This question was posted to my gardening list, and I thought y'all might have the answer.
She beats olive oil and grapefruit juice together (+ a shake of salt and pepper) for a salad dressing, it becomes thick. When she beats olive oil and balsamic vinegar together, it does not. ..also some
salt and pepper in that one, too.
Her question is what is happening chemically that makes the grapefruit juice/oil combo thicken while the vinegar/oil combo does not?