Can DNA samples be taken from food?
All mediums taken to mouth and on which saliva has been deposited may include DNA traces: candies, fruits–or fruit pits–ice cream sticks, chewing-gums, but also cigarette butts or cutlery, may be subject to analyses. There is one precaution to be taken with fresh fruit: once found, they must be quickly frozen. For instance, immediate freezing of an apple core taken at a crime scene will increase chances of finding DNA traces on it and of establishing a genetic profile.
From IGNA – Newletter january 2010