Clarification of Wines Using Polysaccharides Extracted from Seaweeds

Abstract

The stabilization of wines often requires the use of negatively charged clarifying agents to remove proteins. The polysaccharides agar, carrageenan, and alginic acid extracted from seaweeds are negatively charged at low pH and can electrostatically bind and precipitate positively charged proteins from aqueous solutions. The objective of this study was to evaluate the capacity of agar, carrageenan, and alginic acid extracted from seaweeds to flocculate and precipitate proteins in wine. The flocculation and precipitation capacity of proteins by purified carrageenan, dried carrageenophytes, purified alginic acid, and dried alginophytes was 2-fold greater than that of agar and agarophytes. The greater flocculation capacity of carrageenan and alginic acid is likely the result of their greater number of free negative charges relative to those of agar. Although proteins were flocculated by seaweed polysaccharides, tannins were not adsorbed by agar, carrageenan, or alginic acid. The adsorption capacity of alginic acid was maximum at protein levels lower than 50 mg L⁻¹; however, carrageenan adsorbed and precipitated most proteins at concentrations surpassing 400 mg L⁻¹. The protein fraction adsorbed by agar, carrageenan, alginic acid, and seaweeds in Chenin blanc wine was also similar to the protein fraction adsorbed by bentonite. Collectively, results indicate that carrageenan and alginic acid might have a greater wine stabilization capacity than agar without modifying the tannin composition of wines.