Walnut Halves

Walnuts are a very oily nut. As they age, oils from the skins diffuse into the nut and they turn the flesh darker. As the nut oils age, it can make the nut develop a bitter aftertaste.
Chinese, Indian and Eastern European walnuts all have this flavour profile. In contrast, our Californian and Chilean walnuts have a much softer flavour, without the bitterness traditionally associated with walnuts.
As such, they are becoming much more popular with commercial buyers and consumers.