ABSTRACT
Truffles are certainly the most expensive mushrooms; the price depends primarily on the species and secondly on the origin. Because of the price differences for the truffle species, food fraud is likely to occur, and the visual differentiation is difficult within the group of white and within the group of black truffles. Thus, the aim of this study was to develop a reliable method for the authentication of five commercially relevant truffle species via Fourier transform near-infrared (FT-NIR) spectroscopy as an easy to handle approach combined with chemometrics. NIR-data from 75 freeze-dried fruiting bodies were recorded. Various spectra pre-processing techniques and classification methods were compared and validated using nested cross-validation. For the white truffle species, the most expensive Tuber magnatum could be differentiated with an accuracy of 100% from Tuber borchii. Regarding the black truffle species, the relatively expensive Tuber melanosporum could be distinguished from Tuber aestivum and the Chinese truffles with an accuracy of 99%. Since the most expensive Italian Tuber magnatum is highly prone to fraud, the origin was investigated and Italian T. magnatum truffles could be differentiated from non-Italian T. magnatum truffles by 83%. Our results demonstrate the potential of FT-NIR spectroscopy for the authentication of truffle species.
ABSTRACT
Truffles are hypogeous fungi mainly found in Europe and Asia. Due to their special aroma and taste, some truffle species are sold on the international market at an extremely high price. Among the economically relevant species, the white Alba truffle (Tuber magnatum) and the black Périgord truffle (T. melanosporum) are the most appreciated species. The fruiting bodies of the Asian black truffle are morphologically very similar to T. melanosporum, and those of the Bianchetto truffle (T. albidum Pico) are similar to T. magnatum, but are of little economic value. Highly valued species are adulterated with cheaper ones, especially. Because of this problem, the aim of this study was the development of methods for detecting possible admixtures to protect consumers from fraud. This study is based on seven different truffle species (117 fruiting bodies) from different growing regions. Additionally, selected truffle products were included. Using this material, a real-time PCR (polymerase chain reaction) assay allowing the detection and quantitation of Asian black truffles in T. melanosporum up to 0.5% was developed. In addition, a capillary gel electrophoresis assay was designed, which allows the identification and quantitation of different species. The methods can be used to ensure the integrity of truffle products.
ABSTRACT
Marzipan is a confectionary which is mostly offered in form of filled chocolate, pralines, or pure. According to the German guidelines for oil seeds only almonds, sugar and water are admitted ingredients of marzipan. A product very similar in taste is persipan which is used in the confectionary industry because of its stronger flavor. For persipan production almonds are replaced by debittered apricot or peach kernels. To guarantee high quality products for consumers, German raw paste producers have agreed a limit of apricot kernels in marzipan raw paste of 0.5%. Different DNA-based methods for quantitation of persipan contaminations in marzipan are already published. To increase the detection specificity compared to published intercalation dye-based assays, the present work demonstrate the utilization of a multiplex real-time PCR based on the Plexor technology. Thus, the present work enables the detection of at least 0.1% apricot DNA in almond DNA or less. By analyzing DNA mixtures, the theoretical limit of quantification of the duplex PCR for the quantitation of persipan raw paste DNA in marzipan raw paste DNA was determined as 0.05%.
