Clarification from Cooking Issues Blog

For those who don’t know agar clarification see here. For those who don’t know how to clarify liquids with gelatin, here it is: hydrate approximately5 grams of gelatin into 1 kilo of liquid, freeze the liquid solid, and slowly thaw it over cheesecloth in a refrigerator.

One of the interesting properties of gelatin clarification is that the first liquid that drips out of the frozen block is extremely rich in sugar, acid, color, etc.  It is concentrated.  As the block continues to thaw, the liquid becomes more and more watery.  This process allows for an easy way to concentrate flavor without using heat, and to adjust the strength of the clarified product (at the expense of yield) by terminating the clarification process whenever desired.

Simple agar clarification doesn’t work this way.  The new clarification technique is simple forced syneresis (the leaking of fluid from a gel), and doesn’t preferentially drip sugar, acid, and flavor the way an ice cube does.  The agar does hold on to some water (that’s what a hydrocolloid does), so the clarified product is more concentrated than the original; but the product’s concentration doesn’t change over the course of clarification the way it does with gelatin.

To prove it we hydrated 2 grams of agar in a kilo of orange juice, set it, broke it up with a whisk, and drained the clarified juice in 45 gram increments in mise en place cups and measured the Brix of each sample with a refractometer.  We also tasted the samples to see if there were any appreciable difference.

From:
http://www.cookingissues.com/index.html%3Fp=1464.html

Clarify Frying Oil

The idea of using gelatin to clarify stock is relatively new. It first came to my attention around 2009 (I probably first read about it on Dave Arnold's Cooking Issues blog). Gelatin is a protein that forms an interconnected, weblike matrix when dissolved in water. Not only does the gelatin give the water structure (think: Jell-O), it can also suspend other dissolved and undissolved solids in its matrix.

To gelatin-clarify, you first freeze a gelatin-rich stock, then slowly let it defrost in a strainer or wrapped in cheesecloth. As it defrosts, the network of interconnected gelatin proteins traps impurities, letting a crystal-clear consommé drip out of the bottom, with no need to skim, strain, or simmer.

But using gelatin to clarify oil? Now that was something really new, and frankly, if it worked, far more useful for the average home cook, who probably has no need to make consommé but often ends up wondering, "Can I use this oil again?"

I was skeptical. Stock clarification works because gelatin dissolves readily in hot water. Would mixing gelatin-rich water with oil really filter out impurities, when the gelatin is not even technically dissolving in that oil? I happened to have a small pot of particularly well-used oil on hand (previously used to fry a few batches of vegetable tempura, as well as some chicken-fried shrimp). I dissolved a teaspoon of gelatin in a half cup of boiling water, then dutifully stirred it vigorously into the dirty oil before transferring it all to an airtight container and setting it in the fridge to encourage the gelatin to solidify.

From:
http://www.seriouseats.com/2016/06/clean-cooking-oil-with-gelatin-technique.html