Blanching
Cooking Knowledge, Non Recipes, Nutrition

Does blanching kill vitamins?

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Blanching seems to have lost some of its former popularity for a lot of home cooks. Word has been spread that you drain away all the nutrients with the cooking water. And if you compare the sweet and caramelized flavor of sauteed and roasted vegetables with the one of the boiled mush your grandma might’ve served you it’s easy to dismiss this cooking technique as outdated.

However, for me, blanching is still the cooking technique I use the most for vegetables. There are two main reasons for this.

1. The texture of blanched vegetables is the best.

Crispy and juicy: The only way to get that is to blanch your vegetables. Just think of roasted vegetables. Yes, they are sweet and caramelized. But often their texture is mushy or dry. While for some foods that tenderness is desired, like for zucchini or eggplant, for most it isn’t.

I know that some people might’ve grown up with parents or grandparents who boiled their veggies to death. But guess what, you can cook your vegetables for a much shorter time. In fact, blanching is supposed to last for no longer than a few minutes. That way your vegetables will have a nice bite to them.

2. Blanched vegetables have a vibrant color.

I don’t know about you, but for me, roasted vegetables always seem a little sad in color. They aren’t vibrant. They’re dull. The only way to give your broccoli that vibrant green color is to blanch it.

It’s best practice to blanch your vegetables first before sauteeing them.

That’s why blanching is an essential step prior to sauteing vegetables. You give them a nice color and texture beforehand and then just very shortly caramelize them in a very hot pan. Just think of Asian cuisine. Nearly every stir-fry starts with blanching the ingredients either in water or oil.

What science has to say about blanching

There have been a lot of scientific studies that investigate the effect of blanching on vegetables. The two most commonly researched topics are:

  • How does blanching affect the peroxidase activity in a vegetable?
  • Which effects does blanching have on the vitamin content?

The first question might surprise you at first but has a very simple reason. You might’ve heard that vegetables always need to be blanched before freezing. That is because of enzymes in the vegetable like peroxidase which are the main factor for food deterioration.

These enzymes work at a much lower rate in your freezer but they still remain active! So they need to be inactivated by a heat treatment prior to freezing so that your vegetables will last longer in the fridge.

Typically, you will need to blanch your vegetables between 90 – 120 seconds before freezing to inactivate 90 % of the deterioration enzymes.

The vitamin content in vegetables after blanching highly depends on the cooking time. It is generally known that a shorter blanching time at a higher temperature retains more vitamins than a longer blanching time at a lower temperature.

Why not all vitamins are susceptible to loss during blanching

It also depends on the kind of vitamin investigated. Some vitamins like carotene or Vitamin E are heat stable and won’t get lost during the cooking process. Others, such as Vitamin C can have typical loss rates of up to 70 % for leafy vegetables.

Spinach is rich in Vitamin C but you should only blanch it for a few seconds until wilted to retain it.

The most suspectable vitamins for loss are the water-soluble B-vitamins and Vitamin C. The reason for that is that they not only get destroyed by heat but can also dissolve into the cooking water. The fat-soluble A, D, E, and K-vitamins, however, stay inside the vegetable during blanching.

A common method used in traditional German cuisine is to use some of the blanching water to make a sauce. That has proven to be very beneficial in terms of maximizing your vitamin intake. However, that is totally unnecessary if you just blanch your vegetables for a shorter amount of time.

If you blanch your vegetables the correct way – with high heat for a short time – they usually retain between 72 – 93 % of their original Vitamin C content. Other vitamins like Vitamin B2 have an even better retention rate of 90 to 100 % under optimum blanching conditions.

To conclude this discussion: No, blanching isn’t a vitamin killer. However, you should always keep the cooking time short. This is not only better for flavor and texture but also for vitamin retention. I’m going to continue to use blanching as my primary vegetable cooking technique, and so should you.

Resources:

Influence of different blanching methods on colour, ascorbic acid and phenolics content of broccoli

Vitamin retention during blanching of vegetables

Effect of Duration and Temperature of Blanch on Vitamin Retention by Certain Vegetables

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