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I've observed that carrots don't keep well in the freezer if you just put them there. They deteriorate considerably in texture, suggesting to me that some denaturation is going on.

After googling for it, I've found that it's recommended that you "blanch" them first, which amounts to washing them, removing differently coloured spots, cutting them in dices or slices, and boiling them shortly.

Does anybody know the molecular basis for this?

Can any general rules be applied for vegetables depending on the content in starch, carotenoids, etc.?

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5 hours ago, joigus said:

Can any general rules be applied for vegetables depending on the content in starch, carotenoids, etc.?

Blanche them first...

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17 minutes ago, dimreepr said:

Blanche them first...

All of them? Blanch them first not matter which? Potatoes, carrots, cabbage...

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5 hours ago, joigus said:

I've observed that carrots don't keep well in the freezer if you just put them there. They deteriorate considerably in texture, suggesting to me that some denaturation is going on.

After googling for it, I've found that it's recommended that you "blanch" them first, which amounts to washing them, removing differently coloured spots, cutting them in dices or slices, and boiling them shortly.

Does anybody know the molecular basis for this?

Can any general rules be applied for vegetables depending on the content in starch, carotenoids, etc.?

Our experience is the same for carrots.

Even commercially produced carrots seem to loose texture and flavour, though I am not sure that variety doesn't play a part in the lack of flavour.

Wahsing is not part of blanching. That is simply immersing in boiling water or a steam blast and draining/drying.
My aunt used to have a centrifugal (handraulic) spinner for the draining/drying part..

Washing is recommended, particularly with shop bought carrots since they scrub them in some chemical which kills germs but blackens the carrots within a few days if left in the air.

We find that home freezing cannot sustain the range of freezing techniques and products available to commercial growers, who dip things in liquid nitrogen for example.

So we use our freezer differently.

Sometimes we just want to suspend deterioration for a few days to a week so leftovers go straight into the freezer for this time and this works just fine so that we don't have to eat the same things several days on the trot.

Also we try to store stuff that freezes well (or is prefrozen) or cheap at certain times or unavailable at certain times eg Christmas mince pies.

 

2 minutes ago, joigus said:

All of them? Blanch them first not matter which? Potatoes, carrots, cabbage...

I see no point freezing potatoes or cabbage.

They store pretty well in the garden are generally available all year round and take up a lot of space.

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5 hours ago, joigus said:

Does anybody know the molecular basis for this?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4921098/

Quote

The effect of boiling, steaming and microwaving on microstructure, texture and colour of raw and industrially frozen carrots was investigated. The raw carrots, after cooking, showed dehydrated and separated cells with swollen walls. The carrots subjected to blanching, freezing and followed by frozen storage exhibited marked tissue damages indicating deep oriented fissures. Cooking caused cellular dehydration and separation in the tissue, with the same intensity between raw and frozen carrots and independently from the cooking treatment applied. Among different cooking methods, microwaving showed better retention of the initial texture and colour quality for both raw and frozen carrots. On the other hand, the steamed carrots revealed the highest degree of softening and colour differences from the control for both raw and frozen carrots, despite the worst tissue conditions were observed for the boiled carrots.
<...>

freezing (and the following storage commonly applied in an industrial plant) appears as more detrimental than cooking on carrot structure, as large oriented fissures in the parenchyma were observed. Cooking caused the cellular dehydration and the separation in the tissue, with the same intensity in raw and frozen groups and independently from the cooking treatment applied.

Among the cooking practices, steaming highly affected the texture and the colour of carrots under the conditions applied in this study, despite the worst structure conditions were found in the boiled samples. This aspect needs to be deeply investigated. On the other hand, microwaved carrot revealed a good compactness of the cells with a good retention of texture and colour and no significant differences on cooked raw and/or frozen samples.

 

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Thanks a lot for the answers, @studiot and @iNow. Thanks also to you, @dimreepr. I would like to know whether it's in the proteins or the polisaccharides, though. As well as loss in nutritional value.

I should think it doesn't make that much of a difference nutritionally though, as pretty much everything "poli-" (protein or otherwise) hydrolyses in the gastric juices, and is broken into monomers.

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The key to freezing certain things successfully is the speed with which that process is done. Slow freezing generates much larger ice crystals than fast freezing, causing greater expansion within the cells and rupturing them, hence the commercial use of pre-immersing in nitrogen. Clarence Birdseye is the guy that learned this from inuits in Labrador and came up with a way to replicate their method commercially.

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46 minutes ago, StringJunky said:

The key to freezing certain things successfully is the speed with which that process is done. Slow freezing generates much larger ice crystals than fast freezing, causing greater expansion within the cells and rupturing them, hence the commercial use of pre-immersing in nitrogen. Clarence Birdseye is the guy that learned this from inuits in Labrador and came up with a way to replicate their method commercially.

Very interesting. Thanks a lot, @StringJunky.

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Same issue applies to the texture of ice cream. Placed in a standard freezer it’s crustier and doesn’t feel great on the tongue, but pour liquid nitrogen and you not only have immediate ice cream but also some of the smoothest you’ll ever eat. 

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Quick freezing/slow defrosting... Keys to yummier food.

As I understand, it's a question of texture. I wonder how significant all this is nutritionally.

I've read that, after a while, pretty much every macromolecule that you take in is broken down into monomers. The gastric juices are mostly hydrogen chloride, very acidic.

Somehow, your metabolic system is not "interested" in having carrot cellular tissue, but the amino acids it's made of, and such.

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I wonder why almost no mention is made of the vegetables losing lots of their natural healthy components by washing them and boiling them and freezing them and slicing them and slow-freezing them and fast-freezing them and blanching them and bleaching them   and ,,,,  and , , , , ,

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21 minutes ago, Prof Reza Sanaye said:

slow-freezing them and fast-freezing them

This has been mentioned and references, etc., given.

22 minutes ago, Prof Reza Sanaye said:

and blanching them

Mentioned also, and references given.

23 minutes ago, Prof Reza Sanaye said:

and bleaching them   and ,,,,  and , , , , ,

Extreme pH I would expect to more drastically change properties of macromolecules. But I haven't thought about it. Amino acids are notorious for being acidic and basic at different pH's, so they have a multiple-point sigma titration curve, if I remember correctly. If you wish to introduce this into the topic, you're welcome to do it. Please, give references.

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28 minutes ago, Prof Reza Sanaye said:

I wonder why almost no mention is made of the vegetables losing lots of their natural healthy components by washing them and boiling them and freezing them and slicing them and slow-freezing them and fast-freezing them and blanching them and bleaching them   and ,,,,  and , , , , ,

Perhaps because this thread is entitled carrots in the freezer, not vegetables in the freezer.

Or perhaps because your contention is not suported scientifically for carrots.

Or perhaps because folks just don't like assorted slugs, dirt and other material from unwashed carrots in the dinner ?

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5 minutes ago, joigus said:

This has been mentioned and references, etc., given.

Mentioned also, and references given.

Extreme pH I would expect to more drastically change properties of macromolecules. But I haven't thought about it. Amino acids are notorious for being acidic and basic at different pH's, so they have a multiple-point sigma titration curve, if I remember correctly. If you wish to introduce this into the topic, you're welcome to do it. Please, give references.

Very unfortunately , once again you have misread me . . . .   .. 

I said :  

" .....  

of the vegetables losing lots of their natural healthy components by washing them and boiling them and freezing them and slicing them and slow-freezing them and fast-freezing them and blanching them and bleaching them   and ,,,,  and , , , , , "

 

 

4 minutes ago, studiot said:

Perhaps because this thread is entitled carrots in the freezer, not vegetables in the freezer.

Or perhaps because your contention is not suported scientifically for carrots.

Or perhaps because folks just don't like assorted slugs, dirt and other material from unwashed carrots in the dinner ?

Or perhaps because nobody here cares for living "green"  ...............

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7 minutes ago, Prof Reza Sanaye said:

Very unfortunately , once again you have misread me . . . .   ..

That seems to happen quite a lot. Have you figured out what's causing it?

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2 minutes ago, Area54 said:

That seems to happen quite a lot. Have you figured out what's causing it?

Prof seems to be one of the most-oft-misread people since Nostradamus. ;) 

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5 minutes ago, Area54 said:

That seems to happen quite a lot. Have you figured out what's causing it?

Yes , I have 

I still am not an "in-wolf"  . . . . . .. .  

Older members  seem  to be . . . .

3 minutes ago, joigus said:

Prof seems to be one of the most-oft-misread people since Nostradamus. ;) 

And you : one of the most jesting ones , Sir  !!

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3 minutes ago, Prof Reza Sanaye said:

Yes , I have 

I still am not an "in-wolf"  . . . . . .. .  

Older members  seem  to be . . . .

And you : one of the most jesting ones , Sir  !!

What's life without some humour, professor? I think it's the only thing that redeems us a little in this valley of tears.

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Just now, joigus said:

What's life without some humour, professor? I think it's the only thing that redeems us a little in this valley of tears.

I real real agree with you . . .. .Absolutely right . .. I am a physically handicapped person and I  CAN  full well  understand the depth of this statement of yours . . .Many many thanx for that , Very Dear Joigus . . .. . 

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11 minutes ago, beecee said:

Witchitty grubs from Australia: 😁

ali

These are actually better frozen. Put them on a stick, lick them a couple of times, then throw them away and eat the stick. Good fiber.

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