Abdul Hamid, Azizah

Abu Bakar, Fatimah

Universiti Putra Malaysia Institutional Repository

UPM Research Report 1998: Volume 2UTILISATION OF COCOA BY-PRODUCTS FORFOODS AND FOOD INGREDIENTSAzizah Abdul-Hamid and Fatimah Abu BakarFaculty of Food Science and BiotechnologyUniversiti Putra Malaysia, 43400 UPM, Serdang, Selangor,MalaysiaKeywords: cocoa by-products, natural antioxidant, an-timicrobial, functional ingredient, cocoa powder.IntroductionCocoa is the third most important agricultural commodityafter oil palm and rubber in Malaysia. With total productionof approximately 155,000 tonnes of dried cocoa beans in1994, Malaysia has emerged as the fifth largest cocoa pro-ducer of the world. However, this figure represented only10% of the whole cocoa that was extracted and used com-mercially. The remaining pod material is wasted at differentstages of processing in spite of considerable volume of lit-erature on its utilisation. The need for commercial exploita-tion of cocoa by-products from waste has received seriousattention in several cocoa-producing countries. At present,local uses of cocoa by-products are confined to livestockfeeding and fertilising at farm level. Little research has beenconducted to further process cocoa by-products into food in-gredients, particularly as antioxidant and antimicrobial com-pounds. Therefore, this project aims to identify potentialfunctional ingredients like antioxidant and antimicrobialagent in cocoa by-products.Materials and MethodsThree types of cocoa by-products were used, namely cocoanib, cocoa powder and cocoa shell obtained from Kokomal,Teluk Intan, Malaysia. Microorganisms tested were obtainedfrom culture collection of Food Microbiology Laboratory,UPM. Antioxidants and antimicrobial agents were extractedusing a Soxhlet extractor utilising seven different types ofsolvents to provide for a wide range of polarity. Antioxidantactivities were determined using a diene conjugation forma-tion method. Antimicrobial activity was evaluated using pa-per disc method followed by determination of Minimum In-hibitory Concentratiion (MIC). The effects of pH and tem-perature on the antioxidative activities of the extracts werealso determined. Phosphate-HCl, buffer was used for pH 3and 5, while phosphate-NaOH buffer was used for pH 7.9and 11. The temperature studied was 30 to 90°C. Determi-nation of amino acid was carried out using Pico- Tag Method.All experiments were carried out in triplicate. Statisticalanalyses were accomplished using Statistical Analysis Sys-tem software utilising Duncan's Multiple comparison test.Level of significance used was at p::O.05.Results and DiscussionThe project revealed that cocoa by-products contained sev-eral functional ingredients that have potential for commer-cialization, (Abdul-Hamid et al. 1997). Out of 42 extractsfrom six cocoa by-products that were tested, 12 extracts fromthree by-products exhibited high antioxidative activities.Methanol and methanol-residue extracts (residue of petro-leum ether extract) showed the highest activity (Abdul-Hamid et al. 1999a). Three samples exhibited strong anti-oxidative activities, namely natural cocoa powder, cocoa nibsand cocoa shell. On the other hand, alkalised and alkalisedred cocoa powder showed very little antioxidative activities.180In the characterisation study, it was found that the extractswere stable up to 50°C, after which the antioxidative activitystarted to drop significantly. In addition, the antioxidativeactivity was found to increase with increasing pH from 3 to11, indicating strong dependence on the pH of the system.This suggested that the active component in the extract mightbe flavonoid in nature. In this study, three different types ofcocoa powder have been shown to contain quercetin, epi-catechin and rutin. Selected extracts of cocoa by-productscaused variable degree of inhibition on growth of microor-ganisms tested. MICs of the selected extracts range from6.25 to 50mg/ml for gram-positive strains and 12.5 to50mg/ml for gram-negative bacteria. Yeasts were inhibitedonly at higher concentration of 25 to 50mg/ml while mouldswere found to be most resistant to cocoa by-products extracts(Abdul-Hamid et al. 1999b). Based on the results obtainedfrom kinetic of killing assay, the presence of acid (pH) andother unknown compoundls in cocoa powder contributed toantimicrobial activities of the by-products. pH seemed tohave a killing effect towards Eschericia coli 0157:H7 andbacteriostatic effect towards Bacillus cereus. On the otherhand, unknown compound was seen to have bacteriostatic ef-fect towards Staphylococcus aureus. Adding selected cocoaby-products extracts at predetermined concentrations reducedthe relative growth of microorganism in pasteurised milk.Microbial growth inhibition of the extracts added to pasteur-ised milk was dose dependent. However, the range of con-centrations of the extracts used was not enough to preservepasteurised milk at room temperature. In addition, the projectrevealed that cocoa powder has high content of protein(23%) and evaluation of this protein showed that natural co-coa powder contained reasonably high quality protein withpredicted biological value greater than 70.ConclusionsThe study revealed that various cocoa by-products containedseveral functional ingredients that have potential for com-mercialisation, namely antioxidants, antimicrobial agents andreasonably high quality protein. Methanol proved to be thebest solvent in extracting antioxidant and antimicrobial fromcocoa by-products. The antioxidative activities were foundto be stable at temperature below 50°C and exhibited highestactivity at neutral and alkaline pH. The results showed thatcocoa by-product extracts exhibited variable degree of in-hibitory activity against microorganisms tested, with excep-tion of petroleum ether and diethyl ether extracts whose ac-tivities were negligible.ReferencesAbdul-Hamid, A., Nik Mustafa, N.R., Ghazali, Z. and Abu Bakar, F.1997. Functional Ingredients Derived from Cocoa By-Products.Presented at I13C UK Conference on Functional Foods: Con-sumers, Regulation and Marketing Strategies to maintain marketshare., LondonAbdul-Hamid, A., Nik Mustafa, N.R. and Thed, S.T. 1999a. Extrac-tion and Characterization of Antioxidant from Cocoa By-Products. Food Chemistry 64:199-202 Presented at SFRR-ASIAICOSTAM/UNESCO-MCBN workshop on BiologicalOxidants and Antioxidants: Molecular Mechanisms and HealthEffects. Sept. 4-7, Penang. (1997).Abdul-Hamid, A., Gh~, Z. and Abu Bakar, F. 1999b. Screeningfor Compound~ with. Antimicrobial Activities in Cocoa by-Products. Tropical SCIence (Submitted) Presented at MalaysianInternational Cocoa Conference. Nov. 26-27 Kuala Lumpur(1998). 'Supported by IRPA Grant 01-02-04-01/7

Utilisation of cocoa by-products for foods and food ingredients

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Utilisation of cocoa by-products for foods and food ingredients

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