There are a few studies on the effects of various storage treatments for most of the common edible truffles, as in Tuber magnatum and borchii or melanosporum and aestivum. Controlling biochemical and microbiological changes in order to evaluate possible alterations during truffle preservation.
The peridium of truffles has a high concentration of melanin that is difficult to degrade, so it’s a first layer of microbial protection. When we damage that peridium by the dog or the knife at harvest, we provide a path where bacteria come in and rot. So the first point to keep in mind is to avoid these initial damage.
A great work was presented at the conference Tuber2013 by Domingo Blanco: they have seen that in the truffle surface there are 100 million organisms per gram, so it is advisable a microbial surface disinfection.
Even Pseudomonas fluorescens found in the surface of truffles, usually take soil nutrients to help feed the truffle, but once the truffle has been harvested they operate in reverse, getting these nutrients from the same truffle, so affecting them.
The disinfection protocol proposed is as follows:
– Immersion in 50% ethanol and 70% in cold at 4°C
– Beta ray ionizing. It is seen that even some aromatic compound are increased.
These treatments leave truffles virtually sterile and kills microbes and insect larvae. Radiations also decrease truffle respiratory rate which in turn lengthens its life.
– Proposes a laser perforated plastic packaging permeable more to CO2 than O2, so that within the package increases the CO2 and O2 decreases a 10%.
With these treatments we can increase the life of the truffles 4 weeks if only ethanol is used and 6 weeks when combined with radiation!
Let’s see if the industry will adopt these protocols, although I think some advise and training should be done, at least with the small canneries I know…
In a second work by Saltarelli, some fresh samples were kept at 4 degrees C for 30 days, other samples were frozen at -20 degrees C for one month, thawed and preserved at 4 degrees C the remainder were autoclaved. The biochemical parameters studied were sugar and protein content, the activity of some enzymes involved in the central metabolism of the fungi and the electrophoretic pattern of soluble proteins. Total mesophilic bacteria were also counted. The results obtained showed that the storage at 4 degrees C is the treatment that best preserves the biochemical and microbiological characteristics of fresh truffles. Black truffles were more resistant to biochemical spoilage than the white ones, while Tuber magnatum was the most resistant to microbial spoilage.
All the best in this largest day of the year ( the shortest downunder. I know it’s hard, but at least you are in truffle season 🙂
Marcos S. Morcillo
Blanco, D; Venturini, ME; Marco, P; S. Rivera, C. Strategies for the post-harvest handling and conservation of fresh Tuber melanosporum. Tuber2013. Teruel. Spain.
Saltarelli, R; Ceccaroli, P; Cesari, P; Barbieri, E; Stocchi, V. 2008. Effect of storage on biochemical and microbiological parameters of edible truffle species. FOOD CHEMISTRY. 109(1):8-16.