Development and Performance Evaluation of a New Test Kit for Quantifying the Degree of DNA Fragmentation.

BACKGROUND: PCR-based genetic testing of agricultural products and foods is widely used for detecting various analytical targets such as genetically modified organisms and food allergens. However, it is difficult to obtain accurate genetic testing results from processed foods because DNA is fragmented by heat and pressure during food processing. Thus we previously developed an analytical method to quantitatively evaluate the degree of DNA fragmentation for the purpose of quality control of genetic testing for processed foods. OBJECTIVE: Our previous analytical method requires four PCR primer sets, resulting in high reagent costs and heavy analytical workloads. Therefore, we attempted to develop an easy-to-use test kit for quantifying the degree of DNA fragmentation and to evaluate its analytical performance. METHODS: To simplify the analysis procedure, we used only two primer sets. In addition, no-fragmentation control templates were prepared to obtain stable measurement results. The precision of the simplified analysis was evaluated through blind tests among laboratories. RESULTS: It was confirmed that plant species and extracted DNA concentrations had little effect on analysis with the newly developed test kit. In addition, the analytical values indicating the degree of DNA fragmentation exhibited small variability among laboratories. CONCLUSION: We confirmed the high practicality of the developed test kit. Because DNA fragmentation in cells is a universal phenomenon, we anticipate that the test kit will be used not only for quality control of genetic testing but also for food testing, medical diagnostics and other applications in a range of fields. HIGHLIGHTS: The newly developed test kit enables quantitative evaluation of the degree of DNA fragmentation in a simple manner.

Real-time PCR Detection Methods for Food Allergens (Wheat, Buckwheat, and Peanuts) Using Reference Plasmids.

Specific and sensitive real-time qualitative polymerase chain reaction (PCR) methods for the detection of food allergens including wheat, buckwheat, and peanuts were developed that could cancel between instrument effects and avoid risks of false-positives and false-negatives. In these real-time PCR analysis, the cutoff for determination of positive samples was set in every PCR run by using reference plasmids containing known copies of the target sequences. The copy numbers of the plasmids were used to detect the allergenic ingredients corresponding to 10 ppm (w/w) protein in highly processed foods (cooked for more than 30 min at 122 °C). Reference plasmid analysis for each real-time PCR run helped to minimize variability between runs and instruments (7900HT Real-Time PCR systems and Light Cycler Nano). It also helped to avoid false positives due to trace levels of contaminants from the laboratory environment or agricultural products. The specificity of the real-time PCR method was verified using 79 commonly used food materials and some of their relatives. The method was sensitive enough to detect those allergenic ingredients corresponding to 10 ppm (w/w) in seven types of incurred samples. The current official Japanese method was not able to detect the allergens in some of the incurred samples. The developed method can avoid false negatives due to lack of sensitivity and is useful to confirm positive ELISA screening tests.