Drying Mechanisms Help

Well of course it always comes down to price vs quality desired...generally speaking the faster you can dry the fruit the better for preservation of nutrients...but the method may be varied according to specific use...whether food or nutraceutical...

Nice study here on different methods...

...."in order to avoid or slow down food spoilage by microorganism. At this point some understanding can arise derived from the vocabulary employed; common words found are “drying” or “dehydration”, or even “dewatering”. There are various aspects that must be considered when drying small fruits and vegetables, whether for the food or nutraceutical and functional food industries. A system which minimizes exposure to light, oxidation and heat, (i.e. high heat 70 oC and shorter time duration) may help conserve critical bioactive compounds. This review focuses upon conventional and new drying technologies and pre- treatment methods based upon drying efficiency, quality preservation, and cost effectiveness"....

https://www.researchgate.net/publication/275650176_Different_Drying_Methods_Their_Applications_and_Recent_Advances

https://www.dryer.com/Dehydration-101

Thank you this is very insightful.

I would think it depends strongly on which fruit you're dealing with.

Considering the fact that most dehydrators,regardless of method, tend to dry unevenly,it might be a good idea to introduce some of the exit air back into the system,distributed to all levels to ensure a more evenly distributed drying process.

Your list of 'techniques' is a bit confusing too. Except for freeze-drying, there are two fundamental techniques (1) involving heat (2) involving a fan. Or both together. And power source is the other variable you listed: electric, kerosene or solar.

The combination of heat and a fan is always going to be "most effective" for drying, with the caveat that excessive heat will affect quality of the product, and depends on exactly what is being dried, some things being more sensitive to heat damage than others.

Moisture content of the fruit can be measured by loss of weight on drying:

https://www.tovatech.com/blog/4349/moisture-analyzers-2/check-dried-fruit-quality-with-moisture-balance

There is a better overview of all the issues here:

http://www.fao.org/3/a-au111e.pdf

In a dried fruit, the correct moisture content for the end product is critical. Overdrying also means quality loss. Overheating or sun exposure can cause fruit to brown, and loss of vitamins A and C. You could test for vitamin content as well, as a quality measure, and/or measure the final color.

Much depends on what exactly you are drying!

Thank you pal, that pdf was so informative, and right now I'm just looking at dates, grapes and various nuts.

A good rule of thumb is the more surface area exposed to the air the more effective and efficient it will be.

As mentioned already, a vacuum will lower the vaporization point of the water.

Even a slight negative pressure will have an effect.

Good luck!

We were watching TV over the weekend and we saw the answer to your question! The Holy Grail of cooking. It's called the air fryer. TA DA!!! Let me restate - It's called the air fryer. TA DA!!!.

Our good friend Emeril was playing with on and he was amazed at all the things you could do with one of these ovens. Is it a toaster oven? No!!! Is it a deep fryer? No!!! Is it the most handy kitchen appliances devised since home refrigeration?

Watch the commercial and you'll see how a slacker like any of us can make gourmet food that rivals top chefs of the coveted Michelin star rating system.

By the way, I'm doubtful that I've eaten at a Michelin star restaurant. Don't get me wrong, I've had some incredible dinners, but I don't remember any having a Michelin star.

Back to the dehydration issue. Check out Emeril's Air Fryer. Why?

1. It's an air fryer and dehydrator built into one.

2. Emeril is famous and he'd be so embarrassed if he touted a junky product, wouldn't he?

3. No matter what they say, it's not a convection oven.

4. You can purchase one with four easy payments of $49.99 each.

5. Shipping is free, so order NOW.

6. You get a free Power Quick Pot - a $100 value, yours if you call in the next 20 minutes. Operators are waiting.

7. It's better than the Nuwave Bravo - Emeril says so.

8. You can't live without one.

Emeril's Air Fryer

I have never eaten at a Michelin Star restaurant,but I have eaten a so called "steak" or two that had Michelin in raised letters on it.70R15/65 If I recall right.

At least it was the side wall,not the tread.

I've had some that were as juicy as a leather boot! Make that a dried out leather boot that has been baking in the Sonoran Desert for the past 12 years.

Though I didn't check the sidewall for any markings ...

Having designed dry kilns, you will possibly want to determine maximum drying rate and minimum desirable ambient humidity. In some cases you may find that if the drying rate is too high, you dry a surface layer and lose permeability from the interior to the surface, effectively locking a moist core in a dry shell. In every case in drying wood, we had to maintain nearly 100% humidity to attain through drying. Also in most cases, initially a material being dried in a high humidity and heated environment would reject large quantities of free liquid, which would likely be a bad thing for food products where you want to retain flavor and nutrients.

Ambient humidity of the bypass air is significant as is the ambient pressure.

You might also like to look at "freeze drying" to understand how vacuum can be used to dehydrate with minimal temperature increase.

An intermediate process with modest vacuum can create significant drying effect and if the drying rate is kept SLOW enough, cooling is not essential. Need to keep pressure high enough that water doesn't "boil".