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  1. Let's say I am water-blanching 100g of green beans. After the blanching process will the resulting weight be less than 100g?

  2. I aim to dehydrate the blanched 100 g of green beans. Will dehydrating 100g of blanched beans and 100g of unbalanced beans result in the same dried mass?

aztec242
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The weight is more likely to increase than decrease when blanching as some water or (condensed steam if you do it by steaming) will stay on the surface. With something like broccoli that has a lot of surface area that could be quite a lot. With beans less, unless you cut them up and immerse them so the water gets inside.

The dehydrated mass should be the same though. You're aiming to get the water content down to the same level. If you start the dehydrating process with extra water, it will take longer to reach the same point.

You may be concerned about the loss of things that dissolve in the blanching water, and thus losing weight that way. I really don't think you need to be. Most vegetables (including beans) are high in water to start with, and most of what's left is insoluble. This nutrition information table has fat+protein+carbs adding up to about 10%. Of that only the sugar (3.6% of the total weight) is soluble. But (i) blanching is brief and (ii) most of the sugar is trapped in the plant's cells so it won't dissolve out easily until cooked to mush.

Chris H
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    I have tested steaming broccoli and green beans, and the result always weights slightly less than the raw ingredients. Heat will squeeze water out of the vegetables, and they won't absorb back the same volume from the steam. – Luciano Jan 28 '22 at 09:44
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    Interesting @Luciano - I only steam for full cooking (e.g. beans with new potatoes cooking underneath) and never weigh afterwards. I only blanch by immersion, and when I've weighed I've seen an increase. I now wonder about immersion blanching, drying using a salad spinner, and weighing – Chris H Jan 28 '22 at 11:29
  • I suppose blanching could increase the weight, since the vegetables are immersed in water there might be absorption through osmosis – Luciano Jan 28 '22 at 15:49
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    @Luciano The last thing I blanched was probably runner beans, cut up (I either get a glut or the slugs kill the plants early). Then there's a lot empty space to fill with water, no need for osmosis – Chris H Jan 28 '22 at 15:50
  • Since I am concerned about the mass/content of the vegetables other than water. So would it be safe to assume that blanching will change the water weight (probably increase if water blanching than steam blanching) but after the dehydration process, the mass/content of the vegetable will remain the same? I am also concerned if blanching will cause breakage of fiber in veggies like spinach and mushroom. Is that so? Would it cause change in mass though? – aztec242 Jan 29 '22 at 11:56
  • @aztec242 the mass of the vegetable is mostly water. That's why it gets so much lighter when you dehydrate it. Losses other than water will be immeasurably small, so the final dehydrated weight should be the same to within what can be measured with the best kitchen scales. The affect of blanching on fibre content is a different question, but consider this: even if the fibre did break down, would it leave the veg? For that to happen (i) the breakdown would have to result in something soluble and (ii) the soluble product would have to get into the blanching water, from inside the veg – Chris H Jan 30 '22 at 08:26