Modernist Cuisine - Volume 2

10

EXAMPlE REC IPE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

GREEN ASPARAGUS AND MORELS WITH ASPARAGUS JUS Yields 650 g (fo ur portions)

ADAPTED FROM JEAN-GEORGES VONGERICHTEN

INGREDIENT QUANTITY SCALING PROCEDURE
200g 80%
Pencil green asparagus, CD juice with Champion-style juicer.
unpee led 0 Measure 50 gfor recipe.

Asparagus juice, 50g 20% ® Whisk ascorbic acid immediately into fresh juice to prevent browning.
from above 0.4g @) Vacuum seal.
0.16 %
Ascorbic acid (0. 8%)* ® Refrigerate.

jumbo green asparagus, 250g 100% ® Saute for 3 min on all sid es until ju st tender and go ld en.
10%
sta lks peeled (eight stalks) 0 Remove from heat, and reserve.

Clarified unsa lted butter 25g
see page 4·213

jumbo green asparagus, 250g 100% ® Vacuum seal.
10%
stalks peeled (eight stalks) ® Cook so us vide in 85 "CI 185 "Fbath for 12 min, imm ediately remove from bag, and reserve.

Clarified unsalted butter 25g

Morels, 120g 48% @ Meanwhile, sweat together for 5 min until tender and just cooked through.
thoroughly washed

Unsalted butter 50g 20%

Shallot, finely minced 30g 12 %

Vin jaune (or Fino she rry) 25g 10% @ Add to morels, and cook for 3 min.

Heavy cream 15g 6%

Instant hollandaise BOg 32 % @ Warm to 65 "C/ 149 "F.
see page 4·228 @ Dispense from siphon, and fold into morels.

@ Set aside, and keep warm.

Asparagus puree 50 g 20% @ Warm prepared asparagus juice over medium heat.
see page 424 @ Whisk in puree.

Unsalted butter lOg 4% @ Whisk into warm thickened jus until fully emu lsified.

Lim e juice to taste @ Season jus.

Salt to taste

Flaky sea salt to taste @ Reheat reserved asparagus sta lks.

@ Season.

@ Place two so us vide cooked sta lks and two pan fried stalks in center of each plate.

Chive blossoms 10 g 4% @ Garnish w ith warm morels and blossoms.
® Pour jus around plates at table.
(or finely minced chives)

(original1997, adapted 2010) *(%oftotal weight ofasparagusjuice)

THE MODERNI ST KITCHEN 341

••

10

Jus, not Stock tant nonenzymatic browning process that is largely For more on Maillard reactions, see page 3-89.
responsible for the meaty aromas of roasting.
Despite their central role in commercial kitchens,
meat stocks are in reality something of a cheat. Small changes in the temperature or moisture
Stocks were developed as substitutes for an even content at the meat's surface can dramatically
more fundamental and desirable essence of favor one or another of the many reaction path-
cooked meat: its juice, or jus. ways that are possible during cooking. This fact
helps explain why boiled meat, roasted meat, and
Cooking meat causes collagen to shrink, which fried meat all taste different. As the meats cook,
makes the meat squeeze itself to the point that each method of cooking causes different sets of
juice leaks from it. To make jus, you want to create chemical reactions to prevail. These reaction
flavors within the roasting meat, then extract generate many of the volatile compounds that
them. Meat jus is the liquid component of the distinguish the flavor of boiled beef from that of a
cooked flesh that has been separated from the roasted lamb or a fried chicken.
solid parts. When you roast a chicken, steak, or leg
oflamb, you can usually coax out a few table- Unlike boiled meat in a stock, roasting meat
spoons of jus just by pressing on the cooked meat. browns on its surface. The jus forms primarily in
But that's just too little jus to be practical for the the hotter and drier regions, which are reaction
saucing needs of a busy kitchen. zones where watery liquids emerge from inside
and then evaporate, leaving a concentrated residue
The main advantage of a stock in which flavor is of oily and intensely flavored jus to drip into the
pulled from meat and vegetables using slow heat pan below.
and water, is that it secures a substantial portion of
the flavor that jus provides without the need to Water wicks from the interior of the meat to its
roast lots of animals. Stocks simply cost less to surface, carrying with it new raw materials that
make than jus does, and they yield much larger feed the ongoing flavor-generating reactions. But
quantities. because ofFick's law-the rules governing
diffusion of flavor compounds described previous-
A stock does not taste like a jus, however, be- ly in Extracting Flavors-no more than 20% or so
cause the two contain different molecular ingredi- of the water in a roast migrates to the surface to
ents. Analyze the composition ofa jus, and you' ll supply compounds for these reactions. So you
find countless cellular constituents that saturate the never get a whole lot of jus, but the little you do get
water in meat, among them large protein molecules, is almost ethereal in nature.
savory peptides, and amino acids, sugars, salts, and
myriad oily compounds, including lipids and fatty In everyday home cooking, you can typically
acids. harvest enough jus from a roast chicken or leg of
lamb-some ofit as classic, superconcentrated
You'll also find a rich ensemble of flavor com- fond, otherwise known as pan scrapings-to
pounds in jus that form by a complex sequence of prepare enough gravy or soup for the dinner table.
heat-driven chemical reactions called Maillard But busy commercial kitchens must settle for an
reactions. These chemical transformations, first approximation of jus; stocks represent the only
described by the French chemist Louis Camille practical and affordable means to produce rich
Maillard in 1912, occur when you heat at high cooking bases in sufficient volume to meet the
temperature a mixture of certain sugars and amino desires of the diners and the needs of the market.
acids. The Maillard reactions constitute an impor-

Squeezing in cheesecloth is atraditional way to
wring juice from food.

THE MODERNIST KITCHEN 343

PARAMETRIC RECIPE

JUS

Jus (pronounced "zhew" in French) means juice. It refers to a cooking valuable meat just for its jus. Reducing a stock to yield a
simple sauce made from the natural juices that escape from more concentrated, seasoned liquid creates something that
foods-usually meats-as they cook. To make a jus, you collect mimics jus but isn't the same.
those juices and skim off the fat. An unadulterated jus makes a
highly flavorful accompaniment for roasted meats. Modernist tools such as sous vide equipment and pressure
cookers-as well as ingredients such as proteolytic enzymes-
Unfortunately, natural jus is a precious commodity because makes it easy to make good, natural jus with less fuss and
you sacrifice the quality ofthe source food to make it. But you waste. The table below lists several ways to create a thicker
can sometimes collect jus by pressing and sieving trimmed mouth-feel and viscosity; effects on the flavor and yield vary
portions that are not meant to be served and thereby avoid by strategy.

Best Bets for jus

Re c i p e Liquid (scaling) Prote in (scaling) Aromatic (sca ling)

beefjuice n/ a ground beef 100% n/ a
--------------------- ground beef 35% carrot, thinly sliced
beefjus brown beef stock
100% 12%

red wine 30% oxtail, jointed 15% onion, thinly sliced 10%

chicken juice n/ a ground chicken 100% n/ a
--------------------~--------~~--------------------------------~-------------
brown chicken jus brown chicken stock 100% ground chicken wing
15% shallot, thinl y sliced 20%

chicken juice (from 40% chicken foot 8% drie d morel 5.0%
above)

fino sherry 20% thyme 0 .1%

mushroom jus mushroom stock 100% n/ a crimini mushroom, thinly 75%
sliced

fino sherry 20% shallot, thinl y sliced 20%

white port 10% white miso 7.0 %

tamari 1% thyme 0 .1%

mussel jus white wine 10% mussels 100% shallot 10%

pork and Banyuls --· - ------ ----- 75 % bay leaf 0 .01 %
roasting jus 10% 8%
brown pork stock 100% ground pork shoulder I sweet onion, thinly sliced 7%

Banyuls wine 25% ground pork trotter skin I
and meat
carrot, thinly sliced

rare beefjus water 5% beef, cubed 100% n/ a 1.5%
rare salmon jus water 5% 100%
shellfish jus shellfish stock 40% --·-- --------- 100% n/ a

salmon fillet, cubed -- ·-

shellfish heads tarragon ex tract

white wine 38% white pepper to taste

vermouth 13% I
n/ a
vegetable jus onion juice, clarified 100% n/ a

carrot juice, clarified 80%

celery juice, clarified 55%

leek juice, clarified 30%

344 VOLUME 2 · TECHNIQUES AND EQUIPMENT



THICKENING STRATEGIES FOR SAUCES, JUS, AND GLAZES

Strategy He at Speed Yield Note Uses See page

reduce on stove top high fast low high heat strips away volati les red eye gravy 5·101
brown beefjus 348
garlic jus in a jar

reduce by vacuum low moderate low more vibrant flavor pork Banyuls jus 5·19
evaporation after reduction osso buco glaze 5·60
app le and cabbage 389
juice

concentrate w ith agar high fast low the amount of liquid that fruit juices 372

weeps from the gel

determines the intensity

co ncentrate by f reezing low slow low best bet for many liquids; mushroom jus 348
below
yie lds an intense, vibrant flavor shellfish jus 3·356

mandarin juice

thicken w ith fat n/ a fast high rich mouthfeel and a flavor sauce americaine 5·184
(e mulsification)
that varies with the kind of fat constructed veal cream 5 ·31

used; diminishes the intensity jus gras 5·113

of flavors prawn jus 347

smoked salmon jus

thicken with fluid gel varies moderate high vibrant flavor; suitab le only for tajine glaze
liquids that tolerate cooking; pot-au-feu jus
good for th icker sauces 5-49

thicken with gum usually not fast high best bet for raw juices salmis sauce 5 ·125
required and thin sauces rare beefjus 349
jus de roti 4·54
rare sa lm on jus 5·161
truffle jus 4·53

thicken with n/ a fast high good strategy for raw juices garum jus 5·107
pregelatinized starch
and thin sauces; diminishes rare salmon jus

the intensity of flavors sous vide vegetable jus

EXAMPlE RECIPE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

SOUS VIDE MUSSEL JUICE YieldslOO g

INGREDIENT QUANTITY SCALING PROCEDURE Musse lju ice is class ically used to
100% acce ntuate the flavor of seafood
Mussels, rinsed thoroughly lkg CD Vacuum seal in one even layer. broths a nd sauces. This sous vide
with beards removed 0 Steam for4 min. method ex tracts the juices from the
mussels without overcooking them
® Shock in ice-water bath. so the meat can be used as a
ga rnish for cooked fish (see page
0 Shuck, and reserve meat for another use. 5·151). Inspect mussels carefu ll y and
discard any dead or sa ndy she llfish.
® Strain rendered mussel juices from bag and These can spoil the juice.
shel ls.

® Vacuum sea l and refrigerate until use.

(2010)

346 VO lUME 2 · TECHNIQUE S AND EQUIPMENT

1

EXAMPLE RECIPE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

JUS DE LA PRESSE INSPIRED BY ALAIN DUCASSE Yields350 g

INGREDIENT QUANTITY SCALING PROCEDURE
Lobste r heads
600g 100% Q Saute until she ll s are golden and very aromatic, about 10 min.
Clarifi ed unsalted butter
(about four heads) 0 Baste co nstantly with butter to cook through.

60g 10% ® Place heads in basket of wine press.

White wine (dry) 200g 33 % @) Extract juices by crush ing she ll s comp lete ly w ith wine press.
Lobster stock 120g 20% ® Combine with extracted lobste r juices.
see page296 ® Reduce lobster juice by half.
Cognac 30g 5%
Lobster roe BOg 13% 0 Blend with warm reduction until fu lly em ul sified .
Unsalted butter BOg 13%
Olive oil 35g 6% ® Season .
Lemon juice to taste
Salt to taste

(published 2001, adapted 2010)

EXAMPLE RECIPE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

SOUS VIDE VEGETABLE JUS Yields 750 g

INGREDIENT QUANTITY SCALING PROCEDURE
100% Q Prepare vegetab les as noted.
Yellow onions, thinly sli ced 400 g 67.5 %
0 Comb in e, and vacuum seal.
Carrot, peeled and 270g 40%
thinly sliced 30% ® Cook so us vide in B5 °C/ 1B5 OFbath for 3 h.
@) Stra in through fine sieve, and coo l.
Water 160g 30%
® To serve, heat stock to B5 °C/ 1B5 °F.
Celery, peeled and 120g 11 % ® Blend in butter until fu lly emu lsified.
thinly sliced 0 Season .

Leek, white only, 120g
thinly sli ced (from 275 g pee led leeks)

Unsalted butter, cubed 45g

Lemo n juice to taste
Salt to taste
(2010)

EXAMPLE RECIPE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

SOUS VIDE PRAWN JUS Yields250 g
PROCEDURE
INGREDIENT QUANTITY SCALING (!) Comb ine.
100%
Prawn heads 400g 40% 0 Grin d coa rse ly in food processor.
20%
Shellfish stock 160g ® Vacuum sea l.
see page 296 1.5%
@) Cook so us vide in BB oc I 190 °Fbath for1Y2h.
Vermouth (d ry) BOg Shel lfish butter (see page 329) is the
® Stra in thro ugh fine sieve. product of a very different ap-
Tarragon extract 6g @ Wh iskin. proach to extracting flavor than the
see page310 one used here. Try both approach-
to taste 0 Season. es to see what each one offers.
Salt to taste

W hite pepper

(2010)

THE MODERNIST KITCHEN 347

EXAMPLE REC IPE

LAMB GARLIC JUS IN AJAR Yields300g

IN GREDI ENT Q UANTITY SCA LI NG PRO CEDURE
l a mb trim, gro und 1 kg 100%
Frying o il 90g 9% <IJ Pan fry ground lamb until golden.
30% 0 Reserve meat and 10 g of rendered fat.
Carrots, peeled a nd thinly 300g
s li c e d 20% ® Prepare vegetab les as noted.
15% @) Saute together in saucepan with reserved lamb fat, until tender.
12.5%
Shallots, thinly sliced 200g 5%
5%
Sweet o ni ons, thinly sliced 150g 2.5%
0.3%
Fe nn e l, thinly sliced 125g 50%
20%
Ga rlic, pee led and thinly sli ced 50 g 0 .5%
0 .2%
Re d bell pe ppe r, thinly sli ced SOg ® Add to vegetab les, and increase heat to high.
To mato paste 25g ® St ir mixture continuously unti l go lden brown and fragrant, about3 min.
Star anise, crushed 3g 0 Deglaze pot, and stir in browned meat.
® Remove from heat.
Wa t e r 500g
W hite wine 200g ® Divide mixture equa lly between two Mason jars.
@ Seal jars, and place on rack in pressure cooker.
Thyme 5g
Bay leaf 2g @ Fi ll cooker with water to cover bottom 2.5 em I 1 in of jars.
@ Pressure-cook at a gauge pressure of 1 bar I 15 psi for 1Y2 h.
l e mo n juice to taste
Sa lt to taste @ Remove jars from cooker, remove lids, and coo l jus to room temperat ure.
@ Stra in stock.
(2009) @ Reduce stra ined stock until thi ckened, about 12 min, and season.

EXAMPLE REC IPE

MUSHROOM JUS Yie l d s 2 7 0 g

INGREDIENT QUANTITY SCA LING PRO CED URE To make canned juice, use a
Crimini mushroo ms, 150g 60% pressure canner and ventfor10 min.
thinl y sliced <Il Sa ute mus hrooms and sha ll ots toget her in
40g 16%
Shallots, th inly sliced 25g 10% b utte r until deep go lden brown, abo ut 12 mi n.
Cla rified unsalted butte r 200g 80%
Mushroom stock 0 Comb ine with cooked mushroom mixture in For juicing methods, see page 338.
see page296 40g 16%
20g 8% pressure cooker. This mushroom jus is richer and
Fin o sherry more fu ll-flavored than a simple
White po rt (dry) 100% ® Pressure-cook at a gauge press ure of1 bar I mushroom stock. It is impo rtant to
5.6% stir the konjac gum continuously
Mushroom jus, fro m a bove 250g 0.8% 15 ps i for 25 min. for a few minutes to ensure that it
W hite miso 14g 0.8% @) Strain through fine sieve, and discard solids. is fu lly hydrated and that no
Tama ri soy sauce 2g 0.3% ® Measure 250 g of mushroom jus. clumps form .
Thyme 2g ® Blend together unti l disso lved.
Ko njacgum 0.75g 0 Stra in .
Sa lt to taste
She rry vinegar to taste ® Season.

(2 010)

348 VOLUME 2 · TECHNIQUES AND EQUIPMENT

1

EXAMPLE RECIPE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

SOUS VIDE RARE BEEF JUS Yields350 g

INGREDIENT QUANTITY SCALING PROCEDURE Rare beef jus created this way ca n
Beef (preferably a tough cut) 1 kg 100% be used for many purposes.
2g 0.2% CD Cut into 1em I Y2 in cubes . Tougher meats may require more
Bromelain powder(optional, 0 Combine meat and bromelain (optional) time to release their juice.
NOW brand) 5% ® Cook sous vide in 53 oc 1 128 °Fbath for4 h.

Water SOg @) Strain rendered juices through fine sieve, and
Salt to taste measure 300 g ofjuice.
Sherry vinegar to taste
® Comb ine w ith juice.
(2010)
® Season.

0 Vacuum sea l, and refrigerate. Do not reheat
above 53 oc I 127 °F, or jus will coagu late.

3 4a

EXAMPLE RECIPE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

SOUS VIDE BEEF JUICE Yields300 g

INGREDIENT QUANTITY SCALING PROCEDURE This process ca n be applied to all
Ground lea n beef 1 kg 100% types of meats. Using the resulting
CD Vacuum seal. juice, although mo re costly than
0 Cook so us vide in 90 oc I 194 °Fbath for 1Y, h. water, is a more flavor ful alternative
than using water to make broths
® Strain juice, and discard meat. and sa uces.
@) Cool juice comp letely.
® Vacuum seal, and refrigerate until use.

(2010)

THE MODERNI ST KITCHEN 349

•

FILTERING 10

Much of what goes on in a kitchen revolves around be made into constructed creams that have a 351
separating the components ofmixtures. When a consistency similar to that ofdairy cream but with
cook pours a pot ofpasta into a colander, the water dramatically different flavors. Once you have used
runs out through the holes as the colander retains a centrifuge in your kitchen, it's hard to imagine
the steaming pasta. When a winemaker removes going without one.
yeast particles from wine, the segregation process
is more involved, requiring a filtration system that But not every cook has the room or the budget
pumps the wine through a series of cellulose pads for a centrifuge. More conventional separation
that trap the solids. techniques can be faster and easier to use. So we
begin by looking at the simplest and most widely
Cooks use separation techniques to make food used filtering technique: the basic sieve.
smoother, clearer, cleaner, less gritty, and other-
wise finer in some way. Often they want to elimi- Straining and Sieving
nate certain components in the mix to refine a
dish 's flavor or to adjust its texture and mouthfeel. Any home kitchen has a colander and a wire-
In the case of soup, straining out solid particles mesh strainer. These common implements are
that are larger than the tongue can discriminate- handy for separating large, solid pieces of food
about 7 microns, a mere 0.0003 inch, in size- from a pot ofwater or a newly prepared stock.
smooths out the broth. And cooks regularly But they represent the coarser end of a range of
remove selected elements from a dish to improve separation methods. At the other extreme are
its appearance-recognizing, for example, that tools for extracting "fines," which are consider-
diners prefer a clear broth to a turbid one. ably smaller particles.

All methods of filtering segregate solid parti- One step down the separation spectrum from
cles from the liquids in which they are suspend- the standard strainer sits the cone-shaped chinois,
ed. Filters fall along a spectrum defined by the whose supposed resemblance to a Chinese peas-
size of the particles they can remove. The smaller ant's hat earned it that name. The mesh of the
the pore size of the filter, the more pressure you chinois is finer than that of a household strainer.
must apply to force the liquid through the porous Cooks seeking even smoother, clearer liquids can
media. There is a whole toolbox full of filtering line the conical bed of the chinois with cheese-
methods available to Modernist chefs. Some cloth or muslin sheets, which catch even tinier
options separate mechanically; others rely on particles in their cotton-fiber meshes.
gravitational, centrifugal, chemical, or other
phenomena. Even better are laboratory sieves, which special-
ists in the mineral, chemical, and other industries
For example, a centrifuge, although costly, can use to segregate minute particles by size. The
spin foodstuffs at tens of thousands of revolutions finest laboratory sieves feature mesh apertures
per minute, which can lead to unexpected culi- that range down to about 20 microns-that is less
nary possibilities. Using such a machine can allow than a thousandth ofan inch and about one-third
you, for instance, to easily separate the pulp from the diameter of a human hair!
any puree to create a clear, flavorful consomme in
mere minutes. These sieves are relatively inexpensive tools that
can yield purees with a rich, velvety texture or
A centrifuge can spin fat out of all kinds of that can be used to strain a soup and give it a silky
foods. Fats extracted from vegetables and nuts can smooth texture. Some cooks deploy laboratory

Sieves are the most common separationtools inany kitchen.
At the extreme, sieving becomes filtration. an essential technique
of refinement.

THE MO DE RNI ST KITC HE N

STRATEGIES FOR FILTERING LIQUIDS AND CLARIFYING CONSOMMES

Filtering a liquid can remove murkiness caused by droplets only clear liquid to escape. The centrifuge is often the most
of fat, bits of sediment, or other kinds of particles. The process efficient clarification tool because it rapidly separates solids,
can be as simple as pouring a stock or fruit juice through a liquids, and oils all at once.
laboratory sieve or stirring in a fining agent such as bentonite
or methylcellulose. Agar and freeze clarification work Select a strategy that best matches the heat tolerance and
by trapping fines and crystals in a web of gel, allowing the degree of clarification, desired yield, and convenience
you need .

Applications

Strategy Heat Clarity Speed Yield Fruit a nd Meat or High-fat Puree See
vegetable seafood liquid page
juice or broth broth " 351

agar filtration cold very good fast moderate "" " 36 0
"
centrifuge n/ a good to fast high
excellent

enzyme clarification cold to good slow high "
warm

fine lab sieve n/ a adequate very fast high "" " 351
to poor

bentonite or polyclar varies varies slow high " ""

fining widely

protein or hot good to moderate moderate " "" 359
excellent
methylcellulose fining

gelatin ice filtration cold good to very slow low " "" 370
excellent

vacuum filtration n/ a good to varies varies " " "sometimes 356

excellent widely widely

pressure filtration n/ a good to varies varies " "sometimes 358

excellent widely widely

Unfiltered meat Buchner funnel Centrifuge Methocel raft Agar filtration Gelatin ice
stock with coffee filter at27,500g filtration

352 VO LUME 2 ·TECHN I QU ES AND EQUIP M ENT

10

Kitchens everywhere have colanders and
basic sieves. But laboratory sieves come
in amuch broader array of aperture sizes,
ranging from 20 microns to several
centimeters. We recommend having
a70 micron sieve, a120 micron sieve,
and a250 micron sieve for versatility.

sieves to improve their control over the strength precisely. The size of the breading particles on a Tomato juice (below) or meat stock
of the spices they add to dishes. Grinding pep- cutlet determines how well the particles adhere to (previous page) attains arange of clarities
percorns, for example, produces particles in a the meat and how much oil they soak up. These when filtered by various means. In general.
wide range of sizes, which, in turn, impart properties help govern just how crispy and the higher the clarity, slower the filtration
varying degrees of spiciness to food. Smaller crunchy the resulting cutlet becomes as it cooks. or the lower the yield. Each of the
pieces pack more punch than larger ones, and the
tiniest bits can cause overspieing if they are not Filtering by Push and Pull examples below started with 500 ml I
meted out judiciously. Sieving out the finer
powder leaves behind a coarser collection of Sieving and straining rely on the relatively weak Y, qt of source liquid.
pepper fragments that yields a milder, crunchy force of gravity to coax the liquid through a porous
seasoning on, say, a steak. barrier. A pair of somewhat more forceful tech-
niques, vacuum filtration and pressure filtration,
Cooks can also use sieves to manage the comes straight out of Chemistry 101.
properties ofbreaded and fried dishes more

. ~·

)\

Unfiltered Buchner funnel Centrifuge Methocel raft Agar filtration Gelatin ice
tomato juice with coffee filter at27,500g filtration

TH E MOD ERNIST KITCHEN 353

Astandard laboratory BUchner funnel, At the heart of vacuum filtration is the ceramic A paper coffee filter will work, but laboratory
combined with an Erlenmeyer side-arm Buchner funnel, an 1885 invention of the filter paper is a better choice. Standard laboratory
flask and avacuum pump, offers asimple German chemist Ernst Buchner. It is a large cellulose filter papers come in many grades of
and robust way to quickly filter many funnel topped with a cup that has a flat, perforat- fineness, in styles that are less prone to clogging,
juices for sparkling clarity. ed bottom called the frit. The frit provides and in sizes just right for the Buchner funnel being
support for filter paper that sieves solids from used. A good choice of filter paper is one that
liquids as they pass into the funnel, and go retains medium to fine particles from 4-7 microns
through a downspout and into a collection flask and that is still rated as having a medium to fast
(see Filters That Suck, page 356). flow rate (such as Whatman 597 filter paper).
Coarse-spun glass or quartz-fiber prefilters can be
The key to vacuum filtration is the removal of layered on top of the filter paper to catch the
air from the flask by the suction pump (see page biggest particles.
356). The higher atmospheric pressure above the
funnel pushes down on any liquid it contains-or, This apparatus works well for quickly filtering
looked at another way, the vacuum below sucks plant juices to sparkling clarity, but it doesn't do
the liquid through the filter. a very good job on stocks and broths. Fat and oil
tend to flow through the filter paper and may
The setup looks a bit like a chemist's version of a even be broken into finer droplets that make the
drip coffee maker, and it is about as simple to stock more cloudy and turbid than before filter-
operate. The first step is to place filter paper in the ing! If the stock is cool enough that the fat
funnel. It must completely cover the bottom plate droplets are solid particles, then filtering can
and the holes. Wet the paper with some water, remove them. Unfortunately, at temperatures
then turn on the vacuum pump. The filter paper cold enough to solidify the fat, the gelatin in
should be sucked flat against the frit. Then pour in meat juices often can become a problem. Cold
the liquid to be filtered, and wait for it to drip into stocks and broths are thick or even gelled,
the flask. resistant to flowing through a filter.

If the job is small and cost is not a huge concern,
then it is possible to filter a stock or broth to
prepare a consomme with the clarity of, say,
Scotch whiskey in a bottle. Special membrane
filter media have pores rated at 0.22 microns or
finer, which is so fine that filtering the stock (while
warm) will break up the oil droplets into a micro-
emulsion that is crystal clear. A consomme
prepared this way has a remarkably rich flavor
(because it contains all of the flavorful oils) that is
unmatched by consommes produced by other
means of clarification.

Unfortunately, fine membrane filters are
expensive and tend to clog quickly, and the filtered
consomme will become cloudy again ifyou chill it
because the extremely small oil droplets will
aggregate into bigger fat droplets that scatter light.
So this approach to filtering a broth is best done to
order. For convenience, it's possible to buy self-
contained disposable filter cups that have suitably
fine membranes. Each cup will typically filter a
couple of portions before it fouls and must be
discarded.

For any kind of filtering, filters with larger
surface areas will clarify more liquid before

354 VOlUME 2 · TECHNIQUES AND EQUIPMENT

10

HOW TO Clarify Juice With A Buon Vi no Pressure Filter mL 0--500 ml

Thi s pressure fi ltration system was developed to clarify wi nes. But why •s·'· !5%
stop there? It also provides an efficient and compact way to fi lter oth er
cloudy liquid s. The Buon Vi no e lectri c pump pushes juices through ~ m.. 100 - - 400
side-by-side plates and then through paper filters with 1-2 mi cro n po res.
Th e filtered juice is then co ll ected through a hose. The o nly caveat whe n iEX~
using the syste m is that it does not work we ll w ith ge latinous liqu ids such
as meat stocks, which quickly clog the filte r pads. 200--300

1 Wet and insertthefilterpads. 300--200
2 Pump hot water through the filter. Stop when the water co ming off the
400-- 100
pads no lo nge r has a pape ry taste. Slightly acidic water works best.

3 Filter the liquid byfollowingthe manufacturer's instructions. If flow

slows dramatically, stop, and change th e filter pads. Typically, you ca n
filter seve ral gallons before this is necessa ry.

Filter pads sandwiched
between metal frames
and plastic plates

Filtered liquid Collection vessel for Drip tray Electric pump Unfiltered liquid
liquid that leaks

THE MODERNIST KI TCHEN 355





Fining is aversatile technique for fouling. Bigger funnels have more surface area extremely clear fluids. For clarifying plant juices,
clarifying liquids. Fining agents range from and will filter more liquid faster. Ultimately, we find the Buon Vino SuperJet models both
the common (egg wh ites) to the exotic however, vacuum filtration systems can muster simple and effective.
(silica), but all work to improve clarity only so much suck. The vacuum strength can
while minimizing the loss of flavor. Fining
never exceed atmospheric pressure (1 bar I
The word "fining" suggests a kind of precise
15 psi) and in practice won't even reach that level. elegance. Unlike sieving and filtration, which
To filter larger quantities at a faster rate, you separate solids from liquids by strictly physical
means, fining exploits any one of a range of
need a more elaborate piece of equipment, one chemical techniques to improve the clarity or
that uses positive pressure rather than a simple adjust the flavor or aroma of broths, wines, juices,
vacuum. A pressure filter encloses the filter in and other liquids.
between sturdy metal plates. Liquid flows through
channels in the frames to and from the filter pads. Fining agents work by modifying small-
An electric pump then boosts the pressure above molecule compounds, usually organic chemicals,
in ways that make them easier to sieve, filter,
the filter to 7 bar I 100 psi. Specialized pumps centrifuge, or simply settle out of the liquid. These
specialized additives range from proteins such as
used in industry filter at pressures many times gelatin and albumin (egg white) to bentonite (a
higher than that. clay-like mineral ofvolcanic origin) to more exotic
agents like silicon dioxide powder and synthetic
One of the more practical pressure-filtration polymers. Even specialized enzymes are used as
systems for the contemporary kitchen, the Buon fining agents.
Vino Jet brand of filter, is well known to home
vintners. In such units, a pump forces liquid Many fining agents work by electrostatic
through a tight, multistage assembly of alternat-
ing frames and cellulose filter pads. Although the

pump produces only around 2 bar I 30 psi of

pressure, the rigorous filtration process yields

358 VOLUME 2 ·TECHN I QU ES AND EQUIPMENT



attraction. The fining agents carry a positive or Putting a Spin on It
negative charge that attracts the opposite
charge on the target particles. Examples of this Most people have a centrifuge-a machine for
type include proteins such as casein and spinning things fast-in their homes. It usually
albumin, as well as minerals such as bentonite sits in the basement and goes by the name of
and a silica gel (sometimes known by the trade "washing machine." Its spin cycle forces water
name kieselsol). from the clothes by spinning the drum. A salad
spinner dries lettuce in much the same way.
Other fining agents include charcoal and
synthetic polymers such as polyvinylpolypyr- The same principle can be used in the kitchen to
rolidone, or PVPP (brand named Polyclar). separate things by density. The laboratory centri-
These agents are electrically neutral and work by fuge is an exciting new tool for chefs, although it
sticking to unwanted components of mixtures, has been used in science labs for more than a
most notably phenolic compounds and other century. Often the size of a dishwasher, this
chemicals that create astringent flavors or that machine imposes gravity-like forces on the
discolor wine and juice products. They are cup-size vials of liquid it spins around-but it
popular with brewers and vintners because they exerts forces tens of thousands oftimes stronger
tend not to strip flavorful aromatics from the than Earth's gravity.
liquid being fined.
A centrifuge opens the door to a universe of
Most fining agents must be filtered out after unusual concoctions. And each new centrifuge-
they've done their job. But egg whites are a handy born creation can, in turn, serve as the base for
exception to that rule Ifyou whip egg whites into a myriad other preparations in the kitchen.
stock, then simmer the mix until the whites form a
foamy, coagulated raft on top, the albumin pro- The centrifuge gets its name from the centrifu-
teins in the egg whites entrap both food particles gal force it generates when it spins a liquid mixture
and globules of fat that cloud the liquid. Ladle the at high speed. A centrifugal force is the same sort
floating raft out, or just poke a siphon tube of sideways push you feel while driving a car
through it to retrieve the clear fluid below. around a sharp turn at high speed or when sitting
in a fast-spinning carnival ride.
Note that fining always strips out desirable
aromas to the same degree it removes particles. In The most powerful centrifuges can whirl a vial
the case of a traditional consomme, fining re- of fluid around 60,000 times a minute (rpm),
moves the flavorful fat to achieve clarity, which is creating up to 250,000 times that ofEarth's
why it has a weaker flavor than the stock from gravity, which is lg. Just as normal gravity causes a
which it was prepared. rock to sink in water and less dense wood to float,
this artificial form ofgravity forces denser compo-
Plant-derived methylcellulose powder works nents of a mixture, like particles of solids, to sink
much like egg whites, but it diminishes less of the to the bottom of the vial (toward the periphery).
water-soluble, meaty flavor of a stock. Polyclar Meanwhile, lighter components, like oils and fats,
also avoids stripping out aromatics, but the float to the top (near the central axis). Watery
polymer has its own drawbacks: it is less effective solutions settle somewhere in between. Gravity
at removing large quantities of emulsified oils, could achieve similar separation, but inside the
and its very fine particles tend to remain sus- centrifuge, the process happens tremendously fast.
pended in the liquid, so you must filter out the
Polyclar after it has done its job. Ifyou spin just-prepared carrot juice in a
centrifuge, the sharp-tasting pulp will travel to the
Pureed raw meat offers still another alternative bottom of the bottle and form a puck of sediment.
as a fining agent. Whisked into a stock or broth You may even notice that the solid matter contains
and then heated, the protein in the meat first a whitish fraction of bitter-tasting minerals. Above
coagulates in the liquid, then settles to the bottom, the puck, however, will be a very sweet juice
sopping up solid particles and fat as it sinks. This is unlike any carrot juice you have ever tasted.
a trick that Chinese cooks having been using to
clarify broths for centuries. Despite its brawny character, a centrifuge
cannot defeat the physical chemistry that keeps
some common emulsions well mixed. In homoge-
nized cream, for example, casein proteins lock

36 0 VO LUM E 2 ·TECHN I QUES AND EQUIPM ENT















Centrifugation affects different mixtures away fat globules in suspension by enveloping Adding glycerol to an herb puree, for instance,
in different ways. Some need an added them in molecular blankets. Electrostatic charges makes the watery fraction less dense so that it
liquid that is intermediate in density on the casein molecules attract fats to the inside separates more readily from the solids in the mix.
between the lightest liquids and the surface while opposite charges on the other ends Adding sucrose, on the other hand, makes a
densest solids in the mixture. Some need of the protein molecules bond with the milk's watery matrix denser. A sugary additive can thus
more time or centrifugal acceleration. watery matrix. improve the separation of oils and fats from
Experiment to get the best separations. liquids, like milks, that contain water and fat.
In homogenized cream, you can disrupt these
for more on how to use a centrifuge to suspended colloidal particles by adding some Clarity by Ice or Gel
separate cream, see page 366. locust bean gum. A spin cycle in a centrifuge will
then pull the fatty cream right out of the denser Centrifuges, Buchner funnels, and Buon Vino
milk. Perform the cycle under refrigeration, and pressure filtration systems are wonderful tools,
the cream at the top hardens, allowing you to but even if you have nothing more than a freezer,
decant the underlying liquid easily by simply a refrigerator, and a gelling agent such as gelatin
poking a hole in the crust. Et voila! Concentrated, or agar, you can still clarify strained stocks,
fresh cream. sauces, purees, and almost any flavorful liquid to
a gratifying extent. The secret is to exploit the
And not just cream, but lactose-free cream, concentrating effect of freezing, and the net-like
because the lactose sugar remains dissolved in the molecular structure of a gel, which can behave
milk after centrifugation. Also absent from the much like a filter with truly microscopic-even
homemade cream are water-soluble compounds nanoscale-pore sizes.
such as diacetyl, which forms the foundation of
butter flavor. The dairy cream that comes out of a One way to make a filter from fro zen gel is to
centrifuge therefore offers cooks a unique, flavor- add gelatin to the liquid you want to filter and to
neutral dairy fat that has myriad uses in the freeze the mixture. Once it is frozen, transfer the
kitchen. mixture into a strainer placed over a bowl, and
thaw it slowly in a refrigerator for a day or two (see
Additives ofseveral kinds can intensify the How to Filter with Gelatin Ice, page 370).
extent ofthe separation that occurs during
spinning, yielding liquids that are even clearer and The temperature in the refrigerator is cold
more colorful. These agents alter the density of the enough to keep the net of gelatin molecules intact
liquid mixtures that go into the centrifuge bottles.

368 VOLUME 2 · TECHNIQUES AND EQUIPMENT

but warm enough that the ice crystals slowly thaw. considered and later applied successfully in the Syneresis refers to the tendency of
As the freed water trickles down through the kitchens of The Fat Duck. Concentrated, gelati- ge ls to weep liq uid (see page 372). It
gelatin network and into the bowl (in a process nous broths are first frozen, then strained in the is usua lly a p roblem in the kitchen,
scientists call syneresis), it washes out soluble refrigerator over a period of days. The particulates but the gel fi ltration technique
sugars and flavor molecules that have become are trapped in the fine mesh of protein strands. exploits it.
trapped in the gel-including food particles, fat,
and other impurities that can cloud liquids. Meat The technique of gelatin filtration travelled
stocks often contain enough gelatin naturally to across the Atlantic to wd-50 in 2005, after the
gel as they cool, but cooks need to add small New York City chefWylie Dufresne visited
amounts ofgelatin directly to fruit and vegetable Blumenthal at The Fat Duck in England, where he
juices to clarify them in this way. saw a gelatin-clarified venison stock. Dufresne
realized that the same process could work for any
A wonderful aspect of the free ze filtration liquid, including plant juices. All that needed to be
process is the fact that the liquid that leeches out done, he reasoned, is to add the appropriate
of the mix first contains a far higher concentration amount of gelatin (typically l %-2%)to any liquid
of soluble flavor compounds and pigments com- that doesn't already have it naturally.
pared with that which weeps out later. Ifyou don't
mind throwing away some of the overall yield, this The process soon spread widely. Aki Kamozawa
approach thus affords a simple way to select the and Alex Talbot, the authors of the blog Ideas in
intensity of a juice's flavor: just use the fraction Food, learned about the process while spending
with the strength you want. time in the kitchen at wd-50 and then adapted it
to work with agar for vegetarian preparations, thus
Gel filtration has an interesting history. The bringing it full circle to Glock's original approach.
German scientist Gerd Klock discovered a way to They reasoned that mechanically breaking up the
use agar, a gelling agent derived from seaweed, to gel would increase syneresis and accelerate the
filter liquids with remarkably clear results. Glock filtering process by eliminating the slow freeze-
presented this approach at an INICON confer- thaw step. Influenced by Ideas in Food, David
ence where Chefs Heston Blumenthal and Albert Arnold and Nils Noren of the French Culinary
Adria were both in attendance. In discussions Institute in New York City refined the idea to
between Klock and Blumenthal, the possibility of boost its speed and yield. Both techniques are now
applying the technique to gelatinous stocks was used widely in Modernist kitchens worldwide.

THE MODERN I ST KITC HE N 369













EXAMPLE RECIPE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

OXTAIL CONSOMME INSPIRED BY DAVID BOULEY Yields 2.5 kg

INGREDIENT QUANTITY SCALING PROCEDURE
Spanish onions, peeled and halved 25 %
500g CD Sear cut side down until light golden, abo ut 8 min.
Water (two large 2.5%
o ni ons) 0 Coo l.
75 %
50g 1.5% ® Vacuum sea l w ith seared o ni ons.
100%
Oxtail, jointed 1.5 kg @) Cook so us vide in 85 oc I 185 °Fbath for 7 h.
12.5%
Neutral oil 30g 12.5% ® Transfer mixture from bag to bowl, and coo l.
12.5 % ® Strain, discarding onion so lid s.
Brown beefstock 2 kg 7.5%
see page 301 5% 0 Measure 250 g of onion jus, and reserve.
1.5%
Onion jus, from above 250g 100% ® Brown oxtail over high heat on all sides until go lden, about 15 min.
15%
Gin 250g 0.1% ® Comb in e with browned oxta il in pressure cooker.

Veal marrow 250g @ Pressure-cook at a gauge pressure of 1 bar I 15 ps i for 2 h.

Button mu shrooms, thinly sliced 150g @ Strain, discarding so lids.
@ Measure 2 kg of oxta il broth.
Carrots, peeled and thinly sliced 100g
@ M ix 200 g of broth with super methylcellulose.
Celery stalk, peeled and thinly sli ced 30g @ Whisk into ground beef to make paste.
@ Mix paste into remaining oxtail broth for consomme.
Oxtail broth, from above 2 kg @ Simmer consomme on low unt il clarified, about 45 min.
@ Strain.
Ground beef 300g @ Season .

Super methylcellulose SGA 150 2g For photos of the steps involving methylcellu-
(Dow brand) lose, see page 359.

Bay leaf extract to taste
see page326
to taste
Lovage leaves, fin e juli enne to taste
to taste
Salt

Star anise extract
see page326

(2010)

EXAMPLE REC IPE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

PISTACHIO CONSOMME Yields80 g

INGREDIENT QUANTITY SCALING PROCEDURE The remaining nut solids in the
Raw pistachios, shelled 100 g 100% centrifuge bottles are not used for
Sugar 15 g 15% CD Combine. anything in this recipe or these
Grapeseed oil 10 g 10% 0 Roast in 190 oc l 375 °Foven until very dark and sugar volumes, but they're a delicious
Water 300g snack for the chef.
Pistachio oil 20g 100% has caramelized, about 20 min.
20%
® Puree with roasted pistach ios until smooth.
Salt to t aste @) Vacuum seal.
(2009) ® Refrigerate for 12 h.
® Ce ntri fuge at 27,500g for 1 h.

0 Decant clear li q uid through fine sieve, and discard

remaining so lids.
® Season.
® Vacuum sea l, and refrigerate until needed.

376 VOLUME 2 · TECHNIQUE S AND EQUIPMENT





10

CONCENTRATE!

Skilled cooks strive to intensify the flavors in their technique does a great job ofconcentrating
dishes by concentrating the essences of certain nonvolatile flavor components of the original
ingredients as much as possible without signifi- solution such as sugars, salts, and flavor-enhancing
cantly altering them. Concentrating is usually molecules like savory-tasting glutamates and
about removing excess solvent from a food. The nucleotides.
most common solvent in the kitchen is water (but
occasionally alcohol); removing it makes tastes The classic reduction method also tends to
and aromas stronger. There are other times when, thicken the liquid by increasing the concentration
rather than discarding it, collecting the solvent of gelatin, emulsified oils, and any dissolved or
and any flavors it contains is the goal. suspended solids such as sugars or particles in a
puree. Reducing a liquid thus usually changes its
Chefs traditionally strengthen the flavor of a mouthfeel as well as its flavor.
stock, juice, or sauce by subjecting it to a long
simmer to reduce its volume. This process is Unfortunately, these changes are not always for
concentration by evaporation. It works because we the better. The same heat that boils the water also
can evaporate water by using heat. This trusted breaks down or alters some of the most desirable
aroma compounds in the mix. Even worse, higher

STRATEGIES FOR CONCENTRATING

A cook has many options for intensifying the flavor of liquids that come from food . The alternatives range from the traditional
boiling pot on the stove to the more exotic and expensive, such as Genevac's Rocket Evaporator, which is part centrifuge and
part distillery. You can use any of these strategies to concentrate a juice, jus, or broth .

Strategy Description Pros Cons

stove-top boils off water to increase concentration inexpensive, easy slow, many desirable volatile
reduction of those flavor compounds that remain aromatics evaporate away
or are altered by heat

vacuum reduction lowers pressure of air above liquid, inexpensive, straightforward volatile compounds still escape
to set up
increasing rate of evaporation

rotary evaporation distills and captures volatile components captures evaporated volatile expensive, complicated
(rotavap)
selectively at a controlled temperature aromatics, reduces without heat,

and pressure processes large batches

vacuum spins liquids at low speed, distills under simple automated process expensive, complicated
concentration vacuum, and condenses evaporated handles up to six liquids at once,
(with vacuum components precise temperature control,
concentrator) low-speed centrifugation

freeze forms crystals of pure ice that force very inexpensive and simple, slow, limited degree of
concentrating particles and dissolved substances to requires no special equipment, concentration
concentrate in remaining liquid no volatiles escape or change

reverse osmosis forces liquid through a semipermeable energy-efficient, commonly used complicated, not yet adapted

membrane through which water, but not in water purification and wine for culinary use

flavor compounds, can pass making

THE MODERNIST KITCHEN 379

Reducing sauces the old-fashioned way, temperatures evaporate many of the prized increases the evaporation rate at temperatures
with an hours-long simmer, spews some of volatile aromatic compounds in the solution. Food below the boiling point. With low enough pres-
the most aromatic components into the air fragrances filling your kitchen may smell great, but sure, you can vacuum reduce at room temperature
and causes chemical reactions that change they are signs of a deficiency in the reduction or less. The limiting factor in vacuum reduction is
many of the aromas that remain. Newer process: ifyou can smell the aroma compounds, usually the vacuum pump; it must be able to
approaches minimize or avoid these less of them remain in your food. provide enough suction to keep the pressure in the
problems. flask low. This task is not easy because evaporation
Innovative cooks have developed alternative tends to provide plenty ofwater vapor (and other
A motorized asp irator vac uum methods of intensifying flavor that don't pose all volatile gases) to remove. The more powerful the
pump used fo r vac uum red uction the drawbacks of the traditional long simmer. vacuum pump, the lower the temperature at which
wi ll usually work better if you put One trick is to vaporize the liquid in such a way the vacuum reduction operates.
plenty of ice in the water ta nk. that the pot stays cool enough that the remaining
That's because the water absorbs aroma compounds don't degrade. Vacuum You can bring precision to the heating process
heat from the recondensing wate r evaporation can do this, either with a relatively by using a digitally controlled hot plate, preferably
fro m the flask . This enables the simple setup (see page 382) or with much more one that can be stirred magnetically. A magnetic
pump to pull a stronger vacuum. elaborate gear, such as a rotary evaporator (see stirring bar placed in the flask will create a vortex,
Distilling the Essence, page 386) or a vacuum which accelerates evaporation by increasing the
concentrator (see How to Reduce Juice in a surface area of!iquid.
Vacuum, next page). These versatile tools allow
you to make stocks, broths, and other liquids boil Mixing the liquid while it boils also helps you
cooler than they normally would-even below avoid dangerous "bumping," in which large bubbles
room temperature. ofvapor form then violently collapse, tossing the
flask about the hot plate. These bumps sometimes
Although vacuum evaporation avoids the flavor are violent enough to crack the thick flask.
alterations that high heat causes, it shares with
simmering the problem that many of the desirable A vacuum pump for vacuum reduction must be
volatile components are stripped away. The reason capable ofhandling copious amounts ofwater
is simple: boiling in a vacuum is still boiling, and vapor. The simplest solution is to use a faucet
anything in the container that 's more volatile than aspirator. Ifwater consumption becomes an issue,
water will leave first. Concentrating by vacuum a motorized aspirator is a good solution.
distillation, on the other hand, makes it possible to
capture the vaporized aromatics and add them Aspirator-style pumps are designed to withstand
back to the concentrated liquid. continuous exposure to water vapor and condensa-
tion. Other types ofvacuum pumps will also work,
Low-Cost Vacuum Reduction but make sure that they can resist contact with
water vapor. Membrane-type pumps that are
The curious cook can experiment with vacuum intended for use with rotary evaporators or other
reduction techniques at low cost by using a simple water-tolerant vacuum pumps are good choices.
aspiration vacuum system. This setup requires
only a hot plate, a heavy-walled Erlenmeyer filter Used correctly, vacuum reduction can achieve
flask with a high-mounted sidearm port for the effects of classic reduction with liquid solutions
connecting the flask to a rubber tube, and a faucet whose flavor would change if they were subjected
aspirator, motorized aspirator, or other vacuum to a higher evaporation temperature. Say that you
pump that attaches to the other end of the tube are making a fruit coulis (a thick sauce) from
(see Reduction in a Vacuum, page 382). strawberry or raspberry juice. Conventional
reduction methods will give the results a cooked
Vacuum reduction works by lowering the flavor, whereas vacuum reduction preserves more
pressure inside the flask. This decrease lowers the of the delicious raw taste. But, also as in classic
boiling point of water (see page 1·294) . 1t also stove-top reduction, the most flavorful volatile
compounds in the food will evaporate away when a
liquid is reduced under vacuum in this way.

38 0 VOLUM E 2 · TECHNIQUES AND EQUIPM ENT







In the U.S., anyone who distills to The Rotary Evaporator water will evaporate. For example, a 10% solution
create a higher concentration of ofethanol in water has a boiling point at standard
alcohol must obtain federal and A more capable but also more complex and
state licenses because the process expensive refinement of aspiration-type vacuum atmospheric pressure of 93 ·c I 199 •p. The vapor
falls under regulations that cover reduction technology is a rotary evaporator. It is
the production of alcohol. The a laboratory version of a distillation setup that is that it gives off at that boiling point will be about
difficulty of getting these licenses able to work at low pressure and temperature. 55% ethanol and 45% water. So if we were to run a
varies from state to state. Some A rotary evaporator lets you hang on to volatile rotary evaporator with a 10% ethanol mixture at a
states, such as Oregon, sponsor aromatics that escape during conventional
programs that promote and vacuum reduction. The sophisticated device temperature of93 ·c I 199 •p, we could concen-
encourage craft and artisanal evaporates liquid in a spinning flask by gently
distillation, for example. In other heating it with a water bath and by lowering the air trate the alcohol from 10% to 55% in a single pass
parts of the world, you must check pressure above the liquid (using a vacuum pump). through the machine. Ifwe want a higher concen-
with the appropriate local authori- Unlike simple vacuum reduction, it also condens- tration, then we need to send the batch through
ties to ensure that your use of es and collects the distilled vapor, including the the machine several times.
distillation equipment is legal. most aromatic elements .offruits, vegetables, and
pretty much anything that has an aroma. Note that we use the ethanol example because it
A rotary evaporator is often called is familiar. Distilling 10% alcohol to 55% is similar
a "rotavap" in labs, but that term is A rotary evaporator has just a few primary parts to what happens when brandy is distilled from
short for Rotavapor, a trademark (see Distilling the Essence, page 386). A spherical wine or whiskey from fermented mash. Making
ofBuchi, one of the teading evaporation flask is cinched into a motorized yoke your own spirts is not easy to do with a rotary
manufacturers. Yamato, Heidolph, that spins to increase the surface area and thus evaporator, however. First, there are legal issues
IKA, PolyScience, and other speeds evaporation ofthe liquid by spreading it over (see note, above left). Second, the process is very
manufacturers also produce rotary the inside surface of the flask. The flask itselfsits in complex because fermented products contain
evaporators. a temperature-controlled water bath that provides many alcohols and compounds besides ethanol.
heat to drive evaporation. Its neck connects
For more on safe handling of essential oils, see through a vacuum seal to a condenser assembly, Methanol, for example, is usually present in low
page 324. which chills the vapor, thereby causing some ofit to concentrations as a by-product of fermentation. It
condense into a liquid. The condensates drip down
The rotary evaporator was invented into a collection flask. Situated nearby is a vacuum has a boiling point of 65 •c I 148 •p, and thus it
by Lyman Craig and colleagues and pump capable ofreducing the pressure inside the
first described in the journal apparatus by a factor of 100 or so, or from standard becomes concentrated mostly in the foreshots-
Analytical Chemistry in 1950. It was the term for the liquid that first boils off and forms
first sold as a commercial product atmospheric pressure of 1,013 mbar I 14.7 psi to as a condensate at the start ofa distillation batch. In
by Buchi in 1957. low as 10 mbar I 0.15 psi. addition to methanol, foreshots may contain
acetone and other volatile organic substances that
The term "fuse Ioil" is a bit of a The fundamental task of a rotary evaporator is have a lower boiling point than ethanol. The
misnomer. It is used because the to separate liquids that have different boiling foreshots must be discarded because they can be
resulting mixture of organic points. Some examples are ethanol, which has a toxic; they can cause headaches in small quantities
compounds is hydrophobic. But it and more serious illness, including blindness, at
is not a simple oil like a vegetable boiling point of78 •c I 172 •p when pure, and higher doses.
oil-it is a complicated mixture of water, which has a boiling point of 100 •c I 212 •p
flavor compounds. After the foreshots come the so-called heads,
when pure. In a mixture of ethanol and water that the middle run, and finally the tails. Each of these
has a different ratio ofvolatile components. The
is held below 100 ·c I 212 •p, more ethanol than tails often contain alcohols having a higher boiling
point. These alcohols include propyl alcohol, butyl
water will evaporate. alcohol, amyl alcohol, and furfuryl alcohol and are
Note that it is incorrect to say that the ethanol often called fuse! alcohols or fuse! "oils," which is
a misnomer (see note at left). In vodka, fuse!
"boils before the water does," as is sometimes alcohols are considered undesirable, and the tails
stated. A mixture of ethanol and water has a single are discarded. In whiskey, the inclusion of some
boiling point, which is a complicated function of fusels contributes to the characteristic taste.
the proportions and the pressure. It is not the case
that the ethanol boils and the water doesn't; both The art of producing high-quality spirits comes
water and ethanol evaporate from the mixture. from proper management of the distillation run
and optimization ofthe proportion ofheads and
Ifyou are at a temperature below the boiling tails, which may be separately collected then
point ofpure water and above the boiling point of blended or discarded. Each ofthese components
pure ethanol, however, then more ethanol than has a different composition and thus imbues the

384 VOLUME 2 · TECHNIQUES AND EQUIPMENT











Distillation was invented final product with its own flavors and qualities. boiling point, and they very likely can be concen-
2,500 years ago in ancient Persia Making spirits is not as simple as running a trated with a rotary evaporator. Foods are almost
to distill rose water. distillation setup, any more than turning on an always complex mixtures of compounds that
oven means you have mastered baking. This is a typically have different boiling points. Finding
multifaceted topic that is beyond the scope of this the right combination ofsettings (based on an
book; we mention it here just to illustrate the understanding of what happens at the start,
complexity ofdistillation. middle, and end of distillation) requires some
experimentation.
The ethanol example was used only to describe
separation by distillation. More generally, ifyou Reducing the pressure by drawing a partial
have a mixture of multiple liquids, and each liquid vacuum shifts the boiling point of a liquid
has a different boiling point in its pure form, then (whether pure or a mixture) but does not change
the mixture will preferentially evaporate the the relative order of the boiling points. As you
components with a low boiling point if the tem- decrease the pressure to below atmospheric
perature is near their boiling points. The trick to
using a rotary evaporator is to adjust the pressure, pressure, pure ethanol will boil below 78 •c I
the bath temperature, and the condenser chilling 172 •p, water will boil below 100 •c I 212 •p, and
temperature to preferentially evaporate and
condense some components and leave others a 10% mixture of ethanol in water will boil
behind. The details depend on the mixture you are
dealing with. below 93 •c I 199 •p. At any ambient pressure,

Aroma compounds can be smelled precisely however, the boiling point of pure ethanol will
because they are volatile and evaporate into the always be below the boiling point of water at the
air. This fact means that they have a relatively low same pressure. The boiling point of an ethanol-
water mixture will also decrease as pressure
decreases. The key fact to keep in mind when
using a rotary evaporator is that, regardless of
the pressure, when an ethanol-water mixture is
at its boiling point, ethanol will always evapo-
rate more rapidly than water. Similarly, when a
mixture of multiple liquids is at or near its
boiling point, the liquids that, in their pure state,
have the lowest boiling points will tend to
evaporate more rapidly.

Using the vacuum pump, we can lower the
boiling point of a mixture ofliquids within a wide

range- in principle, all the way down to 0 •c I

32 •p_The main reason to lower the boiling point is
to preserve the quality ofheat-sensitive flavor
compounds that would be cooked or altered at
higher temperatures.

The condenser portion of the rotary evapora-
tor condenses out the vapors. Sometimes this is
the desired product; we keep the condensate and
throw out the remnants in the evaporation flask.
That is typically what is done in making spirits
where the final product is the condensate. In
other cases, we want to remove a solvent, so we

3 90 Fresh watermelon juice. before and halfway through vacuum
concentration in aGenevac Rocket. The delicate flavor of
watermelon juice is retained even as water is removed.
This concentration could also be done in a rotary evaporator
(see page 384) or by vacuum reduction (see page 380).

VO LU M E 2 · TE CHNIQU ES AND EQUI PM ENT