Báo cáo nghiên cứu khoa học " COCOA DRYING USING SOLAR DRIER "

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Sấy ca cao là một bước quan trọng trong chế biến ca cao không chỉ cho mục đích bảo quản nhưng cũng là chính ảnh hưởng đến hương vị và chất lượng của các sản phẩm ca cao. Tám máy sấy năng lượng mặt trời được thiết kế, xây dựng và thử nghiệm tại Đại học Cần Thơ, Đại học Nông Lâm, Khoa học Nông nghiệp Tây Nguyên Viện, nông hộ nhỏ ở Cần Thơ, Bến Tre, tỉnh Đắk Lắk từ năm 2006. Kết quả chứng minh rằng trong điều kiện rõ ràng nắng, nhiệt độ trong máy sấy năng lượng mặt trời có...

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