How do you reduce nutrient loss while preparing and cooking?

Nutrient loss does not start in the pot, it starts on the counter. TÜBER, Türkiye's national dietary guideline, ties preventing loss to two things: the cooking method and the preparation conditions. So the washing order, the way you chop and the waiting time are as decisive as the heat itself.

Below we look in order at which step the loss happens in, why the washing and trimming order matters, the part played by water and heat, what the skin holds and when the loss stops mattering.

Which step the loss happens in

What the guideline calls loss is mainly water-soluble compounds; it gives vitamin C as an example. These compounds pass into water, break down with heat and decrease as the cut surface makes contact with air.

The chain therefore starts with preparation: trimming, washing, chopping, standing, cooking and serving. There is a small share lost at every step, and fixing a single step does not save the chain.

The guideline writes the same idea more generally as well: incorrect procedures applied to foods, that is incorrect cooking and storage methods, cause losses of nutrients.

The washing and trimming order

The order is in a single sentence: vegetables are trimmed first, then washed. With root vegetables the roots are cut first and the washing is done afterwards; with greens such as lettuce and cabbage the outer leaves are removed.

During trimming you are asked to avoid contact with the knife and to trim by hand as much as possible. Every cut surface is a new surface opened to water and air.

Setting the order the other way round is a common habit: trimming a washed vegetable brings the cut surfaces back into contact with water. Doing the same work in a different order asks for no extra time, only for the habit to change.

Chopping and standing

Vegetables to be eaten raw, especially greens, are separated into small pieces by hand where possible rather than cut with a knife. Chopped raw vegetables are also asked to be eaten quickly rather than left standing, for the same reason.

The same rule holds for fruit. Not leaving peeled and chopped fruit standing for long both prevents browning and reduces vitamin loss. We covered what the size of the chop changes in this tip.

In practice this means moving the preparation closer to the meal. Chopping the salad as the table is being set, rather than chopping it in the morning and leaving it until evening, gives a different result from the same ingredients.

The part played by water

Vegetables should be cooked without water or with as little water as possible. Because most of the loss comes from compounds passing into water, reducing the amount of water makes a clear difference on its own.

Boiling and pouring away the water is among the methods the guideline plainly asks you to give up. If the water is going to be used, keeping it in the dish gives a different result from pouring it away. We covered the subject separately in this tip.

Where the methods part ways

The guideline recommends giving up frying, boiling and pouring away the water, and long roasting; and applying oven cooking, boiling, grilling and steaming.

There is also a comparison for steaming: compared with boiling in water or cooking in the microwave, the loss is lower, and water-soluble compounds such as vitamin C suffer less loss than with boiling.

Time is part of the method too. Because most vegetables undergo unwanted changes in quality when they are cooked for a very long time, the cooking time is asked to be kept short and the food to be served as soon as it is done. We covered the comparison of methods in this guide.

What the skin holds

Many vitamins and minerals are found in the outer leaves of vegetables and fruit, in the skin or in the parts just under the skin; their concentration is lower in the inner parts.

This is why fruit that can be eaten with the skin should be washed thoroughly and eaten unpeeled, and peeled as thinly as possible if it has to be peeled. The skin also keeps the fiber on the plate.

The habit of peeling thickly loses twice here: the densest part goes, and the amount on the plate gets smaller. All it takes to peel thinly is a sharp peeler.

The step before freezing

There is a defined step for fresh vegetables to be frozen at home: dipping them in boiling water for 2-3 minutes and then taking them into iced water for 1-2 minutes. The guideline writes that this both preserves the color and prevents possible nutrient losses.

This is the step that turns freezing from a source of loss into a storage method. When it is skipped, what comes out of the freezer is different in both color and content.

When the loss stops mattering

There is no need to chase every bit of the loss. The guideline writes that vegetables and fruit can be consumed raw, cooked, fresh, frozen and canned; and that canned and frozen products are nutritious alternatives as long as they are produced without added salt, sugar or fat.

So a vegetable eaten with some loss gives a better result than a perfect vegetable that is never eaten. We covered micronutrients as a whole in this guide; reducing loss is a small but cheap part of that picture.