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Listen to this siteMonday 29 September 2008
Study Duration : December 2006 to May 2008
Contractor : Campden and Chorleywood Food Research Association
Significant economic advantage can be gained by the illegal adulteration of fruit juices by deliberate dilution or extension of the product with cheaper alternative juices. A method to detect fruit juice adulteration is required to establish where fraudulent substitution has occurred and protect the consumer from these practices.
Two projects have been commissioned to carry out this work. The first aims to evaluate the feasibility of using a DNA based technique and capillary electrophoresis “lab on a chip” detection method to identify six fruit species: Apple, Blueberry, Elderberry, Grape, Pear and Pomegranate used in either fruit juice production or as potential adulterants. A separate project aims to detect adulteration of citrus fruit juices by transferring an existing DNA method to the capillary electrophoresis chip (see project Q01114)
The Agency has funded a number of recent projects focusing on transfer of DNA methods to a capillary electrophoresis “lab on a chip” platform. This is a simple, robust format for accurate sizing and quantification of DNA fragments and thus is suited for routine use by Public Analyst laboratories.
A Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) approach will be used to develop a database of DNA profiles that can distinguish the fruit species commonly used in fruit juice production and also potential adulterant fruit species. This method involves PCR amplification of a specific segment of DNA from each fruit species, followed by digestion of the DNA with restriction enzymes which cut the DNA to produce smaller fragments. A profile of restriction fragments, specific to each fruit species is produced and this can be used to identify whether that fruit is present in a fruit juice.
Results (only for completed projects):
A PCR - RFLP profile was successfully generated for all 6 fruit species (apple, blueberry, elderberry, grape, pear and pomegranate) based on amplification and digestion of a “universal” chloroplast gene target.
The RFLP profiles generated allowed successful discrimination of all the fruit species when tested on DNA extracted from fruit and leaf samples. The results also showed that within a single species there was little profile variation across the varieties tested, except for grape and pear. However, problems were encountered with amplification of the target gene from authentic juice extracts prepared from concentrate. A range of extraction methods were tested but consistent amplification of the target gene could not be achieved. PCR products were not of the expected size, multiple PCR product bands were frequently seen and products did not match the amplicons generated from leaf and fruit DNA. The failure to amplify the expected target could be due to genetic differences between fruit varieties used to produce the juice or may be a consequence of the process of producing juice concentrates which may cause degradation of fruit DNA. Further work would be needed to explore these possibilities.
Therefore the RFLP profiles generated could not be used to verify the authenticity of juice samples from concentrate, however the profiles could potentially be useful for investigation of authenticity of fruit based food products such as fruit puree or conserves.
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