Truffles (Tuber spp.) are symbiotic fungi that develop underground in association with plant roots. Food connoisseurs describe their scent as sensual, seductive and unique. These mysterious fungi, however, do not produce their aroma for the mere pleasure of humans. Truffle volatiles act as odorant cues for mammals and insects which are thus able to locate the precious fungi underground and spread their spores. They also freely diffuse in the soil and mediate interactions with microorganisms and plant roots, potentially regulating a complex molecular dialogue among soil fauna and flora. The aim of this review is to synthesize 30 yr of research on truffle volatiles, spanning fields of study from chemical ecology to aroma biosynthesis. Specific aspects of truffle volatile ecology and biology will be discussed, including which species have been studied so far and for what purpose, what ecological role has been demonstrated or speculated to exist for specific truffle volatiles, which volatiles are common or unique to certain species and what their biosynthetic route might be. Future challenges in truffle aroma research will also be addressed, focusing on how high-throughput post-genomic technologies may advance our understanding of truffle aroma biosynthesis and chemical ecology.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.2010.03523.x

Truffle volatiles: from chemical ecology to aroma biosynthesis

This review provides a synthesis, from published and unpublished sources, of records of mycophagy (fungus-feeding) by Australian mammals. Mycophagy is shown to be widespread among Australian mammals, paralleling the previously well-documented situation in North America. Mycophagy appears to be most prevalent within the Potoroidae (rat-kangaroo family) but has also been recorded for a variety of other mammals. Information is presented on the classification, morphology and ecology of the fungi consumed, on the nutritional benefits (or otherwise) of mycophagy, and on the role of mammals in spore dispersal. Fungi whose sporocarps are hypogeal (truffles, false-truffles and sporocarpic Endogonaceae) and which enter into mycorrhizal relationships with plants predominate among the species recorded in mammal diets.

Mycophagy among Australian mammals

Characterisation of aroma active compounds in black truffles (Tuber melanosporum) and summer truffles (Tuber aestivum) by gas chromatography-olfactometry.

Truffles (Tuber spp.) are ascomycete subterraneous fungi that form ectomycorrhizas in a symbiotic relationship with plant roots. Their fruiting bodies are appreciated for their distinctive aroma, which might be partially derived from microbes. Indeed, truffle fruiting bodies are colonized by a diverse microbial community made up of bacteria, yeasts, guest filamentous fungi, and viruses. The aim of this minireview is two-fold. First, the current knowledge on the microbial community composition of truffles has been synthesized to highlight similarities and differences among four truffle (Tuber) species (T. magnatum, T. melanosporum, T. aestivum, and T. borchii) at various stages of their life cycle. Second, the potential role of the microbiome in truffle aroma formation has been addressed for the same four species. Our results suggest that on one hand, odorants, which are common to many truffle species, might be of mixed truffle and microbial origin, while on the other hand, less common odorants might be derived from microbes only. They also highlight that bacteria, the dominant group in the microbiome of the truffle, might also be the most important contributors to truffle aroma not only in T. borchii, as already demonstrated, but also in T. magnatum, T. aestivum, and T. melanosporum.

The Role of the Microbiome of Truffles in Aroma Formation: a Meta-Analysis Approach

Results are presented that were obtained on the geographic traceability of the white truffle Tuber magnatum Pico. Solid-phase microextraction coupled to gas chromatography/mass spectrometry (SPME-GC/MS) was employed to characterize the volatile profile of T. magnatum white truffle produced in seven geographical areas of Italy. The main components of the volatile fraction were identified using SPME-GC/MS. Significant differences in the proportion of volatile constituents from truffles of different geographical areas were detected. The results suggest that, besides genetic factors, environmental conditions influence the formation of volatile organic compounds. The mass spectra of the volatile fraction of the samples were used as fingerprints to characterize the geographical origin. Next, stepwise factorial discriminant analysis afforded a limited number of characteristic fragment ions that allowed a geographical classification of the truffles studied.

P. Cabella

Papers

Bis-methylthiomethane, an odorous substance from white truffle, pico