Introduction to Winemaking Part 2: Must Additions

1. Introduction to WinemakingPart 2: Must Additions Dr. James Harbertson Extension Enologist Washington State University

2. Must Additions • Must is the crushed fruit. • Sugar • Water • Acid • Sulfur Dioxide • Yeast Inoculation and Nutrients • Other additions..

3. Sugar Additions • Sugar additions are allowed in WA • Concentrate or pure sugar, or other fruit • Additions cannot change final Brix past 25. • Can be added after fermentation or before • Process is known as chaptalization, after the French man who popularized it, Jean-Antoine Chaptal. • Regulated in most countries • Illegal in CA and Oregon. • Legal in some AOC’s in France.

4. Water Additions • Water may also be added to dilute juice to a minimum of 22 Brix • This can be done in the form of fermentation facilitation, or equipment flushing • Can be done pre or post-fermentation. • Primarily done to lower eventual EtOH concentration. • Reverse osmosis used to reduce EtOH but very costly. • Better to not make mistake at the outset.

5. Acid additions • In practice it is done to reduce the pH and increase the titratable acidity. • Tartaric acid and malic acid may be added to fermenting juice. • Tartaric is the best choice because it is microbial stable. • For reds done early about a day after skin contact because of high potassium content of skin.

6. Acid Additions II • The magnitude of change from the addition is determined by the buffering capacity of the must. • The increase in TA will be due the difference in the magnitude of the addition and the loss of K2TAR. • The pH change will also be dependent upon the buffering capacity of the must. • In practice additional acid is used to achieve a targeted value. • Acid of known concentration is added to a representative sample and monitored on a pH meter.

7. Sulfur Dioxide • Inhibits and kills native yeast and bacteria • Inhibits oxidative enzymes that cause browning • Decolorizes anthocyanin pigment • Interacts with phenols in the competitive oxidation • Delays non-enzymatic browning

8. Chemistry of Sulfur Dioxide • SO2 HSO3- pKa = 1.86 • SO2 known as the molecular form • HSO3- known as the bisulfite form • Each form reacts differently based on its own specific chemistry.

9. Molecular Form Functions • Inhibits oxidative enzymes • Behaves as competitive inhibitor • Kills wild yeast and bacteria • Effective hydrogen peroxide trapping agent. • Is volatile and detectable by sensory • Pungent metallic odor • Is lost due to its volatility

10. How much is necessary? • From 25 mg/L to 75 mg/L SO2 required to inhibit from 75 to 97% of PPO enzyme. • Laccase a more potent oxidative enzyme found in Botryized fruit requires 150 mg/L (too much). • 0.825 mg/L molecular SO2 is necessary to reduce viable cell population by an order of magnitude (10X). • Assumed that addition for enzyme reduces microflora significantly enough if you are inoculating

11. Free SO2 to achieve necessary molecular • For wines pH 3.5-4.0 about 45-150 mg/L free SO2 necessary for 0.825 mg/L molecular. • Equation can be used for specific cases. • Just plug in your pH to equation and the free SO2 will be calculated.

12. Bisulfite Functions • Decolorizes anthocyanin by binding them • Disrupts conjugated system • Is easily covalently bound by acetaldehyde, keto-acids and sugars. • Bound form disrupts normal equilibrium. • Establishes new equilibrium of bound and free. • Makes estimation of sulfur dioxide difficult. • Forces methodologies to measure bound and free sulfur dioxide. • Current methodologies have problems estimating bound and free form because of differential disassociation constants of bound forms.

13. Yeast and Yeast Nutrients • Grape juice fermentations are done by a strain of Saccharomyces cerevisiae. • They can happen naturally (native yeast that live in the winery), or by inoculation with a commercial strain. • Use of sulfur dioxide and inoculation generally minimize the influence of wild yeast(s) on wine quality.

14. Yeast and Yeast Nutrients II • Inoculation can occur any time after crushing but is usually done after other additions are complete. • Yeast nutrients are generally included in the inoculation step as a safeguard for stuck fermentations. • Yeast nutrients include ammonium salts, amino acids and vitamins. • Not all musts require nutrients but it is easier and cheaper for smaller wineries than having to analyze everything.

15. Other Additions…. • Enzyme Additions • Tannin Additions

16. Enzyme Additions • Direct additions (not on fixed bed) • Sensitive to temperature, EtOH and SO2 • Pectinase-Juice yield enhancement enzymes • Also helps prevent hazes in wines • Glucosidase-Freeing bound volatile compounds • Muscat, Riesling, Gewurtz. contain bound terpenes that can be freed to enhance aroma by using enzyme • Glucanase-Break down colloids that foul filter • Botrytis infected grapes contain colloids that will foul filter and enzyme addition can help.

17. Enzyme Additions II • Enzyme cocktails • Contain peptidase (small proteins), protease (breaks down protein), pectinase, glucosidase activity • Used to help extract color and tannin from skins and will also facilitate tannin seed extraction • Breakdown cell wall of skin and seed to facilitate extractions. • Product does not always work • Window of opportunity for enzyme addition is vague. • Can make mush out of your cap

18. Tannin Additions • Done to modify astringency and help stabilize color • Many different products • Mixture of tannins from different species. • Different species have tannins that are different than found in grapes. • Unclear whether additions are beneficial (Tannin addition products also contain volatile compounds that modify wine aroma as well) • Laws allowing additions are vague and need to be updated