juice of a peach? not likely!
fresh lemon juice (dilute or undiluted) does it: try and see how it works! Sure it works best on BU copper coins, rather be careful with worn ones, because lemon juice will remove oxydation altogether, result: your coin will look like an old spinster in freshly dyed hair...: quite unnnatural I'd say!
(Special tip: whenever you see British Cyprus BRONZE coins, which are advertised as BU but come in a reddish tone, you can be sure that they were polished like hell with lemon juice, lemon juice quite simply turning the original GOLDEN appearance of true BU Cyprus bronze coins into red!)