The Fungal Secret to Divine Dining: mVOCs and Truffle Aroma Unveiled
?? Kustrim Cerimi
PhD Candidate in Biotechnology | Fungi Enthusiast | Advancing in vitro cell culture systems to reduce animal testing in science | Seeking new challenges and opportunities for growth | Made in Kosovo | Kustrim without H
In this blog article you will learn amazing facts about one of the most desired and expensive foods in the world, Truffles!
by Yasmin Nold, Maria Kuzminskaya, Arthur Bilinsky and Hoang Le Nguyen
What do Gordon Ramsey, Louis XIV and a pig have in common??
They all like to eat truffles, of course! This is no surprise since truffles have long been revered by chefs and food lovers alike, earning them the nickname "diamond of gastronomy" or "the Mozart of mushrooms" [1]. Known for their distinctive aroma and flavour, they can enhance a wide range of dishes from pasta to sauces to desserts, which makes them not only a sought-after delicacy but also the most expensive food after saffron, caviar and oysters with prices ranging all the way from around $80 to $3400 per kilogram [2].?
Truffles are a type of edible fungus that belongs to the Tuber genus, with hundreds of different species found around the world. The most known and prized for their strongest aroma profile are black truffles like the Périgord black (Tuber melanosporum), and their milder sibling, the white truffle, like the Piedmont white (Tuber magnatum). Both can be found in Europe, especially France and Italy, where they are also cultivated in truffle orchards, the so-called “truffières”. Unfortunately, these attempts at cultivation did not manage to significantly lower their elite prices since the truffle is somewhat of a late bloomer: it takes between ten and twenty years to mature. This means that most truffles are still harvested from natural habitats with the help of the aforementioned truffle pigs or specifically trained dogs [3, 4].
But do not be fooled, the truffle is not as Europe-centric as it may seem. Different types of truffles can also be found in a place you wouldn′t expect them – in the desert. Black desert truffle genus like Terfezia or white desert truffle species like Tirmania nivea grow and thrive in the Middle East, North Africa and even the Kalahari Desert. These truffles differ from their European dark and knobbly cousins, more closely resembling potatoes than mushrooms and possessing a less powerful aroma. In addition to their bigger size, going as heavy as one kilogram per truffle, and more budget-friendly price, it makes them perfect additions to stews and rice dishes [5].?
There are, of course, many more truffle types on the market. Here is a list of most commonly sold truffle species and their common names [2]:
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But truffles’ legacy does not stop in gastronomy! They also have a fascinating history, wide social impact, and great significance in different areas of research, especially regarding the chemical of volatile organic compounds (VOCs) that give truffles their exquisite aroma.
VOCs and Truffles: Attraction and Manipulation
VOCs are small molecules that are, among others, produced by microorganisms such as bacteria, viruses and fungi like truffles and then released into the air. They are therefore the primary culprits for the truffle’s amazing aroma. Additionally, VOCs may also play a role in microbial communication and defence mechanisms, and they are being studied for their potential applications in fields such as medicine and agriculture.
Truffles in particular have been studied for their production of VOCs, as they are also vital for their survival. In this section, we'll take a closer look at the significance of truffle VOCs and their mechanisms.
Truffles are incredibly popular for their unique flavour, but before they end up on our plates, they have to be found and harvested, as they cannot be specifically cultivated through a faster process. Truffle hunting is a centuries-old tradition that involves the use of trained dogs or pigs to locate these elusive fungi by detecting specific VOCs like dimethyl disulfide, which cannot be smelled by human noses, but influence the aroma profile.
There are hundreds of different VOCs, but the common ones that also humans can smell are [6]:
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But did you know that truffle-hunting pigs were once preferred over dogs because of their superior sense of smell? However, this led to a hilarious problem - the pigs often couldn't resist eating the truffles once they found them! Nowadays, trained dogs are used instead because they have better self-control and are less likely to eat the valuable fungi. Plus, they're easier to handle and don't require as much maintenance as pigs [6].?
The hunt for truffles is not only an important part of culinary culture, but also an opportunity to learn about the symbiotic relationship between truffles and trees.
Truffles are mycorrhizal fungi, which means they form a mutually beneficial relationship with the roots of certain trees. In exchange for carbohydrates, truffles help trees absorb water and minerals from the soil. Truffles can even influence the root morphology and architecture of local trees to increase the success of encountering host plants or promising substrates. The very dominant Tuber melanosporum releases VOCs like ethylene and indole-3-acetic acid, which works as a potent herbicide. Other secreted VOCs, such as 1-Octen-3-ol, induces plant defence genes and can therefore increase the fitness of host plants, which is also beneficial for the truffle. In general, truffles and trees can communicate via VOCs to regulate their interactions and symbiotic living [8].
The life cycle of the symbiosis, as shown below, starts with spores from the fruiting body of truffles, which get dispersed by insects and mammals. The transported spores can germinate on a nutritious medium like the forest ground and start growing their mycelium, which will then interact with the tree roots to form the symbiotic relationship. It is critical for the survival of many tree species, as it allows them to thrive in nutrient-poor soils. Truffles are particularly important for the survival of oak trees, which are one of the most important tree species in the world. Oaks are keystone species that provide habitat and food for a wide range of animals, and they also help to regulate the climate by absorbing carbon dioxide from the atmosphere. Without the help of truffles, oak trees would struggle to survive in many regions of the world. For example, the holly oak, which is commonly found in Mediterranean regions and lives in symbiosis with the mycelium of black truffles (Tuber melanosporum), to overcome the harsh climate conditions in those regions [9].?
Truffles are an important part of the world of VOCs, both for their ecological significance and their economic value. The hunt for truffles is not only a cultural tradition, but also an opportunity to learn about the important symbiotic relationship between truffles and trees. As we continue to explore and understand the world of VOCs, it is important to recognize the significance of truffles and the role they play in the natural world. Now that we've explored the ecological and economic significance of truffles and their symbiotic relationship with trees, let's take a closer look at the history of these elusive fungi.
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Just as rich as the aroma - the history of truffles
It is surprising that truffles, an underground fungus, can be found in the desert. What is even more surprising is the fact that the long history of truffles actually began there as well. The first mentions of them can be traced back to the arid landscape of Syria and the civilization of Amorites.
Clay tablets dating back to 1760 BC contain personal letters of the last Amorite king, in which he complained about the quality of truffles he received, indicating that the king himself was a passionate truffle enthusiast. Therefore, it can be assumed that the truffle was considered a delicacy from the beginning of time.??????
This enthusiasm also carried over to the ancient Greek and Roman civilizations. The Greeks in particular went as far as exploring various uses of truffles, such as employing them as an aphrodisiac. Nonetheless, there were also doubts about the rare fungus which the Greek author Nicander described as “the evil ferment of the earth that men generally call by the name of fungus” around 185 BC [1].
The use of truffles in the Roman Empire was well documented in the famous Roman cookbook, De re coquinaria (The Art of Cookery). Six different recipes for truffles provide you with a glimpse into the Roman imperial cuisine and its use of truffles. This was also the time when the people wanted to know more about these mysterious yet delicious fungi. One famous myth from that time revolved around Jupiter throwing lightning bolts down to earth into oak trees to give birth to the rare truffle [1, 10].???
We take a big leap in time and jump to the Middle Ages which was truly a dark age for the truffle. People started to pick up on the thoughts of the ancient Greeks and grew sceptical of the rare fungus. The strange smell, the fact that they grew under the earth or in strange places near the dead earned them nicknames such as “witch's fares”, and “devil's creations”. The evil food was associated with witches and practically disappeared from sight [a,b]. This only changed at the end of the Middle Ages when historian and humanist Bartolomeo Platina reported on pigs that were used in the search for truffles in 1481 [1].
The revival of the truffle was finally completed with the arrival of the Renaissance where tastes became more important again. Especially Louis XIV's obsession with the exotic aroma brought them back to the rich and noble. The peak of the truffle popularity was in the mid-1800s when they were considered the jewel of cuisine by famous food writers such as Brillat-Savarin. Over 2000 tons were produced annually in Europe and they were a central feature of haute cuisine until much of the land that truffles grew on was destroyed in World War I and World War II [10, 11].
Nowadays, there are only a handful of places left where the growth of truffles still thrives which makes them truly a divine luxury and one of the most expensive spices in the world. The popularity of truffles may have passed its peak and is on the decline, but it is not yet finished. With the ongoing efforts to fully cultivate and grow truffles, we continue to discover new and exciting ways to use them. This ongoing development in the cultivation of truffles provides hope for the future of this prized delicacy.?
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From past to present - the social significance of truffles
As we now know, the history of truffles goes way back to ancient civilizations like Greece and Rome, but truffles were also prized in Ancient Egypt. The Roman philosopher Pliny the Elder even called them "the very highest delicacy of the table". After their slight dip in popularity in the Middle Ages, mostly due to truffles being wicked (or wickedly delicious), they had a big comeback in the Renaissance as a luxurious food item among the nobility in Europe [1].
Due to the rising demand, truffle hunting became a profession in France and Italy in the 19th century and is still practised today [1].
In France, truffle hunting is regulated by law and is limited only to licensed hunters. The hunting season typically runs from November to March, and during this time, there are strict rules around when and where truffle hunting can take place. In France, there are currently about 20,000 truffle farmers who primarily “hunt” Truffles in the regions of Dr?me, Vaucluse and the Alpes-de-Haute-Provence as well in Périgord and currently are responsible for almost 30% of world production [12].
Particularly in Italy, truffle hunting is considered a traditional endeavour; it involves a wide range of skills and knowledge (about climate, the environment and vegetation) related to the management of natural ecosystems and to the dog-truffle hunter relationship. This knowledge is passed on through oral traditions, including stories, fables, anecdotes and expressions that reflect the local cultural identity and create a sense of solidarity within the truffle hunting community [13].
Therefore it is no wonder that there are certain ethics and rituals associated with truffle hunting and is even considered a sacred tradition in some regions of Italy. There are strict rules around how it should be conducted; for instance, hunters are required to ask for permission before entering someone else's truffle grounds and are expected to respect the environment by not damaging trees or disturbing wildlife.
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But because of their high value and high demand not everyone is concerned with those ethics and the prospect of quick money leads to the emergence of criminal energy, as this example shows:
Conflicts in truffle hunting [14]
Nonetheless, truffle hunting is also associated with popular feasts that mark the beginning and end of the truffle season and is for instance highly celebrated in Alba, Italy at the International Alba White Truffle Fair, which is one of the main showcases of Italian gastronomy that includes the truffle world market, folklore events and cooking shows [15].
Since the demand didn’t lessen, the cultivation of truffles became a more and more favourable endeavour and was first attempted in the early 20th century. Although at the time it had little success, the development of modern cultivation techniques in the 1970s made it more profitable; hereby the truffle farmers inoculate the soil with truffle spores and use specific types of trees to encourage truffle growth [1].
Nowadays China is the largest producer of mushrooms and truffles worldwide, as you can see in the table below. Although they are also found in the wild, the majority of them are cultivated on farms, with Sichuan, Yunnan and Tibet being the biggest exporters of truffles [1].
Top 10 of the mushroom and truffle producers world wide (2016) [19]:
Even though they seem similar to the French and Italian black truffles, they are said to have an inferior flavour and taste [17].
This seems to be connected to the widespread urbanisation and industrialization that occurred in China since 1989, which has led to the destruction of much of the natural habitat of the truffle and other plants. As a result, farmers and harvesters have resorted to unsustainable practices in an attempt to save the truffle industry. These practices, such as aggressive techniques like hoeing to pull up truffles, have caused a reduction in the truffles' colony growth. Additionally, harvesting the mushrooms before they are fully matured prevents smaller truffles from developing the flavour and aroma of their superior counterparts. The use of chemicals and inferior soil composition further exacerbates the problem, limiting the growth of truffles and interfering with their taste and nutrient content [18].
In conclusion, truffles are much more than just a highly valued ingredient in the culinary world. The science behind their unique aroma profile makes them incredible survival specialists, manipulating the various trees and plants they form a symbiosis with and attracting many insects and mammals to disperse their spores.?
No wonder humans have been fascinated by truffles and their many possible uses in gastronomy and medicine for centuries, studying possible ways to cultivate them and create even more products with the enticing truffle aroma.?
So, the next time you go out for a fancy meal or decide to try something new in the kitchen, we hope you remember the rich history behind truffles – all the kings, naturalists and gastronomists – that influenced our perception of these expensive fungi and which VOCs are responsible for their incredible aroma profile.
Bon Appétit!
Your Yasmin Nold, Maria Kuzminskaya, Arthur Bilinsky and Hoang Le Nguyen.
Did you like this post? Stay in touch for more upcoming blog posts on the fascinating topic of mVOCs! If you have any questions, comments or critics about this article, feel free to contact me or the authors directly.
Cheers,
Kustrim
Sources:
[1] Nowak, Zachary. 2015. Truffle: A Global History. London: Reaktion Books Ltd. https://press.uchicago.edu/ucp/books/book/distributed/T/bo20172366.html ?
[3] Lefevre, Charles, and Ian Hall. 2001. ‘THE STATUS OF TRUFFLE CULTIVATION: A GLOBAL PERSPECTIVE’. Acta Horticulturae, no. 556 (July): 513–20. https://doi.org/10.17660/ActaHortic.2001.556.75.
[4] Murat, Claude. 2015. ‘Forty Years of Inoculating Seedlings with Truffle Fungi: Past and Future Perspectives’.Mycorrhiza 25 (1): 77–81. https://doi.org/10.1007/s00572-014-0593-4 .
[6] Mustafa AM, Angeloni S, Nzekoue FK, et al. An Overview on Truffle Aroma and Main Volatile Compounds. Molecules. 2020;25(24):5948. Published 2020 Dec 15. doi:10.3390/molecules25245948
[8] Splivallo, Richard, Simone Ottonello, Antonietta Mello, and Petr Karlovsky. 2011. ‘Truffle Volatiles: From Chemical Ecology to Aroma Biosynthesis’. New Phytologist 189 (3): 688–99. https://doi.org/10.1111/j.1469-8137.2010.03523.x .
[9] Lee, Heayyean, Kyungmin Nam, Zahra Zahra, and Muhammad Qudrat Ullah Farooqi. 2020. ‘Potentials of Truffles in Nutritional and Medicinal Applications: A Review’. Fungal Biology and Biotechnology 7 (1): 9. https://doi.org/10.1186/s40694-020-00097-x.