Perlini and Carbonation

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Perlage Systems, Inc. CONFIDENTIAL

P E R L A G E S Y S T E M S I N C .

Factors Affecting Carbonation and Dilution Levels inPerlini Drinks

September 8, 2009

Perlage Systems, Inc.1507 Western Ave. #606

[email protected] www.perlagesystems.com

www.perlini.biz




1 Factors Affecting Carbonation in Perlini

Carbonated drinks made with Perlini are extremely easy to make. There are some basicconsiderations, however, that need to be understood to produce the best results. This

document examines the most important factors affecting the uptake, retention, and effluxof CO2 in the Perlini System, and other factors affecting the quality of the resultingcocktails.

1.1 Temperature

Temperature of the liquids being carbonated is by far the most important variable in theproper use of Perlini. All other things being equal, the capacity of a liquid to absorb CO2is much greater for lower liquid temperatures. As illustrated by the graph below, thedifference in the amount of CO2 that can dissolve in a liquid at near freezingtemperatures versus room temperature (~25 C) is about a factor of two, which is thedifference between a barely carbonated drink and a vigorously carbonated drink. Warm

liquids simply will not carbonate satisfactorily—this is just physics. So, the liquidingredients must be shaken over ice for good effect (or all the liquids used must be pre-chilled to refrigerator temperatures, which is generally not practical).

To ensure that the liquids being carbonated are at the optimal temperature, always completely fill the lower half of the shaker with ice..

1.2 Pressure

The Perlini shaker must be pressurized fully to the pre-set pressure to work properly. Ifthe headspace of the Perlini shaker is not fully pressurized, there may not be a sufficientreservoir of CO2 in the headspace to fully carbonate the liquid ingredients. If the lowerhalf of the shaker is completely filled with liquid and ice, and the headspace is filled tothe proper pressure, there will barely be enough CO2 to effect proper carbonation (butsee the section entitled Volume of Liquid below).




The regulator will stop the flow of gas at the proper pressure (~60 psi) with both thehand-held unit and the commercial pressurizer.

Make sure there are no leaks from either the O-ring area or the seal in the cap. If youhear no audible leaking, and the flow of CO2 has stopped, then the shaker should be atthe proper pressure.

1.3 Shaking the Cocktail

CO2 can only be absorbed into solution through the liquid-gas interface, which is only afew square inches for Perlini. Shaking is what causes the CO2 to dissolve into solutionquickly: the splashing caused by the agitation dramatically increases the liquid surfacearea through which CO2 is absorbed. If the pressurized Perlini were left to sit, it wouldtake hours for the CO2 to dissolve into solution; shaking reduces that time to seconds.There is a balance, however, between shaking too hard which creates many smallsuspended bubbles, and hence nucleation sites (see below), and not shaking hardenough or long enough to dissolve the CO2.

5 - 10 seconds of moderately hard shaking is usually optimal; but this is something thatevery user will have to develop a feel for.

1.4 Volume of Liquid

The greater the liquid volume that you are trying to carbonate, the less CO2 there is inthe headspace of the shaker to dissolve into the liquid and create effervescence. ThePerlini prototype unit is really meant to be a single-cocktail device, with typically no morethan four or five ounces of liquid ingredients. If the lower half of the shaker is filled to thebrim with liquid ingredients, you may have to shake, re-pressurize, and shake again toget enough CO2 into solution.

1.5 Nucleation

All bubbles that you see rising out of a carbonated beverage form either on existingbubbles trapped in scratches in the glassware, or bubbles trapped on impurities like lintor dust, or on dissolved particles with rough surfaces. These "seeds" are callednucleation sites. Clear ingredients (e.g., spirits, water, cranberry juice) have fewernucleation sites than cloudy ingredients (e.g., orange juice, lime juice, pineapple juice,coffee), and tend not to lose CO2 as rapidly in the decompression, resting, and pouringphases.

1.6 Settling Period

Notice that when the cap is slowly loosened to relieve the pressure, the carbonatedliquid "blooms", or foams up. This is largely due to the fact that the shaking actioncreates a lot of fine bubbles, just as with a regular cocktail shaker. These little bubbles

act as nucleation sites, causing the resulting bloom of foam--which is CO2 that nevermakes it to the customer's glass. The longer you wait for the bubbles to die down, themore CO2 will remain in solution. This has to be balanced against increased dilution andlonger drink assembly times (see Section 2 regarding ice and dilution). Under mostcircumstances, 15-30 seconds should be sufficient. Very sweet, viscous drinks mayrequire longer for the foam to die down, as the viscosity will cause the bubbles to persistlonger.




1.7 Post-Shaking Agitation

After the shaker is depressurized, any agitation from stirring or pouring will release CO2.Refrain from stirring in any extra ingredients after shaker is opened, and pour thecocktail quietly down the side of the glass. Tilting the glass, as with a draft beer, will helpreduce the loss of CO2.

1.8 Type of Ice

The ice itself is a source of nucleation sites. The less surface area of the ice, and thesmoother the ice, the better. Five or six cubes of cold-press ice is much better thancrushed ice or ice in odd shapes. Also, the colder the ice, the colder the resultingcocktail, which means greater CO2 absorption, and the less dilution.

1.9 Alcohol Concentration

CO2 is very soluble in water; much less so in alcohol. So you will get the mostcarbonation with drinks that are less alcoholic and more dilute. Pure spirits will certainlycarbonate, but much less so than cocktails that incorporate other low-or zero-proofmixers.

Incidentally, liquids with higher alcohol concentration will also typically cause moredilution. Because alcohol lowers the freezing point of the solution, the resulting mixtureafter shaking will be colder with a high-alcohol content than with a low-alcohol content;and this implies that more ice must have melted to bring the temperature down further.

1.10 Acidity of Solution

The amount of CO2 that will dissolve in solution decreases slightly with increasingacidity. Thus, all other things being equal, tart drinks may absorb slightly less CO2. Thisis a very small effect, however.

1.11 Sugar Content

The amount of CO2 that will dissolve in solution decreases slightly with increasing sugarcontent. Thus, all other things being equal, sweet drinks may absorb slightly less CO2.This is also a very small effect.

1.12 Visual Clarity and Glassware

It is said that we drink with the eyes as much as the mouth, and this is very true withPerlini. Tall, narrow flutes will show off the bubbles better, both because of a longerbubble path as well as the fact that the opacity given to a cocktail by the pulp in juices isless evident in a narrow glass, allowing the bubbles to be seen better.

1.13 Surface Area and Glassware

All CO2 lost from a cocktail once it is in the glass is either from visible bubbles orinvisible molecular diffusion at the top surface of the cocktail. In fact, under mostcircumstances, diffusion is usually by far the dominant mechanism (as much as fivetimes greater). The smaller the surface area at the liquid-air interface, the less gasescapes. So, a tall narrow flute retains dissolved CO2 better than a coupe.




2. Melting of Ice and Dilution

2.1 Physics of Melting Ice in Shaken Cocktails

In a shaken cocktail, the liquid ingredients start out at or around room temperature,typically around 76 F (25 C). The ice starts out at whatever temperature the freezer is

set to, perhaps around 5 F (-15 C). (It is a common misconception that ice is always at32 F. This is indeed the temperature that ice melts at, but it can be any temperaturelower than 32 F; namely, whatever the freezer is set to).

When the ice and liquid are mixed together, the liquid cools down, and the ice warms up.As the surface of the ice warms up to 32 F, it begins to melts. Now, here is the key point:It takes a great deal of energy to melt ice—about 80 calories per gram (this is known inphysics as the heat of fusion). The energy required to melt the ice comes at the expenseof the energy in the liquid; so, the absorption of energy from the liquid by the ice, whichresults in melting of the ice, actually cools the surrounding liquid. The ice continues tomelt until the temperature of the liquid and ice mixture is at an equilibrium temperaturewhere the liquid and the ice are at the same temperature (assuming that not all the ice

has already melted before reaching equilibrium, which is a good assumption since acocktail shaker generally contains a large enough volume of ice to bring the liquid tonear-freezing temperatures). If the liquid in question is pure water, this temperature willbe 32 F. If the liquid contains alcohol, this equilibrium temperature will be less than 32 F,as alcohol has a lower freezing point than water.

Once the liquid-ice mixture reaches equilibrium, no further melting takes place unlessheat is transferred into the system through the walls of the shaker. In the case of Perlini,the walls of which are extremely good thermal insulators (which is why your handdoesn’t get cold when shaking it, as is the case with a metallic shaker), this is a verygood approximation over the time scale of making a cocktail.

2.2 Calculation of Ice MeltThis equation describes the total amount of ice that will melt in a closed insulated systemlike Perlini:

Ml x Cl x ∆Tl = Mi x Ci x ∆Ti + Mm x Cf Eqn. 1

Where

Ml = Initial mass of liquidMi = Initial mass of iceMm Mass of melted iceCl = Heat capacity of liquid

Ci = Heat capacity of solid iceCf = Heat of fusion of ice∆Tl = Change in temperature of liquid∆Ti = Change in temperature of ice

Eqn. 1 assumes that a) there is enough ice to completely cool the liquid to equilibirium,and still have ice left; and b) over the timescale of the trial, the Perlini acts as a perfectinsulator.




Solving Eqn.1 for Mm,

Mm = ((Ml x Cl x ∆Tl) – (Mi x Ci x ∆Ti)) / Cf

Assuming the liquid is water, and that the liquid starts out at 24 C and cools to 0 C, andthe ice starts at -17 C and warms to 0 C, and given the following values:

Ml = 100 gMi = 200 gCl = 1.0 cal/g degCi = 0.5 cal/g degCf = 80 cal/g deg∆Tl = 24 C∆Ti = 17 C

Then the amount of melted ice is

Mm = ((100 x 1 x 24) – (200 x 0.5 x 17))/80

Mm = 39 g

This agrees well with experimental findings for pure water.

The equation for alcohol water mixtures is somewhat more complicated, since theequilibrium temperature for a water/alcohol mixture is less than 32 F; and the degree towhich it is lowered depends on the concentration of alcohol. It is further complicated bythe fact that as the ice melts, the water/alcohol percentage goes up, changing theequilibrium temperature. This calculation is beyond the scope of this paper.

2.3 Rate of Ice Melting

All other things being equal, both the rate of ice melt and the rate of temperature

decrease of the liquid are approximately proportional to the temperature differencebetween the ice and the liquid. The rate starts off high at first, because the difference intemperature between the liquid and ice is at its greatest, and drops to near zero as theequilibrium temperature is reached and the solid and liquid components become closerin temperature. This type of behavior is ubiquitous in the physical world, not just inthermodynamics.

The extreme agitation of shaking a cocktail provides very intimate contact of the liquidand ice, ensuring an extremely rapid approach to equilibrium. Our experiments haveshown that most of the cooling--and hence most of the melting of ice--takes place in thefirst 10 seconds of shaking.

To examine the proposition that most melting takes place during shaking, a knownquantity of various concentrations of vodka, from pure water to pure vodka, was shakenfor various durations over approximately 200 g of ice (i.e., the bottom half of Perlini filledwith ice). After shaking, the liquid was removed from Perlini, its volume measured, andthen quickly put back in Perlini over the same ice. The increase in liquid volume, inmilliliters, represents the amount of ice, in grams, melted during shaking. The mixturewas then left to stand for an additional time in the Perlini, and the quantity of liquid was




then measured again. In this manner, ice melt and liquid dilution can be measured overtime, through the various stages of drink assembly, shaking, and resting.

In trials with 50 g of pure vodka at 76 F, and 200 g ice at 15 F, the result was an averageof 70 g of liquid after shaking 10 sec, or a dilution of ~40%. After returning the liquid tothe Perlini over the same ice, and letting it stand for another minute, the volume of liquid

was less than ~75 g, or an increase of less than 10%.

Conclusion : Most of the ice melting takes place during shaking. Very little extra dilutiontakes place even after another minute, because the system is close to equilibrium.

Perlini and Carbonation

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