The Truffle is a type of mushroom that can only be spawned by a Pig on The Farm when the pig is outside the Barn. Since pigs do not go out of the barn in winter, they spawn no truffles in that season. Truffles sell for a base price of data-sort-value="625">625g.
Despite being spawned by pigs, truffles are not considered to be animal produce, like eggs or milk. They do not receive a price increase from the Rancher profession.
And despite being mushrooms, they technically are also not considered to be foraged items. They are not among the items included in the foraging category at the Stardew Valley Fair, nor are they labeled as either forage or vegetable in your inventory. Nevertheless, their quantity and quality level is assigned in the same fashion as foraged items (not like animal produce). These factors are therefore affected by the Gatherer and Botanist professions, just as with all foraged items.
Truffles not gathered on the 28th day of a season disappear on the following morning, the 1st day of the new season.
On rare occasions, a Truffle can be purchased from the Traveling Cart for data-sort-value="625"1,875〜3,125g.
The トリュフ may be randomly requested during any season at the "Help Wanted" board outside Pierre's General Store for a reward of data-sort-value="1875">1,875g and 150 Friendship points. The Truffle will never be requested unless you own a Pig.
The Mayor's Need Quest, in which Lewis requests Truffle Oil, will trigger regardless of whether or not you own a pig.