Technical Yearbook 2024

NOVEMBER

WIKIMEDIA COMMONS (HTTPS://CREATIVECOMMONS.ORG/LICENSES/BY-SA/3.0/)

VINE AND WINE INNOVATION WATCH

The use of carrageenan in calcium tartrate and protein stabilisation of wines By Karien O’Kennedy

Introduction Calcium-induced instability has emerged as a significant problem in bottled wines due to compositional changes caused by global warming. The appearance of calcium tartrate (CaT) crystals at the bottom of the bottle negatively affects wine acceptability, and current stabilisation strategies that are effective in removing potassium bitartrate (KHT) crystals are often ineffective against CaT crystals. Tartrate ions (T 2- ), resulting from the dissociation of both carboxylic groups of tartaric acid, have a pKa2 of 4.34 in water and are typically present in low amounts in wine, which has a pH range of 2.8 - 4. Recently, research showed that the pH of Languedoc red wine has increased from 3.50 to 3.75 over 35 years. The ongoing climate change is causing a shift in the dissociation equilibria of acids in wine, leading to an increase in T 2- . In addition, global warming increases the amount of calcium ions (Ca 2+ ) in wine. This is because the increasing temperature results in hydric stress and changes in the water equilibrium in grapes. Researchers have found that calcium levels increase seven fold in stressed plants, likely due to calcium’s crucial role in regulating water absorption and water flow in the plasma

membrane of plant cells during drought. These factors contribute to the increased likelihood of CaT precipitation in bottled wine, which can impact consumers’ perception and potentially lead to a decrease in the value and price of wines. A concentration of 60 - 80 mg/L of calcium in wines is usually considered at risk of instability and precipitation, but this is not the only factor determining wine stability. Preventing CaT precipitation is challenging. Although ion exchange resins and electrodialysis are effective, they can affect wine’s chemical and sensory properties. While potassium poly-aspartate (KPA) is an available stabiliser that can prevent the precipitation of KHT, it is ineffective in preventing CaT precipitation. Currently, seeding with micronised CaT is the most effective approach for CaT stabilisation, but it is expensive and time-consuming. Therefore, research is focused on discovering new potential stabilisers that can reduce the likelihood of CaT

precipitation. Carrageenan

Carrageenan is a hydrocolloid derived from red seaweeds, characterised by disaccharide repeating units consisting of 3-linked-β-d-galactopyranoses and 4-linked-α-d

105

TECHNICAL YEARBOOK 2024