According to chef Vu Nhat Thong from Eric Vu Cooking Class, the meat in nem chua is not heated but "cooked" by lactic acid produced by bacteria.

When pork is mixed with sugar, salt, and toasted rice powder, then tightly wrapped, lactic bacteria (naturally present in the ingredients) consume the sugar and release acid. After incubating for hai den ba ngay at 27-30 degrees Celsius, this acid denatures and coagulates the meat's protein, transforming it from a soft, mushy state to a firm, chewy, and pink texture.

This chemical principle is similar to the South American dish ceviche, which uses lime juice to "cook" fish. The difference is that nem chua relies on bacteria to produce acid locally. This highly acidic environment, combined with salt, inhibits mold and pathogenic bacteria, preventing their proliferation.

The nylon wrapper is key to safe nem chua fermentation. *Illustration*

However, lactic bacteria thrive best in an entirely oxygen-free environment. This is why producers must tightly compress the meat and wrap it snugly with a nylon film.

Many mistakenly believe the nylon layer is solely for hygiene or to prevent sticking. In reality, this wrapper creates a "sealed room" that blocks oxygen, allowing beneficial bacteria to dominate the fermentation environment while preventing aerobic bacteria and mold from entering and causing spoilage. The nylon layer also retains moisture and compresses the meat, creating a smooth texture, while the outermost banana leaf wrapper helps maintain a stable incubation temperature.

Without this oxygen barrier, mold will penetrate, causing the fermentation process to go awry. The final product will have a bitter, intensely sour taste, and the meat's surface will turn grayish, similar to beef left exposed to air.

To make safe nem chua, chef Thong emphasizes that producers must adhere to ba mandatory conditions: First, ingredients must be very fresh. Second, all tools must be thoroughly sterilized. Lastly, sugar must not be omitted from the recipe, as it is the food source for bacteria to produce the necessary acid to preserve the meat.

Bao Nhien