If you bite food without intent to chew and eat it, do you need to make a bracha?
The Gemara in Berachos 14a says:
There is a dispute among the Rishonim of how to understand this. Tosefos cites Rabbeinu Chananel that this is assuming the person spits it out, in which case the tasting is not considered a pleasure which needs a blessing
The Tur (O.C. 210:2) and Beis Yosef (ibid) understand the Rambam (Hilchos Berachos 1:2) to mean that one could even swallow the food without needing to make a blessing, up to a revi'is-worth.
The Shulchan Aruch (ibid) codifies the opinion of the Rambam, and cites the opinion of Rabbeinu Chananel as "some say."
The Rema (ibid) says that we follow the lenient opinion in blessings, and therefore we should follow the opinion not to make a blessing even when swallowing.
Within the opinion that the only allowance is in the case of spitting out the food, the Mishna Berura (210:18) applies this to even a case of chewing the food up and then spitting it out.
From all of the above, it should be evident that according to all opinions one would not make a blessing when you do not intend to eat the food that you put in your mouth. Even if you put a revi'is-worth into your mouth, only the opinion which allows swallowing a small amount holds that there is a cut-off point of revi'is.