Citrus fruit keep exceptionally well, staying juicy for weeks, but the skins will wrinkle after about a week, so if you want to use the zest, use it within a few days. The skins of citrus fruit are coated in a light wax to prolong their lifespan. Although it's tasteless and harmless, it's still advisable to rinse fruit in warm water before using the fragrant zest - if you're worried, it is possible to buy unwaxed citrus fruit. Some unwaxed citrus fruit are sold in sealed plastic pouches to reduce dehydration; these are best stored in the fridge and used speedily. Waxed fruit will be quite happy in the fruit bowl. Once squeezed, fresh citrus juice should be used the same day to reap its lively benefits.