Hi M & C,
There are several papers published that use DNA testing to confirm or refute labeled ingredients. If soy DNA is found in a soy free food, it could be because of contamination and not willful substitution. However, when labeled ingredients are not detected by DNA that is valid concern since this technology can pick up trace amounts.
My understanding is that quantitative DNA analysis is available but more costly. Recently a paper was published that used this method and found in some cases significant amounts of chicken in chicken free foods and in other cases did not find any chicken in foods labeled to contain chicken.
This same publisher was the one to publish the paper on the microscopic examination of dog chews. Similar to this one the authors compared what they saw under the microcop to what was reported on the label.
