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ADVANCED WINEMAKING BASICS
Continued


FEEDING YOUR YEAST


"Yeast make the wine. Take care of them."


Yeast Starters

An active culture gets the fermentation up to speed in hours

The preferred method of adding an ADY culture to a must is to add a yeast starter, or activated culture to the aseptic must. This simply means the yeast is introduced to a liquid medium favorable to rapid activation and propagation a day or so prior to adding to the must. The liquid with the activated culture is then added to the must as required, where the yeast culture very rapidly propagates to a desired density.

This method is preferable to adding the ADY culture to the must for several reasons. First and foremost, it results in a rapid fermentation. The flavors, aromas and nuances we want to capture from the must and impart into our wine are often very perishable and dissipate or change within days if not hours. The sooner the yeast can get to work capturing them, the better the resulting wine will be as a result. Adding a starter, as opposed to adding the ADY culture directly from the foil packet, can save one to several days, depending on the yeast strain and the size of the batch of must.

Secondly, it ensures viability of the strain. Normally, when you purchase a sachet of yeast you have no idea how old the ADY culture inside the packet is. Given a constant and acceptable temperature, the culture can survive for years in the foil without detriment. But the foil packets could have been--and probably were--shipped without regard to temperature. The box in which they were shipped could have sat in the sun on the tarmac at Los Angeles International in 110 degrees heat for an hour before being loaded in the plane that took it to your regional airport hub or local point of entry. It was then taken by truck to a transshipment warehouse where it may have dwelled for days in similar heat before being trucked to your city and then to your supplier. If 90% of the culture baked in the process, it will take that much longer for the culture to build to a density conducive to your needs. If 100% of the culture baked, you could easily waste a week discovering that fact, and during that week your must deteriorates and possibly is ruined. By making a stater solution two days before needed, you would have discovered that the yeast was non-viable within a day and still had time to prepare another.

Thirdly, a starter properly made, using water, a small quantity of the must itself or a juice substitute (grape, orange or apple juice) and some nutrients, will acclimate the yeast to its destined environment. When the starter is added to the primary, it will practically explode with activity and do what nature and selection programmed it to do and do it that much more efficiently.

The correct method of making a starter is to rehydrate the yeast, activate its life cycle, and add it to the must. The optimum way to rehydrate the yeast is to add it directly to 1 cup of 100-105-degree F. tap or spring water (the harder the water the better; do not use distilled water). Stir gently, cover, allow to rehydrate for at least 30 minutes, check on it to be sure it is viable, and then leave it another 3 1/2 hours. During this time, allow the starter and must (or fruit juice) to attemperate to within 10 degrees F. of one another, and then add to the starter 1/4 cup of pre-sweetened, reconstituted juice (not pure concentrate) or strained must. Re-cover the starter, set it in a warm place and leave it alone. Check on it 4 hours later to ensure it is viable and add to it another 1/4 cup of juice or strained must. Again, cover and leave it alone for 4 hours. You can now add it to the must or add another 1/2 cup of juice or strained must to really increase the yeast population (at the end of an additional 4 hours, the colony will be approximately 64 times as large as it was when rehydrated). For highly acidic (native grapes) or potentially troublesome musts or juices (like blueberry, peach, or Ribena blackcurrant), the more must you add to the starter, the better acclimated the yeast will be to the conditions they will be living in. There are other methods of starting a culture and most are just as successful, but this method, only slightly varied, was recommended by George Clayton Cone of Lallemand, the makers of Lalvin wine yeasts, and that is good enough an endorsement for me.

Lallemand's scientists found that some musts and juices contain sprays, toxins and excessive SO2 that can be detrimental to the activity of yeast. The dry yeast is like a sponge for the first few seconds in liquid and will absorb everything into the cell that it would normally reject in the rehydrated form. Many home winemakers add the ADY culture directly to the must or juice and get away with it. However, many times it is the beginning of a sluggish or stuck fermentation. There are over 150 billion yeast cells in a 5-gram packet of Lallemand yeast. If you kill off half of them by improper rehydration, you still have 75 billion cells to work with. This 75 billion will go on to do a good job most of the time, but whatever killed off the other 75 billion may have seriously affected the health of the survivors. Can you spell "stuck fermentation?" A little prudence is good insurance.

If you forget to make a starter or simply don't want to, then inoculate the must by sprinkling the ADY culture evenly over the top of the must and DON'T stir it in. Cover the primary and take a peek 12 hours later. If viable, there will be a prominent yeast colony across the surface and evidence in the form of a thin foam and/or a distinctly yeasty smell. Stir it shallowly into the must and 12 hours later stir it deeply. If there is no evidence of the yeast's viability, wait another 12 hours and check again. If still no evidence, inoculate again. Better yet, make a starter. Better late than sorry.


Feeding Your Yeast

Like us, yeast require a balanced diet

The grape is the only fruit that can possess a perfect balance of sugar, acid, amino acids, phenols, nutrients, and water sufficient for making a balanced wine naturally. All other bases (including many grapes deficient in some aspect) require additives -- usually sugar, acid, tannin, and nutrients. Next to sulfite and acids, nutrients are probably the most misunderstood additive we habitually use.

One of the best sources of trace minerals for winemaking is tap water. Many home winemakers suffer the mistaken belief that tap water is bad for yeast and bad for wine. Lallemand, manufacturer of Lalvin wine yeasts, warns against using distilled water in making wine.

"It is difficult to add what distilling takes away. It is much better to use tap water and have healthy yeast than to use distilled water and suffer a sluggish fermentation. Even adding nutrients won't make up for distilled water. The makers of nutrients assume you are using tap water."

Among the nutrients, amino acids, ammonia and nitrogen are more important to yeast growth than even sugar. Sugar provides fuel, but the others provide food. Here are some of the commercial products offered to feed your yeast.

Yeast Nutrient

Various formulations usually containing diammonium phosphate (DAP), trace minerals, vitamins, and, in better formulations, yeast hulls. All non-grape musts benefit from 1 teaspoon per gallon dissolved before the yeast is pitched. Malt extract and lemon juice make a decent nutrient if nothing else is available, but commercial formulations are easily obtained, inexpensive and much better.

Yeast Energizer

Used to enliven a sluggish or stuck fermentation. Contains many ingredients not found in normal nutrient, such as Riboflavin and Thiamine. Best used by dissolving 1/2 tsp. in 1/2 to 1 cup of the must or wine before adding. If the fermentation is "stuck" and not simply sluggish, dissolve in 1/4 cup must and 1/2 cup warm (75 degrees F.) water with a pinch of fresh wine yeast added. Allow to bloom under cover over a 12-hour period. An additional 1/4 cup of must is then added and the yeast given another 12 hours to multiply before the enriched solution is adding to the fermentation vessel.

Diammonium Phosphate (DAP)

This is the basic nitrogen source in nearly all wine yeast nutrients. It can be used to supplement prepared nutrients or can be used by itself.

Fermaid

This yeast nutrient from Scott Labs contains diammonium phosphate, magnesium sulfate, yeast hulls, thiamine, folic acid, niacin and calcium pantothenate. Use of this or Yeastex may reduce incidence of hydrogen sulfide and volatile acidity. Use 0.5 to 1.0 gram per gallon.

Yeast Ghosts (Yeast Hulls)

Consists of the insoluble fraction of whole yeast cells, namely the cell wall and membrane. These materials supply lipids and sterols to the fermenting yeast and adsorb fatty acids which may cause sluggish fermentations. They will improve vinegar and malo-lactic fermentations as well. The use of yeast ghosts seems to reduce the incidence of hydrogen sulfide. Normal use is 1 to 2 lbs per 1000 gallons or 0.45 to 0.9 gram per gallon. At rates above 3 grams per gallon off flavors and aromas have been noted on occasion.

Yeastex-61

Not needed with most fresh grape musts, but concentrates, most fruit, vegetable and flower wines will benefit from its addition. A proprietary formulation of trace minerals, vitamins and organic nutrients. It helps with stuck fermentations. May help suppress hydrogen sulfide in some fermentations. Use 1/2 to 1 gram per gallon (1 gram = approximately 1/4 tsp). It can legally be used by commercial producers at doses up to 8 grams per gallon (accompanied by yeast hulls) when high alcohol wines are attempted.

Other

There are other proprietary yeast foods and nutrients available that, when used appropriately, will benefit your wine. Read the manufacturer's literature to determine if they are right for the yeast you are using and the wine you are making. None are universally appropriate, so get informed and act wisely.


Transferring to Secondary

When moving the must from primary to secondary, take the yeast with the must

I have received many, many emails and letters complaining of a stuck fermentation after moving the must from the primary to secondary. This move is usually made when the specific gravity is between 1.010 and 1.020, so the wine is sweet and alcohol still low. If fermentation is not resumed and completed, the wine may not be ruined, but it will certainly not be balanced. The problem is caused, in most cases, by racking the wine from primary to secondary. This is not the preferred method of transfer.

When a vigorous fermentation subsides, most of the yeast that were suspended in the must begin to settle rapidly to the bottom and into a thick layer of lees. They are quite capable of completing the fermentation from there, but will do so quicker if they are tossed into suspension regularly. That is one of the reasons most recipes tell you to stir the must at least daily -- it not only helps move juices from the pulp, but keeps the yeast suspended longer. Allowing a thick layer of lees to form in the primary and then racking the must into a secondary leaves the lees behind, but it also leaves most of the yeast behind, too.

If the primary has gross ingredients in it (vegetable, berry or fruit pulp, flower blossoms, etc.), strain them through a nylon straining bag and either drip drain or squeeze them as their condition dictates. Soft fruit like strawberries, persimmons, kiwis, pawpaws, etc. should be drip drained or they will release too many very fine particles od pulp into the must and leave a deep layer of gross lees that is a pain to deal with. After removing the fruit, berries, flowers, or whatever, stir the must vigorously to bring the lees in suspension. You can wait a few minutes to allow the heavier particles to settle (seeds, larger pieces of pulp, and dead yeast). Living yeast will remain suspended for a while. Either rack the must into the secondary quickly, leaving only the lees that have settled first, or pick up the primary and pour the must into the secondary using a large plastic funnel. This ensures the yeast are transferred with the must and the fermentation will continue unabated.

Remember, the yeast make the wine. You just prepare a balanced must for them and clean up after they are finished. Take care of them and they will preform as expected.




Last update was September 16th, 2006.


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