Response:

When simmering meat or bones, many people habitually skim off the foam believing it to be residue. However, others leave it, thinking it contains many nutrients. In reality, when cooking at high temperatures, soluble proteins in blood and connective tissue denature and coagulate. These components combine with residual blood, tissue fragments, and some mechanical impurities from the bones and meat, forming a layer of foam on the surface of the broth. This is a normal chemical phenomenon during food preparation. The amount of foam depends on the type of ingredients, the level of initial preparation, and the cooking method.

The foam that appears in the initial stage is not a rich source of valuable nutrients, as many people believe. The natural sweetness of broth primarily comes from amino acids, peptides, gelatin, and minerals released gradually during the simmering process. These substances dissolve into the broth and are not primarily concentrated in the foam layer on the surface. Therefore, skimming the foam does not significantly reduce the nutritional value or sweetness of the broth.

While there is no evidence that this foam causes significant harm to healthy individuals, skimming it off remains a reasonable preparation step. The foam can make the broth cloudy, reducing its clarity and appeal. Excess blood and tissue fragments in the foam can also produce a mild odor, especially for dishes simmered for a long time. Home cooks can skim the foam during the initial 10-20 minutes, when the highest amount of coagulated protein and other components are released from the meat and bones. After this period, the amount of foam often decreases significantly, eliminating the need for continuous skimming throughout the cooking process.

To reduce the amount of foam and help clarify the broth, you can briefly blanch bones or meat in boiling water for 3-5 minutes. Afterward, rinse them clean and replace with fresh water before simmering. This simple yet effective measure removes some excess blood, residue, and odors from the ingredients. Beyond cooking technique, selecting fresh, traceable ingredients and adhering to all preparation steps also play a role in ensuring food quality and safety.

Dr. Ngo Thi Tuong Vi

University of Health Sciences, Vietnam National University, Ho Chi Minh City