Chemical, enzymatic and physical characteristic of cloudy apple juices

Abstract

In this study cloudy juices from six apple cultivars: ‘Alwa’, ‘Fiesta’, ‘Gloster’, ‘Golden Delicious’, ‘Mutsu’ and ‘Pinova’ were characterized in respect of polyphenols content by UPLC, PME (pectin methylesterase) activity, color, viscosity, and stability of turbidity. Apple cultivar affected significantly the chemical, enzymatic and physical properties of juices. Total quantitated polyphenols ranged from 686.63 mg l-1 (‘Gloster’) to 988.63 mg l-1 (‘Alwa’), and polymeric proanthocyanidins were a dominant group of these compounds. All of products contained also high content of phenolic acids, mainly chlorogenic. The thermal treatment of juices did not cause a complete inactivation of pectin methylesterase. Taking into account the % of residual enzyme activity, the pasteurization was more efficient in the case of ‘Fiesta’ and ‘Pinova’ juices (13% and 14% of the initial activity, respectively). Examined juices were characterized by low values of a stable turbidity (18.07–37.75%), despite relatively high viscosity (2.40–9.60 mPas).