CARD 013VIE/05 FERMENTATION AND DRYING TRIAL Can Tho University, 18-23/4/06 Trial Title: Various sized Box and heap fermentations and solar dryer trial Introduction Prior to this trial
Trang 1CARD 013VIE/05 FERMENTATION AND DRYING TRIAL Can Tho University, 18-23/4/06
Trial Title: Various sized Box and heap fermentations and solar dryer trial
Introduction
Prior to this trial, fermentation boxes, of varying sizes and a solar drier were constructed at Can Tho University Fermentations, as described in the materials and methods, were conducted and the drier tested under the prevailing weather conditions in Can Tho The main aim of the trials was to acquaint CTU staff with the methods employed in conducting fermentation and drying trials as well as dry bean analysis and to note whether fermentation parameters were comparable to those encountered in other countries
Materials and methods
In Can Tho Province, there is only one substantial cocoa farmer and he does not grow enough cocoa for CTU to
be able to purchase sufficient beans to conduct this trial Beans were therefore purchased from Ben Tre province as described Pods were weighed prior to breaking and wet beans recovered weighed post pod breaking
With this first fermentation and drying trial conducted at CTU, during April 2006, an attempt was made to conduct experimentation on a number of fermentation parameters during the one trial These factors included:
• Size and surface to volume ratio (SVR) of fermenting mass: Surface to volume ratio is important in
that it affects the rate of air penetration into a fermenting mass It’s affected by factors such as the mass
of beans and shape of the fermenting mass This was attempted using the following treatments:
Treatment 1 (T1): Box fermentation of 100kg wet bean SVR was 12.86 sq M / cu M of beans
Treatment 2 (T2): Box fermentation 50kg wet beans SVR was 16.6 sq M/ cu M wet beans
Treatment 3 (T3): Box fermentation 25kg wet beans SVR was 20.56 sq M / cu M wet beans
Treatment 3a (T3a): Replication of T3
Treatment 4 (T4): Box fermentation of 10kg wet beans SVR was 30 sq M / cu M wet beans
Treatment 5 (T5): Conical heaped shaped fermentation of 25kg wet beans laid on floor lined with
banana leaves and sides covered with banana leaves SVR was 33 sq M / cu M wet beans This method
is typically employed in West African cocoa fermentations
All box fermentations were lined with banana leaves to standardise this aspect
• Length of pod storage: The beans obtained were from three different farmers in one village in Ben Tre
province The local practice is to harvest pods and store them until sufficient pods have been collected, over successive harvest, to conduct a fermentation Fresh beans, in sufficient quantities, could not be obtained The length of pod storage varied from one farmer to the next but an estimate of an average of seven days pod storage was made Because of the difficulty of obtaining fresh pods in Ben Tre, it was decided to transfer future pod storage trials to WASI
• Aeration / Turning regime Each treatment had a turning regime of one turn on the second day of a
fermentation, thereby standardizing this parameter All boxes and the heap fermentation were covered, bottom, sides and top, with banana leaves thereby standardizing this factor The main variable in aeration was therefore the surface to volume ratio which is a function of size and shape of the fermenting mass
• Length of fermentation time: This parameter was varied by taking sub-samples for drying on days 5
and 6 A sample fermented for 5 days before solar drying would be labelled Sun Dried Fermented (SDF5) As they were all placed on the one dryer, their drying time was standardized
Trang 2Illustration 1: Box fermentation at Can Tho
Temperatures were measured simply by taking a reading with a thermometer from the center of the mass on a once daily basis Physical and chemical analyses of samples taken during fermentations were conducted as per the project laboratory manual
Results and Discussion
The first thing noted during this initial trial was that fermentations failed to take off in all treatments except treatment 5 (heap fermentation) This was an extremely unusual occurrence and may be due to the fact that these were the first fermentations conducted at Can Tho University It is considered that, because the beans were broken on a large concreted area, there was probably an absence of fruit flies which are the usual major source of inoculum The second major source of an inoculum is usually the bottom and sides of boxes, from previous fermentations As these boxes were new, an accumulation of microbial flora, from previous fermentations would not be present Because of this problem, only results from treatment 5 are presented and discussed in detail
Temperatures of fermentations
Temperature of Fermentations
30 32 34 36 38 40 42 44 46
Figure 1: Temperature profiles during fermentation
Figure one demonstrates that a satisfactory elevation in temperature only occurred with treatment 5 The next highest was T1 which reached 39oC and this is not considered sufficient for proper flavour development A reason that the heap fermentation proceeded satisfactorily is that inoculum may have been obtained from the
Trang 3banana leaves used to line the bottom and sides of the fermenting mass Also, with the highest surface to volume ratio of all treatments, this may have increased aeration and therefore, accelerated the fermentation
Titrable acidity of whole beans during fermentations
TA Whole beans
0 0.5 1 1.5 2 2.5 3 3.5 4
Figure 2: Titrable acidity of whole beans during fermentation
Figure 2 demonstrates again that only treatment 5 fermented properly Titrable acidity (TA) tends to climb during a fermentation due to the production of acetic and lactic acids by bacterial species This has only happened in this treatment For this reason and the temperature profiles, treatment 5 is therefore the only fermentation which will be discussed in detail further on
pH bean component Treatment 5
3 3.5 4 4.5 5 5.5 6 6.5 7
0 1 2 3 4 5 6
Day of fermentation
Whole bean Kernel Pulp
Figure 3: pH of bean components of T5 during fermentation
Figure 3 demonstrates the pH of bean components during the treatment 5 fermentation Results are similar to the averages of 10 commercial fermentations in Papua New Guinea (Figure 4) This indicates that the method
of not using fermenting boxes, but rather simple heap fermentations is a viable option for farmers in Vietnam It not only makes the fermentation simpler to conduct but also negates the need for expenditure on fermentation
Trang 4pH of bean componnets in typical PNG fermentation
3 3.5 4 4.5 5 5.5 6 6.5
Day of Fermentation
Whole beans Kernel Pulp
Figure 4 Typical pH values (Average of 10 ferments) of bean components during fermentations in PNG
TA bean components in T5
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Figure 5: Titrable acidity levels in bean components during fermentation
of treatment 5
Trang 5TA bean components in PNG fermentations
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Figure 6: Typical Titrable Acidity of bean components during fermentations
(Average of 10) in Papua New Guinea
Figure 5 shows the titrable acidity levels of the various bean components during the treatment 5 fermentation Again values are similar to those of the averages of 10 commercial fermentations in Papua New Guinea (PNG) shown in figure 6 This again indicates the viability of fermentations of this type in Vietnam
First Drying Trial (D1) at Can Tho University (CTU)
Introduction
A 3M x 3M drying bed sized dryer was constructed at Can Tho University (CTU) during the first visit of the Australian counterpart in April 2006 The drying trial was conducted in tandem with the fermentation trial (F1) and is therefore presented in this single document As previously stated, For any given product, drying rate is going to be influenced by a combination of weather and dryer design based factors including; temperature, relative humidity/ rainfall, wind/air velocity, exposure of product surface and solar radiation The dryer design
is intended to enhance all of the above factors during its operation
Materials and methods
Beans were taken from day 5 and day 6 of the fermentation and placed in separate heaps (approx 2 kg wet bean each) on the dryer At the end of the fermentation i.e 6 days all of the fermenting boxes contents were mixed and placed on the dryer to note the rate of drying of a larger mass of cocoa The mass of this bulked sample was 220kg wet beans
Temperature and relative humidity levels, both ambient and within the dryer, were taken using a data logger purchased for the project
Individual samples, from the dryer, were taken from each fermentation treatment sample and the bulk mixture
on a daily basis Tests of moisture pH, titrable acidity (TA) were conducted on these samples as per standard methods of the laboratory manual
Trang 6Illustration 2: Large scale solar drier (3M x 3M drying bed) at Can Tho University
Results and Discussion
Rates of drying and changes in moisture, pH and TA are presented in the following figures 7, 9 & 10 The
conditions inside the dryer compared to ambient are presented in figure 8
Moisture % of T5SDF6 & Bulk sample
0 10 20 30 40 50 60
Figure 7 Drying rate of cocoa in the solar dryer
The results presented in figure 7 indicate a rapid rate of drying, with levels of 6-7% moisture being obtained by day 4 The treatment 5 sample was approximately 2kg The bulked sample of 220kg, as could be expected, dried more slowly but was still commercially dry by day 4 These drying rates compare favourably with standard practices which can take 10-12 days to achiever 7-8% moisture The weather during this drying period was fairly dry, with little rainfall Results are therefore not indicative of what drying rates would be like in an
extended wet period
Trang 7Temp & RH in Drier & Ambient
RH ambient
Figure 8 Conditions of temperature and relative humidity in dryer compared to ambient
Figure 8 demonstrates the much higher temperatures within the dryer compared to ambient Temperatures of over 60oC on the drying bed were obtained between 11AM and 1PM During the night, temperatures were always well above ambient and this is important as beans can re-hydrate if temperatures are not kept elevated Similarly Relative humidity (RH) levels are much lower inside the dryer than at ambient and this will also
result in an improved drying rate
pH of cocoa during drying
4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6
Figure 9: pH of treatment 5 cocoa samples, taken on days 5 & 6 of
fermentation, during drying
Trang 8Titrable Acidity during drying
1.5 2 2.5 3 3.5 4
Figure 10: Titrable acidity of treatment 5 cocoa samples, taken on
days 5 & 6 of fermentation, during drying
pH and TA levels are presented in figures 9 and 10 Both pH and TA do play a role in flavour, with high
chocolate notes usually being associated with a low acid cocoa T5 is the only fermentation which proceeded
properly so only its values should be considered T5 SDF5 had a pH value of 5.48 and SDF6, 5.01 at the end of
drying and this indicates cocoa with similar pH values to West African cocoa which usually has a pH of
5.0-5.2 Most Pacific and SEA cocoas have pH values around 4.6-4.8 and are regarded as too acidic to be a
substitute for West African cocoas
Table 1 pH and organic acid levels of cocoa from the fermentation trial compared to some commercial
Vietnamese samples and Ghana and Malaysian samples * NA not available
Table 1 results indicate that the samples of commercial Vietnamese cocoa are intermediate between Ghana and
Malaysian cocoas as far as acidity and organic acid levels are concerned The fermentation trial T5 samples
were quite similar to Ghana cocoa Fermentation for 5 days (T5SDF5) was less acidic than 6 day fermented
cocoa (T5SDF6) The organic acids were not performed on the fermentation trial samples as the training at
QDPI&F occurred later in August 2006
Summary
This initial trial had the aims of: (1) establishing minimum sizes of fermentation e.g 10kg box, (2) the
suitability of heap fermentations, (3) an effect of length of fermentation time i.e 5 as opposed to 6 day
fermentations and (4) the efficiency of the solar dryer
Trang 9Because fermentations did not proceed properly, apart from treatment 5, no conclusion could be drawn regarding fermentation of 10kg quantities The heap fermentation, covered with banana leaves, did proceed correctly and indicates this type of fermentation can be recommended This is the standard type of fermentation conducted in West African countries The Australian counterpart had noted in previous work in PNG, that a 25kg heap fermentation was the best fermentation method tested in that country for producing a West African type cocoa This recommendation will be made in extension materials to be produced The pH values obtained
in T5 dry beans was very similar to the West African standard A heap fermentation also has the advantage that there are no costs involved for box construction
Results obtained indicated the high efficiency of the solar dryer design However it is noted that this trial was conducted in weather conditions which were dry Results for the dryer in wetter conditions will be presented in further reports of trials conducted at Can Tho University
Trang 10Second Fermentation (F2) and Drying Trial at Can Tho University May-June 2006:
Introduction:
After the first fermentation trial, in which fermentations did not proceed properly in 4 of the 5 treatments, it was decided to repeat some of the fermentations in the hope of obtaining better fermentations and to establish whether the 10kg box fermentations could be successfully conducted in Vietnam Two replicates each of T2 (50kg box) and T4 (10Kg box) were conducted at CTU in May-June 2006 Fermentations did proceed better than the first attempt but temperatures of both treatments did not reach a satisfactory level Treatments were named as they were in the first trial and identified as replicates of those treatments
With drying of the cocoa, a second dryer of 2M x 2M drying bed dimensions was constructed This is the size that would approximate that recommended for smallholder farmers Samples were taken at the end of a six day fermentation period for each treatment and divided into samples for drying on the large scale and small-scale dryers
Materials and methods
Beans were purchased from Ben Tre province as described Pods were weighed prior to breaking and wet beans recovered weighed post pod breaking This gave a wet bean / pod recovery rate, an important factor in commercial considerations
Temperatures were measured simply by taking a reading with a thermometer from the center of the mass on a once daily basis
Physical and chemical analyses of samples taken during fermentations were conducted as per the project laboratory manual
Results and Discussion
Fermentations:
Temperature of Fermentation
25 27 29 31 33 35 37 39 41 43 45
Figure 1: Temperature profiles during fermentation
Figure one demonstrates that satisfactory elevations in temperature still did not occur, although temperatures reached were higher than in the first fermentation trial (F1) This is possibly due to inoculum on the sides of boxes being left over from the first fermentation trial The highest temperature reached was 43oC in treatment
Trang 11two Rep two (50kg box) This temperature is slightly below the ideal level of 45C to 50 C It did however produce a satisfactory cocoa The next highest temperature reached was (40oC) in treatment 4 (10kg box) replication 3 (T4R3) This is below the desired range, but considering that the 50kg quantities also did not come
up to the desired level, it is encouraging that 10kg box fermentations might be successfully conducted in the Mekong Delta region of Vietnam
Titrable acidity whole beans
0 0.5 1 1.5 2 2.5 3 3.5
Figure 2 Titrable acidity of whole beans during fermentation
Figure 2 demonstrates a level of acid production above that which occurred in the first trial The first 50kg box fermentation showed the highest levels of titrable acidity as it did with temperature profiles Although there was
an improvement in fermentation parameters over the first trial conducted at CTU, three of the four fermentations did not reach satisfactory temperature levels and the fermentations are not discussed in any further detail
Second Drying Trial (D2) at Can Tho University (CTU):
Introduction:
A 3M x 4M drying bed sized drier was constructed at Can Tho University (CTU) during the first visit of the Australian counterpart in April 2006 In May, a second drier with bed dimensions of 2M x 2M was constructed for testing as this is the approximate size of what will be recommended for smallholders
Trang 12
Materials and methods
Beans were taken from the final day (6) of the fermentations and placed in separate heaps (approx 2 kg wet bean each) on each dryer
Individual samples, from the dryers, were taken from each fermentation treatment sample on a daily basis Tests for moisture, pH, titrable acidity (TA) were conducted on these samples as per the laboratory manual
Results and Discussion
Temp & RH of Driers at 3PM each day
20 30 40 50 60 70 80
RH ambient
RH Large drier
RH Small drier
Figure 3: Conditions of temperature and relative humidity
in driers compared to ambient
Temperatures and relative humidity levels for the both sizes of driers were encountered Temperatures encountered were noted to be not as elevated above ambient in the first trial Also RH values in the driers were noted to be above ambient on day four The trial was conducted in wet weather and some seepage of water into the wings did occur This probably accounts for this result
Rates of drying and changes in pH and TA are presented in the following figures 4, 5 & 6
Average Moisture % drying beans
0 10 20 30 40 50 60 70
Figure 4 Drying rate of cocoa in the solar dryer