BRITISH scientists say they have found the formula for a perfect bacon butty, after 1000 hours and 700 variations of the beloved sandwich. The experts from Leeds University's Department of Food Science say the secret is in the crispiness of the bacon rashers, the BBC online reported. Four researchers tried different types and cuts of bacon, cooking techniques, types of oil and a range of cooking times at different temperatures. A shortlist was then tested with computers to measure the texture of the butties and 50 volunteers also judged each sarnie. The scientists found that two or three back bacon rashers should be cooked under a preheated oven grill for seven minutes at about 240C. The bacon should then be placed between two slices of farmhouse bread, 1cm to 2cm thick. "We often think it's the taste and smell of bacon that consumers find most attractive but our research proves that texture and the crunching sound is just as, if not more, important, said lead researcher Graham Clayton. The formula is: N = C + (fb (cm) . fb (tc))+ fb (Ts) + fc . ta, where N=force in Newtons required to break the cooked bacon, fb=function of the bacon type, fc=function of the condiment/filling effect, Ts=serving temperature, tc=cooking time, ta=time or duration of application of condiment/filling, cm=cooking method, C=Newtons required to break uncooked bacon.