What you see: Brownish coloring inside your eggplant
What it is: Oxidation
Eat or toss: Eat! This eggplant likely had a traumatic experience (most likely cold temps; possibly it was dropped), but the brown coloring doesn’t signal that any harmful microbes have moved in.
Amy K. of Washington, D.C. got things right when she stored this eggplant on her countertop and not in the fridge (eggplants don’t like being cold). And yet, when she sliced it open, this discoloration, something like the aftermath of a toddler's watercolor session, stared back at her.
She often has this problem with eggplants from her local grocery store. So, when I consulted Chris Gunter, vegetable production specialist at North Carolina State University, he suspected the eggplants are likely being kept too cold en route to the store.
Cold temperatures can damage cells, causing their membranes to leak compounds and enzymes that spur chemical reactions. Those reactions leave behind this unattractive look. An impact, like being dropped or the pressure from sitting at the bottom of a pile of eggplants, could have a similar cell-damaging effect. But, it doesn’t mean that anything unsafe is growing inside the eggplant; it’s still perfectly fine to eat.
The eggplant clock ticks quickly
The lesson for your eggplant parmesan and baba ganoush is simply to act quickly. Too long in the fridge and the eggplant could get weird spots like this. In the short term, many people recommend storing eggplants on the counter, but there they can shrink and wrinkle as the room-temperature air leads to water loss. If you can minimize the time between harvest and dinner, both you and the eggplant will be fare better.
“In our homes we don’t have ideal storage conditions for eggplant,” Gunter said. “Our refrigerators are too cold; the counters are too hot. It’s a stressful environment.”
Chris Gunter. Associate Professor. Vegetable Production Specialist. North Carolina State University.
Eggplant: Recommendations for maintaining post-harvest quality. Marita Cantwell and Trevor V. Suslow. Department of Plant Sciences, University of California, Davis
On Food and Cooking: The Science and Lore of the Kitchen. Harold McGee. p. 269. "Enzymatic browning."