Answered by The Community. Making the world better, one answer at a time. You also perform analysis on food that is know to be a non-GMO food control so you can compare GM and non GM to give a valid result.n the grinding process, airborne particles can travel through the  air and contaminate samples of non-GMO foods. Also a mortar and  pestle that is not properly washed can t … ransfer minute sample. PCR  only needs ONE molecule of DNA to make amplified product.