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Hydrocolloids, Pt. 1

By October 12, 2010Cooking

I started to write this a couple weeks ago, then my parents came to visit and I forgot to clean it up, so the opening few paragraphs there are a little chronologically handicapped.

This past weekend, Sarah and I went to the Ferry Building Farmer’s Market in San Francisco. Aside from it being the most awesomely mind-boggling thing ever, it gave me some direction in terms of what I want to make next. Huckleberries and Matsutake are coming into season here. I know what neither of these taste like, so I’ll try to gun for them while they’re available [editor’s note: huckleberries are delicious — Oct. 12, 2010].

The huckleberry recipe, along with another recipe I’m doing some planning for, delve deeply into use of hydrocolloids. I’ve used these very often through this project, but honestly I’ve done so blindly, with only the slightest attention paid to patterns or understanding. But I decided I’d like to pull back on simply following recipes and start trying to build an intuition for how some of these things are used. My friend Kevin has been baking bread every weekend for months to build an understanding of how breads are made; he wants to understand how they work enough that he might make his own bread from scratch. I’d like to be able to do the same with some of this stuff.

Information on the intertubez seems sparse. A bit of searching turned up this handbook, which I’ve found to be incredibly helpful. I’ve emailed the writer of it with some followup questions, and thankfully he is very friendly and responsive. I emailed Ideas In Food, to ask them if I could ask them some questions, and got a brief response plugging their upcoming book but not much else. Questions on the Alinea Mosaic are going unanswered, I assume because of the momentum behind the opening of Next and Aviary. Amazon lists a few textbooks on hydrocolloids, but they’re up around the $250 mark per pop, which isn’t something I can afford at the moment.

My plan at this point is to try to figure out as much as I can from the khymos Textures handbook. I’m just going to bang at some experimentation and see what I can find. Last night I tried a very simple experiment with gelatin. The Textures handbook mentions that gelatin forms gels at concentrations of 0.5-1.5%. My very first question was “0.5-1.5% of WHAT?” Does that refer to water content, or total weight of ingredients? If the former, how do I measure water content of something?

I asked Sarah’s dad, who teaches Organic Chemistry at the University of Kentucky. He explained that chemists usually express percentages as related to total weight. So 400g water mixed with 100g sugar would demand 5g of gelatin (1% of 500g) to form a gel. This is a pretty great fundamental thing to know.

My next assumption: if gel strength is a product of the ratio of water to gel, then would pure water form a weaker gel than, say, carrot juice, whose weight is comprised of water plus some solids? 500g pure water obviously has ‘more water’ in it than 500g of carrot juice, so would the same amount of gelatin in each result in a firmer carrot gel than a water gel?

I thought so. Then I tried actually doing this. I mixed 50g of carrot juice, sake, and water individually with 0.5g gelatin. From what I’ve read, the ‘grades’ of gelatin sheets refers to their gelling power, with relative weights adjusted to compensate (so 1 leaf of gold gelatin should give a gel that’s just as strong as 1 leaf of bronze gelatin, despite the gold gelatin weighing less). The Alinea book never mentions what grade to use, but gold and silver gelatin are both notably more expensive than bronze, and I imagine a kitchen needing to be profit-aware would opt for whatever’s cheapest, so I’ve been using bronze.

What I found was opposite my initial suspicion; having more ‘non-water stuff’ in my base liquid demanded a need for more gelatin to produce a gel equally as strong as that made from pure water. Martin at Khymos explained this might be due to a number of things; enzymes disturbing the gelling power of the hydrocolloid, solids interfering with the ‘lattice’ that’s made from the gelatin bonds, etc. Having it explained in this way makes sense. And I should point out, too, that I was able to get within very respectable striking distance using the rough figures offered in the Textures handbook. Tweaking from there to try firming something up or softening it down is straightforward.

For my next experiment, I swapped gelatine with agar. Agar can be used at much lower concentrations (0.2 – 0.5%), so because the most atomic my scale can deal with is 0.5 grams, I mixed 100g liquid with .5g agar and tried again. I found again that the carrot gel was much weaker than the water gel, and the alcohol didn’t gel at all. Not even close. My knowledge is too infantile at this point to know why the sake didn’t work; more experimentation needed there.

Comparing the properties of the agar gel with the gelatin, the gelatin gel melts at a much lower temperature; it practically liquifies in my hand if I touch it at low concentrations. Agar has a higher melting point; I think this means that gelatin-based gels ‘melt’ when held in the mouth for a sort time, whereas agar gels maintain some ‘tooth’ and need to be chewed. In most cases in the book when I make a pudding (lavender pudding, soy pudding, etc), I use agar. I imagine this could be because use of gelatin would cause the gel to melt when blended (a necessary step in making pudding). Why I wouldn’t use a different colloid than agar I’m not sure just yet.

Last night I started in on the Matsutake recipe, which involves making rosemary gel with low-acyl gellan. I was keen to make it, just to see how gellan was different from gelatin, which I feel like I have halfway of a reasonable grasp on. The resulting gel was very soft, extremely elastic, and much stronger than gelatin of similar density. From a mouthfeel standpoint, it didn’t seem to melt completely, but did have a melty quality when I rolled it around in my mouth. Sort of like a cream almost, but not quite. It didn’t seem to melt when I touched it, but did ‘weep’ a little water. This latter phenomenon is mentioned in the Textures handbook, but it also calls low-acyl gellan gels ‘brittle’, which I’m not sure I found to be true. This description is one I don’t quite understand yet, however. In the cases of playing with gelatin and agar with the carrot and water, both gels I found to be similarly elastic. I don’t have a clear picture in my head of what it means for a gel to be ‘brittle’.

Oh, also, for the raspberry transparency dish, I had a tough time sorting out what “NH pectin” was. According to the Textures handbook, it is “amidated LM pectin”, which means it’s been treated with ammonia so that it requires less calcium than conventional LM pectins to gel.

Sorry there are no photos here; I’m writing this more as a diary for myself to refer to as needed, as well as to benchmark learning about this stuff. And also to share, because sharing is awesome.