Which method decreases vitamin C and folic acid?

• A. Boiling
• B. Roasting
• C. Steaming
• D. Vacuum packing

Answer: (C)

Vitamin C and folic acid are especially vulnerable to heat and to being in water. When foods are heated in water, these water‑soluble vitamins can leach into the cooking liquid and be degraded by heat, so cooking methods that involve immersion in water tend to cause larger losses. Dry heat, like roasting, can still damage these vitamins, but there’s no leaching into water. Steaming transfers heat via steam and minimizes direct contact with water, so it generally preserves water‑soluble vitamins better than boiling or roasting. Vacuum packing isn’t a cooking method per se; when used with controlled low‑temperature cooking (sous vide), it can reduce oxidative losses, helping retention. In summary, boiling typically causes the greatest decrease in vitamin C and folic acid, while steaming tends to retain more of these nutrients. If a source asserts steaming decreases them the most, note that the usual understanding is that steaming preserves them better than boiling.