The effect of high temperatures on the stability of Potassium Polyaspartate (KPA)

By Karien O'Kennedy

The aim of the study was to evaluate the efficiency of different dosages of KPA over time in wines exposed to high temperatures. Potassium polyaspartate has recently been approved for use as an additive to wines to render them tartrate stable. It has a similar mode of action to metatartaric acid, mannoproteins and CMC in that it prevents tartrate crystal formation. In contrast to CMC it can be used on red wines since it does not affect wine colour.

Project layout:
  • Four different wines were used for the experiments that started in October 2016: two red wines (Chianti 2013 and Chianti 2015) and two white wines (Catarratto 2015 and Chardonnay 2015). 
  • Wines were filter-sterilised and KPA added in three dosages: 5, 10 and 15 g/hl to the red and white wines. CMC was added in the same dosages only to the white wines for comparison. Maximum recommended dosage by the OIV for both products is 10 g/hl.
  • The wines were all protein stable before addition of KPA and CMC.
  • Wines were exposed to three different temperatures: 30, 40 and 50°C for 15, 30 and 45 days.
  • The tartaric stability of the wines were measured before and after the treatments via a cold test as well as a conductivity test. 

Results:
  • All wines treated with KPA and a temperature increase over time showed increased conductivity levels. This is most likely due to loss of efficiency of the KPA or an overall change in the colloidal status of the wine as a result of the high temperature.
  • In two of the wines the highest dosage of KPA was not sufficient to guarantee tartrate stability when the wines were exposed to 50°C for 45 days.
  • Both white wines treated with CMC maintained conductivity values similar to the control kept at room temperature, regardless of increasing temperature and storage time.
  • In the cold test no crystals were observed for the CMC treatments.
  • In the 2015 Chianti and Catarratto, crystals were observed for the KPA treatments: 5 g/hl 15 and 45 days at 50°C, and the 15 g/hl 45 days at 50°C.
  • In the 2013 Chianti, crystals were observed for the KPA treatment:  5 g/hl 45 days at 50°C.
  • The Chardonnay was the most unstable after KPA treatments with crystals in all the 50°C treatments, regardless of KPA dosage as well as in the 10 g/hl 30 days at 40°C.

Significance of the study:

The study shows that in terms of heat stability CMC is more stable than KPA. However in most cases KPA treated wines can remain stable when exposed to temperatures of about 40°C for a few days. KPA therefore presents a very good alternative to traditional cold stabilisation in the case of red wine tartrate stabilisation.
   
Reference:

Canuti, V. et al. (2019). Effects of High Temperatures on the Efficacy of Potassium Polyaspartate for Tartaric Stabilization in Wines. Am J Enol Vitic. July 2019 70: 332-337. DOI: 10.5344/ajev.2019.18077

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