Many people prefer simmering soup over low heat for extended periods, believing this allows nutrients to fully dissolve into the broth. However, this practice lacks scientific basis. Research shows that moderately extending simmering time does aid nutrient release and absorption, but excessive duration can actually degrade nutritional components.
Generally, soup ingredients primarily consist of protein-rich foods like meat. Proteins are composed mainly of amino acids. If heated for too long, these amino acids break down, reducing nutritional value and diminishing the dish's natural flavor.Furthermore, prolonged heating causes varying degrees of vitamin loss in foods. Vitamin C, in particular, is highly susceptible to heat damage, with nearly all of it destroyed after just 20 minutes of boiling. Thus, while a long-simmered broth may appear rich and thick, the evaporation of water actually carries away its nutrient-rich essence.
So, what is the optimal duration for simmering soup? Experts from the Institute of Nutrition and Health Foods at Tongji University conducted a dedicated study on this topic. They selected three representative ingredients for soup preparation: pork knuckle, free-range chicken, and old duck. Testing revealed:while the protein content in chicken and duck broth remained largely unchanged after one hour of heating, with fat levels peaking after 45 minutes. The study concluded that simmering these three ingredients for an average of 1–1.5 hours yields the highest nutritional value, which gradually declines thereafter.
For most meats, the above principles apply. However, some ingredients require shorter simmering times. Fish broth, for instance, should not be cooked excessively due to the delicate nature of fish meat. Once the broth turns milky white, further simmering should be avoided. Prolonged cooking not only degrades nutrients but also toughens the fish, resulting in a coarse texture and poor flavor.Some add tonic herbs like ginseng to soups. Since ginsenosides in ginseng break down during prolonged cooking, losing their restorative benefits, the optimal simmering time in such cases is 40 minutes. Finally, if vegetables are added, they should be incorporated only after the soup is fully cooked and consumed promptly to minimize vitamin loss.