Method for tracing allergens in chocolate by DNA extraction protocols


The number of consumers affected by food allergies is constantly rising, and recent estimates indicate 5% of adults and 8% of children. For example, almonds and nuts are responsible for several particularly dangerous reactions for this category of persons. In this respect, a recent study, conducted by a group of Portuguese researchers (Costa et al., 2015), compares the performance of different molecular techniques based on different DNA extraction methods, for tracing the presence of almond and nut allergens in complex matrices, like the chocolate matrices. The extraction protocols used were: CTAB–PVP (cetyltrimethylammonium bromide–polyvinylpyrrolidone), method with and without RNase, PVP method with and without RNase, and the Nucleospin kits available on the market.  The extracts were assessed by qualitative PCR and real-time PCR. Results showed that the Nucleospin protocol was the most reliable to trace the presence of allergens in chocolate, both for almonds and nuts. By high efficiency PCR, this protocol achieves a limit of detection of 0,005% (w/w), with a linear response. In conclusion the authors highlight that sensibility, key parameter for determining the presence of allergens in complex food matrices, is strongly dependent on the DNA extraction method. The studies carried out to date contribute to the development of reliable methods for controlling crossed contaminations along industrial transformation processes. However, more efforts are required to improve DNA traceability, very important for tracing allergens.


  1. Costa et al., Food Chemistry, 187, 2015, 469-476