What is Potassium Polyaspartate? 

Potassium polyaspartate is the potassium salt of polyaspartic acid, produced from L-aspartic acid, which is a naturally occurring amino acid in wine, and potassium hydroxide (98% purity).

Studies have verified that potassium polyaspartate has stabilizing properties similar to those of the metatartaric acid (MTA) and carboxymethylcellulose (CMC), but is much more stable over time as well as filterable and unaffected by heat, which maintains the quality of the wine while increasing its cellaring or storage potential (shelf-life). Further, it does not have negative impacts on the sensory properties, such as colour, of the resultant wine. It is a completely biodegradable environmentallyfriendly alternative to traditional polyanionic materials. Compared with physical stabilisation techniques such as cold stabilisation, electrodialysis and ion-exchange resins, use of potassium polyaspartate is labour, energy and water efficient, and hence cost competitive.

What is Polyaspartic Acid? 

Polyaspartic acid (PASP) belongs to a class of polyamino acids. Polyaspartic acid is broken by the action of microorganisms, fungi, etc. due to the peptide bond on the main chain of its structure, and the final degradation product is ammonia, carbon dioxide and water which are harmless to the environment.

Therefore,Polyaspartic acid is widely used. It can be found in the fields of water treatment, medicine, agriculture, and daily chemical industry. As a water treatment agent, its main function is to inhibit scale and/or dispersion, and to have a corrosion inhibition effect. As a scale inhibitor, it is particularly suitable for inhibiting the formation of calcium carbonate scale, calcium sulfate scale, barium sulfate scale and calcium phosphate scale in cooling water, boiler water and reverse osmosis treatment. The scale inhibition rate of calcium carbonate can reach 100%. Polyaspartic acid also has a dispersing effect and can effectively prevent corrosion of metal equipment. Polyaspartic acid and organophosphorus corrosion inhibitors have synergistic effects, often with vinyl polymer dispersants (such as polyacrylic acid, hydrolyzed polymaleic anhydride, acrylic acid-ethyl acrylate-itaconic acid copolymer, etc.) The phosphine-based compound corrosion and scale inhibitors (such as HEDP, ATMP, PBTCA, etc.) are compounded into highly effective and multifunctional corrosion and scale inhibitors.

Structural Formula of Polyaspartic Acid
Biodegradability: Polyaspartic acid is a polymerized amino acid having a side chain of a carboxylic acid, and is a polymer obtained by shrinking an amino group and a carboxyl group of an aspartic acid monomer, and has two configurations of α and β. The polyaspartic acid fragments of the natural polyamino acid are all present in the form of α, and the majority of the synthesized polyaspartic acid is a mixture of the two configurations of α and β. The polyaspartic acid obtained by thermal polycondensation is broken by the action of microorganisms, fungi, etc. due to the peptide bond on the main chain of the structure, and the final degradation product is environmentally friendly water and carbon dioxide. The biodegradation rate of polyaspartic acid hydrogel in activated sludge was 76% at 28d.

Benefits & Application of Potassium Polyaspartate: the revolution in tartrate stabilization of wine

Studies have verified that potassium polyaspartate has stabilizing properties similar to those of the metatartaric acid (MTA) and carboxymethylcellulose (CMC), but is much more stable over time as well as filterable and unaffected by heat, which maintains the quality of the wine while increasing its cellaring or storage potential (shelf-life).

Further, it does not have negative impacts on the sensory properties, such as colour, of the resultant wine. It is a completely biodegradable environmentallyfriendly alternative to traditional polyanionic materials. Compared with physical stabilisation techniques such as cold stabilisation, electrodialysis and ion-exchange resins, use of potassium polyaspartate is labour, energy and water efficient, and hence cost competitive. Potassium polyaspartate is thus proposed for use as a stabiliser against tartrate crystal precipitation in wine (red, rosé and white wine), sparkling wine and fortified wine at a maximum use level of 100 mg/L, depending on the level of instability of the wine to be treated.

The European Food Safety Authority (EFSA) evaluated the safety of potassium polyaspartate as a food additive and in its opinion of 9 March 2016 (EFSA Journal, 2016)1 concluded that there was no safety concern from the proposed use in wine at a maximum use level of 300 mg/L and typical levels in the range of 100-200 mg/L. It has accordingly been approved and authorised for use as an additive for wine in the European Union (EU) in COMMISSION REGULATION (EU) 2017/1399 of 28 July 2017 amending Annex II to Regulation (EC) No 1333/2008 of the European Parliament and of the Council and the Annex to Commission Regulation (EU) No 231/2012 as regards potassium polyaspartate and COMMISSION DELEGATED REGULATION (EU) 2017/1861 of 2 August 2017 amending Regulation (EC) No 606/2009 as regards certain oenological practices).

To ensure consistency with international wine standards and to allow importation of wines, sparkling wine and fortified wines to which potassium polyaspartate has been added, it is requested to amend the table to section S15—5 of Schedule 15 Substances that may be used as food additives in the food category 14.2.2 Wine, sparkling wine and fortified wine to include potassium polyaspartate as an additive, at a maximum of 100 mg/L. To enable potassium polyaspartate to be added to Australian produced wine, sparkling wine and fortified wine, it is also requested that Standard 4.5.1 Wine Production Requirements (Australia only) be amended to include potassium polyaspartate in the Table to clause 3, at a maximum of 100 mg/L.

Tartrate stabilization is an important phase of winemaking process. The presence of tartrate crystals in bottle is not desired by consumers, so producers need to make this stabilization in a more reliable way.

Among the two possible strategies to achieve the stability, the subtractive and the additive, the latter is surely the most sustainable and respectful of the original wine composition: it consists in adding to wine substances that inhibit formation of crystals.

Based on these considerations, a major European project, Stabiwine, which involved many partners creating interesting synergies between different competences, was born in 2012. In 5 years of research, a new additive was developed, potassium polyaspartate (KPA), a stable polymer of L-aspartic acid, able to totally inhibit the formation of tartrate crystals even in highly unstable wines, without color loses and without effect on wine filterability.

After a long approval process that led to the inclusion of KPA in the list of food additives within the EU, on October 28, 2017, the EC Regulation no. 1961/2017 definitively authorizes the use of potassium polyaspartate (KPA) as oenological practice in the European Union.

The audiovisuals proposed in this item, presented in a module dedicated to this new additive at Enoforum 2017, describe the main strengths of this molecule.

KPA, the potassium salt of a polyamino acid produced from L-aspartic acid, has now been approved by the OIV for use in winemaking.