Sugars in Winemaking

Sugars and Wine

Without sugars (and yeast) there could be no wine. Yeast convert sugars, through enzymatic actions, into CO2 and alcohol. In the process of doing this, there is a little bit left over that the yeast convert into energy for their own metabolic needs. Thus, sugars provide the raw materials for the alcohol in our wines. After fermentation is complete, they enhance wine in other ways.

The first “numbers” relating to sugar that the author learned were that two pounds of sugar dissolved in one U.S. gallon of water yields a specific gravity of 1.088 and contains the potential to become 12% alcohol by volume (abv).

Types of Sugar

Bar Sugar: This sugar’s crystal size is the finest of all the types of granulated sugar. It is ideal for sweetening finished wine because it dissolves easily. It is also called “superfine” or “ultrafine” sugar. In England, a sugar very similar to bar sugar is known as caster or castor, named after the type of shaker in which it is often packaged. Commercially, it can be purchased as “Baker’s Sugar.”

Barbados Sugar: A British specialty brown sugar, very dark brown, with a particularly strong molasses flavor. The crystals are slightly coarser and stickier in texture than “regular” brown sugar. Also know as Muscovado Sugar.

Brown Sugar: Sugar crystals coated in a molasses syrup with natural flavor and color. Many sugar refiners produce borwn sugar by boiling a special molasses syrup until brown sugar crystals form. A centrifuge spins the crystals dry. Some of the syrup remains, giving the sugar its brown color and molasses flavor. Other manufacturers produce brown sugar by blending a special molasses syrup with white sugar crystals. Dark brown sugar has more color and a stronger molasses flavor than light brown sugar. Lighter brown sugars are more commonly used in winemaking than darker ones, as the richer molasses flavors in the darker sugar tend to mask the bases flavors of the wine, but both have their place.

Corn Syrup: This is basically glucose and water, but may contain some maltose or other sugars. Common, grocery store products may have vanilla added, and/or preservatives that could affect fermentation. Read the label.

Demerara Sugar: A light brown sugar with large golden crystals which are slightly sticky. While this sugar is often expensive, it has a unique, unmatched flavor.

Dextrose: An isomer form (the invert) of glucose, actually called dextroglucose (D-glucose) with a right- axis polarization (a.k.a. “right-handed glucose”) and found naturally in sweet fruits and honey.

Fructose: One of two simple (reducing) fermentable sugars in grapes and other fruit, the other being glucose. Isolated, fructose is approximately twice as sweet as glucose. In wine, a higher fructose concentration will result in a heightened sweetness threshold.

Galactose: An optical isomer form of glucose. Sometimes called lactose, although it is not lactose proper. Not desired as a residual sugar in wine as it oxidizes to form mucic acid.

Glucose: One of two simple fermentable sugars in grapes and other fruit, the other being fructose. Glucose is approximately half as sweet as fructose. An isomer form of glucose, dextrose, is considered to be glucose

Honey: Honeys vary widely, but generally are a complex mixture of glucose (about 30%), fructose (40%) and other sugars (5%) in water with proteins, minerals, pollens and bee parts interspersed. Honey purity and quality also varies widely, as do the “varieties” of honey. “Variety” is attributed to the predominate flower the bees visited while making the honey (such as clover, orange, wildflower, raspberry, sage, heather, etc.).

Invert Sugar: The product of the hydrolysis of sucrose, which is glucose and fructose. Dextrose (an isomer of glucose) and levulose (an isomer of fructose) are obtained by the inversion of sucrose, and hence called invert sugar. Yeast convert invert sugar more rapidly than sucrose, such as simple cane sugar, because they do not have to break the sucrose down into glucose and fructose themselves. Invert sugar can be made by dissolving two parts sugar into one part water, adding two teaspoons lemon juice per pound of sugar, bringing this almost to a boil, and holding it there for 30 minutes (NOT allowing it to boil). If not to be used immediately upon cooling, this can be poured into a sealable jar, sealed and cooled in the refrigerator. Invert sugar should NOT be used to sweeten finished wine as it will encourage refermentation.

Jaggery: Raw or semi-refined palm sugar, made in the East Indies by evaporating the fresh juice of several kinds of palm trees, but specifically that of the palmyra.

Lactose: A sugar comprising one glucose molecule linked to a galactose molecule and found only in milk. It has a slightly sweet taste and is much less soluble in water than most other sugars. The human body breaks it down into galactose and glucose. Because it is not ordinarily fermentable until separated into its component sugars, it can be used to boost residual sweetness.

Levulose: An isomer form (the invert) of fructose, with a left-axis polarization (a.k.a. “left-handed fructose”) and found naturally in sweet fruits and honey.

Maltose: A crystalline sugar formed from starch (specifically malt) and the amylolytic ferment of saliva and pancreatic juice. It consists of two linked glucose molecules and is completely fermentable. It resembles dextrose, but rotates the plane of polarized light further to the right and possesses a lower cupric oxide reducing power.

Molasses: The filtered residue of sugar refinement after the cyrstalized portion has been removed. “Light molasses” is roughly 90% sugar, while “blackstrap molasses” is only 50% sugar and 50% refinement residue. It may have sulfur compounds added to sterilize and stabilize it. This makes it generally undesirable as a sugar for wine, as it could encourage the formation of hydrogen sulfide. It is similar to treacle.

Muscovado Sugar: A British specialty brown sugar, very dark brown, with a particularly strong molasses flavor. The crystals are slightly coarser and stickier in texture than “regular” brown sugar. Also know as Barbados Sugar.

Piloncillo: Mexican brown sugar, which is semi-refined and granulated. It is sometimes sold in solid cone-shaped cakes, where the sugar is scraped off the cake as needed. The taste is quite different than American brown sugar, which is actually refined sugar to which molasses has been added.

Raffinose: A complex sugar (trisaccharide) found primarily in grains, legumes and some vegetables. It has little value in winemaking and is only slightly sweet.

Raw Sugar: Crystalline sugar obtained from the evaporation of cane, beet, maple, or some other syrup. Raw cane sugar is sold as “Sucanat.” Raw beet sugar is said to be unsavory. Raw sugar should not be equated with the product “Sugar in the Raw.”

Residual Sugar: The amount of sugar, both fermentable and unfermentable, left in a wine after fermentation is complete or permanently halted by stabilization. Fermentation is complete when either all the fermentable sugar has been converted by the yeast into alcohol and carbon dioxide as byproducts or when the concentration of alcohol produced reaches a level that is toxic to the yeast and they die. Fermentation is permanently halted by stabilization through several means involving intervention by man.

Rock Candy: Large sucrose crystals, usually clear but may be tinted with flavorings, Some people drop a piece of rock candy in the wine bottle before filling it, where it slowly dissolves and sweetens the wine.

Stachyose: A complex sugar (tertasaccharide) found in a few grains, most legumes and some vegetables. It has little value in winemaking and is less sweet than raffinose.

Sucrose: A natural, crystalline disaccharide found in grapes, most fruit and many plants. This is the type of refined sugar obtained from sugar cane, sugar beets and other sources which, when added to a must or juice to make up for deficiencies in natural sugar, must be hydrolyzed (inverted) into Fructose and Glucose by acids and enzymes in the yeast before it can be used as fuel for fermentation.

Superfine Sugar: This sugar’s crystal size is the finest of all the types of granulated sugar. It is ideal for sweetening finished wine because it dissolves easily. It is also called “bar” or “ultrafine” sugar. In England, a sugar very similar to superfine sugar is known as caster or castor, named after the type of shaker in which it is often packaged. Commercially, it can be purchased as “Baker’s Sugar.”

Treacle: The inverted sugar made from the residue of refinement and very similar in taste to molasses, although treacle is generally darker. There is even a “black treacle” with roughly the same taste as “blackstrap molasses.” If you like the taste, it is more useful in winemaking than molasses.

Turbinado Sugar: A raw sugar which has been partially processed, removing some of the surface molasses. It is a blond color with a mild brown sugar flavor that enhances some wine bases as no other sugar can.

Ultrafine Sugar: This sugar’s crystal size is the finest of all the types of granulated sugar. It is ideal for sweetening finished wine because it dissolves easily. It is also called “bar” or “superfine” sugar. In England, a sugar very similar to ultrafine sugar is known as caster or castor, named after the type of shaker in which it is often packaged. Commercially, it can be purchased as “Baker’s Sugar.”

Sugar Content of Selected Fruit and Fruit Juices

Measuring the sugar content of fruit is, for the layman, an educated estimation at best. Certainly one can crush a bit of the fruit and, using a refractometer, measure the Brix of the juice. Several such samples, averaged together, will yield pretty good numbers one can use with a high degree of confidence. Or, one can chop the fruit, mash it, add pectic enzyme and total water estimated for the wine, and let it sit (covered, of course) for a number of hours (8-12), stirring several times throughout the wait. The pectic enzyme will act upon the structures of the fruit and allow the release of additional juice, acids, sugars, and other constituents. The fruit can then be strained out, pressed, and the expressed liquid added to the liquid bulk. After stirring to integrate, this liquid can be tested with a hydrometer to approximate its sugar content as suggested by its specific gravity. If this is done, the pulp should be integrated back into the liquid to allow the yeast, when added, to go to work on the pulp. They will undoubtedly find additional sugars in the pulp, but exactly how much is something we can only speculate about. There is no way to measure it in the home. So, at best, using the maceration method just described will yield an approximation of the natural sugars the fruit contains. But it will be close enough to calculate how much additional sugar, if any, you need to add to get within the ballpark of where you need to be.

Recipes for making wine from various fruit are but a guide. They reveal a method for making wine from the stated base ingredients, but very often do not reveal if the fruit is freshly picked or obtained at market. Fruit picked at the zenith of ripeness will be much, much more flavorful and sweet than fruit obtained at market. The latter may have been harvested a week or more prior to its appearance at the market, and thus was picked before it was ripe. The best “in-between” compromise is to buy your fruit at a roadside stand — preferably one that serves as an outlet for a resident or neighboring farm. Their fruit typically will have been picked not more than a day prior. But rarely does a recipe reveal the source and condition of the fruit within, or whether is is good quality or average or poor, or if it is from an exceptional cultivar or simply good one. There are many variables the recipe does not reveal. All it will reveal is how much additional sugar the recipe’s creator added to his must. The fruit you use will undoubtedly be different. Measure what you can. Calculate what you must. But if you are in the dark, hopefully this discussion will be of some value.

The United States Department of Agriculture’s Human Nutrition Information Service has long published a research report entitled, Sugar Content of Selected Foods: Individual and Total Sugars. The 1987 version was used to construct the table below, which lists three monosaccharides (galactose, glucose and fructose), three disaccharides (lactose, sucrose and maltose), and combines other sugars (primarily raffinose [a trisaccharide] and stachyyose [a tetrasaccharide]). Total sugars for each entry are real or calculated. The real values are based upon thorough analysis of the representative samples using high-pressure liquid chromatography or gas chromatography. Calculated totals (in brackets) summate the listed individual sugars and are believed to be representative of the fruit. The table below should be useful to the home winemaker desirous of achieving greater exactitude than many recipes offer. Just remember that the numbers below are averages, which implies there is a range of values on either side of the numbers where your particular fruits might fall. Measure and compare.

Be aware that other ingredients not listed on the table below may contain natural sugars. This is especially true of certain grains and legumes that may be used in winemaking. Although their sugar content is low, they still contribute to the whole when used. Also, vegetables, flowers, leaves, roots, barks, seeds, and sap are primary or ancillary ingredients in some recipes and are not included in the table below (although many are in the USDA report). Finally, certain starches can be broken down enzymatically and converted into fermentable sugars. Their influence on the total sugar that gets fermented may be minuscule or substantial, and you may want to do independent research on those ingredients. The author is cognizant of this and does not consider it outside the scope of “normal” home winemaking practice, but does not have their potential values at hand. Perhaps in the future…

Sugar Content of Selected Fruit and Fruit Juices, 100 Grams

[Asterisk = no data for sugar known to be present; dash = no data for sugar that may be present;
[0.0] = no data for sugar thought not to be present; brackets around Total = calculated value]

Post-Fermentation Sweeteners

People have been trying to use artifical sweeteners as post-fermentation sweeteners in wine ever since they were first invented. Most have problems that outweigh any benefit — the main problem being an off-taste.

We will not discuss the artificals here. Instead, we will briefly discuss natural sweeteners or products made from natural sugars themselves and which may prove useful as sweeteners. The jury is still out on them, but this will probably change soon. They are simply described here and offered for your consideration. If you have anecdotal or scientific data to offer regarding these or other products, please feel free to contact the author.

Isomalt: A product made entirely from sucrose and looks much like table sugar. It is white, crystalline and odorless mixture of two disaccharide alcohols — gluco-mannitol and gluco-sorbitol.

Polydextrose: A new, patented food ingredient developed by Pfizer Research. It is a unique reduced-calorie (one calorie/gram) bulking agent that can be substituted for sugars. The possible benefits to the winemaker include sweetness and improved mouthfeel and viscosity qualities.

Stevia: This is a sweetener that is approximately 250 times sweeter than table sugar. It is a plant ( Stevia rebaudiana) that has been used historically in Paraguay as both a sweetener and herbal remedy. Both powdered plant material and a white powdered extract are marketed.

Sucralose: A reprocessed sucrose that is extremely stable and uniform in sweetness over time, temperature, and pH, leaves no aftertaste, and is claimed to be non-reactive. Sold in stores as “Splenda.”

Xylitol: A sugar alcohol, or polyol, found in plants that looks, feels, and tastes exactly like sugar, and leaves no unpleasant aftertaste. It is available in many forms. In its crystalline form, it can replace sugar in c ooking, baking, or as a sweetener for beverages.

Xylose: A normally unfermentable sugar of the pentose class formed by the hydrolysis of xylan; wood sugar. Initially it was believed that yeasts do not ferment xylose to ethanol although many are capable of producing xylitol. Some wild yeasts have been found which can convert xylose to ethanol, but they are not associated with wine. Xylose has a similar name to the sugar substitute called Xylitol, a sugar alcohol. They are not otherwise similar.

Enzymes Associated with Sugars

The following zymase enzymes are associated with the transformation of sugars into alcohol. Only the most important are listed. There are others.

Amylase: An enzyme that hydrolyzes starch to produce dextrins, maltose, and glucose.

Invertase: The enzyme yeast use to catalyze the hydrolysis of sucrose to yield an equal mixture of glucose and fructose, yielding invert sugar.

Lactase: An enzyme that catalyzes the hydrolysis of lactose into glucose and galactose.

Maltase: An enzyme that catalyzes the hydrolysis maltose to glucose.

Zymase: The name given to the group of enzymes which yeast use to transform sugar into alcohol.