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Wine Chemistry Composition of Wine

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Wine Chemistry Composition of Wine 2/25/2014 Chemistry of Juice & Wine We will begin with the composition of must/grape juice and then cover the Wine Chemistry composition of wine. Constituents are covered in highest to lowest Wine 3 concentrations. Introduction to Enology 2/25/2014 1 4 Tonight: Exam # 1 Old English Money vs. US Use Scantron and #2 Pencil Leave one empty seat between you and your 2 farthings = 1 halfpenny neighbor. 2 halfpence = 1 penny (1d) 3 pence = 1 thruppence (3d) All backpacks, bags, and notebooks on floor. 6 pence = 1 sixpence (a 'tanner') 12 pence = 1 shilling (a bob) OR 100 pennies = 1 Dollar You will have 20 minutes to complete the test. 2 shillings = 1 florin ( a 'two bob bit') When your finished hand in your test face down 2 shillings and 6 pence = 1 half crown by section and wait quietly at your desk or 5 shillings = 1 Crown 20 shillings = 1 Pound outside the classroom. Write name on both Scantron & Test 2 5 Tonight's Lecture Metric System Wine chemistry The preferred method of measurement world Juice composition wide (except for the US, Burma & Liberia) Acid and sugar adjustments Look over handout and get comfortable with Wine composition converting US to Metric & vice versa. Units change by factors of 10 Use the handout on conversions of a website to help you out. 3 6 Wine Chemistry 1 2/25/2014 Metric Units Composition of Must Water, 70 to 80%, the sweeter the grapes, the lower the % of water. Most important role is as a solution in which all other reactions take place. Sugars, 15 to 35%, they are about 90% of the soluble solids or extract in the juice. 7 10 Some definitions: Soluble: A substance that can be dissolved, sugar being dissolved in water is an example. Insoluble substances do not dissolve, an example would be mixing sand into water. Precipitate: A substance that comes out of solution in a liquid and reverts to its solid form. Suspended Solids: Solids suspended in the solution that have not settled. 8 11 Sugars (carbohydrates) Metric System The primary sugars are glucose and fructose in about equal amounts. These sugars are both Winey laboratories use the metric system. hexoses (6 carbons) have the same formula European made wine equipment use metric C6H12O6 but different structures. units. Most problems occur when converting between US system and metric system. NASA lost $125,000,000 Mars spacecraft to due incorrect conversion. 9 12 Wine Chemistry 2 2/25/2014 Molecules Containing Carbon Unfermentable sugars Remember from our chemistry review that the Yeast do not have the ability to consume corners of the hexagon represent carbon atoms. ferment every type of sugar. Very small amounts of residual sugar remain in all dry wines due to unfermentable sugars Carbon atoms that are present (mostly pentoses). are at the comers of the hexagon 13 16 Molecules Containing Carbon Measuring Sugars Sugars can be measured directly in the lab Remember from our chemistry review that the through analysis. This is how low levels of corners of the hexagon represent carbon atoms. sugar in finished wines are measured. An oxygen atom Sugars make up a very large percentage of the makes up one juice before fermentation so it is much easier comer of the to measure the sugar by density. hexagon 14 17 Sugars Measuring Sugars Sucrose (table sugar) is a molecule that combines one Degrees Brix (sometimes called balling) is molecule of glucose and one how sugar is represented as a density molecule of fructose. It is measurement. present in native American 1 degree Brix (B) = (% by weight) = 1 gram grape varieties like Concord of sugar per 100 grams solution (water & up to about 25%. Not a lot sugar combined). in Vinifera. Yeast can ferment sucrose. 15 18 Wine Chemistry 3 2/25/2014 Example ~ Brix Standard Specific Gravity Specific gravity is useful when buying or To make a 20 ºBrix solution for calibrating a refractometer mix: selling bulk wine. 20 Grams of sugar Wine is usually sold by the gallon, however 80 Grams of water (80 ml) the amount of gallons will increase or decrease based on a wines temperature. 100 Grams total solution weight So when selling wine it is best to determine the amount of gallons by weight which is constant. 19 22 Other Units for Measuring Sugars Specific Gravity The specific gravity of water in U.S. units is Units of sugar measurement are different # outside of the United States. 8.328 /Gallon, so if the net weight of the wine on the truck is 42,360# then how many gallons Baumé , this method is popular in Europe are there on the truck? Brix = Baumé x 0.55 # Weight (SG x 8.328 /Gallon ) = Gallons Baume is an convenient method because the degrees Baumé approximates what the So # alcohol will be if the juice is fermented dry. 42,360# (0.990 x 8.328 /Gallon ) = 5,138 Gal. 13.5ºBauméferments to about 13.5%Alcohol Why was the specific gravity < 1.0? 20 23 Other Units for Measuring Sugars Methods of Sugar Measurement In brewing specific gravity is the preferred Refractometers: Easy to use and usually method of measuring sugar. more accurate than hydrometers. The changing density of a liquid changes the Using specific gravity sugar expressed as refraction (bending of light passing through density in grams/ml, water by definition has a it) measures dissolved solids. SG of 1.000 1° Brix = SG of 1.004 20° Brix = SG of 1.083 21 24 Wine Chemistry 4 2/25/2014 Methods of Sugar Measurement Methods of Sugar Measurement Hydrometers: Not quite as easy to use but Refractometers Cont. relatively cheap, measures the weight of a Problems: Expensive, delicate instruments, solution by displacement. Can be used alcohol affects refraction, so they cannot be during fermentation but the lower density of used during fermentation. Temperature also alcohol effects the Brix reading. affects refraction so it must be temperature Will read negative at the end of fermentation compensated. because alcohol has lower density than water. 25 28 Optical Refractometer Methods of Sugar Measurement Most hydrometers are calibrated to 60 F or 20 C (68F), so they need to be temperature compensated. The more accurate, the more expensive and delicate. Several hydrometers with different ranges give better accuracy. 26 29 Methods of Sugar Measurement Digital Refractometers Recently portable digital refractometers have Hydrometers can also give false readings by the become more affordable and more popular. presence of suspended solids or gas bubbles. Some hydrometers have internal thermometers Water resistant, for compensation. not waterproof! Using clarified juice reduces error from suspended solids. Spinning the hydrometer dislodges bubbles. 27 30 Wine Chemistry 5 2/25/2014 Hydrometers Adjusting Sugar The sugar left in the wine after fermentation is called the Residual Sugar or RS When adding sucrose the Brix or RS can be added by gm/L to the desired level. To add 0.5 grams/Liter to 60 gallons of wine: 60 Gal x 3.78 L/Gal =228 Liters 228 Liters x 0.5 Grams/Liter = 114 grams 31 34 Methods of Sugar Measurement Adjusting sugar with sweet wine or juice Digital Density To sweeten a must or wine with sweet juice or Meters More wine is simple algebra by using the principle that accurate and easy to the sum of the concentration times volume of each use, they are wine being blended will be equal the concentration definitely worth the times volume of the final wine. investment for commercial wineries. 32 35 Adjusting Sugar Example To adjust 10,000 Gallons of dry wine 0.1% RS Illegal to add to wines in CA. except for to 0.4% RS how much juice at 10% RS do you sparkling wine dosage, but it can be added as add? grape juice or grape juice concentrate. Let X = Gallons of sweet wine to add With homemade wines and wines made outside of California, sucrose (table sugar) (10,000 + X) .4% = {(10,000) (.1%)} + X(10%) can be used for adjusting the sugar level 4000 + .4X = 1000 + 10X before or after fermentation. 3000 = 9.6X Adding sugar does not increase ripeness 312.5 = X (flavor). 33 36 Wine Chemistry 6 2/25/2014 Titratable Acidity TA Acids Present in Juice TA is determined by titration with a base to Juice and wine are dilute acid solutions. The an endpoint of pH 8.2 (phenolphthalein) it is acidic nature of wine has a profound affect then expressed as grams/100ml or on the sensory qualities of wine, microbial grams/liter (g/L) of tartaric acid. stability, color, protein (heat) stability, and Example 8.9 g/L = 0.89g/100ml tartrate (cold) stability. In France TA is expressed as grams of sulfuric acid/Liter g/L tartaric acid X 0.65 = g/L sulfuric acid. 37 40 Principal Acids in Juice Titration Malic acid Tartaric acid Citric acid When performing a the endpoint of 8.2 COO- + H+ pH is just as the solution turns pink. | The endpoint can be difficult to see in COO- + H+ COO- + H+ CH2 | | | red wines. HCH HC-OH HO-C-COO- + H+ | | | HO-CH HC-OH CH2 | | | COO- + H+ COO- + H+ COO- + H+ Disassociated Carboxylic acid groups Before At Endpoint Too Far! 38 41 Principal Acids in Juice Acids Tartaric and malic make up over 90% of grape You can add tartaric, malic, citric, or lactic. For most adjustments tartaric acid is used juice acid. Tartaric acid is rarely found in other because it disassociates best (lowers the pH fruits. Other acids are: lactic, is present in more/gram) and is microbially stable.
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