While the wine and spirits industries faced supply chain and inflation challenges this last year, there were also some liberalizing Alcohol and Tobacco Tax and Trade Bureau (TTB) regulatory developments. Among the modernizing and harmonizing ordinance changes included the most recently published amended TTB authorized list of Wine and Juice Treating Materials and Processes for Domestic Wine Production.1
Wine Treating Materials
The Code of Federal Regulations Title 27, part 24 regulates winemaking.2 The approved materials and processes, within the published limitations in § 24.246, are considered consistent with good commercial practice in the production, cellar treatment, or finishing of wine and, where applicable, in the treatment of juice and distilling material. The recent codification of provisional approvals includes amendments to some fermentation aids, but before getting to the changes, let’s review YAN:
Yeast Nutrients / Fermentation Aids
Microbes like yeasts require nitrogen, vitamins, minerals, fatty acids, and sterols to be healthy and support cell metabolism, rate, growth, protein synthesis, and alcohol tolerance. Some fruit may be deficient in microbial nutrition. Fermentation aids support a robust environment for yeast and malolactic bacteria during rehydration and fermentation. Amino acids, ammonia (NH3), and some peptides contribute to the concentration of yeast assimilable nitrogen (YAN). The amount of YAN in the must varies by fruit variety, climate, cultivation management, harvest maturity, and processing decisions.3 YAN is a measure of ammonia (NH3) and alpha-amino nitrogen by OPA (NOPA), a technique that measures the free amino acids (FAN) except proline.4 Knowledge of available nitrogen is essential for effective fermentation management. Nutrient-deficient must supplementation decreases the incidence of incomplete or stuck fermentation and the prevention of hydrogen sulfide and other sensorily objectionable metabolites.5 Nitrogen addition for ammonia is typically Diammonium phosphate (DAP) or products containing DAP. Musts with excessive nutrients may favor an abundance of microbial growth, including spoilage organisms, and excess nitrogen may lead to urea formation. Urea is a precursor to ethyl carbamate formation, known to be carcinogenic.6, [i] Measuring nitrogen status as YAN is proactive fermentation management toward desired outcomes.
How much YAN is necessary?
To prevent nutrition-related fermentation problems, measuring the initial concentration of YAN in the juice or must is essential. YAN requirements are related to ripeness- the soluble solids content provides a robust guide for YAN content for optimal fermentation performance and quality, e.g., 21 °Brix musts require an estimated 200 mg/L YAN.7 A helpful YAN calculator based on the nitrogen requirements of the selected yeast strain and the initial Brix of the must is available here: https://fermcalc.com/FermCalcJS.html.8
Is YAN all that is necessary?
While YAN is essential to the nutritional nitrogen needs of yeast, it does not address all the micronutrient needs, particularly B vitamins.9 The US TTB Wine Treating Materials and Related Regulations updated the following B vitamin yeast nutrient limitation:
- Biotin (B7): 25 µg/L
- Calcium pantothenate (B5) (expanded permission) 0.48 mg/L
- Previously approved solely as a yeast nutrient in apple wine, now permissible in all juice and wine
- Folic acid (B9): 100 µg/L
- Inositol (myo-inositol) (B8): 2 mg/L
- Niacin (B3): 1 mg/L
- Pyridoxine hydrochloride (B6): 150 µg/L
And the mineral magnesium via
- Magnesium sulfate: 15 mg/L
Before direct B vitamin addition approvals, indirect additions via yeast autolysis products were the only option.
Other recent TTB approvals may be more relevant this season for wines already through primary fermentation. These include several fining agents:
- Potassium Polyaspartate: 100 mg/L
Potassium polyaspartate
While perhaps not as relevant to many hybrid cultivars high in malic acid relative to tartaric acid concentration, cold stabilization treatment can use Potassium polyaspartate (KPA). KPA improves cold stability by inhibiting the nucleation of tartaric acid with the abundant ions potassium and calcium and the subsequent precipitation of these tartaric acid salt crystals (tartrates).10 Tartrates include potassium bitartrate (KHT) and calcium tartrate. Historical tartrate stabilization treatments typically decrease solubility through cold temperature treatments to force KHT out of the wine solution. While very effective for KHT, refrigeration has significant energy input requirements, and precipitation of KHT alters the chemistry: TA and potentially pH and color. Tartrate inhibition from additives may avoid these impacts, although they may present further compromises. Other TTB-approved tartrates stabilizing additives include carboxymethyl cellulose (CMC), gum Arabic, metatartaric acid, mannoproteins, and KPA. KPA offers stabilization efficacy similar to metatartaric acid; however, with greater longevity and without the potential color loss, haze, filterability, and sensory issues of the other agents.11 KPA addition in wine can occur immediately before bottling and is effective at 100 mg/L.12 The prevention of tartrates also reduces or eliminates the cleaning associated with precipitated tartrates adhering in tanks and barrels.
Chitosan
Chitosan was an instrumental discovery for numerous sectors and industries, including food and pharmaceutical. It has low toxicity, is biodegradable, biocompatible in various uses, and has versatile wine functionality13. Despite its low aqueous solubility, its use in winemaking can aid clarification14, wine proteins heat stabilization15, metal chelation, remove ochratoxin16, and control undesirable microorganisms, especially Brettanomyces.17,18 Chitosan has vast application potential because its chemical structure is adaptable to introduce new functions or properties in different forms, such as beads, films, gels, and nanoparticles.19,20
Chitosan synthesis occurs in the cell walls and exoskeleton of a large number of organisms, but only fungally sourced (Aspergillus niger) is approved for use in wine by the OIV (1 g/L)21, and TTB (5 g/L) 1. Fungally derived chitosan avoids the potential crustacean allergy and vegan concerns.
Perspicacious pea protein
Many traditional fining treatments read like a seaside haggis recipe or voodoo potion, relying on natural products, including animal proteins extracted from milk (casein), animal hooves (gelatin), ox blood and egg (albumin), and fish entrails (collagen) to clarify wine, ‘collage‘ in French, or fining. Fining wine often involves adding a colloidal substance whose reactive components flocculate on contact with the wine, causing turbidity and eventual precipitation to the bottom of the container, thus helping either in its clarification, coloration, stabilization, or sensory properties.
There is some social movement to reduce or eliminate the use of all animal-derived winemaking materials. Apart from the substantial variation (specificity and efficacy) inherent in animal products, consumer trends like natural wines, particularly health concerns about allergen status and consideration to vegetarians and vegans, warrant attention to the choice of winemaking ingredients and interest in developing alternatives. Plant proteins and non-proteinaceous fining substances might someday replace fining agents of animal origin. Sources include cereals, pomace, potatoes, and pulses.22
Due to allergen concerns with milk and egg proteins, EU regulations require their declaration on wine labels if the concentration is more than 0.25 mg/L.23 The TTB approved pea protein as a fining agent to remove off flavors from wine and juice at 0.5 g/L.1
Copper sulfate
To remove hydrogen sulfide or mercaptans from wine. The quantity of copper sulfate added (calculated as copper) must not exceed 6.0 mg Cu/L wine. The change allows the residual level of copper to increase from 0.5 mg/L to 1 mg/L.1
Notices of proposed TTB rulemaking for wine are available at https://www.ttb.gov/wine/notices-of-proposed-rulemaking. Many proposal notices are open for comment. Industry members wanting to use a treating material or process not explicitly authorized in part 24 may request authorization. TTB may administratively approve the use of treating materials and processes not listed in the regulations, either as an experiment under 27 CFR 24.249 or for continual use (acceptable in good commercial practice) under 27 CFR 24.250. Applicants for such approvals must submit to TTB a request describing the material or process and the purpose, manner, and extent to which the material or process is to be used; certain samples and test results; and any other relevant information, as described in the regulations.
References
(1) Wine Treating Materials and Related Regulations, 2022. https://www.federalregister.gov/documents/2022/08/24/2022-18060/wine-treating-materials-and-related-regulations (accessed 2022-12-12).
(2) 27 CFR §24.246 Material Authorized for the Treatment of Wine and Juice; Vol. Title 27. https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=1&SID=838d8cad559312d1fdb423e9a6ccc358&ty=HTML&h=L&mc=true&r=SECTION&n=se27.1.24_1246 (accessed 2019-11-09).
(3) Bell, S.-J.; Henschke, P. A. Implications of Nitrogen Nutrition for Grapes, Fermentation and Wine; 2005; pp 242–295.
(4) Dukes, B. C.; Butzke, C. E. Rapid Determination of Primary Amino Acids in Grape Juice Using an O-Phthaldialdehyde/N-Acetyl-L-Cysteine Spectrophotometric Assay. American Journal of Enology and Viticulture 1998, 49 (2), 125–134.
(5) Bisson, L. F. Stuck and Sluggish Fermentations. American Journal of Enology and Viticulture 1999, 50 (1), 107–119.
(6) Monteiro, F. F.; Trousdale, E. K.; Bisson, L. F. Ethyl Carbamate Formation in Wine: Use of Radioactively Labeled Precursors to Demonstrate the Involvement of Urea. Am J Enol Vitic. 1989, 40 (1), 1–8.
(7) Bisson, L. F.; Butzke, C. E. Diagnosis and Rectification of Stuck and Sluggish Fermentations. American Journal of Enology and Viticulture 2000, 51 (2), 168–177.
(8) Gross, S. FermCalc Unit Conversion Calculator. http://fermcalc.com/fermcalc_conversions.html#sgc (accessed 2021-03-30).
(9) Perli, T.; Wronska, A. K.; Ortiz-Merino, R. A.; Pronk, J. T.; Daran, J.-M. Vitamin Requirements and Biosynthesis in Saccharomyces Cerevisiae. Yeast 2020, 37 (4), 283–304. https://doi.org/10.1002/yea.3461.
(10) Bosso, A.; Panero, L.; Petrozziello, M.; Sollazzo, M.; Asproudi, A.; Motta, S.; Guaita, M. Use of Polyaspartate as Inhibitor of Tartaric Precipitations in Wines. Food Chemistry 2015, 185, 1–6. https://doi.org/10.1016/j.foodchem.2015.03.099.
(11) Bosso, A.; Motta, S.; Panero, L.; Petrozziello, M.; Asproudi, A.; Lopez, R.; Guaita, M. Use of Polyaspartates for the Tartaric Stabilisation of White and Red Wines and Side Effects on Wine Characteristics. OENO One 2020, 54 (1), 15–26. https://doi.org/10.20870/oeno-one.2020.54.1.2527.
(12) Martínez-Pérez, M. P.; Bautista-Ortín, A. B.; Durant, V.; Gómez-Plaza, E. Evaluating Alternatives to Cold Stabilization in Wineries: The Use of Carboxymethyl Cellulose, Potassium Polyaspartate, Electrodialysis and Ion Exchange Resins. Foods 2020, 9 (9), 1275. https://doi.org/10.3390/foods9091275.
(13) Castro Marín, A.; Colangelo, D.; Lambri, M.; Riponi, C.; Chinnici, F. Relevance and Perspectives of the Use of Chitosan in Winemaking: A Review. Critical Reviews in Food Science and Nutrition 2021, 61 (20), 3450–3464. https://doi.org/10.1080/10408398.2020.1798871.
(14) Chagas, R.; Monteiro, S.; Ferreira, R. B. Assessment of Potential Effects of Common Fining Agents Used for White Wine Protein Stabilization. Am J Enol Vitic. 2012, 63 (4), 574–578. https://doi.org/10.5344/ajev.2012.12016.
(15) Colangelo, D.; Torchio, F.; De Faveri, D. M.; Lambri, M. The Use of Chitosan as Alternative to Bentonite for Wine Fining: Effects on Heat-Stability, Proteins, Organic Acids, Colour, and Volatile Compounds in an Aromatic White Wine. Food Chemistry 2018, 264, 301–309. https://doi.org/10.1016/j.foodchem.2018.05.005.
(16) Bornet, A.; Teissedre, P. L. Chitosan, Chitin-Glucan and Chitin Effects on Minerals (Iron, Lead, Cadmium) and Organic (Ochratoxin A) Contaminants in Wines. Eur Food Res Technol 2008, 226 (4), 681–689. https://doi.org/10.1007/s00217-007-0577-0.
(17) Petrova, B.; Cartwright, Z. M.; Edwards, C. G. Effectiveness of Chitosan Preparations against <em>Brettanomyces Bruxellensis</Em> Grown in Culture Media and Red Wines. OENO One 2016, 50 (1), 49–56. https://doi.org/10.20870/oeno-one.2016.50.1.54.
(18) Lu, S.; Song, X.; Cao, D.; Chen, Y.; Yao, K. Preparation of Water-Soluble Chitosan. Journal of Applied Polymer Science 2004, 91 (6), 3497–3503. https://doi.org/10.1002/app.13537.
(19) Brasselet, C.; Pierre, G.; Dubessay, P.; Dols-Lafargue, M.; Coulon, J.; Maupeu, J.; Vallet-Courbin, A.; de Baynast, H.; Doco, T.; Michaud, P.; Delattre, C. Modification of Chitosan for the Generation of Functional Derivatives. Applied Sciences 2019, 9 (7), 1321. https://doi.org/10.3390/app9071321.
(20) Aranaz, I.; Alcántara, A. R.; Civera, M. C.; Arias, C.; Elorza, B.; Heras Caballero, A.; Acosta, N. Chitosan: An Overview of Its Properties and Applications. Polymers 2021, 13 (19), 3256. https://doi.org/10.3390/polym13193256.
(21) International Code of Oenological Practices: 2.1.22 FINING USING CHITOSAN (OIV-OENO 336A-2009), 2015. https://www.oiv.int/public/medias/3275/e-code-ii-2122.pdf (accessed 2022-12-14).
(22) Marangon, M.; Vincenzi, S.; Curioni, A. Wine Fining with Plant Proteins. Molecules 2019, 24 (11), 2186. https://doi.org/10.3390/molecules24112186.
(23) Commission Implementing Regulation (EU) No 579/2012 of 29 June 2012 Amending Regulation (EC) No 607/2009 Laying down Certain Detailed Rules for the Implementation of Council Regulation (EC) No 479/2008 as Regards Protected Designations of Origin and Geographical Indications, Traditional Terms, Labelling and Presentation of Certain Wine Sector Products. Official Journal of the European Union 2012, No. 171, 4–7.
(24) Notice No. 176: Modernization of the Labeling and Advertising Regulations for Wine, Distilled Spirits, and Malt Beverages, 2018. https://www.regulations.gov/document/TTB-2018-0007-0001 (accessed 2022-12-12).
(25) Proposal Regarding Labeling Wines Containing Added Distilled Spirits, 2022. https://www.federalregister.gov/documents/2022/06/13/2022-11901/proposal-regarding-labeling-wines-containing-added-distilled-spirits (accessed 2022-12-12).
(26) Standards of Fill for Wine and Distilled Spirits, 2022. https://www.federalregister.gov/documents/2022/05/25/2022-10589/standards-of-fill-for-wine-and-distilled-spirits (accessed 2022-12-12).
[i] Urea is a TTB approved addition for nitrogen. In humans, urea is excreted by the kidneys. Normal values in human urine range from 6 to 9 mg/L, with greater than average levels if protein intake is high. Various wine additives over the years included–blood, mud (bentonite), fish air bladders (isinglass), kelp, gelatin (from animal hides and hooves), egg whites, and a host of other organic and inorganic stuff including toxins like ferrocyanide. It leads one to wonder if some ancient wine makers ever used urine as a nitrogen source. Documented cases of urine use in wine is elusive, but it is not difficult to imagine due to the natural and animal product history of wine additions. Is that food for thought or potty talk?