Alkalized_Cocoa_Powders_Article.pdf

128 57th PMCA Production Conference, 2003

Cocoa powder has gained a significantamount of attention in the industry,not only because of its volatile price, butalso because of the increase in the con-sumption of cocoa powder in non-confec-tionery applications (i.e., dairy and bakerysegments). Because of this growth in use, itis important to understand the uses andapplications of various powders.This papergives an overview of cocoa powder as itapplies to its process and application; iden-tifies the types of cocoa based on the alka-lization process; determines its flexibilityand limitations in a given application; andshows how to select a cocoa powder for aspecific application.

WHAT IS COCOA POWDER?

The FDA defines cocoa powder as thefood prepared by pulverizing the mater-ial remaining after part of the cocoa fathas been removed from ground cocoa nibs.It is the product obtained by grinding thesolids remaining after cocoa butter hasbeen pressed out of chocolate liquor. Thisseparation of cocoa solids and cocoa but-ter is achieved typically through hydraulicpressing. Chocolate liquor contains about54 percent cocoa butter; after pressing,cocoa solids will have about 1012 per-cent cocoa butter.

Cocoa powder evolved in the chocolateindustry as a by-product. The original pur-pose of pressing chocolate liquor was toobtain cocoa butter, which is utilized in themanufacture of chocolate coatings. How-

ever, a variety of new applications, particu-larly in the dairy and bakery industries, andincreased consumption in developing coun-tries have increased demand for cocoa pow-der. There have been several other factorsin the last two years that have contributedto a shortage of supply and increase in costof cocoa powder. For instance, the use ofcocoa butter equivalents and pgpr (a vis-cosity-reducing emulsifier) has reduced thedemand for cocoa butter, thus reducing thecocoa butter/cocoa powder production, andoutsourcing by large manufacturers thatwere once large producers of cocoa butterand cocoa cake has taken some manufac-turing capacity off line. An increase indemand for cocoa powder coupled with sta-tic demand for cocoa butter has created aglobal shortage of quality cocoa powdersand soaring prices. This cocoa supply issuewill remain until the demand for cocoa pow-der is rationalized in line with the relativedemand for cocoa butter.

Like any other ingredient, cocoa pow-ders have a specific role in food applications.They are expected to deliver flavor and colorwhile not imparting any negative attributes.Not all cocoa powders are the same and noone cocoa powder meets the requirementsfor all applications.This means one needs tohave a very clear understanding of whethera cocoa can or cannot perform its functionsin a given application.

COCOA POWDER PRODUCTION

In order to learn about and understand dif-

Alkalized Cocoa PowdersBill DyerBlommer Chocolate Company

Bill Dyer

Dyer is the director oftechnical sales andservice at BlommerChocolate Company.He joined the companyin 1996. Dyer previously workedat Loders Croklaan,Durkee Industrial Foods,and Gill and DuffusProducts.

ferent types of cocoas and how they canbe used in various applications, we needto start with a brief overview of the cocoaprocess, from selection of beans throughalkalization. With this in mind, three sub-jects will be discussed briefly: cocoa beans,roasting process and types of roasters.More time will be spent on alkalizationprocesses and cocoa applications.

The following terminologies will be usedfrequently in the rest of this paper: Nib Shell-free cocoa bean pieces. Chocolate liquor Paste resulting from

grinding nibs. Press cake Cocoa solids remaining in

the press pot after part of the cocoa but-ter has been removed by hydraulic press(the fat content is generally 10 percentto 12 percent).

Kibbled press cake Pieces of crushedpress cake after they are removed fromthe press.

Alkalization A process where nibs,chocolate liquor or crushed press cake(coarse cocoa powder) is treated with asuitable alkali solution and, subsequentto alkali treatment, the moisture isremoved during drying and/or the roast-ing process. Cocoa powders derivedfrom these processing options arereferred to as nib-alkalized cocoa, liquor-alkalized cocoa or cake-alkalized cocoa.Cake-alkalized cocoa is also referred toas powder-alkalized cocoa.

Cake alkalization/powder alkalization refers to the alkalization process wherecrushed cocoa press cake is treated witha suitable alkali solution.

BeansThe making of cocoa powder is a many-step process that begins with the bean.Each step at each stage of cocoa powderproduction can have a large impact on thefinal powder product application. In TheApplication of Cocoa Powders in Choco-late Confectionery, Hans Kattenberg veryclearly shows the correlation betweenbeans from various origins and their char-acteristic flavor notes (Figure 1).

This knowledge is a very helpful toolto predict a flavor profile in powdersbased on a type of bean or a blend of sev-eral beans. Problems can arise due to vari-able climate conditions during a givenyear, changing the profile for a given ori-gin. Political instability can affect theavailabilities of specific types of beans inspecific quantities at times. These unpre-dictable variables have prompted theindustry to put more emphasis on pro-cessing, specifically roasting and alka-lization, which are the two key process-ing steps that can assure quality andmaintain quality consistently.

Roasting

In general, there are three ways to roastcocoa beans or cocoa nibs.

Fluid bed roasters are designed for beanroasting. In these roasters cocoa beans arein constant motion from hot air on an oscil-lating conveyor. These roasters are com-monly used for large-volume operationswhere the objective is to roast one or twotypes of beans.

The second category of roaster is thestatic bed roaster where a bed of beans ornibs is conveyed horizontally or verticallythrough various heating and cooling zones.There are two types of static bed roasters.In the first type, a bed of nibs or wet nibs(after alkalization) travels horizontallythrough several zones where the wet nibsare first dried, then roasted and finallycooled. This type is more practical in thenib alkalization process because thisroaster can be used not only for roasting,but drying as well.

Alkalized Cocoa Powders

An increase indemand for cocoapowder coupledwith static demandfor cocoa butterhas created soaringprices and a globalshortage of qualitycocoa powders.

57th PMCA Production Conference, 2003 129

Origin Typical Flavor ProfileIndonesia Bitter to acridMalaysia & New Guinea Acid to astringentWest Africa Rich cocoa flavorEcuador Floral/perfumy

Figure 1

Flavor Notes of Cocoa Beans

The second type of static bed roaster ismore suited to cocoa beans and not nibs.The beans travel vertically through sev-eral heat zones. Roasting is achieved byforcing heated air through the bed of beansas it travels through each zone. With thisroaster, there are options to sterilize thebeans with a pressure cooker-type systemprior to roasting.This approach allows oneto obtain liquors and powders free ofspore-forming bacteria.

The third roasting method utilizes therotary drum. Rotary drum roasters areused in nib roasting and are the mostwidely used form of roasters.They are alsoused in the nib alkalization process. Afterthe alkalization treatment, wet nibs aredried and roasted in drum roasters. Hotair is blown into a rotary drum, causingmaximum exposure of nibs to heat. Uti-lizing this method, process parameters canbe customized to achieve a range of fla-vors and colors for natural cocoa powders(nonalkalized cocoa powders).

Powders

Cocoa powders are categorized based ontwo factors. First, cocoa powders are cate-gorized by the percent of cocoa butter inthe powder. Powders with 10 to 12 percentcocoa butter are referred to as low fatcocoas. Fat contents of 16 to 18 percentare called medium fat cocoa. Fat contentsof 22 to 24 percent are called breakfastcocoa or high fat cocoa.

Secondly, cocoa powders are further dif-ferentiated based on whether or not pow-ders were processed with alkali at the nib,liquor or cake stages. Powders not processedwith alkali are referred to as cocoa or nat-ural cocoa, and alkalized cocoas are referredto as simply cocoa processed with alkali ordutch process cocoa.

Today, 95 percent of the powders used inthe food industry are low fat. Natural cocoapowder varieties are few because they are

limited to the types of cocoa beans avail-able for blending and to the type of cocoabean roasters. Conversely, there are manytypes of alkalized cocoa powders. By con-trolling the degree of alkalization, the typesof alkali applied, the cocoa bean types andat which stage of the cocoa process the alka-lization takes place, a whole spectrum ofalkalized cocoa powders can be produced.

ALKALIZATION

The alkalization process has been well doc-umented by Mike Kostic. In Cocoa Alka-lization he covers in detail the types ofalkali and the types of alkalizing methods.The purpose of alkalization is threefold: To neutralize the acidity of the cocoa beans

and remove astringent cocoa flavor. To promote reaction between cocoa pig-

ment and alkali in the presence of oxy-gen and heat to develop colors rangingfrom light brown to red, and in somecases very dark colors.

To promote flavor development by pro-moting reaction between protein andreducible sugars present in the cocoabeans.

Alkalized cocoa powders can be obtainedby using any one of these approaches:liquor alkalization, powder alkalization ornib alkalization. Each process results incertain advantages and disadvantages.

Liquor Alkalization

Liquor alkalization is ideal to get mild-fla-vored alkalized cocoa powders. However,the process is limited to the amount of mois-ture that can be added during alkali treat-ment. The ideal amount of water requiredto promote optimum reaction during alkalitreatment is not possible with liquor becausewater and cocoa butter are not miscible andthere is a potential for degradation of thecocoa butter, also leading to viscosity issuesin the finishing of the process. Limitedamounts of water added to liquor to pro-mote alkali treatment will yield a narrow


By controlling thedegree of

alkalization, thetypes of alkali

applied, the cocoabean types and atwhich stage of thecocoa process thealkalization takes

place, a wholespectrum of

alkalized cocoapowders can be

produced.


range of color and flavor profiles. Similarto nib-alkalized cocoa, there is added costwith this method of production since thecocoa butter obtained from this processrequires deodorization.

Powder Alkalization or CakeAlkalization

Powder alkalization is a less sophisticatedprocess requiring a basic reacting vesselwith heat and vacuum capabilities. In thisprocess press cake is crushed to a coarsepowder prior to treatment with a suitablealkali solution. It is a cost-effective optionbecause, unlike nib or liquor alkalization,the cocoa butter is not factored into the costof cake-alkalized cocoa. However, the colorand flavor attributes of cake-alkalized pow-ders are limited. Powder alkalization is use-ful in making very dark cocoa powderswhere flavor is not a criterion. Cocoa pow-ders consist of 19 to 20 percent protein and10 to 15 percent starch.The increased sur-face area in the powder to be alkalizedexposes these proteins and starches to heatand moisture. As a result, during the dry-ing process protein is denatured, givingunfavorable textural effects in dairy and insome confectionery applications. Starchesgo through irreversible chemical modifica-tions due to heat and hydration and as aresult are jellified. Chemical and physicalchanges of proteins and starches duringpowder alkalization also have an impact ongrinding capabilities of batches after thealkalization process. It is difficult to grindalkalized cocoa cake to achieve a fineness of99.5 percent through 200 US mesh, which isthe industry standard. Grinding through-put rates drop significantly in order toachieve a good fineness. The impact ongrinding also relates to the degree of alka-lization; the higher the degree of alkalizationin the cocoa, the greater the decrease ingrinding throughput rates.

Nib Alkalization

Nib alkalization provides the best option.There is less detrimental impact on thecomposition of nibs during alkalizationbecause the components of the nibs arestill in their natural state. By contrast, inchocolate liquor alkalization, all of thecocoa butter is released and nonfat com-ponents are in emulsion phase, making thealkalization less effective.A stronger alkalitreatment to liquor can lead to detrimen-tal effects on cocoa butter. The powder iseven more sensitive to alkalization. In pow-ders, the nonfat components, specificallyproteins and starch, are concentratedbecause the fat is removed and they aresubjected to a maximum exposure as aresult of particle size reduction from grind-ing into powder. Given the physical andchemical state of starting material for alka-lization, it should not be surprising to usthat nib alkalization offers the best resultsfor color and flavor attributes in cocoa.

Another benefit of nib alkalization is thatduring this process spore-forming thermo-phylic and mesophylic bacteria are greatlyreduced. The reduction of these bacteria isespecially beneficial to the dairy industry asthe presence of spore formers in dairy prod-ucts, such as cocoa-flavored milk beverages,can shorten the shelf life drastically.

The disadvantage of nib alkalization isthat powders derived from this process areexpensive. Every pound of nib-alkalizedcocoa results in one pound of cocoa butter,and cocoa butter pressed from nib-alka-lized liquor must be deodorized, which isan added manufacturing cost.

Cocoa butter has the highest commod-ity value in the butter/powder equation,therefore the cost of the powder is dictatedby the cost of cocoa butter involved in nibalkalization (Figure 2). Also, nib alkaliza-tion is more capital intensive, adding tomanufacturing complexity and cost.


There is lessdetrimental impacton the compositionof nibs duringalkalizationbecause thecomponents of thenibs are still intheir natural state.


MATRIX OF PH VERSUS COLOR INCOCOA POWDERSXXXXXXXXXXXX

As we discussed, the objective of alkaliza-tion is to neutralize the acidity and promotethe color development in cocoa powders.There is a close correlation between colorand pH of cocoa powders. Powders withlight brown colors have a pH of 6.5 to 7.0and the pH of darker and red powdersranges from 7.0 to 8.0. Very dark powderssuch as black can have a pH of up to 8.2.

This is seen in Figure 3 where the colorof cocoa paste (25 percent cocoa powder,

75 percent water) is measured by a Hunter-Lab colorimeter.

APPLICATIONS

Cocoa powders are used in a wide range ofapplications in the food industry. It is theonly ingredient that remains as a by-prod-uct in a chocolate plant where chocolateliquor is pressed and yet it is an ingredi-ent that is in great demand in the bakery,dairy and beverage industries.

Color of Cocoa Powders inApplications

Before we discuss the applications, we needto address the unique property of colorsseen in cocoa powders.The colors of cocoapowders in a given application can bedefined similar to food colors, i.e., lakes(which are dyes plated on a carrier), ordyes (which are water-soluble pigments).The visual perception of powder colorsand applications of powders in oil-basedor anhydrous products are analogous tolakes except cocoa powders visual appear-ance is more complex. The powder colorcan vary depending on the cocoa butter aswell as the orientation of the cocoa buttercrystals in the powder. During shelf life,due to fluctuations of temperature, thecocoa butter crystals will melt and recrys-tallize, but never in the original orienta-tion, and the crystals may even shift to thesurface of the cocoa particle.This constantshift in fat crystals changes the appearanceof powders, resulting in different color per-ception of the same powder, and is oftenmistaken for color degradation or for adeviation in color control from the speci-fication.The higher the fat content in pow-der, the greater the changes in visual per-ception. While the visual appearance ofthe powder may be alarming, due to cocoabutter bloom, it will not affect the prod-uct application.

In a water-based application, the pig-


Another benefit ofnib alkalization is

that during thisprocess spore-

formingthermophylic and

mesophylicbacteria are greatly

reduced.


Figure 2

Cocoa Butter/Powder Prices

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

2.75

3.00

Bu

tte

r &

Ca

ke

Ra

tio

s

$500

$750

$1,000

$1,250

$1,500

$1,750

$2,000

$2,250

$2,500

$2,750

$3,000

$3,250

$3,500

$3,750

$4,000

$4,250

$4,500

Fu

ture

s P

rice

72 73

74 75

76 77

78 79

80 81

82 83

84 85

86 87

88 89

90 91

92 93

94 95

96 97

98 99

0001

02

Butter Ratio Cake Ratio Futures Price

The L value is indicative of darkness, the A value is indica-tive of red color and the B value is indicative of browncolor in cocoa powders

Figure 3

Cocoa Powders pH versus Color

0 5 10 15 20 25

NATURAL

DUTCH

REDDUTCH

DARKDUTCH

BLACK B

A

L

PH

ments are dissolved like dyes and the per-ception of color is different.Two powdersmay look similar in their raw form beforebeing placed in an application, but appeardifferently in a water-based application.Conversely, two powders may appear dif-ferent in their raw form and yet result assimilar colors in application. In Figure 4the three powders appear to be different incolor, and the color measured by Hunter-Lab agrees with visual perception. Thesethree cocoa powders are the same but theywere exposed to different temperaturesover time, resulting in a change in thevisual color.

Typical cocoa powder flavors and theirapplications can be seen in Figure 5.

In bakery, dairy, beverage and otherwater-containing product applications thereis enough water for colors to leach out ofcocoa particles to deliver the appealing col-ors in the finished product. In confectioneryapplications such as confectionery coatings,meltaways, oil- or fat-based fillings and insome truffles, water-soluble colors do notplay a role because they cannot deliver col-ors in oil phase. But what is perceived isthe color of the cocoa itself. There are nooil-soluble pigments in the cocoa bean andif they are present in trace amounts, theyare removed along with cocoa butter dur-ing pressing.

Compound Coatings

In compound coatings, the benefits of nib-alkalized cocoa powders are very easilyassessed. Due to the higher flavor and colorintensity of alkalized cocoa powders, areduction in the amount of powder can beachieved in compound formulas (Figure 6).

The graph in Figure 7 shows the sensoryassessment of the two products referredto in Figure 6.The compound coating withalkalized cocoa at a lower application levelfunctions similar to natural cocoa withoutcompromising color and flavor attributes.

Particle Size Relationship toApplication

The industry standard for fineness ofcocoa powders is a minimum of 99.5 per-cent through a US 200 mesh, which means99.5 percent of the particles must beunder 74 microns.The fineness is less crit-ical in baked goods and compound coat-ings. Fineness is less detectible in bakedgoods; in compound coatings a furtherparticle size reduction is done during therefining process. The most critical role ofcocoa particles is in water-based applica-tions such as icings, toppings, syrups, pud-dings, fillings, nougats, aerated creams andtruffles. In these applications, cocoa par-ticles will swell due to hydration leadingto a perception of coarse texture. Thedegree of swelling of particles depends


Due to the higherflavor and colorintensity of alkalizedcocoa powders, areduction in theamount of powdercan be achieved incompound formulas.


Figure 4

Powder Color at Various Temperatures

Type of Cocoa Typical Flavor Common ApplicationsNaturalnonalkalized Milk, cocoay notes Compounds, syrups, bakery

toppings, confectioneryAlkalizedlight dutch Mild, cocoay notes with mild Dairy, beverage, creams,

alkali undertones syrups, toppings, confectioneryAlkalizedred Moderate to strong alkali Bakery, dairy, beverage,

notes creams, confectioneryAlkalizeddark Milk to moderate alkali notes Bakery, confectioneryAlkalizedblack Intensely unique alkali flavors Cookies, coloring agent

Figure 5

Cocoa Powders Typical Flavors and Applications

on several factors in various cocoa pow-der applications: Type of alkalized cocoa powder The amount of water in the formula Processing heat Time line from process to consumption

(aging process and shelf life)Powder-alkalized cocoa powders respondto heat and hydration differently comparedto nib-alkalized cocoa powders. This dif-ference could be due to the state of pro-teins and starches in the cocoa powder.

Denatured proteins and jellified starchesmay behave differently compared to thesame components found in nib-alkalizedcocoa powders.

In an attempt to demonstrate this behav-ior two test models were selected. In thefirst model (Figure 8) samples of cocoapowder and water suspension (1 part cocoaand 10 parts water) were stored at 65Cfor 24 hours to simulate an acceleratedshelf-life condition. Samples were collectedfrom the top, middle and bottom of eachsuspension. Compared to the particle sizeof dry powders We see an increase in thepopulation of large particles.

In the second model, a filling was madewith the same cocoa powders as beforebut using the formula in Figure 9.

Corn syrup, condensed milk and cocoapowder blends were stored at 65C for24 hours to simulate an accelerated shelflife condition.

Sensory (Figure 10) and particle size analy-sis of the fillings show that cake- or powder-alkalized cocoa powders result in a grittinessas a result of swelling of the particle.

PH of Cocoa Powders in Applications

Although the neutralizing of acids in cocoapowders does have flavor benefits, a higherdegree of alkalization can result in per-formance problems. Following are someof the critical factors related to applica-tions and pH of cocoa powders:In baked goods, especially in productswhere leavening agents are used, higherpH cocoa powders will interfere with leav-ening agents, causing larger air bubbles incake and overspreading of cookies.In puddings and pie fillings, excess freealkali in cocoa powders interfere withjelling mechanisms of starch moleculesand, as a result, end products either take along time or fail to thicken.In chocolate syrups and toppings, pH ofthe finished product is targeted to be in


The most criticalrole of cocoaparticles is inwater-based

applications. Inthese applications,cocoa particles will

swell due tohydration leadingto a perception of

coarse texture.


Compound Coating with Compound Coating with Natural Cocoa Powder Alkalized Cocoa PowderSugar 33.8% Sugar 33.8%Fractionated palm kernel oil 31.0% Lactose 4.0%Natural cocoa 8.0% Fractionated palm kernel oil 31.0%Skim milk 23.8% Cake-alkalized cocoa 2.0%Lecithin 0.3% Nib-alkalized cocoa 2.0%Salt 0.08% Skim milk 23.8%Vanillin 0.02% Lecithin 0.3%Artificial flavor 0.02% Salt 0.08%

Vanillin 0.02%Artificial flavor 0.02%

Figure 6

Compound Coatings Natural Versus Alkalized

Figure 7

Flavor Profile of Compound CoatingsNatural versus Alkalized Cocoa

Cocoa

Sweet

Caramel

Alkalized

Natural Alkalized

Dry Particle Size 20 grams of cocoa in 200 ml of water at 160F incubated for 24 hours

Nib Cake Nib CakeTop Mid Bottom Top Mid Bottom

the range of 4.0 to 4.5 because at this rangepreservatives such as potassium sorbateare more effective. Therefore a blend ofnatural and lightly alkalized cocoa pow-ders is ideal in such applications. Theimproper selection of cocoa powders canoften result in a change of viscosity due toparticle swelling.

SUMMARY

We are certain that there is a differencebetween nib-alkalized cocoa powders andpowder-alkalized cocoa powders in millingpowders, in flavor and color, and also inwater-based applications. We are also cer-tain that the cocoa bean contains highamounts of protein and starch, and that pro-tein and starch are sensitive to heat andhydration. However, there is no researchevidence to confirm the relationshipbetween the application responses of alka-lized cocoa powders and the state of pro-teins and starches. We are not certainwhether modification of proteins andstarches in powder-alkalized cocoa powdersleads to difficulties in milling cocoa pow-ders and swelling of particles in response toheat and hydration in applications.

Given the information on how cocoawas processed, one can make a prudentassessment on how best to use this pow-der in a specific application.

Application Suggestions:Identify the application objectives anddetermine if the application is water-basedor fat-based.

In fat-based applications powders shouldbe selected based on color assessmentusing a protocol that is consistent.A quickmethod to assess the color in cocoa is toplace 1020 g of samples to be tested alongwith a color standard in a 95F hot cabi-net for 30 minutes and visually evaluatecolors or measure color by using a col-orimeter.

For water-based applications, cocoa pow-ders may be evaluated in milk. A simpleand quick method is to suspend 2 g ofcocoa and 2 g of sugar in 100 ml of warmlow fat milk (100110F). Milk provides awhite hue, which aids in seeing subtle dif-ferences in color, and its slight sweetnesswill aid in identifying differences in flavorsor unacceptable flavors.

Talk to your cocoa supplier to learnmore about cocoa processing.

REFERENCESChocolate and Cocoa Edited by Ian Knight.

Blackwell Science Ltd., 1999.Kattenberg, Hans R. Manufacturing Confec-

tioner, 1995.Kostic, Michael J. Manufacturing Confectioner,

1997.Meursing, E.H. Manufacturing Confectioner,

1980.Trout, Richard. Manufacturing Confectioner,

2000.


Although theneutralizing of acidsin cocoa powdersdoes have flavorbenefits, a higherdegree ofalkalization canresult in performanceproblems.


Corn syrup 8.0%Condensed milk 35.26%Fondant 34.78%Coconut oil 14%Cocoa 7.5%Lecithin 0.1%Salt 0.11%Vanillin 0.11%Artificial flavor 0.14%

Figure 9

Confectionery Filling

Figure 10

Flavor Profile of ConfectioneryFillings Cake-Alkalized versus Nib-Alkalized Cocoa

Alkalized

Cocoa

Sweet"Fudgy"

Graininess

Cake Alk. Nib Alk.

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