Scorzone, the Italian summer truffle

Historical roots: from ancient Rome to modern gastronomy

Like all hypogeous fungi, the summer truffle has been the subject of millenary legends and traditions. In theancient Greece it was considered the fruit of lightning striking the wet earth, while the Romans regarded it as a symbol of fertility and power, destined for patrician tables.

The summer truffle has always had  a popular connotation compared to the white or precious black truffle, as it grows spontaneously in numerous wooded and hilly areas of the Mediterranean basin. In the Middle Ages, in many Italian regions – especially in the central Apennine area – it was gathered and consumed locally by rural communities as a complementary seasonal resource.

During the Twentieth century, with the development of the international truffle market, the summer truffle has gained increasing commercial importance, establishing itself as a significant resource both for the restaurant industry and the food processing industry.

Genetics and taxonomy: the scientific truth about summer and hooked truffles

The summer truffle belongs to the family Tuberaceae and genus  Tuber, a group of hypogeous ectomycorrhizal ascomycetes that form subterranean fruiting bodies. For decades, the summer truffle (T. aestivum) and the  hooked truffle (T. uncinatum Chatin), harvested in the autumn period, have long been considered distinct species based on morphological and organoleptic differences: the first has a lighter gleba (hazelnut) and a more delicate aroma, while the second shows a darker gleba (chocolate) and a more intense scent.

Molecular analyses conducted by Paolocci et al. (2004) have however shown that  T. aestivum e T. uncinatum constitute a single biological species, with phenotypic variations determined by ecological rather than genetic factors. This discovery led the scientific community to use the name  Summer truffle as the official name of the species (having been first described by Vittadini in 1831), considering  T. uncinatum as a seasonal ecological variety of the same species.

Carpophore morphology

• Peridium: intense black, with pronounced and well-developed pyramidal warts, not transversely striated (unlike the precious black truffle, T. melanosporum);

• Gleba: light hazelnut or beige color in the summer form, dark brown with branched white veins in the autumn form (var. uncinatum);

• Dimensions: from 2 to 10 cm in diameter, variable weight from 20 to 200 grams, rarely higher;

• Aroma: delicate, with notes of undergrowth, hazelnut, and mushrooms, which intensify with maturation and in the autumn variety.

Biology and symbiosis: host plants of the ‘Tuber aestivum’

The summer truffle is a hypogeous fungus belonging to the class of Ascomycetes, which lives in ectomycorrhizal symbiosis with numerous tree and shrub species. The main host plants include:

• oaks (Quercus species, in particular  Q. pubescens e Q. cerris);

• hazel (Corylus avellana);

• hornbeam (Carpinus betulus e C. orientalis);

• linden (Tilia species);

• black pine (Pinus nigra);

• beech (Fagus sylvatica, at elevation).

Terroir and truffle cultivation: soil parameters for success

The  truffle terroir of  T. aestivum is characterized by specific pedological and environmental conditions. Research conducted by Todesco et al. (2019) on highly productive truffle grounds in France demonstrated that:

• the  soil temperature between 6 and 20 °C favors mycelium development, peaking around 20 °C;

• The  soil water potential (pF) optimum is around pF 2 (field capacity), but the species tolerates water stress up to pF 4-5 (wilting point). Practically, pF indicates the 'effort' the fungus must make to extract water from the soil: the summer truffle is a resilient species because it can hydrate even when the soil is very dry and water is strongly retained by soil particles;

• the  fungal DNA production in the soil varies monthly according to temperature and humidity, with summer peaks.

The recent study by Hilszczańska et al. (2024) published in  Journal of Fungi, conducted in Hungary on 3- and 6-year-old plantations, shows how the key factors for mycorrhization success include:

• Soil pH: optimal around  7,6 (slightly alkaline), tolerance from 6.5 to 8.5;

• Calcium carbonate content (CaCO₃): present but not necessarily high;

• Exchangeable calcium content (Ca²⁺): essential for mycelium development;

• Texture: well-drained soils, from silty to moderately clayey (clay up to 40%);

• Organic matter: high (up to 20%), with a C:N ratio around 20:1;

• Structure: good aeration and permeability.

The study also found that  Carpinus betulus shows the highest levels of mycorrhization (over 30%), while undesirable fungi such as  Suillus spp. (42.9%) and  Scleroderma spp. (31.4%) tend to prevail under slightly acidic pH conditions.

Climate resilience: the impact of global warming on yield

A significant study conducted by Steidinger et al. (2022) on 20 sites in Germany and Switzerland, published in  Global Change Biology, analyzed the impact of  climate change on the productivity of  T. aestivum. The results indicate that:

• each increase of  1 °C in summer temperature compared to the 30-year average causes an average decrease of  22% in fruiting body production;

• Summer thermal anomalies of  +3 °C can completely suppress fruiting;

• the reduction of  the growing season of host trees (1 day less) corresponds to a loss of about  22 grams of truffle per hectare;

• the increasingly hot and dry summers in Central Europe – as well as in Italy, adds the author – are significantly reducing truffle productivity.

These data highlight the  climate vulnerability of the species, despite its wide geographic distribution.

Production and harvesting process

The production process of summer truffle includes several phases:

1. Mycorrhization of host plants in nursery by spore or mycelial inoculation;

2. Plant of the natural or cultivated truffle ground;

3. Growth of the fruiting bodies in the soil, at  5-20 cm depth;

4. Harvest with trained dogs;

5. Cleaning, selection and classification by size and quality;

6. Marketing fresh or industrial processing.

Harvest calendar: seasonality and maturation

The summer truffle harvest season varies depending on altitude and latitude:

• summer truffle (T. aestivum s.s.): from  May to September, with quality peak in June-July

• hooked truffle (T. aestivum var. uncinatum): from  October to January, with optimal harvest between November and December

The seasonal overlap between the two ecological forms is common, and it is not unusual to find fruiting bodies at different stages of ripening in the same period.

Truffle economy: production areas in Italy

The summer truffle is present in much of the national territory, with particular concentration in:

• Marche: 23-25 tons/year of  T. aestivum/uncinatum (2024 data, Marche Agricole);

• Umbria: areas of Spoleto, Norcia, Valnerina

• Tuscany: hills of San Miniato, Mugello, Crete Senesi;

• Abruzzo: foothill and mountain belt;

• Emilia-Romagna: Tuscan-Emilian Apennines;

• Piedmont: Langhe, Monferrato;

• Lombardy: prealpine belt;

• Veneto: Lessinia, Euganean Hills;

• Trentino-Alto Adige: alpine valleys;

• Lazio: Simbruini, Prenestini Mountains.

Cultivation and sustainability

the  truffle cultivation In Italy it represents a sustainable and profitable agricultural practice. Scientific studies indicate that:

• truffle grounds cultivated with mycorrhizal plants can enter production after  4-5 years from planting (Todesco et al., 2019);

• the maximum production in well-managed truffle grounds can reach  200-320 kg/ha (exceptional cases in France);

• the  planting density vary from 200-300 plants/ha for Mediterranean soils to 600-1,000 plants/ha for cooler climates;

• the summer truffle promotes  agroforestry systems mixed, biodiverse and low chemical input;

• cultivation enhances  marginal lands and hilly areas, otherwise low-yielding, often abandoned.

Intended uses

The summer truffle is used in three main segments:

1. fresh catering: restaurants, delicatessens, direct sales;

2. export: mainly to France, Germany, Switzerland, USA;

3. processing industry: sauces, seasonings, pasta, preserves, flavored oils.

Usage guide: purchase, storage, and kitchen secrets

Attentive consumers are advised to:

• choose truffles  compact, dry e fragrant;

• avoid specimens  soft, moist or with  unpleasant odors;

• check for absence of  parasites o lesions obvious;

• prefer  medium sizes (20-50 g) for the best quality/price ratio.

To international buyers, the team of  GIFT (Great Italian Food Trade) offers technical and commercial support to get in touch and establish lasting relationships with selected suppliers of authentic Made in Italy excellent truffles.

Attention to the labels of processed products

The summer black truffle is the  reference biomass for truffle-based products (e.g. sauces, oils, creams) artificially flavored with a chemical aroma derived from methanethiol (2,4-dithiapentane), since it has a low cost compared to other species. Especially at the beginning of the season, when truffles are not mature, they cost less and have white flesh. However, it is precisely in this segment that the sensory deception for the consumer lies, as scorzone is used as a 'visual support' (the black bits in the sauce), while the smell is almost always chemical.

Conscious consumers are therefore advised to read very carefully the list of ingredients on the label of processed truffle-based products (e.g. sauces, oils, creams):

• ‘aromi’: the generic wording almost always indicates the presence of synthetic molecules (such as 2,4-dithiapentane), a petroleum/methane derivative that mimics the smell of truffle, masking its authentic organoleptic profile;

• ‘natural truffle aroma’: is the only wording that guarantees the natural extraction of the scent from the hypogeous fungus.

The true truffle is a complex experience, methane chemistry is only a one-dimensional and artificial odor (Mannina et al., 2012).

The ABC of cleaning and preservation

Many consumers make the mistake of treating truffles like a normal potato. Nothing could be more wrong. Here's how to preserve the aroma of the scorzone:

1. Cleaning: only at the time of use

The truffle must be cleaned only a few minutes before being consumed. The soil covering it acts as natural protection against oxidation and mold development.

Tools: Use a brush with semi-hard bristles (a dedicated toothbrush works well).

Technique: Run the truffle under a very thin stream of cold water. Absolutely avoid soaking, as the truffle is spongy and would absorb water, losing its aroma.

Drying: After washing, immediately dab the truffle with absorbent paper to dry it thoroughly.

2. Preservation: ‘breathing’ is fundamental

The truffle is a living organism that continues to emit gas and moisture. If sealed in an airtight container without precautions, it will rot within 24 hours.

The paper: wrap each individual specimen in kitchen absorbent paper.

The jar: place the truffles wrapped in paper inside a glass jar to store in the refrigerator at 2-4 °C for the shortest possible time (maximum 7 days).

Daily change: the paper must be changed every day. If it becomes wet, mold formation and decomposition will accelerate.

Gastronomic uses

The summer truffle is appreciated for its  versatility and the  delicate aroma, characteristics that make it suitable for both raw and cooked preparations. Typical pairings are:

• first courses: egg pasta (tagliatelle and tagliolini shapes), risottos;

• eggs fried eggs;

• white meats: scaloppine, chicken breasts, rabbit;

• fresh cheeses: ricotta, goat cheeses.

The summer truffle can be used both  raw (sliced or grated), and in  light cooking which enhance its aroma without compromising quality. The dosage recommended is 20-30 grams per serving of fresh truffle.

Conclusions

In an increasingly globalized market, the Italian summer truffle (Summer truffle) confirms itself as an excellence capable of combining environmental sustainability and profitability. Its ability to adapt to marginal soils makes it a key player in the European ‘Green Deal’, provided its quality is protected through conscious supply chain management. Choosing the authentic Made in Italy means supporting a unique ecosystem among humans, dogs, and nature.

Dario Dongo

Bibliography

• Hilszczańska, D., Szentgyörgyi, T., Bóna, L., Dancs, G., Merényi, Z., Takács, P., Varga, T., & Bratek, Z. (2024). Analysis of mycorrhization trends and undesired fungi species in three- and six-year-old  Summer truffle plantations in Hungary.  Journal of Fungi, 10(10), 696. https://doi.org/10.3390/jof10100696

• Mannina, L., Sobolev, A. P., & Capitani, D. (2012). Applications of NMR metabolomics to the study of foodstuffs: truffle, kiwifruit, lettuce, and sea bass.  Electrophoresis, 33(15), 2290–2313. https://doi.org/10.1002/elps.201100668

• Marche Agricole (2024).  White truffle, leadership of Marche at risk. https://www.marcheagricole.it/tartufo-bianco-a-rischio-la-leadership-delle-marche/

• Nahberger, T. U., Benucci, G. M. N., Kraigher, H., & Grebenc, T. (2021). Effect of earthworms on mycorrhization, root morphology, and biomass of silver fir seedlings inoculated with black summer truffle (Summer truffle Vittad.).  Scientific Reports, 11, 6167. https://doi.org/10.1038/s41598-021-85497-8

• Paolocci, F., Rubini, A., Riccioni, C., & Arcioni, S. (2004).  Summer truffle and  Tuber uncinatum: Two morphotypes or two species?  FEMS Microbiology Letters, 235(1), 109-115. https://doi.org/10.1016/j.femsle.2004.04.029

• Smith, S. E., & Read, D. J. (2008). Mycorrhizal Symbiosis (3rd ed.). Academic Press. https://doi.org/10.1016/B978-0-12-370526-6.X5001-6

• Steidinger, B. S., Büntgen, U., Stobbe, U., Tegel, W., Sproll, L., Haeni, M., Moser, B., Bagi, I., Bonet, J.-A., Buée, M., Dauphin, B., Martínez-Peña, F., Molinier, V., Zweifel, R., Egli, S., & Peter, M. (2022). The fall of the summer truffle: Recurring hot, dry summers result in declining fruitbody production of  Summer truffle in Central Europe.  Global Change Biology, 28(24), 7376-7390. https://doi.org/10.1111/gcb.16424

• Todesco, F., Belmondo, S., Guignet, Y., Laurent, L., Fizzala, S., Le Tacon, F., & Murat, C. (2019). Soil temperature and hydric potential influences the monthly variations of soil  Summer truffle DNA in a highly productive orchard.  Scientific Reports, 9, 12964. https://doi.org/10.1038/s41598-019-49602-2