Cooking delicious food is an art,
but preserving most of the nutrients it provides is a science.

Probably our biggest concern when cooking at home is whether the food we prepare will be delicious. And that seems like a pretty valid concern to me. Still, apart from the taste, the nutritional value of that food is also a significant factor to bring into play. After all, food is the one that provides us with all the necessary nutrients our body needs to function properly.

What if we could prepare delicious food but at the same time preserve most of its nutritional value? In this story, we’ll see how different methods to prepare and cook fruits and vegetables affect their nutrient content and how we can get the most out of them.

Fruits and vegetables are an essential source of dietary fibre, water-soluble vitamins like group B and vitamin C, fat-soluble vitamin K, and minerals like manganese and potassium. They also significantly contribute to our intake of various phytochemicals, such as carotenoids, some of which our body can convert to vitamin A.

From the moment we purchase them to the moment we eat them, some of these nutrients will be unfortunately lost. Let’s see how we can make the loss the smallest possible.

Even before we buy them, different factors will affect their nutrient composition and potential loss.

Firstly, the cultivar, the country of origin, the type of soil, and the cultural practices employed (fertilisation, attack of insects and diseases, maturity stage) will, among others, determine their makeup.
But, as my colleague, food quality and safety expert Marijan Katalenić already told us in his interview, nutrient loss starts when an ingredient is picked or harvested. That means that the more time passes from the moment of harvest to the moment we buy that food and actually eat it, the more losses will occur.

We don’t have such a big influence on most of these factors, except if we grow our own food. Still, buying fruits and vegetables from local farmers raises the possibility that the time from harvest to buying that food is as minimal as possible.
What we have an influence on is how we will choose to prepare that food. Preparation methods like washing, peeling and cutting, along with different cooking methods, can significantly alter the number of nutrients that will end up in our meals.

Let’s see some beneficial practices that can minimise fruit and vegetable preparation losses.

Choosing fruits and vegetables

Most often, you can buy fruits and vegetables fresh, frozen or canned. The best option when purchasing fruits and vegetables is to stick to fresh or frozen produce. If you are buying them in season, I recommend you buy them fresh.

If you want to buy them out of their season, going with frozen products would be better than choosing imported ones. Also, suppose you don’t have the privilege of buying fresh produce so often. In that case, it is also wise to think about frozen alternatives.
Freezing on its own shows only a slight loss of nutrients. Plus, the food is picked at the optimal ripeness stage and processed in the shortest amount of time. On the other hand, imported fruits and vegetables are often picked when still unripe and transported for a much longer period, resulting in a more significant loss.

Canning includes blanching or cooking and then sterilisation (high temperatures), resulting in much higher losses in vitamins and minerals. Canned fruits and vegetables are my least favourite option when choosing from those three.

Washing fruits and vegetables

Washing fruits and vegetables is essential to remove dirt and a significant amount of potential pesticide residues. Let’s see how we can wash fruits and vegetables most efficiently to keep down the loss of nutrients and try to remove as many residues as possible.

Wash fruits and vegetables whole, with their peel on.
If you cut ingredients before washing, you encourage more water-soluble compounds to leach out.

Don’t let them soak.
When washing your fruits and vegetables, don’t let them sit in the water; rather, rinse them under running water.
Soaking fruits and vegetables in water for up to 30 minutes showed no major reduction in pesticide levels compared to rinsing them under water for a maximum of 5 minutes. But soaking them for such long periods would lead to vitamin losses.

Peeling fruits and vegetables

Of course, particular fruits and vegetables have inedible peels that need to be removed before eating, like avocado, citrus fruits (grapefruit, lemon, lime, orange, etc.), garlic, hard winter squash, melon, onion, tropical fruits (lychee, pineapple, papaya, etc.).
But a considerable amount of fruits and vegetables have an edible peel. Some of these are apples, apricot, asparagus, banana, berries, carrot, cherries, citrus fruits (grated or cooked), cucumbers, eggplant, grape, kiwi, mushroom, parsnips, peas, peach, pears, pepper, plum, potato, squash (if well cooked), zucchini.

Peel is one of the most nutrient-rich parts of the plant. The number of nutrients depends on the type of plant, but in general, unpeeled fruits and vegetables have more vitamins, minerals and phytochemicals than peeled ones.

To put it into numbers, a raw apple with the skin on contains up to:
332% more vitamin K,
142% more vitamin A,
115% more vitamin C,
20% more calcium,
and 19% more potassium than a peeled one.

Unpeeled fruits and vegetables also have a considerably higher amount of fibre; up to 31% of the total fibre content in vegetables is hidden inside the peel.

As we can see, peeling fruits and vegetables dramatically lowers their nutritional value, so why are we doing it in the first place?

One of the main reasons for peeling them is to lower the number of pesticide residues stuck to the outer peel.

There is no doubt that pesticides are widely used in food production to reduce crop damage and increase yields, but contrary to the belief, they can be found both on organically and conventionally grown fruits and vegetables. They are mostly found on the outer peel, but some of them can also enter the inner flesh.

Still, the amount of pesticides allowed is tightly regulated. It is above the upper limit in less than 1% of cases.

Peeling, indeed, is one of the most effective ways to reduce the total amount of pesticides efficiently. Still, through washing, we are already doing a very good job. The difference in reduction through washing and peeling fruits and vegetables is likely too small to be significant.
Considering that, by peeling the skin of fruits and vegetables, we are probably losing a lot more than gaining.
If you still decide to peel your fruits and vegetables, try to remove the least amount of flesh possible.

Cutting fruits and vegetables

You inevitably lose some of the vitamins by breaking fruit and vegetable cells. The longer the cut fruits and vegetables are in contact with the air, the higher the losses will be. So, how can you minimise the losses?

Cut your fruits and vegetables prior to cooking or eating.

Cut fruits and vegetables in big size pieces to minimise the losses.
Logically, this way, a smaller surface will be in contact with the air, thus, resulting in more minor losses.
If possible, cook them whole with the skin on. For example, you will keep more nutrients in if you cook a whole potato with the skin on than the one that is peeled and cut into small cubes. If you desire, you can peel it afterwards, still getting a nutritionally better result.

Cooking fruits and vegetables

Even though many fruits and vegetables can be eaten raw, some need to be cooked before they can be enjoyed (potatoes, for example), but in general, cooking can be beneficial to us for a certain number of reasons.

Benefits of cooking fruits and vegetables:

• Improved digestibility
• Improved texture and flavour (sometimes)
• Elimination of present pathogenic microorganisms (high temperatures can kill microorganisms present)
• Increased bioavailability of various phytochemicals (carotenoids in cooked carrots or tomatoes)

Still, a certain loss of vitamins and minerals is an important downside to cooking.
While you can apply various cooking methods to fruits and vegetables, they can generally be divided into those using water as the cooking medium (boiling, steaming, microwaving) or those using fat (stir-frying, baking, grilling).

As you probably already know, vitamins can be either soluble in water or soluble in fat.
Based on that, when using water as the cooking medium, more water-soluble vitamins may leach into the cooking water, but the opposite will happen when cooking with fat (at a much lower rate). Minerals can also leach into the cooking water, or their bioavailability may change because of the changes in structure. Still, the mineral losses are usually more minor.

Cooking medium is not the only enemy of vitamins and minerals; they also don’t particularly like high heat and prolonged contact with oxygen, especially water-soluble vitamins. So, the higher the cooking temperature and the longer the cooking time, the higher the loss will be. That makes sense.
The most sensitive to high heat and leaching into the cooking medium are vitamin C and folate (B9), both water-soluble vitamins, which show the most significant losses when cooking. So, how can we prevent that from happening?

Steaming and microwaving are shown to be the best candidates when it comes to cooking methods that result in the most negligible loss. They use much less water than traditional boiling, lower heat, and require less time.

Switching from boiling to steaming broccoli could preserve double the amount of vitamin C and folate. Not bad, right?
Plus, steamed broccoli has a much superior taste to boiled one, giving you an even better-tasting result.

Best cooking practices:

If vegetables have edible skin, cook or bake them with the skin on. Potatoes peeled and boiled in the skin show a more significant loss of folate when compared to potatoes boiled in the skin. Plus, it is much easier to peel them afterwards, and you end up with fewer trimmings (less waste).

If boiling vegetables, use the least amount of water possible and try to reuse that water for making stock, soup or gravy. This way, you can preserve some of the micronutrients leaching into the surrounding water when cooking.

Avoid overcooking your vegetables. The longer your vegetables are in contact with the cooking medium, air and high temperatures, the bigger the losses will be.

Fruits and vegetables are very much alive even after being picked or harvested. Their structure is constantly changing, and it can be influenced by many different factors, as we’ve had the chance to see.

By following some of these practices I’ve shared with you today, you are on a good path to getting the most out of your fruits and vegetables!

I hope you’ve found this article useful and feel motivated to start some of these practices in your own kitchens. If you have any questions or doubts, I’m here! Just leave a comment below, and I will come back to you.