Truffles

24.05.17

Truffles are the edible fruiting bodies of fungi that grow underground (in a symbiotic relationship) attached to the roots of particular trees, commonly oak and hazelnut trees. Truffles are a gourmet food highly valued by the food industry around the world. Truffles are eaten fresh and also made into a variety of products including pasta, truffle honey and truffle mustard. Truffles have an estimated shelf life of three to four weeks but this can be lengthened through refrigerated vacuum storage and freezing.

Overview

The truffle forms during summer, grows in size through autumn and is harvested in winter when it has matured. The majority of truffles grown in Australia are the French black, or Perigord truffle grown in the cooler parts of Australia. The estimated production of truffles in Australia is 13,000kg with production slated to exceed 20,000kg by 2020. Truffles are harvested manually after trained dogs detect the strong perfume they emit at maturity.

Australian truffle production has benefited from being able to supply fresh truffles during the northern hemisphere off-season.

Facts and Figures

The main commercial truffle grown in Australia is the French black or Perigord truffle
The main producers of high-quality truffles are France, Italy, Spain and Australia
Truffles are the fruiting body of mycorrhizal fungi and form on the roots of oak and hazelnut trees that have been inoculated with the fungi
Starting with inoculated tree stock usually yields the first truffles four to seven years after planting with maximum yields at around 12-15 years
To locate truffles for harvesting, trained dogs are used to detect the intense aroma emitted by the truffle at maturity
The Australian Truffle Growers Association is the industry body in Australia

Production Status

There are an estimated 200 to 300 truffières (truffle orchards) established across the cooler parts of Australia. About 50-60 of these were producing truffles. Land under truffle production in Australia grew from 250 hectares in 2007 to approximately 600 hectares in 2012.

Truffières are found in all states and territories across Australia except the Northern Territory. Commercially producing truffières are located mainly in the Central and Southern Highlands and Southern Tableland regions of New South Wales, northern Tasmania, the central highlands and Gippsland regions of Victoria and the Manjimup region of Western Australia. However, there are truffières located as far north as Queensland but commercial viability has not been established in these locations.

Map of current and potential growing regions

Uses

Truffles are used as a food flavouring, commonly added directly in cooking or as a garnish. Perigord black truffles (the main truffle produced in Australia) are typically used to enhance the flavour of eggs or starchy foods like pasta and rice or shaved over these dishes immediately prior to serving.

A range of other food products are also produced including truffle butter, truffle mustard, truffle vinegar and truffle honey. The Burgundy truffle, which is not yet widely grown in Australia, can also be preserved in oil.

Production Requirements

Growing regions

Although truffle growing has been established as far north as Queensland, truffles are commercially harvested mainly in the temperate or mediterranean climates of southern Australia. Truffles have been harvested at Manjimup in Western Australia, in Northern Tasmania, in the Yarra Valley, the Otways, Central Highlands and parts of Gippsland in Victoria, the Australian Capital Territory and in the New South Wales Highlands and Tablelands from Jindabyne to Moss Vale and out to the central ranges including Oberon, Bathurst and Orange.

Truffles can be grown on flat or relatively steep land but the right climate, soil and water are important factors for good production.

Soil type

A range of soils are considered suitable from rich volcanic soils to poorly fertile granite soils. Soils high in clay or with a clay B horizon are generally considered unsuitable for growing truffles. Truffles require free-draining soils with a high pH at around pH 8 (pH_water). Liming is often used in Australia on soils of pH 6 or lower to raise the soil pH to required levels. The soil may also need to be managed to correct for other micro nutrient levels. A soil analysis is generally recommended to determine the soil profile and suitability. The knowledge about the full range of Australian soil and climate conditions suitable for growing truffles is still being refined. Some truffières have been established where the soil and climate are considered suitable, yet no viable yields have been achieved. Likely reasons for this failure include initial levels of inoculation on the tree roots, poor site selection and ongoing management of the truffle orchard. This a topic of ongoing research.

Climate

Truffles require hot summers and cold winters. As a general rule, a mean daily temperature of about 20°C in January and about 5°C in July is desirable. The cool climates of southern Australia provide the warm weather that is important for truffle initiation and cold winters that are important for truffle maturation. The truffle matures as the soil temperature decreases through autumn and winter and high-quality truffles are produced when there are regular cold periods.

A minimum rainfall of at least 700mm per year is desirable. There are critical times in the lifecycle of the truffle where the correct soil moisture levels are essential. For example, good rain in the summer months is required for good truffle growth. As different soils have different moisture retention rates, irrigation may be considered a necessity. Trees may also need to be drought-proofed, requiring a good water supply of surface or ground water (ensuring it is not too saline). Over-watering and no watering can both impact on truffle harvest quantities so careful consideration needs to be given to rainfall and irrigation resources.

Varieties

Truffles are produced when the root fungus (mycorrhiza) attached to the roots of trees in a symbiotic relationship, sexually reproduce. The fungus supplies the host tree with nutrients and the host tree supplies carbohydrates to the fungus. Trees are generally inoculated with truffle spores in a nursery and then planted. Both the species of truffle and tree need to be considered when purchasing trees for planting and production. The following is a list of truffle and tree species supplied in Australia. There are currently a number of truffle tree nurseries that supply trees inoculated with truffle spores and some of these nurseries are able to supply trees certified as inoculated and free of contaminating fungi (refer to Industry Bodies and Publications).

Truffle Species

French Black, or Perigord truffle – Tuber melanosporum – has a textured dark brown appearance with red reflections. The truffle is marbled with an aroma of forest undergrowth and damp earth mingled with roasted dry fruits. The taste can be described as finely peppered and long in the mouth. The Perigord is considered the finest grade of black truffle.

Burgundy or summer truffle – Tuber aestivum – has a lighter coloured appearance and is similar to the Perigord truffle but with a chocolate aroma and more pronounced flavour. This variety of black truffle is not as highly valued as the Perigord, but fruits earlier in the season.

Italian whitish or bianchetto truffle – Tuber borchii – colour ranges from pale yellow to reddish-brown. The truffle has a dark brown and white marbled appearance with a mild aroma and nutty flavour.

Tree Species

Evergreen or Holm oak – Quercus ilex – one of the main species grown in Australia for producing T. melanosporum. Can also be grown for producing T. aestivum.

English oak – Quercus robur &nash; one of the main species grown in Australia for producing T. melanosporum. Can also be grown for producing T. aestivum.

Cork oak – Quercus suber – grown for producing T. melanosporum.

Common Hazelnut – Corylus avellana – grown for producing T. melanosporum. Can also be grown for producing T. borchii.

Stone pine – Pinus pinea – grown for producing T. borchii.

Planting and crop management

Soil preparation will vary depending on soil type, pH and nutrient balance. To prepare for planting the soil should be ripped to a depth of at least 600mm and chisel ploughed to 200mm. Some recommend deep ripping to improve soil tilth, root development and water penetration and retention. Planting in early spring is recommended and new trees should be planted well away from existing trees as they may have ectomycorrhizal fungi which will compete with the truffle ectomycorrhiza. Installing trees guards is also recommended until the trees are established. Soil preparation, cultivation and management are subject to ongoing research to determine optimum management regimes.

Weeds, pests and diseases

For truffle production there are two considerations for pest and disease control – the host trees and the truffle fungus. For oak and hazelnut trees, the experience of established truffle growers is that these trees are generally disease and pest free. The use of insecticides and fungicides on the trees is avoided unless absolutely necessary as the chemicals may have a detrimental effect on the truffle fungus. However, weed control is important and developing a weed control strategy is considered essential to managing a truffière.

A major concern for truffle growers is the contamination of their crop from competing ectomycorrhizal fungi. Many Australian trees, including eucalypts, wattles and blackwoods and many introduced trees including willows, poplars and pines, host ectomycorrhizal fungi which then colonise the roots of inoculated truffle trees and replace the truffle fungus. Ectomycorrhizal fungi can also be transported by grazing animals. For this reason it is recommended that plantings are fenced to prevent these animals accessing the tree plantings.

Common to all truffle growing regions around the world is the presence of truffle rot. In Australia, truffle rot has caused crop losses of up to 50% on some properties. Research suggests that there are several factors contributing to the development of truffle rot: the fungal species Trichothecium crotocinigenum; truffles exposed at the soil surface; and consistently moist soil conditions from frequent irrigation.

Suggested techniques to manage truffle rot include managing irrigation for appropriate soil moisture and covering truffles that are forming too close to the surface. Further information on managing truffle rot can be found in the publications Identifying the Cause of Rot in Black Truffles and Management Control Options and Identification and management of the agent causing rot in black truffles – Part 2.

Infrastructure Requirements

The main infrastructure requirements for establishing commercial production of truffles are inoculated trees, irrigation and fencing. Tractors, mowers and labour are also required.

Cleared areas of land are required to ensure that plantings are set well apart from established trees to avoid contamination from other ectomycorrhizal fungi, commonly found on the roots of many Australian and introduced tree species.

Fencing is also required to prevent grazing animals access to the trees as they may transport other fungi and contaminate the ground around the truffle trees, or they may eat the truffles.

Harvesting & Processing

The edible part of the truffle is botanically a fruit that contains spores. It is located up to 30cm below ground and may weigh between 5g and up to 1.2kg. A truffle varies from a roundish to uneven lumpy shape and its skin colour depends on the species of truffle. Plantings using inoculated tree stock generally produce the first harvest in 4-7 years with maximum yield reached at about 12-15 years. In Australia, Perigord truffles are harvested from June to September using dogs that are specially trained to detect the aroma of mature truffles. Once the dog has marked the location of the truffle, the harvestor then digs the truffle out of the ground by hand.

After harvesting, truffles are cleaned and generally graded in accordance with the standard developed and adopted by The Australian Truffle Growers Association in 2012. A sanitary processing environment is required. To ensure maximum freshness, truffles are processed and delivered to restaurants or commercial sellers within 48 hours of being harvested. Truffles generally have a shelf life of 3-4 weeks but can also be vacuum packed or frozen to prolong this shelf life. Some growers also produce truffle products such as truffle butter and truffle honey.

Markets & Marketing

The growth of the truffle industry in Australia has been driven primarily by investment claims and investment schemes. The truffle industry believes there is potential for an increase in domestic demand as well as counter-seasonal exports to northern hemisphere markets. It is also believed that Australia is starting to benefit from proximity to the growing Southeast Asian markets. The Australian Truffle Growers Association has pricing information available online through its members only section and the general public can contact the Association directly for this information.

The export market is considered fundamental to the commercial viability of the Australian truffle industry. The distribution process is still evolving and there are some distributors but larger truffle producers generally manage the sale of their own crop, selling direct to restaurants, retail sellers and the general public (online) and at Growers’ markets. Wholesalers are also used to access the international markets.

Risks & Regulations

Risks/challenges

There is still uncertainty about the range of soil and climate conditions suitable for growing truffles in Australia. Some truffières have been established in many parts of Australia that were considered suitable but no viable yields have been achieved. Likely reasons for this failure include initial levels of inoculation, poor site selection and ongoing management of the truffle orchard. This uncertainty is one of the risks of truffle growing and is a topic of ongoing research.

Regulatory considerations

The Australian Truffle Growers Association has established voluntary grading standards for the sale of Black Perigord truffles for local and export market. These standards include minimum requirements for grading, packaging, transporting and labelling of truffles.

The Association has also established a tree certification system, and certified trees will be available to buyers. Suppliers of certified trees are identified on the Association website.

Publications

Emerging animal and plant industries: Their value to Australia RIRDC report (2014)

Identification and management of the agent causing rot in black truffles – Part 2 – RIRDC Report (2013)

Identifying the Cause of Rot in Black Truffles and Management Control Options – RIRDC Report (2012)

Taking Stock of the Australian Truffle Industry – RIRDC Publication (2008)

Increasing Productivity of Truffiers in Tasmania – RIRDC Publication (2004)

French Black Truffle Establishment and Production in Tasmania – RIRDC Publication (2001)

Other resources

Cultivation of black truffles in Western Australia – Western Australia Department of Agriculture and Food

Industry Bodies

Australian Truffle Growers Association – provides general information about truffle growing in Australia including workshops on establishing and managing a truffière and grading truffles.