Left frozen bloodworms out all night

[Dorkhedeos]

if freeze dried food causes "significant nutrition loss" why do they use them to feed soldiers and astronauts? ive heard from my teachers that freeze dried food is almost the same as the original state.

 

[Boxcar Muzzdogg]

ive heard from my teachers that freeze dried food is almost the same as the original state.

Key word: ALMOST.

I've been looking up info on the freeze drying technique ever since reading Bignose's reply. So far I've seen that the intention of freeze drying is to take the water out while leaving the basic structure of the food the same. However, that does not mean that is what results.

I have read several articles. The articles that claim that freeze dryed food is nutritious are of course from the companys that produce freeze dried food and therefore are not a very reliable source (the equivalent of McDonalds claiming its food is nutritious, which they do claim). Also, these articles never specifically adress nutrition loss, in any amount.

Then there are the articles that adress the nutrition loss in freeze dried foods. At best all I can say is that so far what I have learned about freeze drying is inconclusive, but I still beleive that there is nutrition loss in thawed/refrozen blood worms.

Also, dorkhedeos asked why, if freeze dried food is not nutritious, do they feed it to soldiers and astronauts. Well this is whta I have to say about that. For one thing freeze drying does not take out all nutrition, but does take out some nutrition.

Also, when is the last time you could trust the government to provide you with the best food? We're talking about guys that get paid less than grade school teachers to put their lives on the line in the middle of the desert. Do you really think the government is trying to provide them with the most nutritious meal possible? Its all about logistics and money. Freeze dried food is easier and more cost efficient to transport.

Which brings about another point. If there is no nutrition loss in freeze drying, why is it that frozen foods, although more expensive, are the foods bought most often by experienced aquarists and not the freeze dried foods?

 

[Boxcar Muzzdogg]

Bignose, I've been going through some of my books and freeze dried foods are apparently still nutritious, but not as much so as the frozen foods.

 

[Bignose]

Boxcar, I am still wanting to know, where, in the closed package, the nutrition goes?

And, here is a review of some of the scientific literature:

Title: Effects of initial weight and genetic strain on feed training largemouth bass Micropterus salmoides using ground fish flesh and freeze dried krill as starter diets
Author(s): Kubitza F, Lovshin LL
Source: AQUACULTURE 148 (2-3): 179-190 JAN 15 1997

The authors fed fresh and freeze-dried krill to bass fry and found no difference in final weights based on diet.

Title: Use of freeze-dried microalgae for rearing gilthead seabream, Sparus aurata, larvae - I. Growth, histology and water quality
Author(s): Navarro N, Sarasquete C
Source: AQUACULTURE 167 (3-4): 179-193 SEP 1 1998

The authors fed fresh and freeze-fried algae to larval seabream, and once again no significant changes in size due to diet. They also concluded that there were no water-quality issues based on feeding freeze-dried food.

These were the only ones I could find without doing a much more detailed search, but preliminarily, there does not seem to be any significant affects to the fish from being reared on freeze-dried food over fresh food. If, as you supposed Boxcar, there were significant nutrition loss, I would suspect that young fish grown would be signifanctly smaller or underdeveloped.

 

[Bignose]

here is a little more general article:

Title: Characterization of vacuum microwave, air and freeze dried carrot slices
Author(s): Lin TM, Durance TD, Scaman CH
Source: FOOD RESEARCH INTERNATIONAL 31 (2): 111-117 1998

The retention of the alpha and beta carotene and vitamin C is compared in fresh, vacuum microwave dried, blanched, air dried and freeze dried carrots.

Fresh was the best, but all the drying techniques kept greater than 90% of the vitamins.

I agree that freeze-drying is not perfect, but if this study is typical, keeping over 90% of its nutrition seems like a good compromise. The compromise being the much greater ease of storage -- doesn't need to be kept frozen, and food cannot be kept fresh forever and the slight lack of nutriton. In terms of fish food, if the entire foil square of the frozen food cannot be used, being able to portion the freeze-dried food could be another advantage. Some people are a little weirded out by keeping frozen worms in their home freezer, too. (To me, I keep the fish food in a bag, and its frozen in the little packages, so <shrug>)

I think that the big thing is that for the longest time everyone thought that freeze-dried foods were dramatcially, or in Boxcar's words, significantly less nutritous than the frozen food. But the facts do not bear that out -- Freeze dried food in terms of nutrition is virtually the same as fresh and frozen food.

 

[abstract]

-sorry

 

[Boxcar Muzzdogg]

Your right bignose, I have been doing some research on freezdrying and your right, freeze drying, although not 100% as good as fresh, is still nutritious. Where the nutrition goes when food is processed I can't tell you. Its been several years since I had chemistry.

 

[squeeker]

I am still wanting to know, where, in the closed package, the nutrition goes?

OK, so I don't have any scientific proof to back me up, but the way I understand is that thawing and refreezing, freeze drying, cooking, etc. causes the food to undergo a chemical change, ie, the molecules change shape, structure, organization. This change makes the molecules less processable by the body. Either the molecules require more energy to digest, or the molecules have changed into an unusable/less usable form. So, the nutrition doesn't GO anywhere, it just changes form.

Make sense?

 

[Bignose]

squeeker, you have to distinguish between the items in your list. Thawing, freezing are physical changes. Just changes between liquid and solid state of the water. No chemical reacions. Freeze-drying is also a physical change -- just the removal of water. Again, no chemical reactions. Physical changes are reversable. In this way, the nutrion should not go anywhere, so should not have changed.

If cooked, then chemical reactions take place -- which would change the constiuent molecules. But physical changes, by their definition, do not change the molecules. The topic started when a guy left his frozen food out to thaw -- not cook, not boil, not let mold or bacteria grow on it, just thaw. Which is only a physical change, so nothing should have changed.

 

[squeeker]

bignose,

That makes sense. Thanks for clearing me up!