i'm a novice brewer and i'm finding out more and more that yeast attenuation is critical for producing a good drop. I currently use a large plastic soft drinks bottle for my starter. Results are improving already. I would appreciate some advice on the subject.
source :
http://www.danstaryeast.com/library/pitching_temp.html
Dr. Clayton Cone
2) Mid-Fermentation Nutrient Additions - Are there any advantages, or disadvantages, that may occur by adding yeast nutrients to a beer (or wine) after fermentation has begun, but before the mid-point between the OG & TG?
-Mike Zapolski
RESPONSE:
2. Yeast respond to a fresh source of nitrogen through out its growth phase and early pert of the stationary. The sugar transport systems have a very short life(2+ hours) and enzymes involved need replenishing and a supply of nitrogen. So an incremental feeding is ideal especially to minimize H2S production. This is ideal and begins to be a factor as the O.G increases. With well mashed wort a low gravity would probably not benefit from this. A high gravity fermentation would definitely benefit. There are other things involved in incremental feeding.
All the nutrients up front result in an increased growth of yeast with a lower level of protein when it reaches the stationary phase. Incremental feeding restricts the initial growth but increases the yeast protein level. The higher protein level in each cell increases the fermentation rate and protects the cell against alcohol toxicity near the end of fermentation. Again, this is only beneficial to a higher alcohol fermentation. If you have the analysis of the wort available you can add the exact amount of nutrient. You will need to work with the nutrient supplier. Usually I begin with 1-2 pounds of the product per 1000 gallons(0.5 -1.0 gram / gallon)of wort. That is a safe range to start with. You can go up or down on the next batch according to your evaluation of the current batch.
Dr. Clayton Cone
3) What are the differences between yeast nutrients, extracts, hulls, and energizers? What does each product do to facilitate fermentation? At what stage of the brewing process should they be added to be most effective? Under what circumstances should one use each of these products [what should the brewer look for as an indicator], and what might be a typical amount added to a 5 gallon batch? Is there a product that combines these individual items into a single overall yeast "Superfood"?
-Mike Zapolski
RESPONSE:
3.Yeast nutrient is anything that the yeast needs for a healthy growth and to stay alive during the stationary phase; sugar, useable nitrogen (FAN), minerals, trace elements, vitamins and oxygen. A well balanced nutrient like Fermaid K will supply these requirements. Most all malt wort contains a well balanced diet for low gravity fermentations. Sometimes minerals like zinc and magnesium are on the short side. It is when you move up to higher O.G and higher cereal adjuncts addition that added well balanced nutrients need to be considered.
Extracts are concentrated extractions of malted barley (malt extract) or autolyzed yeast with out the cell wall. Malt extract, as you get in a kit, makes a very good beer. Many of the useable nitrogens are bound up by the Maillard reaction and are not available to the yeast. Yeast extract contain most of the nutrients that the growing yeast require. However you are limited in the amount that you can use. Above a certain level, you may begin to detect it in the flavor of the beer.
Yeast hulls are my favorite. It is probably the best balanced source of nutrient but can be used in a limited amount before you detect it in the finished beer. Lallemand yeast hulls are cell walls loosely separated from the cytoplasm of well autolyzed yeast. These cell walls contain well digested protein that is high in available nitrogen. It also contains lipids that are necessary for yeast growth and protection against alcohol toxicity. Lipids are what you produce when you add oxygen to the fermenting wort.
Diammonium phosphate is an excellent, cheap source of available nitrogen for the yeast. You have to evaluate it carefully for flavor and aroma profile if you use it as a sole supplement.
Energizers is a name that could include any or all of the above. Many distributors have their own formula. Fermaid K is a well balance yeast nutrient that was formulated based on many years of experience of yeast production. There are two new products that have come onto the market recently. They do not replace the need for Fermaid K but augment it: GO-FERM is a product that is used in the rehydration water (not in the wort or must) for Active Dry Beer and Wine yeast. It maintains the vitality of the yeast through out the entire fermentation. This becomes important in higher gravity brews. Servomyces offers a biological source of zinc to the yeast. The biological source seems to make it more available for the yeast.
