Cooking and freezing food, particularly starches

[swieton]

I like cooking big batches of things ahead of time and keeping them in the chest freezer. I live alone, so it's nice to have a nice stew ready to grab whenever. I've also had some really great luck pre-seasoning chicken breasts and freezing them, then cooking sous vide from frozen. Sous vide, a big freezer, a pressure cooker, and some planning ahead have really helped me to be able to fairly easily throw together a meal and sides without a lot of immediate work.

 

However, one area that I've had trouble is freezing starchier things: mashed potatoes or lentil soup / dahl, for example. In both cases they separated and the texture changed badly.

 

Some research I've done points to there being a lot of stabilizers that I could use to prevent this: carrageenan, guar gum, other gums, etc. However, most of the information on them seems to focus on using them as gelling or thickening agents, which is exactly the opposite of what I want (e.g.: http://blog.khymos.org/wp-content/2009/02/hydrocolloid-recipe-collection-v3.0.pdf ).

 

This paper from a Korean university has some good info: foodchem.net/publication/files/2002-03-03.pdf and it sounds like guar gum could be a very effective tool for helping things freeze and thaw better. But I'm still not really clear on *how* to use it. The paper's suggested 0.6% concentration seems like a lot to add to a dish that I don't actually want to thicken noticeably. I do plan to experiment with a few concentrations to see if I can figure out how to work it, but I thought I'd ask.

 

Anyone have any suggestions? Is there a better approach? Is this whole concept just totally boneheaded (... wouldn't be the first boneheaded thing I've done)?

[Lisa Shock]

I have always had issues with freezing potatoes and just generally avoid doing so. I freeze stews then reheat with raw potato in them, long enough to cook the potato. I'm not all that fond of frozen potatoes either, and I can spot a frozen french fry a mile away. (frozen fries are terrible if cooked then left to get cold, fries made from fresh are still edible if they sit around and get cold) I just don't think there's an easy solution for the problem.

 

The additives you mention are probably for things like purees, like cream of potato soup. They don't make a lot of sense for a chunky stew where they won't penetrate the insides of a 2" hunk of potato.

[swieton]

I have always had issues with freezing potatoes and just generally avoid doing so. I freeze stews then reheat with raw potato in them, long enough to cook the potato. I'm not all that fond of frozen potatoes either, and I can spot a frozen french fry a mile away. (frozen fries are terrible if cooked then left to get cold, fries made from fresh are still edible if they sit around and get cold) I just don't think there's an easy solution for the problem.

 

The additives you mention are probably for things like purees, like cream of potato soup. They don't make a lot of sense for a chunky stew where they won't penetrate the insides of a 2" hunk of potato.

 

Agreed, Lisa. I don't really expect there to be any way to fix chunks of potato, but I think there are a lot of things that are closer to purees, such as the potato soup you mention, or mashed potatoes, or other soups, or sauces, and I'd be eager to hear anyone's experiences.

[paulraphael]

I can think of a couple of additives to play with for the purees. This is just theory; I haven't tried any of it. One is low methoxy or low methoxy amidated pectin. The other is xanthan gum. I'd try adding to the milk you use in the mashed potatoes (the pectins would require this; they need calcium to activate). These thickeners are freeze-thaw stable and don't exhibit synerisis, which is the official name for liquids weeping out of a gel.

 

My guess is that potatoes separate after freezing because because potato starch isn't freeze-thaw stable, and that potato starch-thickened gels will exhibit synerisis after thawing but not before. Maybe getting some other thickener in there will help. But I wouldn't bet too much on it.

 

Another thing to try (easy since you have a sous-vide setup) is to retrograde/set the starch when you cook the potatoes you plan to puree. There's a thread on that around here somewhere. I suppose there's a chance that this will reduce synerisis after freezing.

 

One thing to try before messing around with thickeners is to talk to a rep at TIC gums or Kelco. They have experts who give guidance to food industry people. There may be a concoction with a name like MashMaxFreezePro9000 ... and if so they'll probably send you a free sample.

[swieton]

I can think of a couple of additives to play with for the purees. This is just theory; I haven't tried any of it. One is low methoxy or low methoxy amidated pectin. The other is xanthan gum. I'd try adding to the milk you use in the mashed potatoes (the pectins would require this; they need calcium to activate). These thickeners are freeze-thaw stable and don't exhibit synerisis, which is the official name for liquids weeping out of a gel.

 

My guess is that potatoes separate after freezing because because potato starch isn't freeze-thaw stable, and that potato starch-thickened gels will exhibit synerisis after thawing but not before. Maybe getting some other thickener in there will help. But I wouldn't bet too much on it.

 

Another thing to try (easy since you have a sous-vide setup) is to retrograde/set the starch when you cook the potatoes you plan to puree. There's a thread on that around here somewhere. I suppose there's a chance that this will reduce synerisis after freezing.

 

One thing to try before messing around with thickeners is to talk to a rep at TIC gums or Kelco. They have experts who give guidance to food industry people. There may be a concoction with a name like MashMaxFreezePro9000 ... and if so they'll probably send you a free sample.

 

Thanks! That's some good ideas to try!

 

I have some xanthan gum, and I've ordered some guar gum, and I plan on running some tests next week with a control and a few different experiments. The pectin is a really interesting idea - not one I'd run into in my research thus far. I'll definitely have to take a look!

[paulraphael]

Lisa's experience with frozen fries makes me a bit pessimistic ... if anyone could be expected to know about this stuff, it's frozen food manufacturers. I'm under the impression that frozen fries are made from ground up potatoes that are stuck together somehow, which would make them more like a puree than like chunks of tater in a stew. But who knows. Keep us up to date on your tinkering.

[JAZ]

Lisa's experience with frozen fries makes me a bit pessimistic ... if anyone could be expected to know about this stuff, it's frozen food manufacturers. I'm under the impression that frozen fries are made from ground up potatoes that are stuck together somehow, which would make them more like a puree than like chunks of tater in a stew. But who knows. Keep us up to date on your tinkering.

 

That's not usually true -- tater tots are small chunks of potatoes stuck together, but as far as I know most frozen fries are cut from whole potatoes, then blanched in oil. Kenji Alt actually suggests freezing homemade fries after cooking most of the way (here), although he freely admits that he's after McDonalds-style fries.

[swieton]

Some results! After trying a few things, I believe I have a mashed potato recipe that freezes well. At some point I'm going to make it again in a larger quantity so that I can test frozen against unfrozen side by side, but things are looking good so far. After defrosting a sample, the fats had not separated from the mash visibly, and there wasn't any water visible at the bottom of the container or leaking from the potatoes.

 

I designed the recipe below based on the eGullet potato primer for a basic fluffy mash, and used guar gum per the concentrations found in the 2002 paper Freeze±thaw stabilization of sweet potato starch gel by polysaccharide gums, which found that guar gum was among most effective at preventing syneresis. I think in all likelihood the guar gum modification could be applied to other styles of mashed potatoes or purees, but I haven't tested that yet..

 

Here's what I've come up with:

 

• 500g dry, floury potatoes, such as Idaho Russet
• 50g unsalted butter, melted (10% of potato weight)
• 20g cream (4% of potato weight)
• 2.25g salt (0.4% of total weight)
• 1.75g guar gum (0.3% of total weight)

1. The temperature for retrogradation was chosen based on Ideas In Food (chapter “Pasta, Gnocchi, and Risotto” pg. 124-6,) where they note the gelatinization temperature of potatoes is 136˚F - 150˚F.
2. Retrograde the potatoes by cooking in water in a bag sous vide at 67˚C/152.5˚F for 30 minutes.
3. Cool potatoes completely.
4. Cook the potatoes a second time, until tender.
5. Combine salt, guar gum, melted butter, and cream.
6. Pass potatoes through a ricer into a large mixing bowl containing the room temperature butter.
7. Mix.
8. Adjust salt to taste.

[Lisa Shock]

That makes a lot of sense. Guar gum freezes well, holds things together, and holds air bubbles well, for a very long time. I have seen melted ice creams with guar gum hold their texture for days after being thawed. -The frozen ice cream was only a little firmer than the thawed ice cream.