I have been making pesto nearly my whole life, and suddenly, I am having a problem with my pesto turning brown. Of course, pesto will oxidize when exposed to air, so I always put a layer of olive oil on top of my pesto when I store it. But this browning is nearly instantaneous. Parts of it are browning when I remove it from the blender jar. I've never, ever had oxidation happen like this. And when I am serving it, it is brown instead of the bright green that I am used to. It tastes the same, but I find the color less appetizing. This is from basil grown in my garden, so I am wondering if it is possible that certain cultivars oxidize more readily? Is this possible? Maybe it is just not a good basil for pesto? Weird.