Draft Genome Sequences of the Black Truffles Tuber brumale Vittad. and Tuber indicum Cook & Massee

ABSTRACT Tuber brumale and Tuber indicum (Pezizomycetes) are two edible black truffles establishing ectomycorrhizal symbiosis with trees and shrubs. T. brumale is ubiquitous in Europe, and T. indicum is mainly found in China. Here, we present the draft genome sequences of T. brumale and T. indicum.

Hypobaric Packaging Prolongs the Shelf Life of Refrigerated Black Truffles (Tuber melanosporum)

Black truffle (Tuber melanosporum Vitt.) is a fine agro-food product known for its unique aroma and very limited shelf life (maximum of 5–7 days, room temperature). Hypobaric packaging at 30 kPa, a mix of 1% O2/99% N2, and 40% CO2/60% N2 were studied to prolong the shelf life of black truffle at 4 °C in sealed polypropylene vessels, compared to normal atmosphere. Epiphytic microbial population, firmness, weight loss, CO2 formation, and sensory properties were monitored weekly up to 35 days of storage and were related to the volatile profile. Principal components analysis revealed good correlation between the storage time and the decrease of firmness, and the increase of the microbial count and CO2 production. Only truffles stored under hypobaric conditions showed an acceptable quality after 14 days storage. Hypobaric packaging is a cheap strategy to prevent the swelling of vessels caused by respiration and can reduce the deviation from the high-quality level of the fresh product from one to at least two weeks.

Synthesis and ultrastructural observation of arbutoid mycorrhizae of black truffles (Tuber melanosporum and T. aestivum)

Arbutus unedo (the strawberry tree) is a Mediterranean shrub which forms arbutoid mycorrhizae with a variety of Asco- and Basidiomycetes. After the discovery of the mycorrhizal symbiosis between A. unedo and Tuber borchii, in this study, arbutoid mycorrhizae were synthetized in greenhouse with Tuber aestivum and Tuber melanosporum. Six months after inoculation, both species colonized the roots of all inoculated A. unedo seedlings, but mature mycorrhizae were only observed after 12 months. Ultrastructure analysis of Tuber arbutoid mycorrhizae was described for the first time, showing, as observed in typical endosymbiosis, a rearrangement of host cells and the creation of an interface compartment with both truffle species. Immunolabelling experiments suggested that pectins are not present in the interface matrix surrounding the intracellular hyphae. Thus, the ability to establish symbiosis with A. unedo seems to be a common feature in the genus Tuber, opening up the possibility to use this plant for mycorrhization with valuable truffles. This could represent an important economic opportunity in Mediterranean areas by combining the production of truffles, edible fruits and valued honey.

Food Authentication: Identification and Quantitation of Different Tuber Species via Capillary Gel Electrophoresis and Real-Time PCR

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.

Identification of Soils Factors Influence in the Distributions of Tuber aestivum in Transylvanian Subcarpathian Hill, Romania

Truffles are one of the most hunted varieties of mushrooms in Europe due to their high price and their increasingly frequent use in the kitchen. As demonstrated by several studies, soil conditions are among the main factors that influence the spread and development of the black truffle species. The purpose of this study was to identify the soil factors which directly and indirectly influence the distribution of black truffles (Tuber aestivum Vittad.) in Romania and to identify the areas from the Subcarpathian Hills of Transylvania which are highly favourable to their existence and growth, using G.I.S. spatial analysis and databases which include soil characteristics (soil type, texture, gleization, stagno-gleization) and territorial localisation through GPS points indicating the samples of Tuber aestivum. By implementing the statistical model of spatial analysis (BSA – Bivariate Statistical Analysis) for each characteristic, a series of areas were classified into three classes of favourability (low, medium, high) for the growth of Tuber aestivum. The results were validated indirectly by comparing the overlapping of the areas from the high favourability class with the areas covered with tree species from the Quercus genus and directly, through field research (on the surfaces with maximum favourability), done by specialised truffle seekers. The results were validated with a very high confidence rate for both methods (method 1 - overlapping of approximatively 93%, method 2 - Tuber aestivum was identified on 12 out of 15 test surfaces from the high favourability class).

Identification of volatile flavour components of Tuber melanosporum using simultaneous distillation-extraction

Black truffles are famous for their unique flavours. Headspace solid-phase microextraction and the electronic nose have been used to analyse their flavours in some investigations. In a previous work, the volatile flavour compounds in black truffles harvested in China were extracted using simultaneous distillation-extraction (SDE) and analysed using gas chromatography-mass spectrometry (GC-MS). Extraction conditions were optimised in that previous study and are now applied in the present work. The temperature of the solvent flask was maintained at 70°C using a water bath and the samples were placed in boiling water; extraction time was 3 hours. Fifty-seven volatile flavour compounds were tentatively identified, including seven alcohols, two acids, six esters, 12 aldehydes, 14 ketones, two phenols, six pyrazines, six sulphur compounds and three other components. Aldehydes and ketones were present at the highest levels.