Transcription of Quality of cocoa beans dried using a direct solar dryer at ...
1 Journal of the Science of Food and AgricultureJ Sci Food Agric86:1237 1243 (2006) Quality of cocoa beans dried usinga direct solar dryer at different loadingsChing L Hii,1R Abdul Rahman,2 S Jinap2and YB Che Man21 cocoa Downstream Research Centre, Malaysian cocoa Board, Lot3, Jalan P/9B, Seksyen 13, 43650 Bandar Baru Bangi, Selangor DarulEhsan, Malaysia2 Faculty of Food Science and Biotechnology, Universiti Putra Malaysia, 43400 Serdang, Selangor, MalaysiaAbstract: In this study fermented cocoa beans were driedin a direct solar dryer at three levels of loading (20, 30and 60 kg). Surface mouldiness was found to be heavy in the 60 kg treatment, with beans appearing blackish. Allthe dried beans were reasonably acceptable in terms ofvinegary odour and weak in alcohol odour. Weak odourwas also detected for the faecal, rancid and cheesy odours.
2 The 60 kg treatment was rated strong for wet sockodour due to poor drying condition. A significant difference (P< ) was found between the 60 kg treatment andthe lower loading treatments for pH and titratable acidity. A cut test showed that the lower loading treatmentsresulted in a higher percentage of brown beans . The 20 kgtreatment showed the highest cut test score, which issignificantly different (P< ) from the 60 kg treatment. Fermentation index also showed a tendency for lowerloading treatments to have a higher index. No significant difference (P> ) was found among the treatments interms of cocoa , astringency, bitterness and sourness ,betterflavourwasobservedforbeansfrom the 20 kg treatment. No mouldy off flavour was found in any of the dried beans . Overall Quality assessmentshowed that the 20 kg treatment was able to produce reasonably good- Quality beans as compared to other loadingsand therefore is recommended for the direct solar dryer .
3 2006 Society of Chemical IndustryKeywords: cocoa ; drying; solar dryer ;Theobroma cacaoL., qualityINTRODUCTIONSun drying is the most popular method used byMalaysian smallholders to dry cocoa beans . However,the main harvesting season usually coincides withthe rainy season and the risk of mould developmentdue to prolonged drying is possible. Labour is oftenneeded to attend to the drying process, especially inthe event of rain. Hence the direct solar dryer wasdeveloped for smallholders because of its simplicityin design and in operation/maintenance, and abilityto dry small quantities. It uses direct sunlight to drycocoa beans placed inside a transparent transparent enclosure also has the advantage ofprotecting the cocoa beans from unfavourable beans are usually dried as a thin layer ofabout one or two beans thick under typical tropicalweather when using sun drying.
4 Under favourableand sunny conditions, cocoa beans at two to threebeans thick can still be dried without any significantloss in Quality , but Quality loss will be expectedunder adverse weather conditions. Low- Quality beansare not recommended to be made into finishedproducts owing to the presence of off flavours andmicrobiological attempts have been made by variousresearchers to dry cocoa beans in solar dryers. Interms of drying rate and bean Quality , no significancedifference was found between solar and sun ,3 Studies by Bonaparteet shown that beansdried at lower loadings tend to have better colour thanthose dried at higher loadings when using solar , at higher loading , acidity was lower due toa slower drying this study, direct solar dryer prototypesdeveloped for cocoa smallholders were tested interms of bean loadings.
5 The Quality of driedbeans produced was assessed to observe the qual-ity changes that might occur at these AND METHODSE xperimental design and analysesFactorial design was used to assess the effect of wetfermented cocoa loading at 20, 30 and 60 kg, usingthe direct solar dryer prototype at three each replication drying was conducted concurrentlyfor all the loadings to minimize variations (weather,raw materials etc.) that might occur during trials. Thedata obtained from the physical and chemical analyseswere analysed for one-way ANOVA and Duncan sMultiple Range Test using SAS statistical software(Version 8, SAS Institute, Cary, NC, USA) at 95%confidence level. Correspondence to: R Abdul Rahman, Faculty of Food Science and Biotechnology, Universiti Putra Malaysia, 43400 Serdang, Selangor, MalaysiaE-mail: sponsor: Ministry of Science, Technology and the Environment (Malaysia); contract/grant number: 01-04-07-0804(Received 9 January 2004; revised version received 27 February 2005; accepted 22 December 2005)Published online 2 May 2006;DOI: 2006 Society of Chemical Sci Food Agric0022 5142/2006/$ Hiiet of fermented cocoa beansFresh cocoa beans were extracted from ripe cocoapods of PBC clones obtained from Sg.
6 Ruan,Pahang, Malaysia, and fermented in wooden boxes(61 cm) for 120 h with turning afterevery 48 procedureDrying started from 8 to 6 daily. Thebeans were mixed manually every 2 h for the first dayor until superficially dried and every 4 h thereafteruntil the moisture content of the nib reached of moisture content was done on awet basis according to Malaysian Standard MS were taken every 24 h (200 g) before mixingfor solar dryerThe solar dryer prototype consists of two sections,namely the drying platform and the transparent enclo-sure (Fig. 1). The drying platform was constructedwith 1 cm thick plywood measured 153 (length width) and elevated 70 cm above groundlevel. Holes measuring 1 cm in diameter were drilledand arranged in a 2 cm square pitch at the dry-ing platform.
7 The transparent material used for theenclosure was ultraviolet-stabilized polyethylene measuring 10 153 cm were made at theapex, and side apertures measuring 136 along the wooden planks below the transparentwindows to facilitate air testThis was carried out according to the MalaysianStandard MS hundred pieces of driedcocoa beans were cut lengthwise through the middleusing a penknife. Both halves of each bean wereexamined visually in full daylight by an experiencedcocoa grader according to the cross-sectional colour ofthe beans , namely fully brown, partly purple-brown,fully purple and slaty, based on a standard colourchart. The percentage count of each colour note wascalculated for the cut test score (CTS) as shown below:CTS=(10 % fully brown)+(5 % partly purple brown)+(0 % fully purple and slaty)Surface mould assessmentThe dried cocoa beans were assessed qualitativelyfor external mould at levels such as none, light,moderately heavy, heavy and extremely heavy.
8 Theintensity at each level was based on the amount ofmould covered on the dried bean surface, rangingfrom none (0%) to extremely heavy (100%) at 25%coverage interval. Three predefined bean samplesrated at none, moderately heavy and extremely heavylevels were given as references to the trained panels forcomparison during visual assessmentThe dried cocoa beans were assessed qualitativelyfor vinegary, alcohol, faecal, rancid, cheesy and wetsock odours at levels such as none, weak, moderatelystrong, strong and extremely strong. Each level wasbased on the odour intensity of the dried bean , rangingfrom none (0%) to extremely strong (100%) at 25%intensity interval. Two predefined samples rated atnone and extremely strong levels for each odour weregiven as references to the trained panels for comparisonduring odour evaluation of cocoa liquorCocoa beans (500 g) were processed using a laboratorywinnower and breaker (John Gordon, UK) to obtainthe cocoa nibs.
9 The nibs were roasted in an oven(Memmert, Germany) at 140 C for 35 min and cooledTransparent coverAir exitAir cmSide viewFront viewFigure drawing of the solar dryer Sci Food Agric86:1237 1243 (2006)DOI: of cocoa beans dried using a direct solar dryerat room temperature. The roasted nibs were thenground in a laboratory mortar and pestle mill (PascalEngineering, UK) for 3 h to obtain the cocoa cocoa liquor was used as reference. Thesensory evaluation was conducted by 10 trained panelsfrom the Malaysian cocoa nib pH was determined according to the nibs (5 g) were homogenized in 45 mL boileddistilled water. The homogenate was filtered withWhatman No. 4 filter paper and cooled to 20 25 was determined using a pH meter (Mettler Toledo,Columbus, OH, USA).
10 This measurement was takendaily in acidity (TA)The nib TA was determined according to 25 mL of the aliquot collected forpH determination was titrated drop by drop to pH , determined using a pH meter(Mettler Toledo). This measurement was taken dailyin index (FI)This was determined according to the method ofGur eva and cocoa nibs ( g)were added to a mixture of methanol and HCl(concentration 37%) at a volume ratio of 97:3 andhomogenized. The mixture was left in the cold room(temperature 8 C) for 16 18 h and filtered usingWhatman No. 1 filter paper. The filtrate was collectedand the ratio of the absorbance at 460 nm and 530 nmwas determined using a UV-visible spectrophotometer(Shimadzu, Japan).RESULTS AND DISCUSSIONS urface mould of dried beansMouldiness on the bean surface was found to be lightin the 20 kg loading , moderately heavy in the 30 kgloading and extremely heavy in the 60 kg loading , asrated by majority of the panels (Fig.)