by Dave Arnold
Lime Juice and Simple Agar Clarification.
It has been a year since quick agar clarification changed my life. I was looking for a way to clarify lime juice without the help of a $15,000 rotary evaporator or a $20,000 centrifuge. Even if you have the equipment, these techniques produce only small quantities. Simple agar clarification solved all my lime-juice problems, and more. Read the post here.
Why is lime juice so hard to clarify?
- Lime juice can’t be heated much before it tastes cooked
- It must be very fresh — lime juice that is even a couple hours old tastes over-the-hill. Freezing doesn’t prevent this deterioration, and neither does vacuum bagging. Some of the big-kid flavor houses have made great strides in industrial fresh-lime taste, but ain’t nothing like the real thing, baby. Most clarification techniques other than the traditional egg-raft take a lot of time — like days.
Why do I care about clarifying lime juice?
- Are you kidding?
- Gin and Tonics want lime juice, perfect G&T’s are directly carbonated (see here for video), and cloudy lime juice doesn’t carbonate well.
- Clear lime juice tastes incredibly clean
- Clear drinks look more pleasing than cloudy ones, and have a better texture
Simple agar clarification is, as the name suggests, simple. It requires no special equipment, takes about half an hour, and can be done without overheating your juice (you hydrate the agar in boiling water and temper the juice back in). Read last year’s post complete with instructions here. In a nutshell: set your juice or whatever with 2 grams of agar per kilo juice. Break the gel up with a whisk. Put the broken gel in three layers of cheesecloth. Gently squeeze out the clear juice.
Some problems with simple agar clarification:
- It’s easy to over-squeeze the cheesecloth, which makes for cloudy juice. I am pretty good at getting a high yield of clear juice with a technique I call “massaging the sack.”
- Juices that last for a couple of days (not lime) tend to get partly cloudy on the second day. My guess is that some residual agar clumps together overnight. Dunno for sure.
The bad news: I don’t have a way to solve these problems without some heavy duty equipment. The good news: I can solve these problems with a *reasonably* priced centrifuge. The super-speed floor-model centrifuge of my early lime juice tests – which can spin product at 48,000 times the force of gravity – costs well over $20,000, can blow apart if used improperly, holds only 500ml of juice, and is the size of a washing machine. I bought a 3 liter bench-top centrifuge on eBay for about 300 bucks (granted, an unusually good deal). It is safe to use, holds 3 liters a a time, and is the size of two microwaves. It can spin product at 4000 times the force of gravity –plenty of g’s agar clarification. Most centrifuges in this range can be equipped with 4 swinging buckets of 750ml each. Don’t bother getting a smaller one or a larger one. Read about our centrifuge here.
Modified fast (but not as simple) agar clarification technique: Instead of using cheesecloth, break up the agar gel with a whisk, load it into the centrifuge, and spin it for 15 minutes at 4000 g’s. Yield is very high, no operator skill necessary, and the juice doesn’t re-cloud. I had used a similar, but not as effective, technique I called spin-gel clarification before I figured out the simple agar trick (post here); but I was too much of a bone head to combine the two techniques until very recently.
Mini Primer: a Rundown of the Clarification Techniques We Know:
People often ask me about different clarification techniques. Here is a summary.
- Egg raft: You know this one.
- Filtration: I have not had much luck with filtration. I have tried pressure filters, vacuum filters, different filtration media, etc. – but have not been satisfied. Even products with particles big enough to be filtered easily, like stock, tend to clog filters pretty quickly. Chef Angel Leon has the clarimax filtration system – I haven’t used it yet.
- Centrifuge on its own: You need a really fast one. Lime juice can only be directly clarified in a centrifuge when subjected to forces in excess of 27,000 g’s. To make sweet tasting clarified lime in a centrifuge you need 48,000 g’s. Wow.
- Enzyme on its own: The cloudiness in certain juices, like apple juice, is stabilized by pectin. If you add an enzyme that breaks down pectin, these juices self-clarify in the fridge (we use Novozymes Pectinex Smash XXL and Pectinex SP-L, which we also supply –see here). The cloudiness settles to the bottom and the clear juice stays on top. Pour off the clear juice and you’re done. Be careful: don’t stir up the particles at the bottom of your container; they will go right through a coffee filter. The problem with this technique is low yield; the cloudy particles are suspended in a lot of good juice that never clarifies. Thick purees don’t settle out in a reasonable amount of time. Read about the technique in depth here.
- Enzyme plus Centrifuge: Unlike plain enzyme clarification, this technique can clarify thick purees like peach, nectarine, blueberry and strawberry. It also radically increases yield on thin juices like apple juice. We no longer use enzyme clarification without the centrifuge. The technique is simple: blend each kilo of whole fruit or juice with 2 grams of Pectinex SP-L and 1 gram of Pectinex Smash XXL. Allow to sit 20 or 30 minutes, then spin in a centrifuge at 4000 g’s for 15-20 minutes. We get something like 80-95 percent yield depending on the solids content of the product.
- Gelatin Freeze-Thaw Clarification: This was the first non-traditional clarification technique that chefs adopted. It works on almost anything. Hydrate 5 grams of gelatin in every kilo of product. Pour the mixture into 2 inch hotel pans (gastronorms for you Euro types). Allow the mix to sit in the fridge a while so the gelatin can do its thing (the liquid won’t gel at these concentrations) then freeze the mix solid. Place a perforated 2 inch hotel pan inside of a 4 inch hotel pan and line the perforated pan with several layers of cheesecloth. After the mix is FULLY frozen, crack the ice-block out of the hotel pan (don’t use a torch) and put it into the cheesecloth-lined perforated hotel pan. Let the ice thaw in the fridge. What drips out will be crystal-clear. Juices with a lot of pectin require less gelatin. Things like stock that have natural gelatin can be frozen and thawed as-is. If the stock has too much gelatin your yield will be poor. Use a weak stock and reduce it later. Freeze-thaw clarified stock can be reduced a preposterous amount without becoming gluey, because the gelatin is gone. We made the meatiest tasting liquid of all-times using this technique — good stuff. A curious fact about freeze thaw clarification: the liquid that thaws first in any batch is higher in sugar, acid, and color than the liquid that thaws last — so you can’t just use the first stuff that melts and save the rest for later–all the liquid from one freeze-thaw cycle should be batched together. We sometimes intentionally concentrate flavor by only using the first half or two-thirds of the thaw, but some chefs (like Wylie Dufresne, who pioneered this technique with juices as opposed to stock) don’t endorse this technique because the concentration changes the flavor balance (post on this subject here). The advantage of the freeze-thaw gelatin technique is that it works on almost anything. The disadvantages are:
- it isn’t vegetarian (not a problem for stock, but potentially a problem for juice)
- if you don’t leave the gelatin long enough before you freeze it your product can go cloudy
- if you don’t freeze the mix all the way through your product will go cloudy
- if you let the product thaw in the kitchen and it gets too hot, it will go cloudy; if your fridge is too cold (ours runs at 32-34 F) it will take forever to thaw
- even in the best of cases thawing can take a day or two.
- Agar Freeze Thaw Clarification:the same as gelatin freeze-thaw, but with agar instead of gelatin. Use two grams of agar per kilo of product. Make sure the agar boils for several minutes. If you don’t want to heat your product you can hydrate the agar in a small amount of water and then temper it into your product. Make sure the agar/product mix doesn’t get below about 35-40C or it will gel prematurely. After the agar has been hydrated and added to your product, pour it into a hotel pan to set. At 2 grams per kilo, agar will form a light gel. After the agar gels, proceed as for gelatin freeze-thaw. The advantages of agar freeze-thaw clarification over gelatin clarification are:
- it is vegetarian
- it sometimes produces a clearer product
- agar won’t melt, so the product can be thawed at room temp
- if a portion of the agar doesn’t freeze, the gel will still hold and your product won’t become cloudy
- Simple Agar Clarification: See the explanation above. This is the only way to clarify lime juice properly. It is also a good technique for when you need product quickly.
- Simple Agar Clarification Plus Centrifuge: Simple agar clarification augmented with a centrifuge. If you have a centrifuge, this is the best way to clarify in a hurry.