Posted by Dave Arnold
Purpose: Clarify difficult-to-clarify lime juice
Techniques Used: Gel clarification, centrifuging
The holy grail of clarification is lime juice.Â Lime juice doesnâ€™t last long enough to gel clarify, canâ€™t be heated enough for traditional clarification, doesnâ€™t filter well, and takes 48,000 gâ€™s to spin in a centrifuge. In short, itâ€™s a clarification guruâ€™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 havenâ€™t tried is Angel Leonâ€™s burned out plankton filterâ€”he heats up the algae to over 500Â°, grinds it up, and uses it to clarify stocks, which it does surprisingly better than egg whites).Â Anyway, the enzyme I use wonâ€™t clarify at limeâ€™s low pH. Iâ€™m getting one that Iâ€™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 donâ€™t want to heat the lime juice.Â Instead we take 400 ml of lime juice at room temp.Â Then we add 1 gram of agar to 100 ml of cold water and heat to the boil while stirring.Â We slowly add the lime juice to theÂ agar mixtureÂ while stirring.Â The temperature of the final mixture should be roughly 39Â°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 â€˜fuge), we spin it at 4000 gâ€™s for 20 minutes.
For you algebra junkies I arrived at 39Â°C using the formula:
[(mass juice)(temp) + (mass water)(temp)] / total mass = Total temp
(400 ml*20Â°C + 100 ml*95Â°C) / 500ml = 39Â°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 hasnâ€™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.