We do not eat meat or poultry in the Nine Days with certain exceptions notably Shabbos. It is customary to taste the Shabbos cooking on erev Shabbos afternoon to check the flavouring. During the nine days, is it necessary to spit this small quantity of food out or can one swallow it? I once asked a shaaloh and was told it is permitted to swallow but must not eat a large amount. I recently heard in a shiur that it’s better not to swallow the food. CYLOR of course but where does the argument originate?
Per Shmiras Shabbos Khilchasa 42:61 on Erev Shabbos during the Nine Days, you may also taste the food. However, one should try not to swallow food containing meat ingredients
In the sefer Tshuvos Avigdor Halevi (Rav Nebontzal) page 390:24 he holds even to taste is assur.