you can try
$('.showFood').on('click', function () {
$('.showFood').removeClass('selected');// here remove class selected from all showfood
$(this).addClass('selected');// here apply selected class on clickable showfood
$('.targetFood').hide();
$('#food' + $(this).data('target')).show(function() {
$('#food' + $(this).data('target')).toggle("slide");
});
});