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Dehydrating

 
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I got into in interesting discussion with another homesteader. Do you blanch foods before you dehydrate them?
 
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I am sometimes not even wash them or when I wash the fruits/veg, I let them dry before putting in the drying machine.

Blanching before seems counter-intuitive to me.

What are the reasons for blanching before?
 
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Yes for most vegetables, so all root veg, peas, beans etc. but not for fruit. So I guess it's a yes to anything that would be eaten cooked. As to why two reason I believe it stops some of the enzymes that cause the vegetables to lose quality, and the other is that hard things dry faster once cooked in my experience.
 
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Your produce/fruit might be infested with insect eggs. dehydrating it will not kill them, so they can hatch and take over your pantry.
1) Blanch before dehydrating
2) Pasteurize after dehydrating
3) Freeze after dehydrating

Then you have enzymes and microbes that will break down your food, and so to stop the process you will have to do some type of pre-treatment.
1) Sulphur (this is what the big companies use)
2) Ascorbic Acid
3) Acidic Fruit juice
4) Honey
5) Blanching for vegetables and fruits

If you are only going to keep your dehydrated fruits for 8 weeks or so, then the treatments are not really needed, (mines hardly every last that long).

Blanching is also a good way to wash of dirt/soil from your produce and also to kill human pathogenic microbes/parasites that are on the skin surface. But if it is from your own farm/garden then it really doesn't matter, because you are already got them and your body has developed an immune response to them.
 
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I don't blanch anything, and I dry a lot of vegetables, because we cannot buy any fresh non-local vegetables from December to May in my region. Sure, we have stored root veg, and fresh leafy greens from the greenhouse, but we will not see any fresh summer vegetables such as broccoli, eggplant, tomatoes, etc all winter and spring. I dry things on trays on the roof, because I live in the desert.

Here's what I dry, all without blanching. They seem to last in the same condition and flavor for at least one year, sometimes more.
Broccoli, cauliflower. I make sure to slit the stems so they'll dry faster, though.
Eggplant in bite-size pieces, zucchini in thin chip-type slices, bitter gourd in thick slices.
Turnips, beets, in chunks or slices.
Shelled peas. Green beans cut in half inches.
Tomatoes cut in sections like an orange and standing up on the skin side.
Herbs: easy and great, but a lot of them keep growing through the winter in my greenhouse.
Fruit: apricots, apples, bananas in bite size chunks.
Leafies: My greenhouse prduces greens through the winter, and lots of dried leafy greens are available in the market here so I rarely dry my own, since they take so much space to spread out to dry, and are hard to keep from blowing around on the roof.

All the American books and advice say to blanch vegetables, but local people here don't, so I dried a lot of stuff with my students without blanching. But then I thought maybe it really would be better to blanch, so I tried it three times. Cauliflower turned much darker after blanching. Green beans turned bleached white after blanching so I composted them. Broccoli that was, granted, a bit old and aphidy, I blanched, but when it was half dry it stank, so I composted it.

I get great results without blanching, and don't seem to have much deterioration over the year.
 
John F Dean
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I have never blanched before dehydrating.  I have never encountered problems.  My friend was shocked.  So, of course, I got curious.
 
S Bengi
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I have never blanch/pasteurize my own produce either, I am sure that historically no one did this when they got their produce onsite or from the same local farmer. But with the current industrial agriculture it makes a lot of sense to pasteurize our milk and foods that we will dehydrate or even ferment. Who knows what pesticide/microbe we will be eating if we don't 'wash/blanch' it off with hot water. For my own produce, even carrot. I just pick it and eat it, no washing, with my crusty dirt filled hand, and if I dehydrate it, ditto.
 
Rebecca Norman
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Rebecca Norman wrote:I don't blanch anything, and I dry a lot of vegetables,

... But then I thought maybe it really would be better to blanch, so I tried it three times. Cauliflower turned much darker after blanching. Green beans turned bleached white after blanching so I composted them. Broccoli that was, granted, a bit old and aphidy, I blanched, but when it was half dry it stank, so I composted it.



After reading this thread, I thought I'd try blanching one more time, but -- Ugh! Nope, not for me!

The blanched broccoli turned black on the floret part, and yellowish brown on the stems, whereas the raw broccoli dries green. It did dry faster, and the stems were easy to peel after blanching, but the final result is unappetising.
drying-vegetables-on-the-roof-in-ladakh.jpg
Drying vegetables in high desert sun under a screen
Drying vegetables in high desert sun under a screen
dried-broccoli-black-is-blanched-and-green-is-dried-raw.jpg
Blanched broccoli turned black and raw broccoli stayed green when dried
Blanched broccoli turned black and raw broccoli stayed green when dried
 
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We always very lightly steam blanch green beans, peas, sweet corn, broccoli, cauliflower, and asparagus. This process inactivates enzymes that would otherwise turn sweetness into starch and the eating quality is better than not blanching.  If I were to dehydrate carrots and beets, etc. I would do the same for those veggies but we prefer to store them "live" in the root cellar. Our dryer keeps sunlight off the veggies so the color is retained. You can read about our dryer here: http://geopathfinder.com/Solar-Food-Drying.html
 
Rebecca Norman
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trees food preservation solar greening the desert
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Thank you Larisa, that is really good to know, because I believe from your popular dryer design that you have extensive experience drying vegetables. If I ever make a shaded dryer, I'll keep in mind to try a blanching comparison again. In my climate, just drying in the sun under a screen works great, but I'd like to make a shaded dehydrating cabinet someday.
 
Larisa Walk
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At minimum, to preserve nutrients that are bleached out along with the vibrant color, you can simply put your food screens under a "tent" of black fabric. The tent can be made by using another screen on top of the food screen to keep the fabric from sticking to the produce. Put a window over this and you're at the stage we were when we were experimenting with this concept. Tilt it all slightly and you're completely there. No need to "build" a dryer completely. This concept also works with a car parked with its biggest window facing the equator, screens inside with black cloth over the food and the windows down about an inch.
 
Rebecca Norman
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Larissa, have you tried blanched and unblanched food? Which things have you compared?

In the high desert conditions here, your type of dryer might actually burn foods that contain a decent amount of sugar, such as tomatoes or fruit. Our school used to have a dryer built by a student, that was somewhat like yours, and I found that seabuckthorn berries and tomatoes would actually burn blackish and taste burnt. It was fine for less sweet things, like eggplant and leafy greens, and I also learned to angle it away from the south so it wouldn't get so hot. Here, the air is so dry most of the time, often below 20% rh, that additional heat is not needed to reduce the rh. I am planning to make a screened cabinet that will allow air to circulate freely through it, but have some sort of roof that will shade food from midday sun, and protect from the rare light rain that we occasionally get. Unfortunately due to Covid, there's a severe shortage of carpenters and furniture makers in our area this year, so I'm using a low tech screen instead.
 
Larisa Walk
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Blanched versus unblanched - most notable difference in green beans and sweet corn. More palatable, sweet, and tender when blanched. One of my first forays into drying food was to make "leather britches" where you take a needle and thread and string up green beans to hang and dry. The name should have been a clue as they were about as edible as leather britches - maybe if you were starving you might want to eat them. If you're not convinced, you need to experiment on a small scale before committing big batches. As for using our dryer design in other climates, you can permanently tone down the efficiency by using a paint color other than flat black. Dark blue or brown works too. But rather than making this a permanent "fix" I suggest using shading over the glazing that can be removed when conditions like cloudy weather would warrant the full heat output of the collector. A sheet, cardboard or window screening can be placed over all or part of the collector as needed to reduce the heat input. You will still have the passive air flow through the slightly tilted unit as hot air will still rise and draw off moisture. No sun on food, rain no problem, critters kept out. Having the screens in a single layer, not stacked, makes solar drying more possible in all climates as you're not trying to move moist air through multiple layers of screens/food. As for burnt or carmelized foods, that is also possible here in the midwest. We've had it happen with sweet corn, tomatoes, and even melon. The first time it happened I thought the corn was ruined, but found that in some recipes the carmelized flavor was an additional bonus. And for tomatoes, a little blackening gives the flavor of roasted tomatoes without the effort and energy inputs. Really nice added to chili along with some of the carmelized corn. The melons are still edible with a different flavor profile. Not sure if I would strive for this outcome with melons but putting very sweet foods in the "lower" trays, positioning dryer off the north-south axis (face to the south east), or using shading, reduces the chances of this happening on extremely hot days.
 
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John F Dean wrote:I got into in interesting discussion with another homesteader. Do you blanch foods before you dehydrate them?


Hi everyone, I've been just reading and unsure if this is how we reply and post.. if I'm doing it incorrect please advise.
I don't blanch anything before dehydrating, however I do soak the fruits and veggies for about 10-15 minutes in a regular peroxide (1 tbsp to 1 gal) water bath, then rinse and dry. For delicate produce like leaves and thin skinned fruit the soak time is shorter.
Also removing the produce as opposed to draining the soaking water out is preferred as any grit from the garden will settle to the bottom of the pail.  
 
John F Dean
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Hi B Bailey,

Welcome to the Permie site.
 
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Not sure everybody interprets the same when talking of blanching. Maybe should introduce it.
Blessings.
 
John F Dean
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Hi Eduardo,

That is because everyone has a different approach. To make the question  more simple I left it at blanch or not.  Yes, some people blanch for a second others for minutes.  And the exact medium as to what the blanching is done in can vary as well.
 
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Excellent topic. I'm glad for everyone sharing.
I've never blanched any of my food before drying living in Iowa.
I have been using excalibur dryer and vacuum seal in bags when done.
I haven't had any issues but I like the dryer you've built, Larissa.
I'm going to seriously consider doing this for next year.
Thanks so much for sharing!
 
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I hadn't thought of using peroxide, B. Bailey.
I will give this some thought.
 
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Mostly I do not blanch. I mostly just wash things the same way I would if we were going to eat it right then.
 
Larisa Walk
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To be clear, when I said I blanch it's not a matter of "disinfecting" or cleaning the produce. I blanch to partially cook the food so the finished outcome is enhanced. For instance, with sweet corn, the cobs are steamed until the color slightly changes to a brighter color, beads of "sweat" on the kernels. It's a bit on the underdone side for eating for most folks, but enough so that the corn will stop its march to starch which is what mature corn kernels are all about. The same for beans and other seeds that are trying to store up energy for future germination. I don't time any of the blanching as it depends on how big a batch is in the pot, but the color shift is what I'm going for, pulling the produce out of the pot as soon as it gets the brightness in color that I want, then putting the hot produce directly in the dryer, getting it spread out right away to stop the cooking process. For some non-fruit veggies, like asparagus, the texture is better in my opinion if lightly steamed first. But some veggies are better left alone, such as peppers and eggplant. If you're unsure, experiment to see what you like.

As for washing before drying, I try not to do it immediately before processing but rather when the food is harvested. I usually pick for the dryer in the afternoon so I can have ready to go produce ready first thing the next morning to get it into the solar dryer early. I also have the kitchen set with whatever cutting tools/bowls/etc. needed so I can get to work right away. The exception to this advance harvest and prep is fresh herbs/greens which are picked after the morning dew has evaporated. I'm careful when I pick (nothing with obvious dirt splash or bird poo) and put these items into the dryer without washing first.
 
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