Sunday, November 22, 2009

Umami Taste in Wine: The role of amino acids and 5’-ribonucleotides as primary taste components in wine.

Alrighty then - here is a life's WORK IN PROGRESS that I first proposed with sensory specialists at Cal Poly San Luis Obispo (Bob Noyes, Joe Montecalvo, and others) a long, long time ago. This is still speculation and I looking for anyone interested in pursing a formalized study!! Back when I first wrote this (over 10 years ago) many people were still throwing bread and food at me during my presentations. Tomatoes, especially cherry tomatoes, made for particularly excellent projectiles and it is interesting to note how those same fruit/vegetables contribute to satisfying our need for umami taste. When eaten, however, not used as weapons.

The long and short of this is the descriptors consistent with lees stirring Chardonnay and other white wines fit descriptors for umami taste; rich, full, creamy, etc. There is a corresponding mouthfeel component and these combine to fit umami taste descriptions to a tee. Extending the maceration of red wines would also be consistent with this hypothesis and additional contact with the yeast during this process may contribute significant levels nucleotides, the umami taste potenitometer, to the equation. And finally ahe primary taste charcteristics assoicated with aging sparkling wine en tireage and the development of rich, almost savory, Sherry flavors from contact with the flor yeast are lumped in here as well. This would account for the 'softening' of bitterness and astringency and increase in richness of flavor that is noted with longer maceration of red wines, etc.

Modern production techniques, ripeness levels, specialized yeast strains and post fermentation handling and treatments can all contibute to the increase in umami taste compounds in wine. I will be posting a video explanation of umami (in the context of truths, myths, half-truths and downright lies) shortly and set up a link for anyone interested.

Taste a plain, uncooked mushroom and then compare to a mushroom you have nuked in the microwave in a plastic baggie for 30 seconds. Apart from the 'mushroomy' aromatics you will experience the genesis of umami taste firsthand.

For anyone interested here is the info!! Tata for now and proceed with caution. Or use this as a sleep aid tonight. I wonder if anyone is working on a technology for bathrooms to replace magazines and newspaper with on demand internet and email access? Crap (figuratively speaking), another project.

Umami taste has gained much attention and formal recognition from the sensory science community as a 5th primary taste category in addition to sweet, sour, bitter and salty. Glutamic acid and 5’–ribonucleotides, which is known to synergize the intensity of umami taste of glutatmate, are found in sufficient concentration levels in wine to play an essential role in forming the taste and flavor profile and intensity of quality wines. The correlation of these compounds to desirable taste and flavor characteristics of wine has been referred to (Peynaud[1]) but never fully analyzed. The umami taste sensation, derived from glutamates and 5’-ribonucleotides, is well documented as an attractive, primary taste component of myriad food products. Additionally there are several amino acids that have been identified that add a sweet taste to foods, notably praline, arganine and alanine that are found in sufficient concentrations to be considered as taste contributors.

A preliminary review of existing studies shows sufficient levels of naturally occurring umami taste substances in both wine grapes and finished wine to warrant further study of this hypothesis. Glutamic acid, a natural compound found in wine grapes and a precursor to glutamate taste substances, and 5’ -ribonucleotides, which are associated with yeast fermentation and the enzymatic decomposition of ribonucleic acid from yeast cells. The contribution of glutamic acid (more correctly glutamate) to the taste of wine is acknowledged by Emile Peynaud in his books Knowing and Making Wine and The Taste of Wine: “Among the amino acids, however, glutamic acid should perhaps be accorded a special mention. Its appetizing flavor is well known, salty, and mellow at once. If some 200 mg/l were present in a wine, its effect on the taste would not be negligible.” Synergized by 5’ –ribonucleotides, lesser amounts of glutamic acid would contribute significantly to the taste and flavor of wine.

Alanine, proline, glycine and arginine have been found to contribute a sweet taste in various foods and are associated with the “sweet” taste of crab and other seafoods (Umami, the Fifth Basic Taste[2]) These amino acids are found in significant levels in wine grapes and wine as well. Understanding the importance of the umami taste in wine, now recognized as the fundamental taste of seafood, tomato, asparagus, mushrooms and cheese, will lead to a better understanding of standard of viticultural and winemaking processes. Implementing practices in the vineyard and winery that create higher concentrations of the appropriate precursors and optimize umami taste intensity in wine can maximize desirable taste characteristics.

Recognition of amino acids and ribonucleotides as taste/flavor contributors.

Sugar-free extract
Wine makers and viticulturalists have recognized a flavor in wine which has come to be known as sugar-free extract. This flavor is associated with a “sweet” taste found in wines devoid of appreciable levels of sugar compounds.

Correlation of umami taste to bitterness suppression
Increased amounts of free amino acids and ribonucleotides in food products have been correlated with reduced bitterness and acidic “bite.” This effect is similar to the flavor enhancement achieved when wine is aged for extended period on the lees deposited during and after fermentation.

Compounds associated with umami taste found in wine grapes and wine
mg/l in grapes
mg/l in wine
Glutamic Acid
Precursor to glutamates and glutamine.
Salts of glutamic acid: compounds responsible for primary umami taste.

Potentiometer for umami taste intensity provided by yeast excretion and autolysis. Ribonucleotides have been shown to magnify umami taste from glutamates nine-fold[3]. “from 0.6-1.4 mg/l fo the nucleotides ADP, AMP, CMP, UDP, UMP and UTP were found…The nucleotides may act as reinforcers of flavors and in flavor formation in sparkling wines[4]

0.6-1.4 mg/l
Produced instead of glutamate in presence of ammonia in grapes (present in grape juice at concentrations of 24-309 mg/l with and average of 123 mg/l, nad in in wints from a few milligrams to about 50 mg/l with and average of about 12 mg/l[5]), depriving wine of umami taste. Studies show warm growing conditions increase levels of ammonia, creating glutamine in lieu of glutamate, requiring higher degree of fruit ripeness to achieve desirable umami taste. This correlation may help explain the phenomenon of how wine grapes in Bordeaux and Germany can achieve physiological maturity at lower sugar levels than the same grape varieties grown under warmer conditions, such as Napa Valley.

Amino acids with sweet taste characteristics found in grapes and wine
“The tastes of amino acids have traditionally been represented by one dominant taste, such as sweet (Ala, Gly, Pro, Ser, etc.)…[6]

Proline is usually the highest concentration of amino acid:
· 0-4600 mg/l, 742 mg/l average for 78 determinations in grapes4.
· 30-3558 mg/l, 869 mg/l average for 42 determinations of wine[8].
· Represents as much as 90% of the total nitrogen in Cabernet Sauvignon.
· Proline is partially used during fermentation, restored by yeast autolysis.
Pg. 2478, Umami, a fifth basic taste
Pg. 248, Umami Taste of Seafoods, Komata
· Must – 4-2360 mg/l, wine 0-2311[9]
· “Arganine levels increased approximately 20-fold during the fruit ripening period of several grape cultivar and at maturity arganine contributed the largest fraction (up to 50%) of N to total berry N.” R. Kruegar and W.M. Kliever, Arganine Metabolism, International Symposium on Nitrogen in Grapes and Wine, 1991, pg. 291

Wine descriptors consistent with umami taste descriptors
Sweet, savory, brothy, creamy, mouthfeel, mellow, rich, etc.
Wine flavor descriptors –
Red Wine: body, extract, ripe, beefy, sweet, mushroomy
White Wine: creamy, mellow, sweet, smooth, rich, ripe

Viticultural implications
Amino acid concentration and distribution in relation to:
1. Vine variety and clone.
2. Rootstock selection
3. Vine vigor and vegetative growth, total vine management in relationship to soil and climate.
4. Fertilization “amino acid concentrations in juice were highly correlated to total N” pg. 197, Must and Wine quality, International Symposium on Nitrogen in Grapes and Wine, 1991, S.E. Spade. “wines from non-fertilized vines scored lowers in aroma, intensity, flavor and overall wine quality.”
5. Crop yield
6. Vintage conditions (higher levels in “quality” vintages)
7. Ammonia/glutamine and reduced umami taste potential in relationship to growing conditions:
Bordeaux vs. Napa Valley
Riesling in Germany and development of “protein” taste

Fermentation and umami taste enhancement
1. Yeast contribution
2. Maceration
3. Red wine fermentation is conducted with the inclusion of grape solids. The pumping over or submersion of the cap keeps yeast cells constantly moving during the maceration period. Extended maceration of red wines creates a flavor profile consistent with umami taste characteristics, and may explain the softening and reduced bitterness and astringency of red wines made with extended maceration.
4. White wine fermentation is generally shorter in duration and conducted in the absence of grape solids. The umami flavor enhancement occurs during the aging period of the wine in contact with the lees resulting from fermentation.
5. Malo-lactic fermentation
6. Proteins

Cellar techniques and umami taste enhancement

Lees contact and lees stirring (including extended maceration for red wines):
Many white wines benefit from contact with spent yeast cells during post-fermentation aging. These flavor distinctions are consistent with enhanced umami taste characteristics: reduced impression of bitterness, rich, mellow, creamy, etc. The spent yeast cells would provide a source for 5’-ribonucleotides that would act as the potentiometer to synergize existing glutamates in the wine.

Champagne aging en-tirage
The aging of Champagne and sparkling wines on the lees after secondary bottle fermentation creates flavor distinctions consistent with enhanced umami taste characteristics: reduced impression of bitterness, rich, mellow, creamy, etc. The spent yeast cells would provide a source for 5’-ribonucleotides that would act as the potentiometer to synergize existing glutamates in the wine.

Flor yeast formation and ribonucleotides
Ammonia additions improve quality, page 228, Amerine, Wine Production and Technology in the United States
[1] E. Peynaud, Knowing and Making Wine, 48, (1981) The Taste of Wine
[2] Umami, the Fifth Basic Taste
[3] Helen Conn, “Umami” the Fifth Basic taste, Nutrition and Science, No. 2, pp. 21-23, March/April 1992
[4] M.A Amerine and C.S. Ough, Methods for Analysis of Musts and Wines, pg. 155 (1980)
[5] C.S. Ough, American Journal of Viticulture. 20, 213-220 (1969)
[6] Shinya Fuke and Tetsuji Shimizu, Sensory and preference aspects of umami, Trends in Food Science and Technology:4 (8) 246-251 41 ref. (1969)
[7] C.S. Ough, Vitis, 7, 321-331 (1968)
[8] C.S. Ough, Vitis, 7, 321-331 (1968)
[9] C.S. Ough and O. Bustos, Wines Vines (50)4, 50-58 (1969), C.S. Ough, unpublished data

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