Acid-Cooked Shrimp Ceviche Tacos

Using a microplane grater, zest 4 limes to yield 1 tablespoon of zest. Juice the same limes to yield 0.25 cups (60ml) of juice. The citric acid concentration in fresh lime juice (approximately 6% by weight) will denature the proteins in the shrimp through acid coagulation rather than heat.

Combine lime zest, lime juice, diced shrimp, tomatoes, avocado, cilantro, minced garlic, salt, and pepper in a non-reactive glass or ceramic bowl. The acid will begin breaking down the shrimp proteins immediately. (Use a non-reactive bowl - metal can impart off-flavors when exposed to acid for extended periods.)

Toss ingredients thoroughly and refrigerate for exactly 15 minutes at 37°F (3°C), stirring every 5 minutes. The shrimp should turn opaque and firm as the proteins coagulate - this is your visual indicator that the acid has 'cooked' the proteins.

Warm tortillas in a dry skillet over medium heat (325°F/163°C surface temperature) for 30 seconds per side until pliable and lightly spotted.

Spoon 0.5 cup of ceviche mixture down the center of each warmed tortilla. Fold and serve immediately to prevent the tortilla from becoming soggy from the acidulated liquid.