Should you make your pumpkin puree by baking or by steaming?

Cooking makes food easier to digest and therefore increases nutrient absorption. But, the way you cook your food can alter the amount and the type of nutrients (vitamins, antioxidants, etc.). Baking pumpkin in the oven mainly destroys some of the heat-sensitive vitamins (vitamin C and B vitamins). On the other hand, vitamin A, minerals, and fiber are little or not at all affected by heat. Steaming preserves nutrients better.

Which nutrients are affected by cooking?

The following nutrients may be affected during cooking:

• Water-soluble vitamins: vitamin C and B vitamins, including thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), folic acid (B9), and cobalamin (B12)
• Fat-soluble vitamins (vitamins A, D, E, and K)
• Minerals (potassium, magnesium, sodium, and calcium)
• Antioxidants (polyphenols, flavonoids)

Baking

The most affected vitamins by the dry heat of oven cooking are water-soluble vitamins (B and C). Antioxidants (polyphenols, flavonoids) break down due to the presence of oxygen in the air and high temperatures. Higher temperatures and longer cooking times cause greater degradation of vitamins and polyphenols. Cutting the pumpkin in half across its middle, remove the seeds and placing it skin-side up on a baking pan reduces the exposure of the flesh to oxygen and thus better preserves antioxidants.

However, heating to 350°C does not only have negative effects. It increases the bioavailability of beta-carotene (provitamin A). Researchers who examined the effects of heat treatment on different varieties of pumpkin found that cooking makes beta-carotene more accessible. The breakdown of cell walls during cooking releases beta-carotene and facilitates its absorption by the body. Fat-soluble vitamins (A, D, E, K) and minerals are much more stable and therefore less affected by heat.

Steaming

As a gentler, waterless method, steaming is one of the best cooking method to preserve nutrients, even those that are sensitive to heat. According to one study, vitamin C (ascorbic acid) is reduced by about 50% and polyphenols by 49.68-64.94%; this represents a lower loss than with other types of cooking.

Tips for minimizing nutrient loss during cooking

1. Shortening the cooking time minimizes losses.
2. Do not use too high a temperature, otherwise there will be greater losses.
3. Save the cooking liquid if you decide to boil the pumpkin, as some of the nutrients are found in this liquid.
4. Cut the pumpkin in half instead of into small pieces. Increasing the contact surface minimizes losses.

In conclusion, the loss of vitamins B, C, and polyphenols is slightly higher in baking than in steaming. Nevertheless, these are the two best cooking methods that have the least impact on the nutritional content of pumpkin.

Cooking pumpkin directly in water results in even greater nutrient loss. Water-soluble vitamins and minerals end up in the water, which is discarded after boiling. Boiling food in water is therefore the worst cooking method, resulting in the greatest losses.

References:

• Cooking and the human commitment to a high-quality diet
• How Cooking Affects the Nutrient Content of Foods
• In vitro bioaccessibility of β-carotene in pumpkin and butternut squash subjected to different cooking methods
• Impact of Heat Processing (Boiling, Roasting, Frying) on Nutrient Retention
• Cooking effects on bioactive compounds and sensory acceptability in pumpkin (Cucurbita moschata cv. Leite)