About Truffles
There are many different types of truffle appreciated for culinary uses. We grow the Black Winter Truffle (Tuber melanosporum) which is regarded as the best of the commercially tamed truffle species. (The far rarer White Winter Truffle (Tuber magnatum) has eluded all attempts to farm it and is only found in the wild)
Equally elusive, are all attempts to adequately describe the aroma and taste of a truffle. Tests have found over 150 different compounds make up the aroma alone. Additionally no two truffles smell the same (although ones from the same tree are generally close, even the next season). Broadly described, they range from a deep rich earthern scent to a heady solvent like nature. Mushroom, freshly mown hay are some other phrases. One of the best descriptions we've determined to date is a simple, pleasant honey note to the aroma for under-ripe truffles whereas warm molasses is a better descriptor for the full spectrum of aroma from a properly mature truffle.
When harvesting it's the difference between "nice sweet smell" and "oh wow, <urge to bury nose into the ground>"
Selecting truffles
If you are fortunate enough to be presented with a choice, then the first consideration is which smells best to you. Opinions on the best aroma and taste are subjective and up to the cook.
But there is also Ripe, old/overripe, unripe to consider, both when buying and when a truffle is already in your refrigerator.
RIPE: Make sure the truffle is firm to the touch, and has a very slight give when pressed lightly, (about as firm as an unripe orange, or a skinned garlic clove, but dont bruise it). There should be no question as to whether it has an aroma, and there is nothing subtle about the overall perfume. When cut it will show an even black colour with distinct white veins.
OVER RIPE: Too soft indicates drying out, or getting too old. A "cabbage" like smell is a sure indication of overripe. Yeasty red wine scents are also questionable. When cut it will show some areas appearing a little moist, these show the most movement when you squeeze the sides. Also the veining has less contrast.
UNDER RIPE: Hard as piece of wood, no give, lighter (brown) in color is immature and harvested too early. The aroma may have some nice top notes, but seem a bit thin in comparison to a fully ripe truffle. You will be taking a second smell and wondering what's missing. When cut they may appear normal or have areas lighter in color, which will "shatter" rather than slice. {if really close to being ripe a few days stored properly "might" help}
http://yarravalleytruffles.com.au/blog/ripe-overripe-underripe-all-in-one-pre-season-truffle/ -blog article has photo of various ripe tissue
Truffle Standards
Simply put, we believe a truffle is all about Taste and Aroma. No matter how much we love them, they cannot be called pretty, so shape is irrelevant beyond restaurant presentation considerations, and even then all truffles can be cut to deliver nice round slices.
We endeavour to only market the best quality truffles. Truffles are judged on ripeness, aroma, size, and overall quality. Initial assessement occurs after discovery, before the truffle is removed from the ground, mostly on aroma, but also firmness. (see above)
The UN guideline below is used as a basis, with additional judgement. We believe that as growers it is our responsibility to ensure that everyone has the best truffle experience possible. This ultimately affects the Australian public's perception of truffles, and the industry as a whole. (Truffles failing to meet our standards for sale will be used for experiments, mostly in our own kitchen. All in the name of research of course)
A copy of the latest UN standards can be found at UNECE 2017 Standards pdf
The comments on shape in the UNECE standard are mostly related to traditional cookery, where the skin is removed first (in Europe the truffles are often brushed, not washed, some people believe they keep better this way, but others don't like paying for attached dirt)
Note that Extra Class states "They must have a rounded shape, more or less regular and lobed." -not perfectly round golf balls, larger truffles are typically lobed, (but not grown flat between two rocks)
It is becoming more common to wash the truffle before use, with trimmings getting diced into the dish, truffle butter, etc, and the larger shavings used in final presentation. Therefore shape isn't as relevant as it used to be. An irregular shape means more trimmings and less truffle, therefore shape is reflected in the UN standards.
(The only people I have ever heard complain about shape, are resellers. Chef's and gourmets focus on the importance of aroma and flavour. Noone who understands truffle selects a pretty truffle over a pungent one.)
Size has a similar bearing, on the standards, the larger the truffle, the less of it is skin, therefore less trimmings. Additionally a small truffle has a larger surface area/weight ratio which leads to a faster loss of aroma and weight.