fermentation. He indicated that whilethere may be variances in FAN levels dueto testing regimens, the numbers are accu-rately representative of FAN levels inmead musts.

ResultsThe Florida Tupelo must had an OG of1.110, and contained 10 parts per mil-lion FAN. The sterility check showed >1x 106 yeast/100 milliliter, typical ofSaccharomyces, but most importantly, 0Viable Bacteria/100 milliliter. Thatfinding indicated that the practice ofpreparing traditional mead musts with-out heat or the use of sulfites may becapable of producing a good medium forclean fermentations.

Sample 2, the Florida Orange Blossom,had an OG of 1.110, with 5 ppm FAN.The must from Pure Clover (Sample 3)also registered an OG of 1.110 and 14ppm FAN. Sample 4, the Buckwheat, hadan OG of 1.106 and 21 ppm FAN, rein-forcing the widely held belief that darker

www.beertown.org November/December 2005 ZYMURGY 2 1

The challenge of making mead isachieving the perfect honey fermenta-

tion—clean, with zero or absolutely mini-mal off flavors. It optimizes the characterof a spectacular honey, yielding aromaticsand flavor reflecting its finest properties.

Simply, it comes down to a series of steps:pitching a vigorous, healthy yeast popula-tion, low lag times, effortless and robustyeast reproduction, successful competi-tion or K-factor activity, and a steady,healthy ferment to completion.

Reference texts for wine production, brew-ing, and yeast performance and technolo-gy for the beer and wine industries num-ber in the dozens, but at present there arenone for mead. But we can begin to piecetogether a plan for moving mead fermen-tations to quality levels reserved for thefinest wines and most consistent beers.

Yeast requires nutrients to grow, to metab-olize sugar into ethanol and to stayhealthy in the process. Everything getsinto or out of the yeast cell through thecell wall, and the plasma membrane is thebarrier that can disrupt fermentation ordamage the cell. Membrane health is crit-ical to maintaining healthy functions fromstart to finish. Keep that bugger fat andhappy, and life (and your mead) is good.Fail to meet the membrane’s needs, andeverything deteriorates in a hurry.

Growth nutrients include carbon, nitro-gen, phosphate and sulfate. Carbon isavailable from the sugars in the medium.Nitrogen and phosphate are problematicin mead musts.

While it has been accepted that meadmusts are low in free amino nitrogen(FAN), I have been curious to know exact-ly “How low is low?” I set out to determine

the FAN content of musts from four pre-ferred meadmaking honeys. I boughtFlorida Tupelo and Orange Blossom frommy local farmers market, and Clover(Kroger) and Buckwheat (Private Selection)from my local grocery. I contacted Dr. BenGavitt at the Cornell University/New YorkState Agricultural Extension Service WineLab and arranged to have the musts ana-lyzed as well as a sample of pure cherryjuice and a finished bottle of mead.

The ProcedureTo approximate a standard gravity meadmust, I measured 100 milliliters of honeyinto a sanitized Pyrex vessel, and dilutedthat to 400 milliliters with steam distilledwater. I dissolved the mixture by stirringwith a sanitized spoon, and transferred100 milliliters of the mixture to a sterilevial. I used the remainder of the liquid tomeasure and record the specific gravity ofall of the samples. The samples wereshipped via FedEx to NYSAES Lab.

AnalysesSample 1, the Tupelo, received a FANanalysis along with a sterility check. Theother must samples received only FANanalysis. The finished mead receivedresidual sugar analysis, ETOH, sterilitycheck and a microbial analysis.

Gavitt reported that all samples arrived ingood condition, and showed no signs of

OOppttiimmiizziinngg HHoonneeyy FFeerrmmeennttaattiioonn

by Ken Schramm

MASTERING MEAD

Yeast requiresnutrients to grow,to metabolize sugarinto ethanol andto stay healthy in

the process.

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musts contain more nutrients. Still, 21ppm is a long way from the 300 ppm mostwinemakers seek from a wine must des-tined for more than 12-percent alcohol.

Sample 5 was pasteurized cherry juicefrom Swanson’s Juice Mill in Bear Lake,Mich. Its OG was 1.047, and it contained262 ppm FAN, above the level of 200ppm commercial winemakers would con-sider adequate for a lower gravity must.That said, most meadmakers would notuse more than 1 and perhaps 2 gallons ofjuice in 5 gallons of must, and that dilu-tion would leave the available nitrogenlevels below the optimal range.

Obviously, the amount of FAN in thesemusts is well below what is needed for ahealthy fermentation. The actual FANcompounds in the honeys I had analyzed

were not determined, but there is someinformation on amino acids in honey fromDr. Jonathon White’s “Composition ofHoney,” published in “Honey, AComprehensive Survey,” edited by EvaCrane, Britain’s master authority on honey.

White documents a number of importantamino acids in honey, including com-pounds with high yeast uptake levels suchas lysine, methionine, isoleucine, leucine,

and glutamic and aspartic acids. While thevariety of amino acids is largely positive,their concentration in a must dilution isperilously low. Interestingly, the mostprevalent amino acid in honey, proline,cannot be assimilated by yeast.

Vitamins and MineralsAs the yeast population makes the transitionfrom growth to fermentation, its needschange to include the sugar that it will gath-er from the must, and vitamins and miner-als to conducts its metabolism. The mostcritical of the vitamins is biotin, but the yeastneeds thiamine, niacin, pantothenate, andthe minerals magnesium, calcium, man-ganese, potassium, zinc, iron and copper.Many of these micronutrients are utilized inthe process of transamination, in whichamino acids are broken down and thenreassembled by the cell to build the lipidlayers in the plasma membrane. Nitrogen isalso a metabolic need. During the fermenta-tion, nitrogen is used in transporters thatmove sugars across the plasma membraneagainst the concentration gradient.

“Biotin takes part in all major biochemicalreactions that involve protein synthesis, innucleic acid synthesis, in carbohydrate metab-olism, and in the synthesis of fatty acids. Itsdeficiency is clearly shown by poor growthand damaged plasma membranes.” (YeastTechnology, Reed and Nagodawithana).

Reed and Nagodawithana document biotinlevels in average beer wort of .56µg/100 ml.Levels in undiluted honey are quoted byKitzes, et al, at .066µg/100g, which wouldrepresent one-quarter to one-third of the lev-els found in a honey must. Thiamine (vita-min B1) is used by yeast in amino acid syn-thesis. It is also needed in the sugar-to-pyru-vate-to-ethanol pathway. The same twosources note levels in wort of 60 µg/100 ml,and levels in honey of ~5/6 µg/100 g. Honeymusts will likely be low in pantothenate, keyto the production of serine and methion-ine—amino acids used in the plasma mem-brane. Pantothenate deficiency causes yeastto produce high levels of H2S and its charac-teristic rotten egg smell. Lastly, riboflavin,another key vitamin, is present in wort at 33-46 µg/100 ml and in ~5/6 µg/100 g of honey.

Minerals important for growth and metab-olism in a healthy yeast population include

2 2 ZYMURGY November/December 2005 www.beertown.org

Brix range of must S. G. Target YANC* Level

21 1.087 200 ppm

23 1.096 250 ppm

25 1.106 300 ppm

27 1.115 350 ppm

REFERENCE: Bisson and ButzkeSG Conversions: USDA Tables

*YANC is Yeast Available (assimilable) Nitrogen Content, which combines all available nitrogen fromboth organic (amino acids) and inorganic (ammonia or urea) sources.

Target Nitrogen Levels

calcium, magnesium, potassium, phospho-rus and zinc, which are present in honey inminor to absolutely negligible quantities.The exception may be potassium.

Minerals are also a large part of the buffer-ing capacity of must. Clayton Cone notesthat potassium levels above 300 ppm arecritical to maintenance of pH levels.Haydak, et al, reported levels from 100ppm in light honeys (not enough) to over4700 ppm in darker honeys (more thanenough). The average of 205 ppm for lighthoneys, however, would predict a substan-tial shortfall when diluted with water atratios of 3:1 or 4:1. When potassium levelsdrop below 300 ppm, pH levels in the cellcan drop below 2.7, and metabolic activitywill virtually cease. Especially in the case oftraditional and show meads, early monitor-ing of the pH is a wise preventative meas-ure. Bisson also comments on the need toestablish potassium levels early, as well asthe strong possibility that potassium plays arole in strengthening the plasma mem-brane’s resistance to ethanol toxicity.

As the fermentation progresses, environ-mental and metabolic stress on the plasmamembrane increases. Several key func-tions rely heavily on good membranehealth, including: 1.Transport of a declining supply of sugarfrom the medium into the cell.

2.Transport of ethanol and CO2 throughthe membrane out of the cell.

3.Maintaining resistance to ethanolabsorption into the cell through themembrane against an increasingly hos-tile concentration gradient.

4.Absorption of ongoing metabolic nutri-tional needs and survival factors.

Thus it is important to build healthy cellwall mass during lag and growth phases,and to maintain it during the entirety ofthe stationary phase.

Fermentation ProtocolsI have been utilizing staggered addi-tions of a combination of 1 gramdiammonium phosphate (DAP) and 0.5gram Fermaid K (Lallemand’s micronu-trient blend) at pitch and at 24-hourintervals for three days. Fermentationtimes have been reduced, and theresulting meads have been of very high

quality, requiring less aging to reachdrinkable maturity.

Lallemand recommends rehydration of theyeast in water supplemented with theorganic nutrient Go-Ferm. The yeast mem-branes are devoid of a number of micronu-trients needed to develop the yeast biomassrequired for high gravity musts and thesubsequent stress of higher alcohol levelslater in the fermentation.

Cone stresses the importance of keep-ing the yeast in the growth phase.“Yeast produce 33 times as much alco-

hol per cell during the growth phasethan it does in the stationary phase. Sothere is an advantage to keeping theyeast growing as long as possible. Thereis also an advantage to adding the DAPin as many increments as possible. Thiskeeps the yeast growing as long as pos-sible and also keeps a fresh supply of Navailable for the yeast to metabolizeand build up its protein content.” Theyeast will also continue to absorb andutilize oxygen in the growth phase. Forwinemakers, the practice of pumpingover would get that oxygen into thefermenting must.

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The goals are to prolong the growth phaseas much as possible without overfeedingthe yeast, to provide a source of micronu-trients and to supplement potassium lev-els, in particular the lighter-colored hon-eys with lower mineral levels. For tradi-tional 5-gallon mead fermentations with agravity above 1.120, the keys are:

1. Rehydration at 104º F with Go-Ferm orother organic rehydration nutrient at arate of 1.25 grams nutrient per gram ofyeast. In all cases, addition of nutrientsby weight will be more accurate than byvolume. Volumes are included for theconvenience of those without the bene-fit of gram measurement devices. This

equates to 3.0 lbs/1,000 gallons.2. Addition of 3 grams (approximately0.75 teaspoon) Fermaid K, plus 4grams (1 teaspoon) DAP per 5 gallonsof must with a vigorous aeration at theend of the lag phase (six to 12 hours, atthe start of obvious fermentation activi-ty). This equates to 21 ounces FermaidK plus 28 ounces DAP per 1,000 gal-lons. For gravities above 1.125,increase these amounts by an addition-al 25 percent.

3. Addition of 1 gram (0.25 teaspoon)DAP, plus 1 gram (0.125 teaspoon)Fermaid K with a vigorous aeration at12-hour intervals until 50 percent sugardepletion or five days, whicheveroccurs first (7 ounces DAP plus 3.5ounces Fermaid K per 1,000 gallons).

4. Supplementing the potassium levels toa minimum of 300 ppm with a potassi-um source. Food grade potassiumhydroxide is an option for commercialmeadmakers, but its handling and usewould be problematic on smaller scales.For home meadmakers, potassiumbitartrate or potassium phosphate areviable options.

Role of pH in Better DetailDrs. Roger Morse and Keith Steinkrausestablished many years ago that low pH ina fermenting mead must can lead to aslowdown in fermentative activity and aprolonged and unhealthy fermentation.

Bisson explains the phenomenon in hertext on fermentation for her course at UC-Davis. Movement of amino acids acrossthe cell membrane (by transporters, ortrans-permeases) is coupled to protonmovement into the cell. Those protonsmust then be transported out of the cellby ATPase pumps (at the expense of oneATP > ADP hydrolysis per transport).When the pH drops, additional protonsenter the cell due to passive proton flux. Ifthe number of protons inside the cell wallexceeds the capacity of the ATPase pumpsin the membrane to evacuate them, aminoacid uptake slows and fermentative activ-ity is reduced.

Bisson also notes that fermentations thatfalter and stick can be extremely difficultto restart, making the maintenance of anappropriate pH all the more important.

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No-Heat Methods, Melomelsand Metheglins, andMicroorganismsIn The Compleat Meadmaker, I make thecase for preparing mead musts without theuse of any heat or must sanitation process-es beyond the requisite rigorous adherenceto equipment sanitation. Although tradi-tional mead musts may be largely devoid ofcompetitive microflora, the application ofthat method to melomels and metheglinscreates a window of opportunity for anyorganisms that come to the must throughfruits or spices. That fruit can bring a loadof microflora is obvious; less obvious is thefact that the environs in which spices areharvested—and the processes by whichthey are prepared for market—are rife withpoor sanitary practice and opportunity forexposure and contamination.

The threat from microflora on fruitappears to be backed up by the analysis ofthe finished raspberry mead I sent to theCornell lab.

Sample 6: Raspberry Mead15.0 lb (6.8 kg) Michigan raspberries15.0 lb (6.8 kg) Raspberry Blossom

Honey0.5 tsp DAP 0.25 tsp Fermaid K at pitch, 24, 48 and72 hours.

Original Gravity: UnknownFinal Gravity: 1.002 (corrected to 1.009post lab)

Analysis Data:ETOH: 14.1%Residual sugar: 3.7% (w/v)Glucose: 25.6 g/lFructose: 11.9 g/l

Viable yeast/100 ml: 5Viable bacteria/100 ml: >1 x 106Comments: “Yeast typical of Saccharomycesstrains. Bacteria are long rods formingshort chains (Lactobaccillus).”

The bacterial population in this sample isconsiderable. Several possible sources ofcontamination include process, equipment(racking cane, bottles, cork, which receivethe same sanitation practices as the “clean”sample) and the lead suspect, fruit.Possibilities are airborne and bird- or insect-carried bacteria and yeast, bug parts or

extraneous plant matter. Data aside, thismead was very tasty, and was well receivedby different audiences at several tastings.

Fruit and spices will add organisms thatcompete with your yeast population, notonly for food, but also for nutrition. Thegrowth needs of bacteria and wild yeaststrains are in most cases almost identical tothose of your chosen/pitched yeast strain—nitrogen, oxygen and B-vitamins. If the com-peting microflora are at phases that allowthem to consume and utilize the availablemust nutrients, they will have a huge advan-tage in their war to dominate the environ-ment and compromise your fermentation.

My initial conclusion from this data was thatthe use of sulfites might be preferred to min-imize bacterial contamination. On furtherthought, however, the recommended proce-dure is to prepare and initiate fermentationin a smaller honey must. For a 5-gallon batchof a fresh fruit melomel, start with 2.5 gallonsof water and 8 pounds of honey. Rehydrateyeast with Go-Ferm or equivalent and waterat 104º F. Aerate the must thoroughly andpitch. When the must has moved throughthe lag, add 3 grams Fermaid K (1.5 tea-

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spoons). When the must is fermenting vigor-ously (two to three days), add the fruit orpressed fruit juice and the remainder of thehoney. This will create a healthy yeast popu-lation to compete with any bacteria or wildyeast present on the fruit. Continue withstaggered additions of DAP at 1 gram or 0.25teaspoon every 12 hours, plus 0.5 gramFermaid K (0.125 teaspoon) until 50 percentsugar depletion. These numbers can bescaled to commercial volumes.

It is important to note that microflora maybe present and capable of activity beyondthe point at which the yeast ceases fermen-tation. Especially in musts that may finishwith considerable residual sugar becausethe yeast has reached ethanol tolerance, orthose that finish with low alcohol levels(below 10 percent), or both, it is criticallyimportant that the amounts of nutrientused do not exceed that which will be con-sumed by the yeast during growth and fer-mentation. Excess nutrient at that pointwill simply serve to nourish organisms thatmay harm your mead.

Ken Schramm is author of The Compleat

Meadmaker.