by Dan McFeeley

After a long and fruitful life, University of Cornell apiculturist Dr. Roger A. Morse passed away in his sleep in May 2000. He was 72. A prolific writer, Morse had a unique gift for communicating the science of apiculture to the often harried and hard working beekeepers who had little time for sifting through the many technical journals and treatises in bee research for the practical solutions they needed. His legacy continues in his books and through his teaching influence in the graduate seminars he taught at Cornell.

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A carry over of his passion for beekeeping, mead and meadmaking also occupied Morse's interests. Beginning with his graduate school research for the Masters degree at Cornell during the 1950's and continuing through the 1970's, Morse was able to make new forays into the science of honey fermentation that left a lasting impression on how many meadmakers think about the whys and hows of meadmaking. Morse maintained this interest throughout his life, writing a number of journal articles on meadmaking independently and with professor Keith Steinkraus, also from the University of Cornell, plus patenting the techniques he and Steinkraus developed for commercial meadmaking. He also wrote an introductory book on mead titled 'Making Mead' and made an appearance in the video 'The Magic of Mead' (Dauenhauer Production 1991).

Although there had been other investigations into meadmaking in the past, mostly focusing on the use of nutrient additives, none were as scientifically thorough or as comprehensive as those of Roger Morse. His work, however, is an amalgam of new observations on the fermentation of honey, along with a sometimes dated wine science. As a result a careful assessment of his research findings is necessary in order to fully appreciate the scope of his work. This brief review is based on Morse's published works on mead, a list of which appears below.

Morse's interest in exploring possibilities for commercial meadmaking began during his graduate school years at Cornell with his observation of a surplus on the market of dark honey. These honeys would likely be too strong in flavor for everyday table use, Morse surmised, but might lend themselves to the production of mead. Unfortunately mead had a poor reputation at that time, according to Morse's research. Meads were usually overly sweet in order to mask off flavors from poor fermentation. Volatile acidity levels were often high, indicating bacterial contamination from poor sanitation. The fermentations themselves were long and strained, lasting for many months. And, as Morse concluded through his research, a majority of meads produced in the U.S. prior to and during the early 1950's were made primarily for Jewish sacramental purposes. Commercially produced meads could be found for general public consumption but they were rare in comparison.

Lengthy fermentations were characteristic of these meads to the extent that even today there can be found meadmakers who insist that a prolonged fermentation, along with an extended aging period, are an expected part of the process of making a good mead. It would be necessary to analyze the causes of these problems in order for ventures in commercial meadmaking to be successful. Production standards required meads to be brought to completion within a much more reasonable time, with clean fermentations leaving no off flavors requiring long periods of time to age out. Consistency of quality would need the assurance of meadmaking techniques that gave the meadmaker more control over the process. This was all the more imperative given the fact that the repeal of Prohibition had occurred hardly less than twenty years before Morse began his research, and its memory still lingered. Public opinion of U.S. made wines at that time was poor, often holding wine to be little better than a cheap form of alcohol. Tastes in dry and subtle wines, always at a low point, had plummeted even lower. Sweet and fortified wines dominated a market making a shaky comeback, as big and bold in one dimensional flavor as the tail fins on a 1950's Chevy, with U.S. tastes and expectations in wine following suit. Meads beset with the kinds of problems Morse was encountering would never survive on the early post Prohibition market unless drastic changes were made.

The thesis research Morse undertook during the early 1950's at Cornell University was an initial foray into meeting these issues. Titled "The Fermentation of Diluted Honey," the completed 1953 Master's thesis paper was both ambitious and far reaching, exploring a number of important topics and problems in meadmaking and laying a foundation for further research that would be carried out in the 1960's. The literature search for the project was especially difficult. Morse was unable to find anything published on the manufacture of mead prior to the repeal of Prohibition and had to draw from the literature on the making of honey vinegar along with material on meadmaking published after the 1930's. The focus of the thesis was on exploring the use of nutrients in aiding fermentations that had long been reported as difficult and overly long, with additional but brief attention given to fining, acidity, volatile acidity, aging, and other topics.

According to the available research on honey composition at that time, Morse felt that honey was lacking in essential nutrients, as well as being poorly buffered against pH swings and lacking in sufficient acidity needed by the yeasts for a good fermentation. A simple nutrient formula consisting of 2 grams each of ammonium phosphate, urea, cream of tartar, and citric acid was designed to meet these deficiencies and tested for the 1953 experiments. The must used in all experiments was made up of two pounds of honey dissolved in 1/2 gallon of distilled water which, although not measured for this series of experiments, would have yielded a specific gravity of approximately 1.140. Under these conditions the nutrient aided honey musts outperformed the control group batches which used no aids for the fermentation. In addition, Morse also found that performance could be influenced by the type of varietal honey. Buckwheat honey fermented more easily than the clover and orange blossom honeys used in the experiments. As Morse would detail more clearly in his 1966 research with Keith Steinkraus, the lighter honeys were the most difficult to ferment while the darker honeys in comparison appeared to have more of the essential nutrients and minerals needed by the yeasts. Even filtering the honey prior to dilution to honey must had a detrimental effect on the fermentation, apparently removing components in the honey needed for yeast fermentation. As a result, Morse concluded that filtered honey should used as a sweetening agent and not for the primary fermentation.

An unusual departure in these experiments was to avoid boiling or even pasteurizing the honey must at lower heat temperatures. Boiling the must is a well known method in meadmaking used since early Medieval times, however, Morse took the more scientific approach of pointing out that the yeasts found in honey are osmophilic, meaning they are specifically adapted to survive in the high osmotic pressures found in honey but not at the lower densities of standard honey musts. As Morse stated throughout his publications, the osmophilic yeasts found in honey cannot survive once the honey is diluted to must. There was no point in either boiling or pasteurizing honey must since the yeasts found in honey could not grow once the honey was diluted to levels used for fermentation. Certainly there were no ill effects to the meads. Morse tested the finished meads under laboratory conditions and found that all of them were microbiologically stable. Another important note — Morse found that boiling the honey must depleted it of nutrients needed by the yeasts for a good fermentation. Musts that had been boiled required additional nutrients in order to keep pace with other meads.

Another series of experiments was undertaken with professor Keith Steinkraus and the results published in 1966. The existing literature on mead was reviewed with much the same results as before. As Morse and Steinkraus found, honey fermentations were often reported to be extremely long, sometimes lasting months to a year with resulting off flavors from yeast autolysis, and bacterial contamination leading to high levels of volatile acidity. This project went much further than Morse's graduate school research in the 1950's, delving into the distinctive factors affecting the fermentation of honey and proposing solutions intended to improve commercial meadmaking.

A central feature of the 1966 project was once again research into nutrient additives. Two formulas were devised and tested, one supplying salts and citric acid, the other vitamins and small amounts of organic and inorganic nitrogen. The formulas were as listed below:

Formula I Formula II
ammonium sulphate 1.0 gm biotin 0.05 gm
potassium phosphate 0.5 gm pyridoxine 1.0 gm
magnesium chloride 0.2 gm meso-inositol 7.5 gm
sodium hydrogen sulphate 0.05 gm calcium pantothenate 10.0 gm
citric acid 5.0 gm peptone (Roche) 100.0 gm
ammonium sulphate 861.45 gm
_______________ _______________
Total 6.75 gm Total 1000.00 gm

Formula I was added at 6.75 grams per liter of honey must; formula II at 0.25 grams per liter honey must. The formulas were tested individually and in combination. The best results were obtained with a combination of formulas I and II. Fermentation ensued rapidly and finished in two weeks at over 13% alcohol. Formula I alone outperformed meads fermented with formula II, suggesting that nitrogen and phosphate were more vital yeast nutrients than the vitamin supplements provided by formula II. Meads made with ammonium sulphate and potassium phosphate as the sole supplement were somewhat more sluggish in comparison to meads made with formulas I and II yet reached 12% alcohol in 18 days. Morse and Steinkrause concluded that nitrogen sources were more important than vitamin supplements as meads using formula II alone reached 10% alcohol in 18 days.

This series of experiments was conducted using clover honey as the base, however, another series was carried out using buckwheat honey. Similar results were obtained with the noted performance of the control mead, using no supplements at all. This mead reached 10% alcohol in 18 days without a leveling off of the fermentation, once again suggesting that darker honeys are higher in nutrient content as compared to the lighter honeys such as clover honey. Individual varietal honeys were also found to vary in fermentability. Clover honeys were all found to be more difficult to ferment than the darker honeys, for example, but some did better than others. This should be expected in a natural product such as honey, whose composition is dependent on regional floral sources and seasonal variations.

The importance of the pH of the honey must for ease and efficacy of yeast fermentation was also uncovered. Morse and Steinkraus found that there was a specific pH range at which the fermentation proceeded easily and with little hinderance, so long as no other factors were impeding it. Between pH 3.7 and 4.6, the meads finished out with little difficulty. At pH values above and below this range, however, the fermentation would be slowed and even stall out at more extreme values. Using citric acid in formula I often caused the pH to drop below 3.0, making it necessary to add citrate as 2.53 grams citric acid and 2.47 grams sodium citrate. In this way the honey must was buffered to a more favorable pH range and required less adjustment. In general, Morse and Steinkraus recommended a starting pH of 3.7 as the best compromise for a must low enough in pH to inhibit bacterial growth while still at the proper range needed to ensure a healthy fermentation.

Variations in temperature of the fermentation and size of the inoculum starter were found to have effects on the fermentation of the honey must. For a series of experiments using the Steinberg 618 yeast from the University of Cornell collection, it was observed that fermentation rate increases with temperature, but for temperatures over 90 F the rate of fermentation would slow after almost a week and then drop off prematurely. Temperatures at 55 F resulted in sluggish fermentations that hardly rose above 4% alcohol. For a range of 75 to 80 F, the fermentation would be complete in two weeks, with alcohol over 12%. Inoculum size was compared using two yeast starters, 10% by volume and 0.4% by volume. A starter inoculum of 10% initially provided a more rapid fermentation than 0.4%, but began leveling off after the first burst of activity. After 10 to 12 days there was little difference between the two starters with both reaching over 12% alcohol in two weeks. On the other hand, for low fermentation temperatures at approx. 60 F or lower, a 10% starter inoculum outperformed a 1% inoculum.

Yeast strain selection was examined, but on a limited basis using the strains available through the University of Cornell collection, with the exception of a Maury yeast from England. Yeast 618, Steinberg, was a consistent rapid fermenter, yielding meads with good flavor and above average stability during storage. The Maury yeast, recommended in the British literature on mead and beekeeping, was a rapid fermenter but had problems with haze and clearing. Yeast 605 performed well, almost as well as yeast 618, while yeast 223, having a good reputation for wine production, was less satisfactory in mead fermentations, yielding less alcohol content than yeast 618.

Morse and Steinkraus summarized their 1966 experimental results concluding that with proper control of four simple factors, nutrient levels in the honey must, pH range, temperature, and yeast strain selection, even the light honeys could be fermented out in approximately two weeks, leaving an alcohol content of 12 – 13 % by volume. Starter inoculum size did not seem to have a significant effect on fermentation time overall, except for cool fermentation temperatures. Pilot-plant production of mead based on these findings was outlined as follows:

  1. Crystallized honey was heated to 140 to 150 F, then diluted to approximately 21 Brix. Clover honey was preferred.
  2. Additives equivalent to Formula I and II were added to the honey must.
  3. The pH was adjusted to 3.7 – 4.0 using either sodium hydroxide or hydrochloric acid.
  4. Forty gallons of honey must were added to a 55 gallon oak barrel, inoculated with 0.5% by volume yeast 618 (Steinberg) and sealed with a fermentation lock.
  5. The honey must was fermented at an ambient temperature of 65 F.
  6. Upon completion of the fermentation, the mead was aged in the barrel for 6 months.
  7. Total acidity was adjusted to 0.6% with either citric or tartaric acid.
  8. The mead was pasteurized at 145 F for five minutes, then bottled while still hot.

The resulting mead was light and dry, little or no harsh or bitter flavors, with good stability. Alcohol content was approximately 12% by volume. The color was very light, almost colorless. Flavor was mild, with only a hint of clover honey flavor. A 1973 study by Steinkraus and Morse analyzing ten commercially produced meads, and mead produced by the Cornell University "rapid fermentation" method (patented in 1971) showed the following results. The Cornell University mead was among the driest meads at 5.2% reducing sugars, alcohol content was 12.2% by volume. Its pH was 3.42, suggesting a good balance of sweetness and acidity. The ash content was the highest at 0.5201% (next highest was 0.2627%) which was attributed to the use of nutrient and additive formulas developed by Morse and Steinkraus. With the exception of Kerenoff Honey Wine (2.5% reducing sugars), all the other meads were very sweet, ranging from 10.2% to 27.8% reducing sugars. The Cornell University mead was also free of off flavors, something difficult to assess in the sweeter meads due to the masking effects of the high levels of reducing sugars.

Light dry meads, with mild and clean flavor, were hardly to be found on a market dominated by overly sweet meads. This was in step, however, with changing U.S. tastes in wine at that time, which reflected a growing appreciation of dryer and more subtle wines. Certainly the outlook for mead as an alternate market niche was beginning to look promising, particularly for meads that were subtle in flavor and not cloyishly sweet. For commercial meadmakers wishing to venture into this market, the Cornell University method of making mead offered new means of controlling the fermentation and ensuring consistent high quality. Morse and Steinkraus' optimism for commercial production of mead, however, ran out with the fluctuation of world honey prices. The surplus market became a shortage during the 1970's, dashing their hopes. Morse, however, continued to consult and advise on meadmaking.

Morse's research into meadmaking, both independently and later with Keith Steinkraus, was a significant breakthrough in many ways. Prior to Morse's research, no one else had made as thorough an investigation into the fermentation characteristics of honey. Achieving consistent fermentation times of two weeks with little off flavors was unheard of. A light dry mead was a rarity in those days, compared with the sweet meads being made at the time when Morse and Steinkraus were developing their meadmaking techniques.

Morse's influence in meadmaking continues. An article by respected meadmakers Ken Schramm and Dan McConnell 'Mead Success: Ingredients, Processes and Techniques,' appearing in the Spring 1995 issue of Zymurgy, touched on and updated many of Roger Morse's ideas, including pH monitoring, a recommended pH level of 3.7, and so on. Ken and Dan also conducted a number of seminars for the homebrewing community, bringing Morse's ideas out of the relative isolation of his published articles and helping to make them everydayprinciples in making a good mead. Thanks to the efforts of Ken and Dan, Roger Morse's findings on the science of honey fermentation have become familiar ideas to meadmakers.

More examples abound. Clayton Cone, former technical advisor to Lallemand Inc., a major Canadian based yeast company, wrote a web paper titled 'The Basics of Mead Fermentation' (available at http://consumer.lallemand.com/danstar-lalvin/InFerment/Mead_Basics.html) working from his specialized knowledge of yeast biology and fermentation and showing a strong consilience with Morse's original work in the advice given on pH monitoring, nutrient levels, and inoculum size. The Beverage People, a winemaking/homebrew supply company based in California, sells a meadmaking nutrient supplement based on the formula designed by Morse and Steinkraus.

As telling as Roger Morse's influence into the science of honey fermentation has been, it was a pioneering work carried out in the 1950's and 1960's with an emphasis on the commercial production of mead. Honey is a remarkably unique product of nature, however, much of the research conducted into its equally unique biochemical properties has been focused mostly on simple chemical analysis, or areas relevant to the food industry. The mead equivalent of contemporary modern day wine science, i.e., an analysis of the fermentation properties of honey that ultimately affect the flavor profile of the finished mead, is needed to build upon Morse's foundational work.

Resources

  • R. M. Kime, R. A. Morse, K. H. Steinkraus. "Mead: History, Current Technology and Prospects." American Bee Journal, February 1998.
  • Daniel S. McConnell and Kenneth D. Schramm. "Mead Success: Ingredients, Processes and Techniques." Zymurgy, vol 18 (1) Spring 1995.
  • Roger Morse. The Fermentation of Diluted Honey. Masters Thesis, Cornell University, 1953.
  • Roger Morse. "Honey Wine." Gleanings in Bee Culture, vol. 82, 1954.
  • Roger Morse. "Wines from the Fermentation of Honey." Honey: A Comprehensive Survey. E. Crane, editor. New York: Crane, Russak & Company, Inc., 1975.
  • Roger Morse. Making Mead: History, Recipes, Methods and Equipment. Wicwas Press, Cheshire CT., 1980.
  • Roger Morse and Keith Steinkraus. Method for making Wine from Honey. US Patent No. 3, 598, 607.
  • C. L. Stong. "The Amateur Scientist: Mead, the Drink of the Vikings, can be made (legally) by fermenting honey in the home." Scientific American, vol. 227 (3) Sept. 1972.
  • Keith Steinkraus and Roger Morse. "Factors influencing the Fermentation of Honey in Mead Production." Journal of Apicultural Research, vol. 5 (1) 1966.
  • Keith Steinkraus and Roger Morse. "Chemical Analysis of Honey Wines." Journal of Apicultural Research, vol 12 (3), 1973.
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