
This sweet and sour shrimp pairs crisp, golden battered shrimp with a glossy pineapple-ketchup sauce for the perfect balance of tangy and sweet. Colorful bell peppers and red onion add crunch, making it a restaurant-style seafood dinner that comes together beautifully at home.
Pat the shrimp very dry with paper towels. Pour about 3 inches of neutral oil into a small, heavy pot and heat to 325°F. If you do not have a thermometer, drop in a little batter; it should sizzle, float right away, and stay pale rather than browning instantly.
Make the batter by whisking together the flour, baking powder, cornstarch, salt, turmeric, and white pepper in a bowl. Just before frying, whisk in the sesame oil and cold seltzer until the batter is smooth and lightly thick.
Dip the shrimp into the batter, letting any excess drip off. Fry in batches, adding the shrimp one at a time so they do not stick together. Cook for about 2 minutes per batch, turning as needed, until lightly golden and crisp.
Transfer the fried shrimp to a wire rack set over a baking sheet to drain. Repeat until all of the shrimp are fried.
In a wok or large skillet over high heat, add 2 tsp of the frying oil. Stir-fry the red onion, red bell pepper, and green bell pepper for 30 seconds. Push the vegetables to the sides, add the remaining 1 tsp oil to the center, then stir in the ketchup and cook for 20 seconds to deepen the flavor.
Add the pineapple chunks, pineapple juice, water, red wine vinegar, and sugar. Stir well and bring the sauce to a gentle simmer. Cook for about 2 minutes so the flavors combine.
While the sauce simmers, fry the shrimp a second time in batches. Raise the oil to 350°F before adding the shrimp, then fry for about 2 minutes at roughly 325°F after the temperature drops. This second fry keeps the coating extra crisp.
Let the sauce continue to simmer until it lightly coats the back of a spoon. If it looks too thin, simmer briefly until slightly reduced.
Add the hot fried shrimp to the wok and toss gently 3 to 4 times, just until lightly coated in sauce. Serve immediately for the crispiest texture.
Use club soda or sparkling water if you do not have seltzer. Do not overcrowd the fryer or the shrimp will lose their crisp coating. For the best texture, toss the shrimp with the sauce just before serving; leftovers can be refrigerated for up to 2 days, though the coating will soften.