Work

Development of a model to study browning caused by tyrosinase in grape must

Year: 2024

Type: article

Abstract: Enzymatic browning caused by polyphenol oxidases, tyrosinase and laccase, continues to be one of the main problems in winemaking. Therefore, wineries are very interested in studying the mechanisms of browning and procedures for decreasing the use sulphur dioxide. This research proposes a model to study tyrosinase activity from grape must using different substrates: one monophenol ( p -hydroxybenzoic acid), two diphenols (caftaric acid and (−)-epicatechin) and one triphenol (gallic acid). The kinetic constants of tyrosinase, Vmax and K M , indicate that caftaric acid is the best substrate for tyrosinase, followed in decreasing order by (−)-epicatechin, gallic acid and p -hydroxybenzoic acid. This last acid does not appear to be susceptible to browning by the action of grape must tyrosinase. The influence of pH, temperature and ethanol on grape must tyrosinase were also determined and the results indicate that tyrosinase Vmax increases when pH and temperature are higher and that the presence of ethanol reduces it. • A method to study the grape must tyrosinase activity is proposed. • This method has been proved with caftaric, gallic and p-hydroxycinnamic acids and (−)-epicatechin. • The kinetic constants, Vmax and KM, of grape tyrosinase have been determined for different substrates. • Caftaric acid is the best substrate for grape tyrosinase of all those studied • The influence of pH, temperature and ethanol on the kinetic constants have been studied

Source: Food Chemistry

DOI: 10.1016/j.foodchem.2024.141457