Posted by Dave Arnold
Purpose: Clarify difficult-to-clarify lime juice
Techniques Used: Gel clarification, centrifuging
The holy grail of clarification is lime juice. Lime juice doesn’t last long enough to gel clarify, can’t be heated enough for traditional clarification, doesn’t filter well, and takes 48,000 g’s to spin in a centrifuge. In short, it’s a clarification guru’s nightmare.
We like clarification. We use traditional clarification, filtration clarification, distillation clarification, centrifugal clarification, enzymatic clarification, centrifugal enzymatic clarification, gelatin clarification, agar clarification. Wylie tells me gellan gum works too. (Just about the only clarification I know of that we haven’t tried is Angel Leon’s burned out plankton filter—he heats up the algae to over 500°, grinds it up, and uses it to clarify stocks, which it does surprisingly better than egg whites). Anyway, the enzyme I use won’t clarify at lime’s low pH. I’m getting one that I’m told will, but even if it does work, enzymatic clarifications are rarely as clear as gel clarifications.
The solution: Spin gel, gel-centrifugal clarification.
We decided to use 0.2% agar for this clarification. Agar needs to boil to hydrate, but we don’t want to heat the lime juice. Instead we take 400 ml of lime juice at room temp. Then we add 1 gram of agar to 100 ml of cold water and heat to the boil while stirring. We slowly add the lime juice to the agar mixture while stirring. The temperature of the final mixture should be roughly 39°C, which is above the gel point of agar (very important!). We then load the mixture into centrifuge bottles and let it set in the rotor (less disturbance of gel). After the agar is set (after about 15 minutes in our refrigerated ‘fuge), we spin it at 4000 g’s for 20 minutes.
For you algebra junkies I arrived at 39°C using the formula:
[(mass juice)(temp) + (mass water)(temp)] / total mass = Total temp
(400 ml*20°C + 100 ml*95°C) / 500ml = 39°C
Voila! Spin gel clarified lime juice!
BTW, we chose agar because its gel structure is the most porous of any hydrocolloid and readily weeps liquid even if it hasn’t been frozen. Right now our yield is about 75%.
PS: I tried it with gelatin at our normal ratio of 5 grams per liter and it did not work.