Gel Clarification Recap: Gelatin Freeze-Thaw and Quick Agar

Agar against gelatin for freeze-thaw

Dave Arnold lists the wins of agar over gelatin: because the agar forms a gel, any part left unfrozen will not cloud the product even if you freeze it imperfectly; agar rafts do not melt until very hot, so they thaw much faster than gelatin ones; and he finds the product more sparklingly clear. Its one disadvantage is that gelatin dissolves with only a little heat, while agar must be boiled and held for several minutes to fully incorporate, too much heat for delicate products. A fix is in the flowcharts on pages 249 to 255.

Two problems remain. Even with agar, freeze-thaw takes a couple of days, fine for strawberry juice but unacceptable for lime juice, which must be used the day it is made. And what drips out changes over time: the first thing to thaw is the last thing that froze, the sugars, acids and other concentrated flavours, and the drip gets weaker as thawing goes on. You must pool all the drippings, or the flavour will be unbalanced.

When to use gelatin freeze-thaw

For a drink made with meat stock, such as a bullshot, always use gelatin freeze-thaw. Not only because the stock already contains gelatin: with any other clarification method the gelatin stays, and when you reduce the stock to concentrate flavour, which he always does for cocktails, by a factor of 4 or more, it turns gluey and unusable. Gelatin freeze-thaw removes the gelatin as it clarifies, so the stock can be reduced hugely and still end thin and limpid, even cocktail-cold.

• Add a little water to the stock before freeze-thawing, since most stocks have too much gelatin to work well. At most, the stock should just barely gel when cold; even better, just barely not gel. After the clear consomme drips out, reduce away the extra water.
• His savoury shot: concentrated gelatin-free consomme, centrifuge-clarified tomato water, iSi rapid-infused jalapeno tequila, a pickled cherry tomato and a healthy dose of salt.

Quick agar clarification

With quick agar clarification, anyone can clarify anything in under an hour, including—finally!—lime juice.

In 2009 he found he could clarify with agar simply by breaking the gel with a whisk to increase its surface area and letting it leak. Agar gels are very porous and want to leak; you have to work hard to stop them. So freeze-thaw and its equipment are unnecessary. With no freeze-thaw cycle, the first drop tastes the same as the last, and because nothing is frozen you can clarify booze that will not freeze (hydrate the agar in water first, since booze cannot get hot enough).

It is not perfect. It takes some skill and a knack, calls for a lot of messy hand-straining through cloth (see the flowchart), so it is awkward for large quantities, and is rarely as perfect as freeze-thaw: some agar gets into the product and can form visible wisps if left overnight. Still, it is his go-to method when he is away from his centrifuge.

Recap

• Freeze-thaw agar: less labour, more foolproof, and the product never reclouds, but it needs a lot of freezer space and a couple of days.
• Quick agar: great for small quantities you want to clarify quickly and use the same day.
• The cost of all gel methods is yield: some liquid always stays in the gel raft, so expect to lose at least a quarter of the product, sometimes more.