Cut surfaces of fruit and vegetables often become dark because
Cut surfaces of fruit and vegetables often become dark because
dirty knife makes it dark
oxidation of tannic acid in the presence of trace of iron from the knife makes it dark
dust of the air makes it dark
none of the above.
Solution
When fruits and vegetables are cut, enzymes like polyphenol oxidase can react with tannins in the presence of oxygen, causing the production of dark-colored compounds. The presence of trace amounts of iron from the knife can further catalyze this oxidation process, leading to the darkening of the cut surfaces.