Browning can be prevented by avoiding contact of oxygen with the substrate. A number of means are available to limit the activity of the phenol oxidase enzyme. This works by reducing the contact with air and thus slows down the browning reactions. Concentrated sugar solution also depresses enzyme activity. Boiling or steaming The boiling water or steam is used to inactivate the enzyme to control the browning.
Enzymes are proteins, easily denatured by heat as in blanching or cooking.
Hence browning does not occur in cooked fruits and vegetables. The activity of phenol oxidase, like that of all enzymes, is pH dependent. Altering the hydrogen-ion concentration of the fruit may effectively block its action. Lemon or other citrus fruit juice may be used, as may a solution of cream of tartar. A solution of ascorbic acid is effective in preventing browning.