27
Additives and Processing Aids

27.1 Introduction

The standard of identity for wine in most wine‐producing countries requires that wine be solely the product of complete or partial alcoholic fermentation of grapes, but also allows for additions of other materials to juice or wine. Materials used in winemaking must be explicitly allowed, that is, if a material is not expressly permitted for use in winemaking, then it is assumed to be forbidden.1 Some of these additions have been practiced for centuries or even millennia, as in the case of “plastering” a wine with gypsum (CaSO₄) to lower wine pH,² but others date to the last decade, and new additions are approved periodically.³

27.2 Regulations and terminology

As a general rule, approved materials are expected to leave the wine recognizable as wine, or as stated in the United States Code of Federal Regulations, 27 CFR 24.246 [1]:

Materials used in the process of filtering, clarifying, or purifying wine may remove cloudiness, precipitation, and undesirable odors and flavors, but the addition of any substance foreign to wine which changes the character of the wine, or the abstraction of ingredients which will change its character, to the extent inconsistent with good commercial practice, is not permitted….

Wine additions are distinguished from wine adulteration (Figure 27.1), in which unallowable compounds are added to improve the flavor or color of a wine or to decrease production costs, for example, because the adulterant is less expensive than the wine. Adulterants may be safe for use in food but disallowed because they are not a natural component of a wine (e.g., food dyes to increase red color), or they may be unsafe for use in food (e.g., ethylene glycol to increase perceived body, Chapter 28). An additional distinction can be made between true additives versus processing aids [2]:

• Additives describe compounds that are expected to stay in the finished product to exert their effect (e.g., bisulfite, tartaric acid).
• Processing aids are substances that are added during processing but remain at undetectable or insignificant concentrations in the finished product, either because they are removed intentionally, are converted into other naturally occurring substituents, or else were present at minimal concentrations throughout processing. Some processing aids leave traces that are problematic for a segment of the population, such as allergenic protein fining agents (Chapter 26.2).

Figure 27.1 Flow chart showing the distinctions among additives, processing aids, and adulterants

Regulations that allow for additions will usually specify additional restrictions regarding usage, which may include:

• The maximum allowable addition and/or the maximum residual amount in the finished wine.
• A description of when the addition may take place (e.g., before fermentation versus in the finished wine), or the types of conditions that the material may be used to remedy.
• Limits on impurities, origins, or methods of preparation of the materials.

Such restrictions can be seen in the following specific examples from different regions. Acacia (gum arabic) is approved for use in the United States (27 CFR 24.246) [1] at concentrations up to 1.92 g/L to stabilize wine by preventing potassium bitartrate precipitation (Chapter 26.1). Other uses, such as improving mouthfeel, are not stated and thus not allowed. Ferrocyanide fining (Chapter 26.2) is legal according to Australian and New Zealand regulations (Standard 4.5.1) [3] but winemakers are required to leave residual iron in the wine after treatment (as an assurance that the wine is not overfined, Chapter 26.2). Furthermore, among a multitude of other limits, OIV regulations (International Oenological Codex) [4] stipulate a maximum level of free cyanide upon testing a solution of potassium ferrocyanide.

Finally, most wine regions require that winemakers record the identity, amount, and date of any material used during winemaking (with the exception of filtration aids), and that this information be available for audit. The reason for this is not just to ensure that only approved materials are used, but also to provide for traceability of the use of specific additive lots and to account for any losses of what amounts to a highly taxed and regulated product.

27.3 Additives and processing aids: functions and comparison across regions

The function of most additives and processing aids fits into one of the following four categories, although a few processing aids fit into more than one:

• Antimicrobial. The major antimicrobial agent used in wine production is SO₂ (usually added as potassium metabisulfite, Chapter 17), which displays efficacy against a broad spectrum of microorganisms. Other antimicrobials are often more selective: sorbic acid is effective against yeast but not lactic acid bacteria (LAB), and the converse is true for lysozyme. The antimicrobials are additives except for the processing aid dimethyl dicarbonate (DMDC), which is a broad‐spectrum sterilizing agent; where legal it may be added to wine (or other beverages), typically at concentrations up to 200 mg/L. The activity of DMDC is believed to result from its electrophilicity and ability to react with a broad range of nucleophiles, including thiols and amine groups in the active sites of enzymes [5]. The half‐life of DMDC in model wine is ~ 30 min at room temperature, as it will react with other wine components to yield less harmful products in insignificant amounts, for example, with water to produce methanol and CO₂ (Figure 27.2). As a result, DMDC is typically only used just prior to bottling to ensure a sterile product (particularly for sweeter wines that are more prone to spoilage).
• Stabilizing, clarifying, and purifying. Most of the materials in this category are fining agents that serve as processing aids (Chapter 26.2), although an important exception is inhibitors of potassium bitartrate precipitation like gum arabic that function as additives (Chapter 26.1). Materials to prevent oxidation are also in this category, which includes both inert gases as well as antioxidant additives (such as SO₂ mentioned above, Chapter 24).
• Correcting natural deficiencies of the must or wine. Regions may allow for the addition of sugar, acid, tannin, and water, although the timing and extent of these adjustments can vary across regions and within a region. For example, in the United States, federal regulations allow for amelioration of must or wine with sugar, acid, and water up to 35% by volume, so long as the titratable acidity does not fall below 5 g/L (27 CFR 24.178). However, the state of California Administrative Code (Section 17010(a)) does not allow for sugar additions, and allows water addition to musts to “facilitate winemaking,” including to decrease the potential alcohol content of must and prevent stuck fermentations.
• Yeast nutrients and microorganisms. Regions generally allow for inoculation with yeast and LAB, and for addition of some nutrients, particularly those most often deficient in grape juice, like yeast assimilable nitrogen (often in the form of diammonium phosphate, Chapters 5 and 22.3).

Figure 27.2 Reaction of dimethyldicarbonate (DMDC, left) with water to yield methanol and carbon dioxide

The materials approved for use in each country are found in regulations associated with wine production. Differences among regulations and the resulting impacts on trade have been reviewed [6]. With a few exceptions, the lists tend to be similar, although the names or specific forms or amounts of active compounds may vary; for example, both the citrate and sulfate salts of copper are permitted in Australia, but only copper sulfate is permitted in the United States. Several databases are available for accessing or comparing up‐to‐date regulations in a more convenient fashion, including FIVS‐Abridge and the Australian Wine Research Institute (AWRI) – Permitted Additives and Processing Aids databases.

A comparison of allowed additives and processing aids is shown in Table 27.1 for three sets of regulations: 27 CFR 24, subparts F and L, of the United States of America [1]; Standard 4.5.1 of the Commonwealth of Australia [3]; and the Oenological Codex of the International Organization of Vine and Wine (OIV) [4], which had 46 member countries as of 2015. As a caveat, many subregions or appellations within these larger jurisdictions will often have more stringent regulations that would disallow specific additions, as was described in the case of water and sugar additions in California.

Table 27.1 Comparison of permitted materials for winemaking according to OIV, Australia, and US regulations. Additions of water, juice, sugar, distilled grape spirits, and active microorganism cultures are also permitted, but are not included in this table. Category: M = preventing microbial spoilage; S = stabilizing, purifying, or clarifying wine; C = correction of natural deficiencies; N = fermentation nutrient; P = processing aid, does not remain in wine. Regulations: A = Australia; U = United States; O = OIV; Blank = permissible under all three jurisdictions at the time of printing

Reference	Additive/Aid	Category					Major uses	Regulations
		M	S	C	N	P
26.1	Acacia (gum arabic)		x				Inhibit tartrate precipitation
9, 24	Acetaldehyde		x			x	Color stabilization (polymeric pigment formation), but only in juice prior to concentration	U
26.2	Activated carbon		x			x	General fining agent
26.2	Albumen (or whole egg whites)		x			x	Polyphenol removal
	Argon	x	x				Protection of wine from oxidation	A, O
22.2	Ammonium salts, e.g., (NH4)2PO4 or (NH4)2SO4				x	x	Nitrogen source. Specific salts allowed can vary among countries
24	Ascorbic acid, erythorbic acid		x				Antioxidant
26.2	Bentonite		x			x	Protein removal, settling aid (helps lees compaction)
3, 26.1	CaCO3		x	x		x	Deacidification, tartrate stabilization
22.2	Ca pantothenate				x		Vitamin B5 supplement	A, U
26.1	Carboxymethyl cellulose salts		x				Tartrate stabilization	A
3	CaSO4			x			Lowering pH in production of sherry‐type wines	U
	CO2	x	x				Protection of wine from oxidation; flavor
26.1	Ca tartrate		x				Seeding for Ca tartrate stabilization	A
26.2	Casein	x					Polyphenol removal
	Chitin‐glucan		x				Fining of metals and other components	O
	Chitosan	x	x				Fining of metals and other components; antimicrobial (Brett.)	A, O
3, 22.1	Citric acid	x		x			Acidulant
10, 26.2	Cu (II) salts (sulfate, citrate)		x				Removal of odorous H2S and mercaptans, cupric citrate allowed in AUS, OIV
	Defoaming agents (e.g., PDMS)					x	Control of foaming during fermentation
	Dimethyldicarbonate (DMDC)	x				x	Broad‐spectrum antimicrobial, forms methanol and CO2 upon hydrolysis
	Enzyme – amylases					x	Conversion of starch to fermentable sugars
2, 19	Enzyme – carbohydrases (pectinases, hemicellulases, cellulases)					x	Increase juice extraction, clarify and stabilize wine
	Enzyme – catalase and glucose oxidase (GOX)	x				x	Glucose removal by enzymatic conversion to gluconic acid; process forms H2O2 which can be removed by catalase	U
	Enzyme – lysozyme	x					Active against LAB
5	Enzyme – protease		x			x	Protein stabilization	A, U
5	Enzyme – urease		x			x	Removal of urea to prevent ethyl carbamate formation
	Ethyl maltol, maltol		x				“To stabilize wine” as a flavor enhancer; may not be used in vinifera wines	U
26.2	Ferrocyanides and FeSO4		x			x	Removal of copper or other metals, mercpatans
26.3	Filtration aids (diatomaceous earth, cellulose, etc.)			x		x	Assist in clarification
3	Fumaric acid	x		x			Acidulant, general antimicrobial	U
26.2	Gelatin/collagen		x			x	Polyphenol removal
	Cork granules		x			x	Flavor a	U
17	Hydrogen peroxide		x			x	Removal of excess SO2	A
	Ion‐exchange resins			x			Acid adjustment, considered a “process” in US
26.2	Isinglass/fish glue		x			x	Polyphenol removal
3	Lactic acid			x			Acidulant
3	Malic acid b			x			Acidulant
26.1	Metatartaric acid		x				Inhibit tartrate precipitation	A, O
26.2	Milk products (e.g., skim milk powder)		x			x	Polyphenol removal
24	N2	x	x			x	Prevent oxidation
25	Oak/oak chips					x	Flavor a
24	O2					x	Controlled oxidation
26.2	Phytates		x			x	Removal of transition metals	A, O
26.2	Plant proteins		x			x	Polyphenol removal	A, O
26.2	Polyvinylpolypyrrolidone (PVPP)		x			x	Polyphenol removal
26.1	Potassium bitartrate			x		x	Seed crystal for tartrate stabilization
3, 26.1	K2CO3/KHCO3				x	x	Deacidification, tartrate removal
17	Potassium metabisulfite (K2S2O7), SO2	x	x				Antimicrobial and antioxidant
26.2	Silica gel (SiO2)		x			x	Cofining with protein fining agents, assists with settling prior to filtration
18	Sorbic acid or K sorbate	x					Prevent yeast growth
22.2	Soy flour (defatted)				x	x	Nitrogen source	U
14	Tannin		x				Mouthfeel, cofining with protein fining agents
3, 26.4	Tartaric acid b			x			Acidulant
22.2	Thiamine				x	x	Vitamin B1 supplement
22.2	Yeast, autolyzed				x	x	Nitrogen, other nutrients; can bind inhibiting compounds
26.1	Yeast mannoproteins		x				Tartrate stabilization	A, O

^a The US Code of Federal Regulations states that oak chips and cork granules may be used to “smooth wine,” a fantastically ambiguous definition.

^b The US Code of Federal Regulations requires that tartaric acid be a “byproduct of wine manufacture,” but no such restriction applies to malic acid, which can be produced by chemical synthesis and be used as a racemic mixture.

References

1. 1. Title 27‐Alcohol, Tobacco Products and Firearms, Chapter I, Subchapter A, Part 24. Wine. United States Code of Federal Regulations, Washington, DC, 2015.
2. 2. Robin, A.‐L. and Sankhla, D. (2013) European legislative framework controlling the use of food additives, in Essential guide to food additives , 4th edn (ed. Saltmarsh, M.), The Royal Society of Chemistry, pp. 44–64.
3. 3. Australia and New Zealand Food Standards Code – Standard 4.5.1 – Wine Production Requirements. Australian Government, Federal Register of Legislative Instruments, 2014.
4. 4. International Oenological Codex. Organisation Internationale de la Vigne et du Vin, Paris, France, 2014.
5. 5. Golden, D.A., Worobo, R.W., Ough, C.S. (2005) Dimethyl dicarbonate and diethyl dicarbonate, in Antimicrobials in food , 3rd edn (eds Davidson, P.M., Sofos, J.N., Branen, A.L.), CRC Press, pp. 305–326.
6. 6. Juban, Y. (2000) Oenological practices: the new global situation. Bulletin de l’OIV (France) , 73, 20–56.

Notes

1 Most countries will allow for wineries to petition for the use of unapproved additions, particularly in cases where an addition is approved for use in other foods and also used in winemaking in other countries. Furthermore, countries will often have separate categories for wines that are produced with unapproved (but food-safe additives) so long as the wine is labeled appropriately, for example, “wine with natural flavors.”

2 As one example, The Rational Manufacture of American Wines, published by Osterreicher & Co. in 1872, describes the use of many modern wine additives, including tartaric acid, egg whites, isinglass (for fining), sulfur dioxide (through burning of sulfur wicks), and cellulose paper (as a filtration aid). Several other questionable – and currently illegal – additions are described, including glycerol, orris-root, butyric ether (aka ethyl butyrate!), and sulfuric acid. A chapter on “compounding” to simulate prestigious European wines like red Bordeaux is also included.

3 Similar statements can be made about approval of new winemaking processes, such as electrodialysis or reverse osmosis.