In highly processed food products such as gelatin and gelatin containing
food and pharmaceutical products, DNA is degraded
into short fragments. This issue caused some difficulties in PCR
amplification as reported by earlier researchers (Mafra, Ferreira,
& Oliveira, 2008; Martín et al., 2007). The essential prerequisite
for PCR amplification is therefore obtaining sufficient template
DNA for analysis. For this reason, DNA isolation was performed
using a commercial kit under optimized column-binding conditions
adjusted for maximal recovery of short DNA fragments.
Many primers have been published based on both mitochondrial
and nuclear genes to trace either bovine or porcine DNA in a variety
of food products. In this experiment, to detect the presence of small
amounts of DNA in gelatin, primers were selected from conserved
regions of mitochondrial genes (cytochrome b). The high copy number
of mitochondrial DNA per cells and the probability of their survival
under different processing conditions ensure amplification of
the expected PCR products even in samples containing small
amounts of DNA (Rodriguez et al., 2004). Furthermore, primerbinding
sites were selected to amplify specific short fragments of
DNA, because of degradation due to gelatin processing.