The Curious Red White Conundrum

As you probably know, virtually all red wine grapes have white juice. One day, I found myself wondering why? I asked Carole Meredith PhD, the leading grapevine geneticist in the U.S. She explained: “The red grapes that have white juice are all varieties of Vitis vinifera, the European wine grape.  These red grapes have color pigment in the berry skin, but not in the berry pulp. As to why, one can only speculate. The skin color of the fruit presumably helps to attract birds or other fruit-eating animals, which will then disperse the seeds. There would be no adaptive advantage to also having pigment in the pulp, which is not visible. Red apple varieties, for example, have pigment in the skin but not in the pulp.” I thought: So that’s it. But Meredith went on, “Then again, look at plums – some have color inside and some don’t.” Hmmm.