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I have a bumper crop of french beans, runners, and (earlier in the summer) peas. I know that we're supposed to blanche vegetables prior to freezing and my general purpose cookbooks tell me how long to give each vegetable.

I believe that blanching helps retain flavour, colour and vitamins. But I don't understand how or why. It seems counterintuitive that the best way to preserve the vegetable immediately prior to freezing, as close to its natural state as possible, is to apply heat via boiling water.

You would think that just picking the vegetable and bundling it into your freezer as fast as possible would be the best way to preserve colour, vitamins etc.

Tea Drinker
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2 Answers2

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To prevent the vegetable from going 'off' in the freezer.

From answers.com:

Blanching is the scalding of vegetables in boiling water or steam. Blanching slows or stops the action of enzymes. Up until harvest time, enzymes cause vegetables to grow and mature. If vegetables are not blanched, or blanching is not long enough, the enzymes continue to be active during frozen storage causing off-colours, off-flavours and toughening. Blanching time is crucial and varies with the vegetable and size of the pieces to be frozen. Under-blanching speeds up the activity of enzymes and is worse than no blanching. Over-blanching causes loss of flavour, colour, vitamins and minerals.

Tobias Op Den Brouw
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    In some cases it also [alters the vegetable's respiration](http://dx.doi.org/10.1016/S0925-5214%2898%2900066-0) helping it freeze better. – papin Aug 11 '10 at 13:30
  • I believe you - the link doesn't make a connection between the respiration and it freezing better, though. – Tobias Op Den Brouw Aug 11 '10 at 13:33
  • Thanks, that's a pretty clear answer. And the extra info about the importance of not under/over blanching is useful. – Tea Drinker Aug 11 '10 at 14:39
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    I'm not saying this is right or wrong (it _sounds_ right to me). However, I would take answers from Answers.com and Yahoo! Answers with a grain (pile) of salt. I find the quality and accuracy to generally range from questionable to atrocious. Please don't interpret this as a comment on the quality of your answer, just a general advisement. – hobodave Aug 11 '10 at 18:26
  • @hobodave - oh, very seconded! – Tobias Op Den Brouw Aug 11 '10 at 21:25
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    Here is a published scientific paper that makes similar claims: http://postharvest.ucdavis.edu/datastorefiles/234-376.pdf , an excellent list of vegetables with their appropriate blanching times: http://extension.missouri.edu/publications/DisplayPub.aspx?P=GH1503 , and the best FAQ out there on freezing foods: http://www.uga.edu/nchfp/questions/FAQ_freezing.html – Naseer Aug 18 '10 at 16:55
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We have cut off our corn & immediately frozen it for years with no blanching. Guest at our table ask how our corn taste so fresh. We tell them: immediately freezing the cut off corn stops the enzyme growth continuing. Zero degree freezer does the same thing. The color and taste even 2 yrs. later is perfect. Save yourself a lot of work - don't blanch. Many do it just because Grandma always did - Grandma didn't have a freezer, she canned!

We do the same for our green beans too. They come out of the freezer in the winter months just like garden fresh...with no blanching. Do the extra work of blanching if it makes you feel better, or try this once and you'll be amazed at the ease and good taste of unblanched frozen corn & greenbeans.

KatieK
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David Blowers
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    That doesn't make sense, and is easily tested by doing batches of blanched and un-blanched veges. The blanching is to break down enzymes. The enzymes in particular are chemical catalysts that make the cells grow. they work fine in the freezer, just a little slower. In some vegetable the results are quite spectacular even after just a month in the freeze, as the vegetable continues to grow without fresh nutrients, is sort of soft explodes! Not very appetising. Yes corn isn't top of the list for this effect, but as per OP, beans and peas are! – TFD Sep 28 '12 at 13:38
  • @TFD: How do you explain why David's green beans still look great out of the freezer then? – Tootsie Rolls Oct 29 '13 at 16:07
  • I would guess that pods react differently than separated beans/peas. I do not have the science to back this up however. – Eris Jul 25 '15 at 22:34