Also, since the baking soda is fairly alkaline, it's fairly antimicrobial in nature as well. Many pathogenic type microbes like and thrive in in-between a slightly to moderately acid environment, and many are killed by even moderate alkalinity.
Same reasoning behind why gargling with warm salt water tends to help with sore throats--kills the germs with it's alkalinity.
(this ph thing also works internally, and is quite interesting. I've done experiments wherein i've eating a more alkaline reacting diet for long periods of time, and wouldn't even get a hint of a common cold for that duration. My longest period without even a slight, common cold was about 2.25 yrs, and what changed it was visiting the in laws during the holidays, and feeling obligated to eat foods, combinations, and amounts i wouldn't normally [and very acid reacting], and i immediately got sick. Anyways, i've experimented enough to be convinced. If i feel a cold coming on, i immediately discipline my diet and eat very alkaline reacting and 9 out of 10 times nip the cold in the bud. Modern, mainstream medicine doesn't know everything yet.]