Apple pie's most notable ingredients might include a flaky crust, a sprinkle of aromatic cinnamon and plump apple slices. One small, but important constituent of traditional apple pies and tarts is lemon juice. Tart and acidic, lemon juice balances the sweetness of an apple pie as it keeps the sliced apples from discoloring due to oxidation. Lemon juice substitutes must also keep apples looking fresh as they add a tart note to the pie's flavor.
Cider vinegar comes from apples, so its tangy flavor goes well with fresh apples. Lemon juice and cider vinegar have a similar acidity, but vinegar's more pronounced acidic flavor comes from its high concentration of sour-tasting acetic acid. Like lemon juice, cider vinegar will keep sliced apples from turning an unappetizing brown. When substituting apple cider vinegar for lemon juice, use half the amount the recipe requires and replace the remaining volume with water. For example, if a pie requires 2 tbsp. of lemon juice, add 1 tbsp. each of cider vinegar and water instead.
Dark and pungent, commercial balsamic vinegar imparts sweetness and tartness to an apple pie. Substitute commercial balsamic vinegar in a 1-to-1 ratio with the recipe's specified quantity of lemon juice. Although the rich, syrupy product Italians call balsamico tradizionale also bears the name balsamic vinegar, its complex taste would overwhelm an apple pie; use standard or commercial balsamic vinegar, not the traditional sort.
Oranges readily double for lemons in an apple pie, although their juice is sweeter and less acidic. Orange juice has a sufficiently high concentration of citric and ascorbic acids to keep apples looking fresh in a pie or tart. Fresh-squeezed orange juice works as well as juice from a carton or concentrate. If the recipe calls for both lemon juice and water, double the amount of juice and subtract an equivalent amount of water to compensate for the oranges' lower acidity.
Although white wine lacks the acidity of lemon juice, it contains sufficient malic and acetic acids to preserve the appearance of an apple pie filling as it cooks. The elements that make up a good drinking wine are the opposite of those that make a good substitute for lemon juice; a harshly acidic wine may not charm oenophiles, but it comes closer to the acidity of lemon juice than a milder wine would. Use twice as much wine as the recipe calls for in juice to offset the wine's lower acid content. To compensate for the additional liquid, remove an equal amount of water or other liquid from the pie's recipe.