performence of different drying methods

Original article

Performance of different drying methods and their effects on the

chemical quality attributes of raw cocoa material

Tagro Simplice Guehi,1* Irie Bi Zahouli,2 Louis Ban-Koffi,2 Monke Adrien Fae1 & Jean Gnopo Nemlin2

1 Unite de Formation et de Recherche des Sciences et Technologies des Aliments (UFR-STA), Universite d’Abobo-Adjame. 02 Bp 801 Abidjan 02

Cote d’Ivoire

2 Station de Recherche et de Technologie, Centre National de Recherche Agronomique (SRT-CNRA). 08 BP 33 Abidjan 08 – Cote d’Ivoire

(Received 13 January 2010; Accepted in revised form 27 April 2010)

Summary Studies were carried out to investigate the impact of different drying processes on the chemical quality traits

of raw cocoa beans. The pH of less fermented cocoa is higher than the well-fermented cocoa’s. The sun-dried

beans pH ranged from 4.5 to 5.5, while the pH of both oven- and mixed-dried beans was between 3.8 and 5.2.

The sun-dried beans contained lower volatile acidity than oven-dried beans. Artificially dried beans resulted

in higher free acidity content when compared to both sun- and mixed-dried beans. Ammonium nitrogen

content in raw cocoa beans is not influenced by the drying methods. Free fatty acid content increases slowly

but remains below the critical value of 1.75% whatever the drying processes. While oven-dried beans show

the FFA content above 0.70% both of sun- and mixed-dried beans are associated with FFA content below

0.70%.

Keywords Chemical quality, cocoa, drying methods.

Introduction

Cocoa beans are the seeds from fruit pods of a tropicaltree botanically known as Theobroma cacao L. (FamilySterculiaceae). Each pod contains 30–40 beans embed-ded in a mass of mucilaginous pulp within the pod. Thebean pulp is rich in fermentable sugars, such as glucose,fructose and sucrose, and has a low pH of 3.0–3.5,mainly because of the presence of citric acid. Cocoabean is the principal raw material of chocolate manu-facture (Ardhana & Fleet, 2003). Theobroma cacao isgrown mostly in the wet tropical forest climate which iswithin 20� of latitude of the equator at countries such asCote d’Ivoire, Ghana, Nigeria, Cameroon, Brazil,Equador, Papua New Guinea, Indonesia and Malaysia(Beckett, 1994). World production of cocoa beans wasabout 3 888 000 t in 2006 ⁄07 crop year, and nearly 70%of this quantity was produced in West Africa (WorldCocoa Foundation, 2008). Cocoa is a crop that needs tobe fermented and dried before export. The processing ofcocoa beans consists of two major steps namelyfermentation and drying (Wood & Lass, 1985). Fer-mentation and drying are both essential steps for thequality of final product. Upon harvesting of ripe cocoa

pods, the beans and associated pulp are removed fromthe pod and subject to microbial fermentation as thefirst stage in preparation for chocolate production.Fresh cocoa beans are fermented for 5–7 days and driedimmediately after fermentation to safe moisture level of7.5%. The importance of bean fermentation in contrib-uting to chocolate quality has been recognised for over100 years, and numerous studies have been conducted indifferent countries to determine the microbial speciesassociated with this process (Schwan et al., 1995). Thesefermentations are generally conducted as traditional,indigenous processes, the details of which have been wellreviewed (Roelofsen, 1958; Lehrian & Patterson, 1983;Lopez & Dimick, 1995; Thompson et al., 2001). Micro-bial action during fermentation solubilises the pulpmaterial surrounding the beans and produces a range ofmetabolic end-products (e.g. alcohols, organic acids)which diffuse into the beans to cause their death. Thesechanges induce an array of biochemical reactions withinthe beans and generate the chemical precursors ofchocolate flavour, aroma and colour (Lehrian & Patt-erson, 1983; Jones & Jones, 1984; Hansen et al., 1998;Hashim et al., 1998; Thompson et al., 2001). Duringfermentation the temperature of the beans will rise fromambient to about 50–55 �C because of the exothermicoxidation reaction (Wood & Lass, 1985). After the endof fermentation, the moisture content of the whole

*Correspondent: Fax: +22520374300;

e-mail: [email protected]

International Journal of Food Science and Technology 2010, 45, 1564–15711564

doi:10.1111/j.1365-2621.2010.02302.x

� 2010 CNRA-Universite d’Abobo-Adjame

beans is approximately 60% and this must be reduced to7–7.5% before the cocoa can be stored, sold, trans-ported and exported to European countries. So thebeans are dried immediately to avoid over fermentation,which could lead to product deterioration. Drying isusually carried out using natural sun and artificial hotair techniques (Mc Donald et al., 1981). Natural orartificial drying methods may be chosen, depending oncharacteristics of each species, the amount of harvestedseeds, and on weather conditions prevailing after seedswere harvested. Natural cocoa bean drying is directlydependent on weather conditions. The disadvantage ofthe method lies in the need for intensive human labourand in turn leads to poor operational performance.Cocoa smallholders produce in small quantity wouldprefer sun drying, while for the bigger plantation the hotair (artificial) method is preferred (Wood & Lass, 1985).During drying, the cocoa beans undergo various chem-ical and biochemical changes that form the necessaryflavour and aroma precursors needed during processing.Cocoa beans constitute an inexpensive fat source andare the principal raw material of chocolate from Africaand both Central and South America (Tafuri et al.,2004). Nowadays, one of the most widespread concernsin advanced technological countries is food quality andsafety. The economy of most developing countries,based primarily on their agricultural resources, isstrongly dependent on the often rigorous and rigidquality standards set by developed countries. Ivorianraw cocoa bean quality did not escape being degraded asthe liberalisation of the cocoa-producing chain in 1999and the reasons were unspecified (DGTCP (DirectionGenerale du Tresor et de la Comptabilite Publique deCote d’Ivoire), 2004). Indeed, as this liberalisation anddislocation of the Ivorian traditional control quality andthe cocoa producers framing system, agricultural prac-tices varied on the region and sometimes on theproducers in the same area. Thus, in Cote d’Ivoire, itis difficult to talk about cocoa post harvest treatments.However, Guehi et al. (2008) have identified thecommon practices about fermentation and dryingmethods in Cote d’Ivoire. The predominant processingof fermentation for Ivorian raw cocoa productionconsists of ferment beans in heaps in small farms or inwooden boxes in big farms without turning. In Coted’Ivoire, cocoa fermentation usually lasts between 4 and5 days on weather conditions and time during the cocoaseason. Fermentation generally takes shorter at the startand peak of the cocoa crop but longer towards the endof the crop when there is less mucilage available forfermentation. At the end of fermentation, Ivorian cocoaproducers spread freshly fermented beans on a meshedwooden tray with area about 30–90 cm and raised 1 mabove ground level, mats, polypropylene sheets or theconcrete floor of a cocoa house each day to a depth ofnot less than 5 cm and mixed constantly to promote

uniform drying and to break agglomerates. Althoughsun drying is the preferred method for Ivorian produc-ers, since some years artificial drying method is moreand more employed in the big cocoa farms. Probablysuch variations in agricultural practices in Ivorian cocoachain could be explained why the quality of Ivorian rawcocoa is more and more degraded. Therefore, it isimportant to identify the factors that reduce commercialvalue by studying the chemical quality of Ivorian beansresulted from different durations of fermentation anddried by different drying processes. The objective of thisstudy did not focus on postharvest handling andtechnology processing of cocoa beans at the farmer’slevel in Cote d’Ivoire.This study aimed to evaluate the performance of some

cocoa drying methods in terms of chemical quality ofraw cocoa beans such as acidity (pH, free and volatileacidities, ammonium nitrogen contents and free fattyacids content) during fermentation.

Materials and methods

Cocoa

The ripe cocoa pods (Theobroma cacao L.) of mixed-hybrids were harvested by hand during the big 2005cocoa season (from December to February) in theexperimental cocoa station of Centre National deRecherche Agronomique (CNRA) located at Bingervilleregion of Cote d’Ivoire, a moderate hot rainy regionwith an average of 28–29 �C during the harvest season, alow altitude, below 500 m, 70–80 mm ⁄month rainfall.

2.2 Cocoa pod storage and breaking

The cocoa pod storage time is 4 days at ambienttemperature at the field. The pod storage time is thetime that the pods were stored after harvesting butbefore breaking using a piece of wood billet as abludgeon as reported earlier (Meyer et al., 1989). Podbreaking using wooden billet involves one or two sharpblows with the edge of the billet. The distal portion ofthe pod falls away and the beans remain attached to theplacenta from which they can be easily extracted. Thebeans were removed from placenta being careful toexclude any germinated, black or diseased beans orpieces of shell or placenta fragments.

Cocoa fermentation

Cocoa beans were fractioned into seven same subsam-ples (about 25 kg). One type of fermentation wasstudied as reported earlier by Mounjouenpou et al.(2008): six boxes fermentation, where the beans of eachfraction were put in banana leaves placed in woodenboxes measuring 35 · 35 · 35 cm3. Fermentation was

Performance of different drying methods T. S. Guehi et al. 1565

� 2010 CNRA-Universite d’Abobo-Adjame International Journal of Food Science and Technology 2010, 45, 1564–1571

carried out in each box using 25 kg of fresh beans during1, 2, 3, 4, 5 and 6 days respectively for the boxes no. 1, 2,3, 4, 5 and 6. The heap of wet cocoa beans was thencovered in the box with other fresh banana leaves andother banana leaves were used to insulate the top ofbox. Initial turning during fermentation was done after48 h and additional turning 48 h thereafter to facilitateadequate aeration of fermenting mass and to ensure thatbeans from the top and bottom are thoroughly mixedtogether. A fresh layer of banana leaves were added tothe original leaves after each turning to ensure ade-quate insulation. Fermentation experimentations wereconducted triplicate.

Drying methods

After fermentation, cocoa beans were fractioned intothree same parts. Fermented beans of each fraction weredried according to a specific method. All drying methodsprocessing is stopped when the moisture content ofcocoa beans reached 7–8%.

Sun drying methodsNatural or sun drying process consistent to exposecocoa beans from 9 am until to 6 pm (C9) is consideredas standard drying method. So characteristics of driedbeans resulted from both other experiments were com-pared against this sun-dried beans. Two batches, one ofwhom is respectively unfermented and fermented beanswere separately spread thinly on a meshed wooden traywith area about 30–90 cm and raised 1 m above groundlevel and sun-dried until they reached moisture contentof about 7%. The beans were mixed each 1 h to ensureuniformity.

Artificial hot air drying methodsRaw cocoa beans were artificially dried using an air-ventilated oven at temperature of 60 �C (EV34) untilmoisture content of 7% as reported (Hii et al., 2009).The beans were spread thinly in single layer (about2 cm thick) on a meshed sample tray with squareopenings. Heat was generated by the heater integratedinto the side walls of the oven and the hot air flowedthrough the samples. The exhaust air escaped through aventilation hole (diameter 4 cm) at the back of theoven. The beans were mixed every 2 h to ensureuniformity. Drying was conducted for 8 h daily, andthe beans were left to temper at room temperatureovernight. The tempering step is a common routine incocoa drying, and the purpose is to redistribute theinternal moisture to the outer beans layer after eachdrying cycle.

Combination of sun and artificial drying processThe unfermented and fermented cocoa beans were driedby a mixed drying process consisting primarily sun

drying from 9 am to 6 pm daily until moisture of 25%and consecutively by artificial drying process using anair-ventilated oven (C9 EV18) until moisture content of7%.

Analytical methods

Moisture contentThe beans used in each experiment were weighed priorto mixing during drying by using an analytical balance.The moisture content (%) of the beans was determinedwith reference to the dry weight of the beans as earlyreported (Guehi et al., 2007). The measurement wasperformed in triplicates.

Chemical acidities and pHThe methods used to quantify, volatile and freeacidity, and ammonium nitrogen contents, and todetermine pH were described by Pontillon & Cros(1998). Five grams of ground nibs was homogenised in45 ml boiled distilled water. The mixture was filteredwith Whatman No. 4 filter paper and cooled to20–25 �C. The resulting filtrate was measured for pHusing a pH meter (Consort P 107) which had beencalibrated with buffers at pH 4 and 7 as described byHii et al., 2009). A further 25-ml aliquot was titratedto an end point pH of 8.1 with 0.01 N solution ofNaOH. Titratable acidity was calculated using theformula proposed by Hamid and Lopez (2000). Thevalues reported as meq of sodium hydroxide per 1 g ofdry nibs. Acidities were measured in triplicates tocheck the good fermentation and conservation of thesamples.

Free fatty acids content.About 15 g of dried cocoa beans were carefully shelledmanually. Cocoa nibs were frozen in liquid nitrogenbefore finely grinding in a kitchen-scale coffee grinding(Moulinex, France) to the smallest particle (size< 500 lm). Ten grams of cocoa powder was put inWhatman cartridge and soaked in 350 ml of petroleumether (Prolabo Normapur, type 40–60 �C) for one night.Cocoa butter was extracted on a Soxhlet apparatus for8 h. After eliminating the solvent in a rotary evaporator,FFA contents were quantified in triplicates by theofficial method 42-1993 (IOCCC, 1996) as reportedearlier (Guehi et al., 2008).

Statistical methods

All analytical experiments treatments were conducted inthree replicates. The experimental data were analysed byusing one-way anova using the SAS software GLMprocedure (SAS Institute, 2002) and mean comparisonusing the Newman–Keuls test at 95% confidence level(P < 0.05).

Performance of different drying methods T. S. Guehi et al.1566

International Journal of Food Science and Technology 2010, 45, 1564–1571 � 2010 CNRA-Universite d’Abobo-Adjame

Results and discussion

Effect of drying methods on pH of raw cocoa material

Figure 1 illustrates the influence of drying processes onthe pH of raw cocoa beans. In term of pH, whatever theduration of fermentation process, comparison was alsomade against the sun-dried beans obtained from otherexperiments. For fresh beans (0 day fermentation) andcocoa beans fermented during 2 and 4 days, the pH ofmixed-dried beans is not significantly different from thatof sun-dried beans except the day 6 fermented beans.The sun-dried beans pH ranged from 4.5 to 5.5, whilefor the oven- and mixed-dried beans registered pH wascomprised between 3.8 and 5.2. The differences may beexplained by several factors such as exposure times todrying air, drying air temperature, relative humidity inthe drying site, nature of drying air flow and the speedwith which moisture migrated from the inner cocoabeans structures to their surface as previously indicatedby Franke et al. (2008). Indeed artificial and mixeddrying processes are faster with little time needed for thecocoa beans to have their moisture reduced from about60% to around 8% than the natural drying process. Sothe pH value for sun-dried beans is usually higher (lessacidic) than artificially and mixed-dried beans becauseof the slow and gentle drying process that enable theevaporation of more acetic acid (Hii et al., 2009). Thelower pH of unfermented cocoa beans could beexplained by the bean pulp which has a low pH of3.0–3.5, mainly because of the presence of citric acid(Ardhana & Fleet, 2003). Generally, the pH of fer-mented beans falls within the values reported for most

dried cocoa beans. Indeed these results were notsignificantly different (P < 0.05) from the pH valuesof both best fermented beans sourced from West Africawhich is around 5.5 (Franke et al., 2008) and thestandard Malaysian estate beans, which is about 4.4–4.7(Nazaruddin et al., 2006). In conclusion, the pH ofIvorian cocoa beans resulted from each treatment wasfound to be acid as well as all current raw cocoa beanswhatever the duration of fermentation.

Effect of drying methods on volatile acidity of raw cocoamaterial

The impact of drying processes on the volatile acidity ofraw cocoa beans is shown in Fig. 2. The results showthat the changes in volatile acidity content of cocoabeans depend on drying methods. Indeed sun-driedbeans contain lower volatile acidity than oven-driedbeans for both fresh beans and fermented beans. Solar-dried beans present a volatile content below 1.0 meq ofNaOH ⁄g while that of oven-dried beans ranged from1.0 to 2.4 meq of NaOH ⁄g whatever the duration offermentation. For the beans fermented during 6 days,the volatile acidity content of sun-dried beans is notsignificantly different from the content both of oven andmixed-dried beans.Highest volatile acidity in beans fermented during

2 days could be explained by the accumulation of aceticacid which is mainly produced through oxidation ofethanol in the presence of oxygen by acetic acid bacteriafrom the second day of fermentation processing (Hiiet al., 2009). The lowest volatile acidity content in bothsun- and mixed-dried beans is because of the fact thatgenerally volatile acidity is removed as acetic acid from

0

1

2

3

4

5

6

Day 0 Day 2 Day 4 Day 6

pH

Duration of fermentation (days)

C9 EV34 C9EV18

Figure 1 Effect of drying methods on pH of raw cocoa beans. C9: sun

drying method EV34: artificial hot air drying method, C9EV18:

combination of sun and artificial drying methods.

0

1

2

3



Vol

atile

aic

dity

con

tent

(m

eq o

f N

aOH

per

g)

C9 EV34 C9EV18

Figure 2 Effect of drying methods on volatile acidity of raw cocoa

beans. C9: sun drying method EV34: artificial hot air drying method,

C9EV18: combination of sun and artificial drying methods.



fermented beans during a slow and gentle drying processas natural process contrary to artificial drying processwhich would dry faster and break the diffusion path ofthe acetic acid during moisture removal because of itshigh drying rate (Jinap et al., 1994a,b). Indeed duringdrying, acetic acid is evaporated off along with themoisture removal process because of its volatile nature.However, the lactic acids contained inside cannot beevaporated off as it is not a volatile compound (Hiiet al., 2009).In conclusion, beans solar-dried from 9 am to 6 pm

daily for 1 week and subsequently dried in an oven at60 �C were of comparable quality to sun-dried beans.Both of these were of better quality than beans oven-driedat 60 �Cas previously concluded by Jinap et al. (1994a,b).A large number of reports have referred to the high acidityand poor flavour development of artificially dried beanscompared to sun-dried beans with similar levels offermentation (Shelton, 1967; Jinap et al., 1994a).

Effect of drying methods on free acidity of raw cocoamaterial

Figure 3 shows the effect of drying methods on freeacidity of raw cocoa beans. The changes in free aciditycontent show that artificially dried beans have resultedin high acidity when compared to both sun- and mixed-dried beans whatever the duration of fermentation.Indeed, artificially dried cocoa contains 2.5, 4.5, 4.2 and3.4 meq of NaOH ⁄g respectively for fresh beans andbeans fermented during 2, 4 and 6 days. If the fermen-tation is stopped after 4 days, there is a danger of awinning of acidity and flavour acidity (Chong et al.,1978; Duncan et al., 1989) because of the important

production of acetic acid in the presence of oxygen byacetic acid bacteria from the oxidation of ethanolinitially produced by yeasts (Schwan & Wheals, 2004)and other organic acids such as lactic acid. The slightfree acidity content of beans fermented during 2 dayscould be explained by the fact that biochemical changesin the sugar of the pulp around the beans lead to theformation of only the ethylic alcohol and not of acidiccompound. Acidity of beans is influenced by severalfactors and fermentation method is known to be crucial.Meyer et al. (1989) found that fermentation in boxes hasbeen shown to produce more acid beans than eitherheap or tray fermentation. The lower free aciditycontent in beans fermented during 6 days might bebecause of biochemical changes in the heap of fermentedbeans leading to the formation of slight concentration oflactic acid because of the turnings made at 48 and 96 hof fermentation causing the slowing of lactic bacteriagrowth, the probable loss of these acidities duringfermentation by exudation of acidic liquid and not bychemical degradation (Jinap et al., 1994a). After all,most studies have shown that removal of moisture frombeans increases their acidities (Hii et al., 2009). Freeacidity content of mixed-dried beans is similar to thequality of sun-dried beans as previously found by Jinapet al. (1994a) which clearly demonstrated that beans airblown for 72 h and subsequently dried in an oven at60 �C were of comparable quality to sun-dried beans.Both of these cocoa were of better quality than beansoven-dried at 60 �C (Jinap et al., 1994a). As previ-ously concluded, sun-dried beans and mixed-dried beanshave resulted in low free acidity when compared toartificially dried beans because of the sun drying processsufficient time for the volatilisation of acids (acetic acid)from the beans and thereby reducing the acidity. Indeed,during drying, acetic acid is evaporated off along withthe moisture removal process because of its volatilenature. However, the lactic acids contained insidecannot be evaporated off as it is not a volatile compound(Hii et al., 2009). So sun drying, if done properly,produces the best quality beans (Crespo, 1985). Accord-ing to Bonaparte et al. (1998), this method, however, isinefficient and produces beans of inconsistent qualitywhen drying conditions are unfavourable. Furthermore,it appears that drying of fermented beans at highertemperature such as artificially or oven drying processresulted in inferior quality cocoa with respect to beansacidity. High acidic beans are always associated withoven drying process.

Effect of drying methods on ammonium nitrogen of rawcocoa material

The effect of drying processes on ammonium nitrogen ofraw cocoa material is presented in Fig. 4. Ammoniumnitrogen content increases according to the duration of

0

1

2

3

4

5

6



Fre

e ac

idit

y co

nten

t (m

eq o

f N

aOH

per

g)

C9 EV34 C9EV18

Figure 3 Effect of drying methods on free acidity of raw cocoa beans.

C9: sun drying method EV34: artificial hot air drying method,




fermentation whatever the drying method. Low ammo-nium nitrogen content is expected to the short durationof fermentation especially in the early stages, and highammonium nitrogen content is found in cocoa beansfermented during long duration. Indeed ammoniumnitrogen content varies from about 200 to above600 ppm from the beginning to the end of fermentation.These observations demonstrate clearly that dryingmethods show no significant differences in ammoniumnitrogen content because of the fact that ammoniumnitrogen is not a volatile compound. However, ammo-nium nitrogen might be produced during fermentationfrom the degradation of cocoa beans nitrogen com-pounds, such as total polyphenols, flavonoids, epicate-chin, catechin; the formation of precursors of pyrazines(Jinap et al., 1994b; Hashim et al., 1997); and theproteolysis of proteins and the oxidation of amino acidsand peptides by the suppression of nitrogen under thecontrol of amino acid oxidase and glutamine synthesisenzyme. The presence of relative high concentration ofammonium nitrogen in all samples could be because ofthe storage of cocoa pods during 4 days before breakingand to the boxes fermentation method. In additionprobably, long duration of fermentation could lead tothe production of much ammonium nitrogen throughamino acid oxidase enzymes activities as previouslydescribed by Jinap et al. (1994a) and glutamine synthe-sis enzyme and then cocoa beans becomes dark inappearance. These enzymes activities originated fromboth endogenous source (beans) and microbial sourcesuch us Bacillus sp. could generate ammonium nitrogenduring fermentation (Jinap et al., 1994b).

Effect of drying methods on free fatty acids of raw cocoamaterial

Free fatty acids (FFA) content increases slowly butremains below the critical value of 1.75% in cocoa beans

whatever the duration of fermentation (Fig. 5). FFAcontent varies from 0.4% to 1% for both fresh andfermented cocoa beans. Among three dried samplesstudied, oven-dried cocoa beans show higher FFAcontent than both solar- and mixed-dried beans. Indeedartificial drying process leads to the FFA content above0.70%, while both sun and mixed drying processesproduce raw cocoa beans with FFA content below0.70%. Slighter increasing in changes FFA dependingon the fermentation duration indicates no significantdifference (P < 0.05) within fermented cocoa beans. Solimitation of cocoa beans fermentation duration to6 days does not seem to be critical to increase thechances for FFA formation. FFA content of mixed-dried beans is similar to the quality of sun-dried beansdemonstrating that beans air blown for 7 days andsubsequently dried in an oven at 60 �C were of compa-rable quality to sun-dried beans. Both of these cocoaswere of better quality than beans oven-dried at 60 �C.This result is probably because of the break of trigly-cerides obtained from the liquefaction and the diffusionof cocoa butter during the faster process of oven dryingmethod. Higher variations of FFA content correspond-ing high standard deviations observed in the same cocoabeans sample are probably because of a high heteroge-neity of beans qualities and certainly to the growth ofsome lipolytic fungi such as Mucor sp. and Rhizopus sp.Indeed circumstantial evidence presented the FFAformation in cocoa beans is because of microbialenzymatic activities in the combination with certainfactors such as the quality and the physical integrity ofbeans and not to endogenous plant lipases as previouslydemonstrated by Guenot et al. (1976) and Guehi et al.

0

100

200

300

400

500

600

700

800



Am

mon

ium

nit

roge

n co

nten

t(p

pm)

C9 EV34 C9EV

Figure 4 Effect of drying methods on Ammonium Nitrogen of raw

cocoa beans. C9: sun drying method EV34: artificial hot air drying

method, C9EV18: combination of sun and artificial drying methods.

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00



Fre

e fa

tty

acid

s co

nten

t (

)

C9 EV34 C9EV18

Figure 5 Effect of drying methods on free fatty acids of raw cocoa

beans. C9: sun drying method EV34: artificial hot air drying method,




(2008). Microbial lipase activities hydrolysed the esterbonds between fatty acids and hydroxyl functions ofglycerol in triglycerides of cocoa butter and liberatedfree fatty acids which content increased. As the qualityof our beans and their integrity were high, a littleamount of free fatty acid was formed. Indeed, whateverthe drying process, cocoa beans resulted showed FFAcontent below critical content of 1.75% according toEuropean directive (EEC, 1973). According to Guenotet al. (1976), high FFA contents above 1.75% weremostly observed in poor-quality raw cocoa beans. Thisobservation confirms that all samples obtained from ourstudy are of best quality in term of FFA content andindicates clearly that any appropriate cocoa dryingprocessing do not have an appreciable impact on FFAformation.

Conclusion

Although drying processes has shown no great effect onammonium nitrogen and free fatty acids formation incocoa beans, the changes in acidic characteristics such aspH, free and volatile are largely dependent on the dryingmethods. Among cocoa samples resulted from ourstudy, sun-dried beans and beans air blown for 7 daysand subsequently dried in an oven at 60 �C were ofbetter quality than beans oven-dried at 60 �C. So sundrying method of cocoa beans is best for optimalquality. Fermentation duration has a significant impacton the formation of ammonium nitrogen which origi-nated from the decomposition of polyphenol com-pounds. The results obtained from this study areessential in understanding and solving the problemsassociated with the quality of raw cocoa beans material.Further research is needed to carry out the effect of thestorage time before breaking pods and their sanitaryquality on physico-chemical and microbial qualityattributes of industrial raw cocoa material aimed toimprove globally the quality of raw cocoa beans sourcedfrom Cote d’Ivoire.

Acknowledgments

This research was supported by Centre National deRecherches Agronomiques (CNRA) cocoa program ofCote d’Ivoire. The authors are grateful particularly toDr. Firmin ABOUA, Senior Researcher and to thesupport given by the Unity of Research and Formationin Food Sciences and Technologies (UFR-STA) ofUniversite d’Abobo-Adjame.

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