you can add more of the acid used in the reaction, if you are making what i think you are you have too much un-reacted NaOH, adding some more *BL will fix the problem. You can also add vinegar to the solution, although it takes quite a bit to alter the PH and can alter the normal taste of the final products, although it does work. best bet is add a little more of the acid you used in the reaction bit by bit and check the ph as you go till you get it to 7