Notes on Gelatin

[For the most basic text, please refer to Regan Daley’s, In the Sweet Kitchen. It’s a great book that details many of the basic ingredients we use every day. Another succinct source is Gillian Hirst’s article from The Courier-Mail, July 15, 2008. Please see brief additional references at the end.]

What is gelatin? Gelatin is an ingredient used to thicken liquids. It is made from collagen. (Collagen comes from connective tissue and bones – both animals and fish.) Agar agar is a seaweed based product and can also be used to gel. (You may also see Kanteen or Carrageenan. These are also plant-based.)

How does it work? When you add gelatin to water, it swells and absorbs water. You can heat it and it will dissolve. However, it is not completely gone. Instead the protein molecules are suspended in the liquid. As the liquid cools, the protein molecules form structures. Because they are hydrophilic (water loving), they hold the water in place.

Types of gelatin: Gelatin (or agar agar) can be found in powdered or sheet form.

1 envelope of Knox gelatin is about .25 oz (.256 grams) and gels 2 C liquid

There are many conversion equations on the web. Powdered agar agar can be substituted 1:1 for powdered gelatin. For every teaspoon of agar powder, you can use 1 T of agar agar flakes. You can adjust the proportions to get stiffer or less stiff gels. I’d also suggest looking at the package or information from the supplier.  Variations in agar powder purchased at Asian markets may exist.  [You can go to this other article that also discusses variations in sheet gelatin.  Or search on egullet where extensive discussions about variety and quantity of sheet gelatin can be found.]

*****In order to understand some of the differences between the gelatin types and gelatin in general, I decided to run some controlled experiments.*****

Experiment 1: It’s always fun to play with gelatin but not as much fun if the gelatin fails to set. Fresh pineapple is supposed to inhibit the gelling process because the enzyme bromelain (protease) will break down the proteins provided from the gelatin. (It’s a bit ironic because bromelain is a protein itself.)

I wondered whether you could get rid of the effect with just a small amount of cooking. (Canned pineapple is cooked but the cooking is much greater in order to insure a healthy product for consumers. At home it might be possible to cook for a very short time and preserve some of the more natural look and feel of the pineapple.) In this experiment, I compare fresh pineapple with canned and briefly cooked pineapple to see what happens.

IMG_2763Cond. 1: control – no pineapple
Cond. 2: fresh pineapple
Cond. 3: canned pineapple
Cond. 4: pineapple sautéed just 5 minutes

IMG_2764Liquid: 1 C water with a little juice

IMG_2673Gelatin: Knox

Procedure: I sprinkled the Knox over the liquid and let stand 5 minutes. Then I cooked until it went clear. I poured the liquid into the bowl and then repeated this procedure for the remaining bowls. I chilled the bowls for 3 hours.

Result: I asked several other people to judge the texture of the bowls. The only bowl that did not set up was the fresh pineapple bowl. You can see this visually in the pictures by comparing the liquid nature versus the solid nature. Thus, you can use a very short cooking time for fresh pineapple when making gelatin desserts.

IMG_2767IMG_2768IMG_2771IMG_2772

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Experiment 2: I loved the texture of Johnny Iuzzini’s strawberry-cherry compote and how so little cooking time was needed. In order to understand the differences between agar types and gelatin (and types of gelatin), I decided to do a basic experiment to explore texture differences.

IMG_2774

Cond. 1: Knox envelope (1/2 envelope or 0.127 grams)
Cond. 2: agar agar, powder, envelope – find in Asian stores (0.127 grams)
Cond. 3: agar agar, flakes, Eden foods – find in Whole Foods (2.5 grams Used)
Cond. 4: Gelita small sheet in yellow envelope (3 sheets – based on the back of the envelope information)
Cond. 5: Rousseau large sheets (silver) from L’Epicerie (2 sheets – based on information from seller’s site and rule of thumb)

IMG_2776Liquid: 1 C juice, Knudson mango lemonade

Procedure: Each type of gelatin requires a different cooking procedure. After dissolving each type of liquid, they were put into bowls and refrigerated.

A) Knox needs to be sprinkled over cool liquid and allowed to soak for 5 minutes. Then you just cook until it dissolves. B) Agar agar needs to be put into the liquid. You bring the liquid to a boil, reduce the heat and cook for 5 minutes. C) The gelatin sheets need to be soaked in cool water. Then you ring them out gently to remove excess liquid and place them into the liquid you’d like to gel. This liquid is then heated until the sheets are dissolved.

Results:

1. The first time I ever cooked agar agar was from a package from the Asian market. It was powder and as I cooked it, you could “smell the sea” but the finished product tasted like gelatin. Both types of agar did not have that smell. However, after cooking the agar pots and pouring into the bowls, the agar bowls had less liquid. On the web, you can find places where they say that agar sets more solidly than regular gelatin. This is true when you control for the initial amount of liquid but may be due to evaporation and not gelling properties.

Second, the gelling properties were vastly different. All the regular and sheet gelatins produced gels that were similar with differing levels of gel. The Knox produced a gel that was exactly as expected. The most gelled was the Gelita short sheets. Given what happened, I’d guess that the back of the envelope was incorrect and going with the rule of thumb 1.5 or 2 sheets would have been better. (If you read Hirst’s article, Gelita has some variability and therefore you might have to play around with the proportions.) The Rousseau sheets produced a texture similar to a slightly thicker panna cotta – it was beautiful.

The quality of the flaked agar agar was more like a pudding. This was some what true for the powdered agar agar.

Third, for taste I had many people trying the bowls of mango gelatins. The regular and sheet gelatins preserved the flavor of the juice. The agar bowls had a changed flavor – they were almost tangy and tart, as compared with the others. This might not be due to the seaweed and could be due to the concentration of the liquid based on the additional cooking time needed to set the agar. Everyone had different opinions about what they liked.

My take: I can see how mixing the different gelling agents would produce interesting results and would like to explore this issue in more depth. There are interesting geling agents out there that are not available in regular grocery stores. I’d like to explore those as well. In terms of procedures, what I’d also like to understand is probably how much more the different gelling agents solidify over time – Although all the bowls set by 3 hours, some bowls were set in 2 hours. We didn’t try them for 6 hours. Does the process of solidifying last for more than 6 hours and the bowls would have become even more solidified?

References (not listed above)
1)answers.com on gelatin
2)How does gelatin gel
3)Science post on gelatin

1 Comment Add your own

  • 1. Peaches and other updates « Etudes in Food  |  August 26, 2009 at 12:09 pm

    […] that I’ve added a full page treatise on gelatin and added travel pages for Oahu and the Big Island (albeit not as long as Maui.)  We’re […]

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