pitching (using full packets of dry yeast in small experimental batches) and the results were wine. In beer brewing, over pitching tends to reduce the esters that are produced during the lag phase, and which are an important part of certain styles which are expected to be consumed young. But in wine (particularly red) aren't the fermentation esters expected to age out?

Little over or under is no big deal. Yeast multiply until they have a colony sufficient to perform the task at hand, alcoholic fermentation. More yeast may reduce the time to produce the colony, less, the opposite. Staying roughly in the vicinity of the guidelines is sufficient.

 

[sour_grapes]

In beer brewing, over pitching tends to reduce the esters that are produced during the lag phase, and which are an important part of certain styles which are expected to be consumed young.

I am not a brewer or a microbiologist. I find that assertion surprising, and wouldn't mind knowing more about that. Can you point me to any information on that point?

 

[JimInNJ]

I am not a brewer or a microbiologist. I find that assertion surprising, and wouldn't mind knowing more about that. Can you point me to any information on that point?

https://wyeastlab.com/pitch-rates

https://www.northernbrewer.com/documentation/YeastPitchingRates.pdf

http://www.cara-online.com/blog/understanding-and-controlling-yeast-growth-in-the-brewery/

It is often discussed in the homebrew forums. Hefeweizen is one style where intentional under pitching is sometimes recommend to increase esters. I've never done careful side by side experiments with pitch rates as a variable, but in general I've always preferred my beers where I may have erred on the side of over pitching vs under.

 

[Ajmassa]

I was under the impression that over pitching can have the opposite effect and slow things down.
Too much in there multiplying and they are all fighting for food. Meaning you would just have a lot of starved yeast creating loads of problems. Better to have fewer and healthy than more and starved. I have absolutely no info to back this up tho.

 

[JimInNJ]

I'm really scratching my head about nutrient competition. If there are plenty of cells they won't need to reproduce, so they won't need certain nutrients? Or they are all coming out of hibernation hungry?

With beer it was generally considered that dry yeast came to the job well fed and in sufficient numbers to get right to work, whereas liquid yeast was depleted, in need of nutrients, and especially in need of O2.

 

[balatonwine]

https://wyeastlab.com/pitch-rates

https://www.northernbrewer.com/documentation/YeastPitchingRates.pdf

http://www.cara-online.com/blog/understanding-and-controlling-yeast-growth-in-the-brewery/

I see a lot of opinions there only. No links to any peer reviewed, published studies.

 

[balatonwine]

The oft repeated advice is:
24 ºBrix or below, 1 gram of wine yeast/gallon of must.
25 ºBrix or above or otherwise stressful fermentation,1.25 grams of wine yeast/gallon of must.

Maybe oft repeated is "wrong". Or oft repeated is oft repeated simply because it is just a rule of thumb which is easy to remember (1g:1gal).

I prefer to follow the manufacture recommendations.

Right on the package of the commercial yeast I buy:

Normal conditions: 20g/hl

High sugar: 30g/hl

20 g/hl * 1hl/100l * 100l/26.4 gal = 0.76 g/gal. (not so easy a number to remember compared to 1g:1gal)

(or if using the UK gallon conversion which further confuses the issue)

20 g/hl * 1hl/100l * 100l/22 gal = 0.91 g/gal.

And:

30 g/hl * 1hl/100l * 100l/26.4 gal = 1.1 g/gal.

30 g/hl * 1hl/100l * 100l/22 gal = 1.36 g/gal.


But quite frankly, this is mostly, IMHO, an issue of economics. That is, the amount recommended will get the job done. Adding more is just wasting money buying yeast.

 

[wxtrendsguy]

Normal sugars with Brix < 25 we inoculate with 15g/hl rehydrated with a product called Dynastart. Pretty much flawless fermentations always to completion if not too chilly.

 

[JimInNJ]

I haven't seen much by way of good peer reviewed studies relating to the effect of higher beer yeast pitching rates. I assume that suppliers such as Wyeast and White Labs have access to that science, but I realize that they have business interests that may influence their recommendations. I have not seen much on the forums where hobbyists have actually observed the purported negative consequences of over-pitching.

Here is one study I found relating to wine: http://www.ajevonline.org/content/55/4/363

They were looking at K1-V1116 in high gravity ice wine. In a nutshell, they found that 0.2 g of active dried wine yeast/L did not finish the job, but that 0.5 g/L did. They also found benefits from a stepwise acclimatization procedure after rehydration before inoculation, and from adding a yeast micronutrient supplement during yeast rehydration.

Hunting around the internet I see many recommendations very similar to balatonwine's supplier's: Normal conditions: 20g/hl, High sugar: 30g/hl.

I also frequently see 25g/hl as a starting point with a recommendation to increase in cases of high Brix or high SO2. I saw one warning not to go beyond double that starting number because of unneeded cost for no benefit and a vague concern for early autolysis.

For my situation (small batches where the cost of yeast is not a concern) I conclude that there is no harm in pitching as high as 50g/hl. And no benefit from going higher.

I do find it odd that the recommended dosage for the rehydration nutrient Go-Ferm does not include any upper limit:
30 g/hL based on a yeast inoculum of 25 g/hL. If using more or less yeast, respect a ratio of 1 part yeast to 1.25 parts Go-Ferm.

 

[JimInNJ]

I think I found the answer to my question regarding no stated upper limit on Go-Ferm. In spite of all the hype about essential vitamins (panothenic acid, biotin) and minerals (eg magnesium, zinc, and mangansese) and amino acids, it consists entirely of autolyzed yeast.

Fermaid-K, which does contain various vitamins and salts, has a specific dosage recommendation.

 

[salcoco]

piratically speaking the desire is to start fermentation without a long lag phase. long lag phase especially for fruit wine can be a problem. peach, strawberry and watermelon wines come to mind where awaiting the start of fermentation the lag phase can cause the fruit to deteriorate giving the wine off tastes. under these conditions a yeast starter with higher yeast colony would reduce the lag phase and improve the fermentation.