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(1) In the food-processing industry, blanching is the processing of fruits and vegetables in hot water. This prevents them from darkening and makes the vegetable cells permeable to sugar molecules, which facilitates jam-making. Blanching is also used in the production of raisins and the withering of grapes in the production of sweet and ordinary wines. Blanching for one to three minutes shortens the withering process two to three times.
(2) In the tanning industry blanching is used to remove the residues of subcutaneous cellulose tissues from the lower (flesh side) of skins. After blanching, the surface of the flesh side becomes very smooth, and after dressing and glazing, it becomes lustrous. Skins are also blanched to achieve uniform thickness and to remove defects that cannot be removed by polishing after the application of coatings on the outer side of the skin.