Re: Scientific evidence concerning frozen veggies
I cannot say I have any authority in the subject, but it is part of what I am studying although its from my point of view as a chemist rather than as a nutritonist/dietician.
The points that had been raised here has been quite accurate in terms of frozen vegetables.
There is actually no harm in feeding your pets frozen vegetables. I think the major concern will actually be the water content than anything else. But then again, if you have the choice of feeding them fresh vegetables, why serve it frozen?
Frozen vegetables had been on on the receiving end of alot of flak. Admittedly, it used to be true in the sense that technology then was not as advance as technology now. Frozen vegetables has come a long way from being really horrible to eat with to being actually acceptable palette wise.
Lets look at vegetable from the chemistry point of view. Vegetables are technically categorised as Low GI carbohydrates, full of fibres in terms of cellulose and hemicellulose, beneficial vitamins especially water soluble vitamins and some minerals.
Water soluble vitamins. Beside A,D,E,K which belongs to fat soluble vitamins, water soluble meant that it need water to transport, synthesize and store. The downside is also because it is water soluble, it will also be rapidly lost through loss of water.
While certain water soluble vitamins are susceptible to oxidation like thiamin, the processes are different from those for the fat soluble vitamins. Processing medium or the environment is a critical factor in influencing the stability or retention of water soluble vitamins. Being water soluble, any processing and storage which increases the exposure of the vitamins to aqueous media will potentially lead to the leaching of the vitamins.
The B’s vitamins like Biotin, Thiamin, free folic acid, pantothenic acid and Vitamin C are also lost more readily at alkaline pHs. Other chemical processing agents will also contribute to the destruction of vitamins. Biotin for example is readily oxidized in the presence of H2O2. presence of transition metals like Cu2+ and Fe3+ in processing water will catalyse the oxidative properties of ascorbic acid to dehydro-ascorbic acid and then further oxidized to diketoglulonic acid with loss of bio potency.
Physical factors can also influence the loss of vitamins during processing and storage. EM radiation in the visible and near UV region is one such factor with riboflavin and pyridoxine two examples of vitamins that are photochemically degraded with attendant loss of vitamin potency. Temperature can also affect the loss of vitamins. Although certain vitamins like biotin and riboflavin are heat stable, but vitamin c, thiamin and folate for example are lost during heating.
After all the mumble jumble, your vegetables, despite as one said require transportation, etc... as long as the vegetable remains whole, capsicum for example and you only prepare it when you want to eat it, you will be able to have the optimum nutritional value you can get from that capsicum.
As mentioned, the vitamins are sensitive to transitional elements not just in the water but also to the point when you use your knife (the blade is metal) to cut through the vegetable, although minute, there will be an oxidation going on there.
To sum it up, although the technology in freezing vegetables has improved leaps and bound, in terms of holding up to nutrition, it is still inferior when compared to fresh vegetables. So, technically, if you are feeding your pigs frozen vegs, you are basically feeding them empty calories. just plenty of fibres but without much nutrition.
hope that helps.