MOLEC­U­LAR GAS­TRON­OMY

LAB TECH­NIQUES FOR THE KITCHEN

Guru Magazine - - Contents - NATASHA AGA­BALYAN• FOOD GURU

Wouldn’t it be nice to cre­ate some fancy Miche­lin Star food at home? Food Guru Natasha dons her chef’s whites and plays with some whizzy kit. Recipes in­cluded! Watch out He­ston Blu­men­thal.

Molec­u­lar gas­tron­omy is now well known and used by chefs, whether in fine din­ing restau­rants or quaint lit­tle bistros. It has even started to creep into our kitchens. The art of mix­ing science and food is on ev­ery­one’s lips: whether it’s try­ing out a new tech­nique at home or in­dulging in ex­per­i­men­tal din­ing, we all want a taste of the ac­tion. Where do th­ese in­trigu­ing tech­niques come from – and where is molec­u­lar-cui­sine head­ing? As a food-lover and sci­en­tist, I di­vulge how spe­cialised tech­niques have gone from the lab to kitchen. White coats are es­sen­tial in both…

Starter: The spin-y ma­chine soup

The most danger­ous ad­di­tion to the kitchen is what we sci­en­tists call a ta­ble-top cen­trifuge. De­signed to spin at huge speeds, some­times gen­er­at­ing up to 13,000 times the force of grav­ity, it al­lows us geeks to sep­a­rate a liq­uid into its dif­fer­ent parts based on weight. For ex­am­ple, freshly squeezed or­ange juice con­tains sug­ary wa­ter and fruit bits. Af­ter spin­ning, heav­ier parts will be found at the bot­tom of the tube, the ‘pel­let’, whilst lighter parts will re­main in the top layer, the ‘su­per­natant’. This method is used ev­ery day around the world, for in­stance to iso­late blood cells from whole blood and ex­tract pro­tein from bac­te­ria. With an eye for ad­vanc­ing the cook­ing process, ex­per­i­men­tal chefs have seized upon this su­per-spin ma­chine – to clar­ify a juice or broth, for ex­am­ple. As food fash­ion leans to­wards the re­fined, light and fra­grant tastes of­ten found in Asian cui­sine, a cen­trifuge could sep­a­rate out the cloudy and messy parts of a stock, while re­tain­ing those beau­ti­ful in­fused flavours.

WARN­ING: I will not be pro­vid­ing a do-it-your­self recipe to go with this up-and­com­ing tech­nique be­cause cen­trifuges can be ex­tremely danger­ous. When spin­ning at such high speeds around their cen­tral ro­tor, cen­trifuges cre­ate huge amounts of force that, if un­bal­anced, can lead to dev­as­tat­ing re­sults (think ‘bye-bye kitchen’). A rule of ut­most im­por­tance in the lab is that a cen­trifuge needs to be per­fectly bal­anced. Tubes of fluid must be placed sym­met­ri­cally within the cir­cu­lar spin­ning bowl: if you place one tube con­tain­ing 50ml in the cen­trifuge, you must place an­other tube of ex­actly equal vol­ume (e.g. 50ml of wa­ter) on the op­po­site side. If you don’t, you are likely to end up with a shat­tered ma­chine – or worse: su­per high-speed cen­trifuges have been known to crash through walls and ceil­ings. You have been warned!

Main Course: Mod­ern day boil-ina-bag

Sous-vide cook­ing means ‘ un­der vac­uum’ in French. The idea be­hind this method is to cook food (meat in par­tic­u­lar) at a tightly reg­u­lated tem­per­a­ture. So if you’re keen on that per­fectly medium-rare steak or ten­der and moist chicken, this is the one for you. A wide range of ma­chines and bags are avail­able for cook­ing sous-vide. How­ever, cheaper so­lu­tions are also avail­able to achieve the same tem­per­a­ture con­trol: you can get sim­i­lar re­sults with a sealed jar or oven bag and a mod­ern oven or wa­ter bath whose tem­per­a­ture you can con­trol to one or two de­grees. There are many ben­e­fits to cook­ing sous-vide. Firstly, cook­ing at such pre­cise tem­per­a­tures means a minute or two of over-cook­ing will not ruin your food – a per­fect stress-beater when cook­ing steaks at a din­ner party. Se­condly, the con­trolled tem­per­a­ture means food is cooked very evenly – of par­tic­u­lar im­por­tance when cook­ing chicken or pork, when it is no­to­ri­ously dif­fi­cult to get the bal­ance of per­fectly moist but not un­der­cooked white meat. The meat is also cooked very evenly. This is be­cause the vac­uum-sealed meat is sur­rounded by the hot wa­ter from all sides. An­other ad­van­tage to this method is that it’s com­pletely con­sis­tent – once

you’ve worked out your times and tem­per­a­tures, you’ll get a per­fectly juicy steak ev­ery time. Best of all, cook­ing within a vac­uum seals in all of the vapours around the meat dur­ing cook­ing, giv­ing you dishes that are al­ways tasty, juicy and ten­der. Check out the rec­om­mended link be­low for recipes to try.

Ac­com­pa­ni­ment: Beau­ti­ful food bub­bles

Spher­i­fi­ca­tion is a less stress­ful tech­nique that doesn’t re­quire ac­tual cook­ing; it is some­times also re­ferred to as ‘mak­ing caviar’. The process in­volves mak­ing lit­tle gelati­nous spheres from a liq­uid prepa­ra­tion. Dis­cov­ered by Unilever in the 1950s, the tech­nique started to hit the big time in Fer­ran Adria’s renowned molec­u­lar gas­tron­omy restau­rant elBulli in Spain. Adding a layer of tex­ture and in­trigue (and, of course, artis­tic plate set­ting), th­ese lit­tle beads are still all the rage in fine din­ing. Two main meth­ods are used by chefs to cre­ate beau­ti­ful lit­tle spheres; the choice de­pends on the cal­cium con­tent of the liq­uid. Here comes the chem­istry: if the liq­uid con­tains no cal­cium, it is mixed with sodium al­gi­nate, a gum-like sub­stance ex­tracted from brown sea­weed, and then dripped drop-by-drop into cal­cium chlo­ride or cal­cium car­bon­ate. This tech­nique is called Ba­sic Spher­i­fi­ca­tion and has both pros and cons. On the plus side, it cre­ates spheres with a very thin outer layer so that they dis­solve beau­ti­fully in the mouth. How­ever, the jel­li­fi­ca­tion process doesn’t stop when the spheres are re­moved from the cal­cium bath and washed, so they need to be sent out of the kitchen pronto if you don’t want your guests to be chew­ing on a gob­stop­per. An al­ter­na­tive tech­nique, used for liq­uids con­tain­ing cal­cium or with a high acid or al­co­hol

con­tent, is called Re­verse Spher­i­fi­ca­tion. The liq­uid is first mixed with the cal­cium chlo­ride and then dropped into an al­gi­nate bath. The cal­cium chlo­ride causes the al­gi­nate pro­tein strands to be­come cross-linked, form­ing a gel. Mak­ing the bead de­pends on how you drop this gel into the al­gi­nate wa­ter: a larger drop will cre­ate a large sphere; a small drop, a dainty lit­tle bead. It goes with­out say­ing that some dex­ter­ity is re­quired for this one! This method gives the food blob a thicker mem­brane, but you are able to make beads from most any liq­uid and the jel­li­fi­ca­tion process is stopped by rins­ing the beads in wa­ter.

Ready to try it out? Di­rect from the elBulli kitchen, this Moz­zarella bead recipe is de­lec­ta­ble (kindly pro­vided by Molec­u­lar Recipes): For the Moz­zarella mix, you will need 220 g Buf­falo Moz­zarella 150 g Moz­zarella whey 70 g dou­ble cream 4 g salt For the Al­gi­nate bath 1.5 litre wa­ter 7.5 g sodium al­gi­nate Your first step is to pre­pare the al­gi­nate bath. Mix the sodium al­gi­nate with the wa­ter us­ing a blender un­til the al­gi­nate is com­pletely dis­solved. Bear in mind this might take some time. Leave it in the fridge for 24 hours. For the moz­zarella balls, shred the moz­zarella and blend to­gether with the whey in a blender un­til you ob­tain a grainy so­lu­tion. Boil the cream and add it to the moz­zarella mix and blend for an­other 10 sec­onds. Now add the salt and mix. To make your spheres, re­move the al­gi­nate bath from the fridge and pre­pare the moz­zarella mix in your pre­ferred spher­i­fi­ca­tion tool (whether it’s a spe­cial spoon, sy­ringe or pipette – see our top tips on spher­i­fi­ca­tion be­low). Care­fully drop the mix into the bath, mak­ing sure the beads don’t touch so that they don’t stick to­gether. Leave the balls in the bath for about 12 min­utes

and re­move with a slot­ted spoon. Rinse with wa­ter and strain them care­fully. Serve im­me­di­ately with toma­toes, basil, olive oil and a gen­er­ous grind­ing of pep­per. Or you could store it in a plas­tic box in the fridge for later. If you’re feel­ing am­bi­tious and want to try your hand at a ba­sic spher­i­fi­ca­tion recipe, this recipe will give red wine a com­plete change in tex­ture and taste! For the sodium al­gi­nate bath, you will need 3 g sodium al­gi­nate 325 ml wa­ter For the cal­cium chlo­ride bath 5 g cal­cium chlo­ride 1 litre wa­ter For the spheres, use around 200 ml of a liq­uid of your choice, be it wine, soy sauce or any­thing else that ti­ti­vates your taste buds. The first step is to dis­solve the sodium al­gi­nate into wa­ter un­til you have a pow­dery so­lu­tion (an im­mer­sion blender is good for this). Bring the so­lu­tion to the boil and then let it cool at room tem­per­a­ture. Next pre­pare the cal­cium chlo­ride bath sim­ply by dis­solv­ing the cal­cium chlo­ride in the wa­ter. Now mix your cho­sen liq­uid with the sodium al­gi­nate so­lu­tion at a 2:3 ra­tio of liq­uid to sodium al­gi­nate. Tak­ing your favourite spher­i­fi­ca­tion tool, gen­tly drop the liq­uid into the cal­cium chlo­ride bath and let the beads ‘cook’ for a minute be­fore re­mov­ing them with a slot­ted spoon, rins­ing them in wa­ter and drain­ing.

Re­mem­ber to serve th­ese im­me­di­ately!

Dessert: Dry ice sur­prise

Us­ing dry-ice and liq­uid ni­tro­gen in cock­tails has be­come quite pop­u­lar of late, with the lay­ers of smoke adding a cer­tain mys­tique. But be­ing so near liq­uid ni­tro­gen can be danger­ous.

Liq­uid ni­tro­gen’s main pur­pose is for rapid freez­ing: it is used to freeze sam­ples of tis­sue and for stor­ing sperm and eggs. It is also of­ten used for cool­ing com­put­ers in cer­tain set­tings. With a tem­per­a­ture of -196°C (or less), drop­ping an ob­ject into liq­uid ni­tro­gen has the ef­fect of freez­ing it in­stantly. Liq­uid ni­tro­gen piqued the in­ter­est of forwardthinking chefs in the search for the per­fect ice cream. When mak­ing ice cream, the liq­uid must be frozen slowly and reg­u­larly remixed dur­ing the freez­ing process to cre­ate an even tex­ture. The longer the mix takes to freeze, the more ice crys­tals are formed and the ‘grit­tier’ the ice cream will be. Pre­par­ing ice cream in liq­uid ni­tro­gen means a very fast freez­ing process – and very few ice crys­tals. This cre­ates a much smoother and creamier ice cream – all for your de­light.

WARN­ING: once again, this is not one to try at home! Liq­uid ni­tro­gen is treach­er­ous: liq­uid ni­tro­gen evap­o­rates very rapidly when poured (this is what also makes the ex­cit­ing smoke) – but it ex­pands so rapidly that one litre of the so­lu­tion can cre­ate up to 700 litres of gas. This could de­plete the level of oxy­gen in a room very quickly – with po­ten­tially fa­tal re­sults. Most labs will keep their stock in in­su­lated con­tain­ers stored in rooms with spe­cialised ven­ti­la­tion and alarms in case of a spill. But if you hap­pen to be trained and have reg­u­lated ac­cess to liq­uid ni­tro­gen (or know some­one who does), why not try this gor­geous ‘Ber­ry­li­cious’ ice cream recipe in be­tween some cen­trifuge ex­per­i­ments! You will need: 5 or more litres of liq­uid ni­tro­gen Gloves and gog­gles A plas­tic or stain­less steel salad bowl 950ml whip­ping cream 425ml ‘Half and Half’( half light cream and half milk) 350g sugar 500g of mashed mixed berries 2 tea­spoons of vanilla ex­tract Mix the whip­ping cream, the ‘half and half’ and the sugar us­ing a wire whisk un­til the sugar has dis­solved. Put your gloves and gog­gles on and pour a small amount of liq­uid ni­tro­gen into the bowl con­tain­ing the mixed cream and sugar. Con­tinue to stir while adding more liq­uid ni­tro­gen slowly. As soon as the base starts to thicken, add the mashed berries and stir vig­or­ously. When the ice cream be­comes too thick for the whisk, use a wooden spoon. Once it be­comes too hard, re­move the spoon and sim­ply pour the re­main­ing liq­uid ni­tro­gen on to the ice cream. Wait for all the liq­uid ni­tro­gen to boil off be­fore serv­ing.

Ex­tra in­for­ma­tion

For ev­ery­thing and any­thing you may need to be­come the best molec­u­lar gas­tron­omy chef, check out the Molec­u­lar Recipes store on­line! They also have lots of handy in­for­ma­tion: 10 tips to cre­ate a per­fect sphere

An in­tro­duc­tion to sous vide cook­ing Sous-vide supreme has some great sug­ges

tions for the per­fect sous-vide cook­ing times!

A video show­ing the ‘ se­cret to ul­tra­smooth Ice Cream’ with liq­uid ni­tro­gen

ABOVE: Green tea af­ter tKe VSKerL­fiFatLRn process.

BE­LOW: Im­age courtesy of

Tiny Ur­ban Kitchen.

Natasha Aga­balyan is on her way to be­com­ing a Doc­tor of Cell Bi­ol­ogy in Brighton, UK. In be­tween drink­ing far too much cof­fee and blog­ging at The Science In­for­mant, she has a love of find­ing out in­ter­est­ing tit-bits from all as­pects of life. You can fol­low her on twit­ter at @SciencIn­for­mant.

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