Tahini adds two key things to hummus. Firstly, extra flavour. The rich sesame taste. It's not sweet and it tastes quite nutty and earthy and has a slightly bitter after-taste. It packs a bit of punch and adds a lot of underlying flavour to traditional hummus. Secondly, texture. Tahini is oozing and sticky and helps to create that smooth and oily hummus texture we know and love.