Integrity of nuclear genomic deoxyribonucleic acid in cooked meat: Implications for food traceability

It is essential to isolate high-quality DNA from muscle tissue for PCR- based applications in traceability of animal origin. We wished to examine the impact of cooking meat to a range of core temperatures on the quality and quantity of subsequently isolated genomic (specifically, nuclear) DNA. Triplicate steak samples were cooked in a water bath (100 degrees C) until their final internal temperature was 75, 80, 85, 90, 95, or 100 degrees C, and DNA was extracted. Deoxyribonucleic acid quantity was significantly reduced in cooked meat samples compared with raw (6.5 vs. 56.6 ng/mu L; P < 0.001), but there was no relationship with cooking temperature. Quality (A(260)/A(280), i. e., absorbance at 260 and 280 nm) was also affected by cooking (P < 0.001). For all 3 genes, large PCR amplicons ( product size > 800 bp) were observed only when using DNA from raw meat and steak cooked to lower core temperatures. Small amplicons (< 200 bp) were present for all core temperatures. Cooking meat to high temperatures thus resulted in a reduced overall yield and probable fragmentation of DNA to sizes less than 800 bp. Although nuclear DNA is preferable to mitochondrial DNA for food authentication, it is less abundant, and results suggest that analyses should be designed to use small amplicon sizes for meat cooked to high core temperatures.