Báo cáo Nghiên cứu khoa học Cocoa drying using solar drier

Collaboration for Agriculture and Rural Development (CARD) Program 118 COCOA DRYING USING SOLAR DRIER Project title: Cocoa fermentation, drying and quality assessment in Vietnam Project code: CARD 013/05VIE Authors: Nguyen Van Thanh1, Huynh Xuan Phong1, Neil Hollywood2 and Ha Thanh Toan3 Project implementing organizations: 1 Biotechnology Research and Development Institute, Can Tho University, Vietnam 2 Queensland Department of Primary Industries and Fisheries, Australia 3 Can Tho University, Vietnam SUMMARY Drying of cocoa is an important step in cocoa processing not only for preservative purpose but also is the main affect to flavour and quality of cocoa products. Eight solar driers were designed, constructed and tested at Can Tho University, Nong Lam University, Western Highlands Agricultural Science Institute, smallholders in Can Tho, Ben Tre, and Dak Lak provinces since 2006. Results demonstrate that in clear sunny conditions, temperatures in the solar drier can obtain around 60oC. Temperatures in the solar drier are always higher than ambient about 10 to 15oC even at night. In the dry season, cocoa beans could be dried only on 4 to 5 days and 6 to 7 days in the wet season. When cocoa beans could be dried effectively will be avoid over fermentation and reduce mould contamination. These are very important because over fermentation and mould contamination can produce some off-flavours and lead to down-grading of the cocoa. Using the solar drier (450, 250 and 100 kg/time) will help to shorten the time of drying, reduce loss of cocoa and labour, improve the quality of cocoa, and increase income of smallholders. 1. Introduction West Africa is the main cocoa producing area with amounting to about 72% of the world cocoa production. Four major West Africa countries are Côte d’Ivoire, Ghana, Nigeria, and Cameroon. Pacific Asia area accounts for about 15% and America is 13% of 3.5 million tons cocoa beans in over the world (Phuoc, 2006). According to the ICCO, the world will be lack about 102,000 tons cocoa bean in 2010 - 2011 because of the decreasing of cocoa bean in 2008 - 2009 crops. There are some reasons that lead to decrease cocoa production are insecurity politics, natural calamity, old and stunted cocoa tree, lack of land in some main cocoa producing countries. For some nine decades, global cocoa production has increased steadily and consistently to keep with the ever- increasing needs for cocoa bean. Consumption has increased on average by 3.5% per annum over recent years and is projected to increase by 1.5 - 3.5 per annum over the coming 5 years (Knight, 1999). In 1998, the Ministry of Agriculture and Rural Development carried to investigate cocoa tree and set a new goal of having 100,000 ha of planted cocoa by 2010. Vietnamese Cocoa Development team was established in March 2005. The aims are impulse the development of cocoa cultivation and recognized the cocoa as a new long-time industrial tree in Vietnam. By the end of year 2006, the total cocoa has been inter-plant on plantations about 7,300 ha with some major provinces are Ben Tre, Tien Giang, Ba Ria-Vung Tau, Dak Lak, and Binh Phuoc (Hoa, 2007). CARD 013/05 VIE – Cocoa fermentation and drying 119 Figure 1 Diagram of Solar drier Drying of cocoa is an important step in cocoa processing not only for preservative purpose but also is the main affect to flavour and quality of cocoa products. In many countries, including parts of Vietnam, sun drying is the main method to dry cocoa beans. This is a very simple method and the most effective to drying of cocoa bean. This allows acids in the cocoa to evaporate off and produce a low acid, high cocoa flavoured product. However, in the unfavourable condition of the weather, especially in the wet season, the drying takes longer, cocoa may will be over fermentation and mould contamination that can produce some off-flavours and lead to down-grading of the cocoa. One on many major activities of the scientific project “Cocoa Fermentation, Drying and Quality Assessment in Vietnam” is apply and test the solar drier for cocoa drying. The solar drier has be studied, constructed, and improved by the Cocoa Research team between Queensland Department of Primary Industries and Fisheries, Australia and Biotechnology R&D Institute, Can Tho University (CTU). Solar driers have a drying bed in center and two beside right triangle wings. They uses rocks painted black to collect heat from the sun and vent the hot air through the drying bed, especially at night time when the temperature of ambient is lower. They also have a roof that can be lowered when it rains and at night and this saves having to move the cocoa around. 2. Results and discussions In the first stage of the project, 9m2 drying bed solar drier (450 kg/time) was constructed at CTU. Many experiments at CTU and results of two cocoa farmer surveys in Ben Tre show that the capacity of this solar drier is too larger than smallholder requirements. Because of over 90% smallholders in Ben Tre has under one ha of cocoa inter-planted area and the production is around 20 - 250 fresh bean for one time of fermentation. Otherwise, the price of solar drier is too expensive. The new solar drier with 4m2 drying bed that can satisfy to smallholder requirements and lower price was improved, constructed and tested. Nguyen Van Thanh, Huynh Xuan Phong, Neil Hollywood & Ha Thanh Toan 120 The results demonstrate similar drying rates for the large and smaller dryer. Figure 2 shows that the temperature in two drier is almost the same and always higher than ambient. In all drying time, the humidity in solar drier is always lower than ambient. Moisture loss is the same rate in all eight treatments and reached to desire moisture only 4 to 6 days (Fig. 3). The project has conducted at Can Tho University, Nong Lam University, Western Highlands Agricultural Science Institute, smallholders in Can Tho, Ben Tre, and Dak Lak provinces for 2 years. These institutions have cocoa research group and these provinces are the major area producing cocoa in Vietnam. In 2007, there were eight solar driers were constructed and tested at these institutions and smallholders. Some main results achieve as follow: Less time and labour are the most important. Temperatures in drier remained 10 to 15oC above ambient and reached to 60oC in the clear sunny conditions. Moreover, the humidity in solar is always lower than ambient (Fig. 4). Figure 5 shows again the same change of temperature and humidity in figure 2. Fig. 6 demonstrates that in dry season, with drier, cocoa beans were dried only 4 to 5 days against 6 to 7 days of sun drying. In the wet season, the time for drying cocoa was usually longer than 10 days (average 8 - 10 days) belong to weather conditions. When the solar drier was used in wet season, the required time for drying cocoa was about 6 - 7 days (fig. 7). Short drying time is also very important to guarantee the flavour and quantity of cocoa. Solar driers are suitable for the weather condition in the Mekong delta so they can be used in whole year, more effectively in the wet season because that time is also major flush in cocoa production. Cocoa beans were dried continuous not only on day time but also on night. Therefore, cocoa beans can be avoid over fermentation (rotten Temp & RH 25/4/06 0 20 40 60 80 100 120 00 :00 01 :00 02 :00 03 :00 04 :00 05 :00 06 :00 07 :00 08 :00 09 :00 10 :00 11 :00 12 :00 13 :00 14 :00 15 :00 16 :00 17 :00 18 :00 19 :00 20 :00 21 :00 22 :00 23 :00 Time of day Te m p & R H Temp Dryer RH Dryer Temp Ambient RH Ambient Fig. 4 Temp. encountered in sun dry with and without solar drier Fig. 5 Temp. and RH encountered in solar drier and ambient Temperature during drying 0 10 20 30 40 50 60 70 0 2 4 6 8 10 12 14 16 18 20 22 24 Time of day Te m pe ra tu re Solar drier Sun drying Ambient Fig. 2 Conditions of temperature and RH% in drier compared to ambient Fig. 3 Drying rate of cocoa in the solar drier T emp and RH of Dr yer s 20 30 40 50 60 70 80 1 2 3 4 5 6 Day of dr yi ng Temper atur eambient Temper atur eLar ge Dr yer Temper atur eSmal l Dr yer RHAmbient Rh Lar geDr yer RHSmal l Dr yer M o isture% D rying B eans 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 0 1 2 3 4 5 6 D ay o f drying F2T2R2 Big Dryer F2T2R2 Small Dryer F2T4R2 Big Dryer F2T4R2 Small Dryer F2T2R3 Big Dryer F2T4R3 small Dryer F2T4R3 Big Dryer F2T4R3 small Dryer CARD 013/05 VIE – Cocoa fermentation and drying 121 stage) and reduce mould contamination. These are very important because over fermentation and mould contamination can produce some off-flavours and lead to down-grading of the cocoa and buyers will pay less for it. Using cocoa solar drier is decrease greatly drying surface on the same quantity of fermented cocoa beans (50 kg/m2 against 5 - 10 kg/m2). Labour is also decrease because they resolve the problem in that the cocoa has to be shifted undercover during rain and night time, moved around during the day to position them in the sun and turned cocoa beans. Traditional sun drying methods (fig. 9) are small quantity, thin layer (only 1 or 2 layer of cocoa bean) and turned frequently. In wet season, the cocoa has to be shifted undercover and moved more frequently during rain. Fig. 8 Cocoa dried by the traditional sun drying methods (7&8 d) compared to cocoa died on a solar drier (5&6 d). Fig. 6 Moisture loss in cocoa bean Fig. 7 Drying time in dry and wet season moisture loss in wet & Dry weather 0 10 20 30 40 50 60 0 1 2 3 4 5 6 7 Day of drying % m oi st ur e Dry weather Wet weather Moisture loss 0 10 20 30 40 50 60 70 0 2 4 6 8 Day of drying M oi st ur e Solar drier Sun drying Fig. 9 Some traditional sun drying methods Fig. 10 Solar driers were constructed at smallholders lholders in Can Tho, Ben Tre and Dak Lak provinces Collaboration for Agriculture and Rural Development (CARD) Program 122 Solar driers must be initially invested only and not be spent much money for operation and maintenance. With the aims are decrease the price and more corresponded to requirement of smallholders, belong two scale of drier is introduced above; a new solar drier with 2.34m2 drying bed was constructed and tested. Results demonstrate that this drier is also effective drying and satisfying to requirement of small scale of cocoa inter-planted farmers. These farmers ferment and dry the cocoa beans that were produce by themselves. However, for using effectively of solar drier, there are some important points should be remember when installation and operation the solar driers. Driers are placed on the open and clear area, so that the driers can receive maximum energy of sunshine. Moisture in solar drier is easy to evaporated and removed stagnant water that can be drop back (especially in the morning) to dried cocoa beans. This assists to reduce the erosion of metals by high acidity water evaporated from fermented cocoa beans. Driers should be placed in South - North direction because two wings can receive equal and full energy from sunshine all day. Polycarbonate roofs are cleaned frequently because clean roofs can receive more effectively energy and sunshine. In wet season, solar drier could be jointed with 2 - 4 filament lamps (100W/220V) to increase drying rate (need only in long-time rainstorms). 3. Conclusion Based on the scale of planted cocoa and financial capacity, smallholders can invest a suitable size of solar drier. Smallholders ferment and dry the cocoa beans that they produced pods by themselves can invest the smallest one - drier with 2,34m2 drying bed, capacity is 100 kg/time. Smallholders cultivate cocoa trees and buy pods from neighboring farmers should build a 4m2 drying bed solar drier that can dry about 200 kg fermented cocoa beans one time. The 9m2 (450 kg/time) drying bed solar driers can satisfy to commercial buyers/companies who are large scale of buying, fermentation and drying cocoa beans. Using the solar driers will help to shorten the time of drying, reduce loss of cocoa and labour, improve the flavour and quality of cocoa, and increase income of smallholders. Moreover, employees in rural areas are lack for plant, harvest and pre-processing at that time. This also takes part in hasten to mechanize and apply the progressive science and technology in agricultural works. Because of special requirements of cocoa drying process, the solar driers can resolve the problem of cocoa drying, especially in the unstable of the weather conditions and long time, heavy rain. Wet season is also the major harvest of cocoa in Mekong delta as other provinces in Vietnam. References 1. Hollywood, N., Brown S., and Toreu B., 1997, A Design for improved efficiency in the solar drying of cocoa. 2. Hollywood, N., Ha Thanh Toan and Nguyen Van Thanh, 2008. Cocoa processing methods for the production of high quality cocoa in Vietnam. Agricultural Publishing House, Ho Chi Minh City, Vietnam. 3. Knight, I., 1999, Chocolate and Cocoa: Health and Nutrition, Blackwell Science Ltd. 4. Nguyen Van Hoa, 2007, Overview of presence and future of planted cocoa by 2010 in Vietnam, Encourage Agriculture and Technology Workshop, Vietnam Ministry of Agriculture and Rural Development. 5. Pham Hong Duc Phuoc, 2006, Cocoa Planting Manual in Vietnam, HCMC National University Publishing, Vietnam. CARD 013/05 VIE – Cocoa fermentation and drying 123 6. Roelofsen, P.A., 1958. Fermentation, drying, and storage of cocoa beans. Adv. Food Res. (8), 225-296. 7. Sukha, D. A., 1997, The influence of fermentation and drying on the flavour and quality of selected cacao (Theobroma cacao L.) genotypes. M.Sc. Research Project. Faculty of Engineering, the University of the West Indies, St. Augustine. 8. Wood, G.A.R. and R.A. Lass, 2001. Cocoa. 4th edition. MPG Books Ltd., Bodmin, Cornwall.