Authentication of prized white and black truffles in processed products using quantitative real-time PCR

Abstract

Truffles, such as Tuber magnatum and Tuber melanosporum, are greatly appreciated throughout the world, both as fresh fruiting bodies and as ingredients in processed products. Diagnostic methods are therefore required to check the identity of truffles in this kind of food. The present paper reports the application of microscopic and molecular techniques to authenticate truffle species in commercial products. Through the application of microscopic techniques, it has been possible to distinguish spores in a cream that could be ascribed to the truffle species (T. magnatum, the highest priced truffle) declared on the label and also spores of a less prized and aromatic truffle that was not indicated on the label. Good quality DNA was quickly obtained in a few hours using a kit generally employed for DNA extraction from soil. A new primer pair was developed to authenticate T. magnatum in commercial products and it was employed in a quantitative PCR assay (qPCR). T. melanosporum, which was neither indicated on the label nor recognized in the processed products containing truffles, was also detected in a cream and its amount was quantified by qPCR. This method can therefore be used to detect fraudulent practices and to protect the consumer of truffle delicacies.

Truffle Research in the Post-Genomics Era

“…Thanks to the development of kits employed for DNA extraction from soil microorganisms in the era of metagenomics, which is the study of genetic material recovered directly from environmental samples (first developed for aquatic environments but soon turned to the complex environment of the soil, Venter et al 2004), good quality DNA can be obtained in a few hours from a complex matrix such as soil. Since the matrix of processed food is likewise complex because of the presence of PCR inhibitors, a fast DNA kit for soil has been validated by Rizzello et al (2012) as a reliable tool for DNA extraction from processed products containing truffles, such as cream-and butter-based products. Beside this, Rizzello et al (2012) set up a quantitative PCR protocol to authenticate and quantify T. magnatum (patent N. 1408735, Mello et al) and T. melanosporum in different food matrices below the average limit of detection of conventional PCR, which was 0.032 ng/μl.…”

“…Since the matrix of processed food is likewise complex because of the presence of PCR inhibitors, a fast DNA kit for soil has been validated by Rizzello et al (2012) as a reliable tool for DNA extraction from processed products containing truffles, such as cream-and butter-based products. Beside this, Rizzello et al (2012) set up a quantitative PCR protocol to authenticate and quantify T. magnatum (patent N. 1408735, Mello et al) and T. melanosporum in different food matrices below the average limit of detection of conventional PCR, which was 0.032 ng/μl. The optimized assay revealed the incorrect labelling of some processed products that contained more but less aromatic species than those declared.…”

Ectomycorrhizal Fungi and Their Applications

“…A qPCR assay has been developed to authenticate and quantify T. magnatum and T. melanosporum in food matrices that have undergone intensive transformation processes, such as cream and butter (Rizzello et al 2012 ). This method is promising in detecting the incorrect labeling of processed products and can therefore be used to protect the consumer and to assess food quality.…”

Can the soil geology and chemistry analysis of a site predict the geographic origin of wild edible mushrooms (Porcini group)?

“…Molecular analysis of proteins and fatty acid profiles as well as DNA barcoding have been widely used to identify the origin of food products [29][30][31][32][33]. Although molecular techniques are theoretically informative and precise, they involve high processing costs and do not allow us to clearly distinguish product authenticity, i.e., the geographical site of origin.…”