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The prevention of browning during drying by the cold dipping treatment of sultana grapes
Author(s) -
Radler F.
Publication year - 1964
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740151209
Subject(s) - browning , polyphenol oxidase , chemistry , sugar , ripening , food science , enzyme assay , phenols , horticulture , enzyme , botany , biochemistry , biology , peroxidase
The activity of an active polyphenol oxidase which is mainly located in the skin of sultana grapes decreases during ripening, but it is still active at full maturity. It is suggested that the browning of untreated grapes during drying is mainly caused by this enzyme. The dipping process, used to increase the drying rate, prevents browning, but it does not affect the enzyme or its activity directly. The drying rate is increased without a corresponding increase in oxygen uptake of the fruit, so that it is concluded that the enzyme is unspecifically inhibited by rising sugar concentrations, and not by components of the dipping solution. The prevention of browning of drying grapes can be achieved by an increased drying rate without dipping treatment. A mutant “Bruce's Sport” of the grape variety Thompson's seedless, which yields light‐coloured raisins, does not contain an active polyphenol oxidase, but contains similar amounts of phenols.