Methods for the Detection of Cannabis trace in cooked food

In this study, we aim to develop methods to detect trace Cannabis in cooked food. We compared the use of chemical method and DNA analysis. Firstly, the Cannabis materials were identified by the macroscopic features, presumptive colortesting, and then confirmed by TLC analysis in hexane-dioxane-methanol (7:2:1). This solvent system gave the best resolution for cannabinoid separation in our hands. Thirty-six samples of dried and fresh Cannabis leaves that were boiled in water for 5 min to 8 hr were subjected to TLC and DNA analysis. The results illustrated that all treated samples showed the same TLC fingerprints indicating the presence of (THC), (CBD) and (CBN). However, only the fresh marijuana leaves which were boiled for 5 min showed the 197-bp mitochondrial trnL-trnF PCR-amplified fragment. Hence, the results suggested that TLC technique is more robust for THC detection in processed Cannabis. In addition, DNA analysis which can be categorized as confirmation method for Cannabis detection seems to be limited when DNA from heat-treated materials were analysed. The experiment suggested that detection of heat-treated Cannabis is possible by TLC. In the future, we aim to test for the presence of Cannabis trace in food, particularly curries and noodle soup which Cannabis is often use as additives.