Canola oil creates a moist, tender crumb; its mild taste doesn't interfere with the sweetness of carrots and currants or the ginger's bite. Be careful not to overmix the batter, as doing so can make the muffins tough. Substitute raisins for currants, if you prefer. You can freeze completely cooled muffins in a large zip-top plastic bag for up to two months. Thaw at room temperature, or heat in a microwave on HIGH for 20 to 30 seconds.