Greenclaws, so YOU were one of the ones my Son was pitching the food to...LOL
I told him to watch the table while I did my presentation in the other room on Marine Fish nutrition and DIY foods. I came back 40 minutes later and and he pulls a wad of cash out of his pocket and said "I made a few sales." He then hands me my phone and he says "Oh yeah I swiped some cards on your Squared reader." (I didn't even know he knew how to use it...

)
So then the guys at the next table over said he was stopping people walking by and showing them feeding videos on his iPod. Did I remind you he was 13 years old....HAHA
Anyway, the ascorbic acid is not an exact science, in that I have no published lab tests on exactly how long it helps preserve freshness in OUR foods. I was told by a published Marine Biologist who made foods as well for personal use, that the ascorbic acid roughly cuts the rate that the HUFA (Highly Unsaturated Faty Acids) break down in half, verses the same pack of food without. This helps the food stay fresher in your freezer. I can add that my LFS used to buy my "old stock" when it was over 30 days old in my freezer and I didn't want to ship to a store and have it sit in their freezer. He has been feeding food that is 6-8 months old with no ill effects.
He also explained that one of the biggest "problems" with frozen foods is combating the breakdown of the fatty acids in the foods. By using clean food sources, and avoiding fish like salmon, mackerel, eels, silversides you can start off on the right track. The most important factor is it get your food blend into the freezer and flash freeze it ASAP. (Enter our $3,000 HOBART freezer) Another thing that can help is to not let your pack of food sit out of the freezer for any longer than necessary each night when you feed.
When searching for Ascorbic Acid make sure it is a pure powder and has no rose hips or other common supplements. I use a food grade, buffered version in a powder form, diluted with RO/DI. We mix large batches of food and add the Ascorbic Acid as an antioxidant.
I don't know how big a batch you are making, but I would say if you are making an 8-10 pound batch of total volume raw ingredient weight, that a two teaspoons diluted and distributed throughout the mix would be safe.
There are a lot of people who dose Vit-C as a carbon source, but you want to use the minimal effective amount to avoid kicking off any blooms. In your ten pound batch two teaspoons would be divided amongst 18 packs of food at 9 oz. On a daily basis this is a minimal amount.
One thing that is also interesting about Vit-C is that there is a secondary benefit, which is also up for debate as to effectiveness, but I have found it to work. Over the past year, every fish I have purchased was placed into a QT tank dosed with Brightwells liquid Vit-C. I had read an article that stated that Vit-C can actually stimulate new fish to eat and acclimate better.
Can I prove it, nope. But last year when I flew to ORI and toured 5 other wholesalers in LA, I bought several fish over the next months and suffered not a single loss or refusal to eat. Does the Ascorbic Acid help kick off the amazing feeding response in our foods? I'm not sure.....
By the way if you have a "Chef Smart" store near you they have awesome strainers and bowels, dirt cheap.
I have a pic of my son at the trade show with a customer, but I'm not sure on the rules for posting, since it has my banner in the pic. It is pretty cool though to see the little squirt in action...
I hope I helped answer you question....don't hesitate to ask anything else.
This info is interesting as well:
http://www.advancedaquarist.com/2012/3/chemistry">http://www.advancedaquarist.com/2012/3/chemistry</a>
Good Luck,
Larry