Does the questioner want to ask "Why does the color of kiwi fruit turn black when squeezed with milk?" Produce protein clots. Kiwi fruit is rich in vitamin C, and milk contains protein. The two will react to form protein clots, causing the color to turn black. Kiwi fruit and milk cannot be squeezed together. Not only will the appearance be unsightly, but it will also affect the digestive function of the gastrointestinal tract and cause adverse reactions such as abdominal pain, bloating, and diarrhea.