http://revach.net/article.php?id=3956

Section: Halacha   Category: Food
Nine Days - Sometimes Eating Meat Is Required
The Mishna Brura writes that unlike the Rambam who holds that making a bracha in vain is an isur D'oraisa, most Rishonim argue and hold that the isur is only D'rabanan.  Therefore the Piskei Teshuvos (215:17) concludes that if one makes a bracha and then realizes that the item he is about to eat may not be kosher, it is better that he not eat the item and violate the isur of making a bracha in vain rather than eating a non-kosher item and violating a [possible] D'oraisa prohibition.

On the other hand, the Piskei Teshuvos quotes from the Be'er Moshe (4:24) that if one made a bracha on a milchig item and realizes that he is fleishigs, as long as at least an hour has passed and he has no meat in his teeth he may taste the milchig item so as not to violate the isur of bracha l'vatalah. 

This halacha is relevant to the Nine Days as well.  If someone makes a bracha on fleishigs or wine and then remembers that it is the Nine Days, the Piskei Teshuvos (551:40) writes that he may taste the meat or wine, so as not to make bracha L'vatalah.