Explanation:
According to https://oureverydaylife.com/lemon-juice-stop-apples-browning-21624.html it days that"
Chemical Reaction
Once added to sliced apples, the ascorbic acid, or vitamin C, in lemon juice creates a barrier between the oxygen and the polyphenol oxidase. Until the lemon juice has evaporated or been completely absorbed, the oxygen reacts with the ascorbic acid, preventing the apple from turning brown".
