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Determination of Optimal Surface Area to Volume Raio for Thin-Layer Drying of Breadfruit (Artocarpus altilis)


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Experiments to determine the optimal size shred of breadfruit for sun drying in the Caribbean were conducted and verified. To determine optimal shred size, ease of shredding and handling as well as the drying characteristics were considered. Additional experiments compared the drying characteristics of breadfruit to several types of produce more readily available for use in the laboratory and examined the effect of alternative bases or backgrounds for sun drying. An optimal surface area to volume ratio is recommended and found to dry breadfruit under average Caribbean conditions (27-3C, 60-65% RH, ~800 W/m 2 solar radiation and 1.5-2.0 m/s prevailing winds) in about three hours.
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International Journal for Service Learning in Engineering
Vol. 2, No. 2, pp. 76-88, Fall 2007
ISSN 1555-9033
Determination of Optimal Surface Area to Volume Ratio
for Thin-Layer Drying of Breadfruit (Artocarpus altilis)
C. George
Assistant Professor
School of Engineering,
University of St. Thomas
St. Paul, MN, USA
R. McGruder and K. Torgerson
Seniors, School of Engineering,
University of St. Thomas
St. Paul, MN, USA
Abstract- Experiments to determine the optimal size shred of breadfruit for sun drying in
the Caribbean were conducted and verified. To determine optimal shred size, ease of
shredding and handling as well as the drying characteristics were considered. Additional
experiments compared the drying characteristics of breadfruit to several types of produce
more readily available for use in the laboratory and examined the effect of alternative
bases or backgrounds for sun drying. An optimal surface area to volume ratio is
recommended and found to dry breadfruit under average Caribbean conditions (27-30 ˚C,
60-65% RH, ~800 W/m
solar radiation and 1.5-2.0 m/s prevailing winds) in about three
Index Terms - Breadfruit drying, open sun drying, shred size, thin-layer drying.
A large portion of agricultural surpluses are lost in developing countries. To process and
preserve post-harvest produce successfully, spoilage agents must be destroyed and nutritional
value preserved. One method of preserving post-harvest surplus is drying. The water content of
the produce must be reduced to a level insufficient for growth of microorganisms and a level low
enough to slow down the action of enzymes. The reduction of water content is produce-specific
with critical levels often cited to be about 10-15% moisture, depending on the commodity.
Breadfruit (Artocarpus altilis) is a carbohydrate found throughout the islands of Oceania and
the Caribbean and is commonly consumed in the green, partially immature stage as a
Breadfruit is highly perishable with post-harvest ripening and softening in just 1-3
days after harvest which restricts its marketing and limits its export potential as fresh produce. It
is a seasonal crop producing one or occasionally two crops per year. It is estimated that between
50-70% of the available breadfruit in Haiti is lost to spoilage.
The motivation of the study
documented in this paper was to recommend a breadfruit dehydration process that was fast,
inexpensive, safe and suitable for the Haitian climate and culture. However, any area where
breadfruit grows readily can benefit from these results.
International Journal for Service Learning in Engineering
Vol. 2, No. 2, pp. 76-88, Fall 2007
ISSN 1555-9033
Dried products can be used in a variety of ways. Dried breadfruit can be ground finely and
made into flour. It can also be re-hydrated before cooking. As part of a larger program of food
processing directed toward village level entrepreneurs, drying breadfruit can increase food
supply, improve seasonal food choice, possibly generate income, and decrease excessive
dependence on imported processed foods.
The drying strategy for any given application should consider batch size, drying
characteristics of the products, initial and final moisture contents of the product, availability and
reliability of electrical power, weather conditions, production capacities and investment
capabilities of the farmers, and potential markets for the dried product. The socio-economic
condition of the users needs to be given top priority.
A review of the literature concerned with the general study of drying agricultural products
often involves predicting the produce behavior during drying or examines different drying
technologies. Numerous articles in the literature look at the drying kinetics of produce.
Experimental studies are aimed at investigating the most suitable drying conditions (temperature,
air velocity) while still maintaining high quality of food (nutrition, color)
as well as minimizing
or eliminating commercial energy usage. These semi-empirical studies entail multiple regression
analysis and statistical tests to confirm the consistency of a selected model and the choice of
correlation coefficients. Theoretical modeling investigations apply mass and energy balances
across a thin-layer of product subjected to a set of temperature and flow conditions and utilize
numerical methods to solve the coupled equations.
Such studies look to understand the
drying phenomenon or to further reduce drying time by looking at intermittent and stepwise
drying as an alternative to continuous drying.
Enclosed drying methods provide protection
against rain and contamination and usually reduce drying time. Enclosed systems described in
the literature increase post-harvest efficiency or reliability by having precise control over drying
Mechanized drying is usually the fastest with optimized conditions, but requires
fuel or electricity to operate. Solar cabinet or tunnel drying uses some technology, have lower
operating costs and can be completely passive (natural convection)
or use mechanical fans
(forced convection)
The most common method for drying produce is open air drying which can be done in direct
sunlight or under shaded conditions. Sunlight heats food effectively driving out moisture but
direct sunlight and heat can destroy fragile vitamins and can cause food to lose color.
Breadfruit can tolerate direct sunlight with good preservation of protein, carbohydrate and trace
and thus is a suitable candidate for open air sun drying. However, there is no tradition
of drying breadfruit or preserving breadfruit in Haiti or other islands of the Caribbean. Some
traditional preserving techniques for breadfruit exist in the South Pacific. Dusting with wood ash
has been used to prolong the shelf life of breadfruit in Pohnpei, in the Federated States of
In this case the ash alkalinity is hostile to molds and bacteria. Breadfruit has also
been preserved by a combination of drying and smoking. It can be cut into slices, suspended over
a fire and then smoked with green tree bark. Fry- drying has also been documented as an option
for preservation.
Any strategy for the preservation of breadfruit in Haiti should avoid requiring electricity
(unavailable or unreliable) or the burning of biomass (to avoid further Haitian deforestation).
Thus smoking/drying over a fire or fry-drying are not realistic approaches to harvesting surplus
breadfruit. However, the Caribbean has ample sunshine throughout the year, thus sun drying
could be a promising option for some of its food preservation needs.
International Journal for Service Learning in Engineering
Vol. 2, No. 2, pp. 76-88, Fall 2007
ISSN 1555-9033
The relative humidity of the ambient air is one of the key drying variables. As dry air moves
over moist produce it absorbs water from the produce. The resulting air temperature decreases
and its relative humidity increases. The drying capacity of air can be increased by heating it.
Enclosed drying strategies often include heating of the air by using solar or biomass heat.
Drying temperatures must be in a range that are high enough to give rapid moisture removal but
not so high as to cook the produce. If the temperature is too high the food can cook on the
outside causing the produce to ‘case harden’, a situation where the outer layer is hard and
prevents moisture in the inside from escaping.
The core of the produce remains moist and will
eventually mold.
Cutting large size produce into small pieces has been mentioned by authors
15, 19
as a way to
accelerate drying due to increased surface area of the product and also avoid case hardening. For
general food drying, it is commonly recommended to cut produce into thin pieces of not more
than about 0.6 – 1.0 cm (
A sweep of the literature only found one reference to
breadfruit drying
which led to an internal report that documented breadfruit cut into 1 cm thick
slices for use in a passive solar dryer.
These authors successfully dried breadfruit in the Pacific
Islands until it was dry and brittle. Their study examined post-drying storage requirements in
tropical conditions. No other papers were found that explicitly considered optimal shred size to
promote efficient produce drying.
The series of experiments documented in this paper were performed as part of a larger
recommendation for a cost effective process to harvest unused breadfruit. Currently small scale
farmers do not preserve breadfruit in the Caribbean. The research outlined in this paper was done
for the Committee on Development for the Methodist Church of Haiti. During a preliminary
process exploration conducted in July 2003, several small scale farmers in Haiti were asked to
sun dry 25 kg of breadfruit. The farmers used a large knife to peel off the outer skin, remove the
hard inner core, and then sliced the breadfruit into lengthwise pieces. Each of the farmers sliced
the breadfruit a little differently and often the slices became thicker with each consecutive
breadfruit. The slicing process was somewhat difficult and took a long time. The slices dried
unevenly. Only a small percentage of the breadfruit dried in the same day. Case hardening of the
thick pieces was observed. In general the farmers were interested in preserving breadfruit but felt
the process too cumbersome and unreliable. These conversations with the farmers resulted in a
two step drying strategy which first emphasized fast and consistent shredding and then looked at
both sun and passive solar drying. A robust manual shredder was designed
and is currently
undergoing an extended field test in Haiti. This paper examines the optimal ratio of surface area
to volume as a parameter related to sun drying and has been shared with the Methodist, Catholic
and Baptist ministries in Haiti.
The following technical specifications were laid out as the basic guidelines to meet the breadfruit
drying requirements:
Dry nine square meters of breadfruit during clear sunny weather with average ambient
temperatures of 29 degrees C, 60-70% relative humidity, and direct beam solar radiation
of about 800 W/m
Reduce the moisture of a load of breadfruit to storage safe conditions from 70% moisture
content to 10-13% moisture content in less than one day with minimal user effort and
process cost.
International Journal for Service Learning in Engineering
Vol. 2, No. 2, pp. 76-88, Fall 2007
ISSN 1555-9033
Three laboratory experiments were performed to determine the optimal shred size and base
background for breadfruit sun drying. The laboratory results were then verified under average
Caribbean conditions.
Surface Area to Volume Ratio: Shred size Experiment
This experiment investigates the shredding, handling, and drying characteristics of several
different shapes and sizes of potato pieces. Potatoes were used because they are readily available
in Minnesota. There are two basic shapes called “shreds” and “slices.” Shreds are those pieces
that are produced using a grating element with aligned holes, and have a shape approximated by
a rectangular prism; slices are simply thin, cross-sectional cuttings of the potato and are shaped
as closed cylinders. For the remainder of the paper all pieces will be referred to as shreds, unless
commentary is being made specifically about the “slice” shape.
The equipment used in the experiment is listed in Table I. A modified electric food
dehydrator was used to dry all shreds to a fully dry state. Fiberglass screen inserts were cut to fit
the dehydrator’s four drying trays to ensure that they would support even the smallest of shreds.
The four trays were numbered 1-4 and stacked in ascending order from the bottom. The trays
were always kept in this order during drying so that any effects on drying characteristics based
upon position within the dehydrator could be monitored. The test procedure consists of shredding
potatoes with commercially available graters with hole sizes of 0.635, 0.9525 and 1.27 cm (1/4,
3/8, 1/2 inch). Using a dial caliper several selected shreds were measured. The average length,
width, and thickness of the shreds and the initial mass of the slices and the drying tray were
recorded. The loaded trays were placed in a food dehydrator (set to 54˚C), and the mass of the
loaded trays was recorded every 10-15 minutes. The test was deemed complete after consecutive
readings spanning at least 40 minutes yielded the same mass.
Item Description Manufacturer Model # Serial #
Electric food dehydrator American Harvest FD50/30 39NZB145309
Electronic digital balance Denver instruments XP-3000 X010456
Dial caliper Rutland G3104342 N/A
Adjustable cheese slicer Target N/A N/A
Grater with ¼ in holes (0.635 cm) Target N/A N/A
Grater with
in holes (0.9525 cm) Target N/A N/A
Grater with ½ in holes (1.27 cm) Target N/A N/A
Metal mixing bowl Target N/A N/A
Fiberglass screen Ace Hardware N/A N/A
Russet potatoes N/A N/A N/A
Breadfruit N/A N/A N/A
Squash N/A N/A N/A
Butternut squash N/A N/A N/A
Eggplant N/A N/A N/A
In addition to these objectively measured quantities, a number of other subjective
observations were made during testing. The use of only one operator for all tests allowed for the
subjective measures to be used reliably. A tradeoff chart was used to compile all numerical and
subjective results as they related to the various types of shreds, and to determine the best shred
type for the drying process. In this tradeoff chart, values of 1-4 were assigned to each shred type
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within each category, where 1 indicates the least desirable performance and 4 denotes the most
desirable performance for that category. A brief description of the meaning of each category and
criteria for how scores were assigned follows below:
Drying Time: A numerical measure of the time taken for a shred type to dry to 15%
moisture content. To accommodate the quickest overall system, a low drying time is best.
Grating Force: A subjective measure comparing the perceived amount of force required
to move the produce over the grater associated with each shred type; to accommodate
ease of use in a manual process, low grating force is best.
Grating Time: A subjective measure comparing the perceived amount of time necessary
for a given grater to shred an entire potato. To accommodate the quickest overall system,
a low grating time is best.
Degree of Clogging: A subjective measure comparing the tendency of the graters
producing the various shreds to become clogged. For ease of use and system quickness,
low clogging is desirable.
Ease of Handling/Spreading: A subjective measure comparing the ease with which
various shred types could be handled and adequately spread out on the drying surface. In
the interest of ease of use and system quickness, shreds that were easy to handle and
adequately spread out were best.
Space Utilization: A subjective measure comparing the ability to spread a given shred
type out on the drying surface, while still making efficient use of the entire surface. To
facilitate system quickness and capacity requirements, efficient space utilization is best.
Breadfruit Correlation Testing
A second experiment compared the drying characteristics of breadfruit with potatoes, squash,
butternut squash and eggplant. Breadfruit shreds “smaller” for a given grating hole than potato.
When potato is shredded, a measurable amount of water is removed by the mechanical action.
Breadfruit does not exhibit any mechanical dewatering. Thus, this experiment was done to find
an acceptable laboratory alternative to breadfruit. The experiment varied the tested produce
while keeping a grater hole of 1.27 cm (½ in) constant for all tests. The produce was compared to
find a product with shredding and drying characteristics most similar to breadfruit. Again, all
produce shreds were dried in an electric food dehydrator to a fully dried condition.
Base Material Test Using Design of Experiments (DOE) Techniques
This experiment investigated the key design factors in the design of solar collectors to
determine if a black base or a base with higher thermal storage further accelerate drying. A four
factor, half-fractional factorial Design of Experiment (DOE)
was run in order to systematically
vary the following factors:
Factors to Test:
a) Base material
b) Paint type
c) Thermal storage material
d) Surface area
Factor Low/High Levels to Test:
a) Plywood / Sheet steel
b) Glossy Black / Matte Black
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c) 0 g / 750 g of charcoal
d) 0.0645 m
(100 in
)/ 0.0967 m
(150 in
) (achieved using either flat or corrugated
Response to Measure Progress:
a) Peak air temperature at 420 seconds approximately 1.9 cm (¾ inch) from the base of
the collector and percent of peak temperature after 700 seconds.
The objective of the experiment was to create a theoretical model of the system to determine
the combination of conditions that could make sun drying most effective. The equipment used
for the experiment is listed in Table II.
Item Description Manufacturer Model & Serial #
Agilent Benchlink data logger Agilent 34970A/ RS232
Type K thermocouple Omega N/A
Halogen light bulb with reflector Home Depot N/A
1 ft
wood box (0.3m x 0.3m x 0.3 m) N/A N/A
Sheet metal tower 3ft tall (0.91m) Home Depot N/A
Corrugated glossy black wood base N/A N/A
Corrugated glossy black aluminum base N/A N/A
Corrugated matte black wood base N/A N/A
Corrugated matte black aluminum base N/A N/A
Flat glossy black wood base N/A N/A
Flat glossy black aluminum base N/A N/A
Flat matte black wood base N/A N/A
Flat matte black aluminum base N/A N/A
Charcoal briquets 750 g Kingsford N/A
A 0.9 meter (3 foot) sheet metal tower was placed over a 0.3m x 0.3m x 0.3m (1 ft
) wooden
box. The bases were approximately 25 cm x 25 cm (100 in
) and were placed in the box. The
corrugated base was built to provide more surface area in the same rectangular footprint. The
average height of the corrugation was 5 cm (2 in) creating a total surface area of 0.967 m
). A halogen light bulb with reflector was positioned at the top of the tower and was directed
such that the light shined directly down the tower. The light bulb was chosen due to its high
filament temperature of 3600 K, which produces light in wavelengths closely simulating solar
radiation. A type K thermocouple was secured approximately 1.9 cm from the base and was
connected to an Agilent Benchlink data logger to continuously monitor air temperature. The
tower, box and light bulb were cooled to room temperature before each trial. The data logger
was turned on for exactly 60 seconds at which time the lamp was plugged in and the apparatus
was run for exactly 6 minutes without interruption. After 6 minutes of run time, the light bulb
was unplugged and the data logger was allowed to run for an additional 5 minutes.
Breadfruit Sun Drying
To substantiate the laboratory experiments breadfruit was processed and sun dried in the
Caribbean. Breadfruit was shredded with a 1.27 cm (½ inch) hole shredding disk, loaded on
fiberglass screened trays and placed in the sun on the island of St. Vincent in the West Indies
between March 19
, 2004 and March 24
, 2004. Ambient temperatures and relative humidity,
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air velocities, incoming solar heat flux, and the mass of the breadfruit, was recorded by 2 people
every 30 minutes. The equipment used is listed in Table III. Five different bases were placed
under the screens. The bases and their intended improvement in parentheses are as follows:
Plain tray placed in the grass (control)
Plain tray placed in the grass, raised 15 cm (6 inches) off the ground (increase airflow)
Tray placed in the grass with black collector plate placed below (increase temperature)
Tray placed in the grass, raised 15 cm (6 inches) off the ground, with black perforated
collector below (increase temp. and airflow)
Tray placed in grass with reflector directing additional solar radiation on the breadfruit
(increase incident solar energy and temp.)
Item Description Manufacturer Model and Serial #
Air velocity meter Omega HHF615M/ 70342
Thermometer/hygrometer Omega RH20F/ 200-03-11395
Thin film flux sensor Omega HFS-4/ O4018707
Polder balance Polder N/A
Digital thermometer Omega HH82/ 76JY0195
Type K thermocouples Omega N/A
Breadfruit trays University of St. Thomas (UST) N/A
Shredded breadfruit N/A N/A
Surface Area to Volume Ratio: Shred size Experiment
The mass over time was measured for three shred sizes and two slice sizes. A representative
drying curve is shown in Figure 1. The key feature to note about drying curves is that there is an
initial region in which water content decreases linearly, followed by a region characterized by a
dramatic decrease in the drying rate as the product reaches a low mass water content. For
comparison of shred drying performance, a final water content of 40% was chosen because it
consistently falls upon the linear portion of the drying curve for potatoes.
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Drying Curve: Potato
0.635 cm (1/4") Grating Holes
0 20 40 60 80 100 120 140 160 180
Time (Min.)
Water Content (kg/kg)
The average dimensions of each shred type (length, width, and thickness) of 5 random
samples were used to approximate the shreds as rectangular prisms. In the case of a slice an
average diameter was used to approximate a cylindrical prism. The ratio of average surface area
to volume ratios was calculated. This ratio is the defining feature of a given shred type. A
summary of all measured quantities for each shred type appears in Table IV, and the complete
tradeoff chart appears in Table V.
Grating Hole Size
or slicer thickness
Average Dimensions
of 5 random piece
Surface Area/Volume
Ratio =
Time to Dry to 40%
Mass Water Content
small shreds 0.635 cm x 0.165
cm (1/4” x
w = 0.27
l = 3.15
t = 0.13
24.0 (61.0) 31.3
0.9525 cm x 0.165
cm (3/8” x
w = 0.63
l = 5.27
t = 0.23
12.2 (31.0) 30.4
large shreds 1.27 cm x 0.279 cm
(1/2” x 0.110”)
w = 1.27
l = 4.88
t = 0.37
7.4 (18.9) 35.8
slice 0.254 cm
d = 3.71
t = 0.34
6.9 (17.6) 44.2
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Degree of
Ease of
3 4 2 1 1 2 13
4 3 3 2 4 4 20
2 2 4 3 3 3 17
slice 1 1 1 4 2 1 10
Based on the trade-off criteria, it was determined that the medium shreds, those shreds with a
dimensional ratio of 12 (cm
), are the best overall shape and size for all aspects of the shredding
and drying process. Indeed, shreds of this configuration facilitate quick and efficient drying, and
are easy to shred and handle. Breadfruit shreds at about this ratio when 1.27 cm (½ inch) grating
holes were used.
Breadfruit Correlation Testing
The quantities used to compare the various types of produce included initial percent water
content by mass, shred surface area to volume ratio for a given shredder hole size, and time to
dry to 40% mass water content from initial condition. The surface area to volume ratio, as
before, was calculated using average length, width, and thickness dimensions of the shreds, and
approximating the shred shape as a rectangular prism.
The results from Table VI suggest that butternut squash is clearly the closest test surrogate
for breadfruit. Butternut squash closely matches the characteristics of breadfruit on all measures,
varying by just a few percent on any of them.
Produce Type Initial Mass %
Water (%)
Surface Area/Volume Ratio
Ratio =
Drying Time (min)
Eggplant 91.8 5.5 (13.9) 46.6
Potato 78.0 7.4 (18.9) 35.8
Squash 84.8 13.0 (33.1) 34.4
Butternut Squash 76.3 12.3 (31.4) 29.0
Breadfruit 72.0 11.6 (29.6) 30.1
Base Material Test Using Design of Experiments (DOE) Techniques
The experiment set-up and results are presented in Table VII. The DOE did not yield a
theoretical model for test system performance. Using commercial analysis software
based on
Analysis of Variance (ANOVA) methods, it was found that none of the factors tested statistically
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affect the two responses more than any other factor. Thus, no coded equation or model was able
to be determined for the system to predict performance. Essentially, none of the tested factors
significantly affect peak air temperature within this system or the retention of thermal energy
within the system. Thus any combination of the tested factors will yield a satisfactory and
statistically equivalent temperature. Thus, the base material, paint type, and surface area
(corrugation) employed for the base should be chosen based upon practical considerations such
as availability, sustainability and cost.
Std Run Factor 1
Factor 2
Paint Type
Factor 3
Factor 4
Response 1
Maximum Air
deg C
Response 2
Fraction of
Temperature at
700 s
6 1 Aluminum Flat Black yes 1.00 52.22 0.58
3 2 Wood Glossy
no 1.00 65.38 0.56
13 3 Wood Flat Black yes 1.41 56.30 0.63
4 4 Aluminum Glossy
no 1.00 50.78 0.72
12 5 Aluminum Glossy
no 1.41 52.11 0.68
15 6 Wood Glossy
yes 1.41 80.26 0.44
10 7 Aluminum Flat Black no 1.41 48.32 0.75
14 8 Aluminum Flat Black yes 1.41 83.21 0.41
1 9 Wood Flat Black no 1.00 76.51 0.45
7 10 Wood Glossy
yes 1.00 58.42 0.60
16 11 Aluminum Glossy
yes 1.41 59.75 0.58
2 12 Aluminum Flat Black no 1.00 39.93 0.69
11 13 Wood Glossy
no 1.41 68.56 0.59
5 14 Wood Flat Black yes 1.00 62.48 0.57
8 15 Aluminum Glossy
yes 1.00 59.70 0.58
9 16 Wood Flat Black no 1.41 46.58 0.77
Breadfruit Sun Drying
The total solar radiation heat flux averaged 825 W/m
, ambient temperatures ranged from 27-
30º C and ambient relative humidity was 60-65%. Prevailing winds averaged 1.5-2.0 m/s
throughout testing. All test configurations produced completely dried breadfruit shreds within +-
5 minutes of each other. This confirmed the base material experiment done in the laboratory. The
base background has little effect on the breadfruit shred drying. The test was repeated with
consistent results over three different days. The shreds repeatedly took about three hours to dry
when placed in the direct sun. The optimal surface area to volume ratio of 12 (cm
) dried the
breadfruit shreds uniformly. Figure 2 shows the breadfruit sun drying.
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To keep the total dehydration equipment cost to an affordable $10 per family with about 10
families in one cooperative the authors recommended that small farmers invest in a manual
that produces a surface area to volume ratio of 12 (cm
) and dry the subsequent
breadfruit shreds in the direct sun on any surface available or convenient surface. It is
acknowledged that the open sun drying design affords no protection of the breadfruit product
from rain, pests or dust. However the additional costs of an enclosed dryer or retractable
protective cover would not be warranted at this time. It is more important to introduce the idea of
food dehydration and to establish a mind frame of preserving surplus food. It is vital that the
early adopters have success with the process strategy. Manual shredders and dehydration training
will be implemented into six women’s cooperatives in Haiti in a program of food processing
directed toward village level entrepreneurs. Results have also been shared with Methodist,
Catholic and Baptist ministries in Haiti. It is hoped that these results could benefit other
communities in Oceania or the Caribbean to process breadfruit, an under utilized food and add to
greater sustainability in food processing at a local level.
We would like to acknowledge funding from the Ireland Fund supported by the Lily Endowment
through the Beyond Career to Calling project at UST and Mr. Larry Mathews. We would also
like to thank J. Emiliusen, T. Mauritzen, Dr. Charlie Keffer, Erica McIntosh, Mary Schmitz and
Dr. Ashley Shams for their help on-site in St. Vincent and Mr. Don Moran and all the volunteers
at Compatible Technology International for their dedication and support in Minnesota.
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... These values comply with the present findings. George et al. (2007) reported increasing drying rates with increasing surface areas. Average surface area of bean seeds was reported as 200.62 mm 2 under rain-fed conditions and 239.99 mm 2 under irrigated conditions (Kibar et al., 2014). ...
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Beans usually have similar physical attributes; thus, it is difficult to distinguish them manually. Size, shape, and mass attributes of seeds help in breeding, selection, classification, separation, and machine design. This study was conducted to determine physical attributes of 20 bean genotypes with the use of image processing techniques. Color characteristics of the present genotypes were also determined. Then, four different machine learning algorithms (MLP, RF, SVR, and k-NN) were employed to predict seed mass. Among the present genotypes, Güzelöz and Özdemir genotypes had the highest size, shape, and color characteristics. Highly significant positive correlations were encountered between projected area-equivalent diameter (r = 1.00), between geometric mean diameter—surface area and volume (r = 1.00). On the other hand, highly significant negative correlations were seen between sphericity—elongation in vertical orientation (r = − 0.98). In hierarchical cluster analysis for physical attributes, Alberto–Aslan and Aras 98–Şahin genotypes were identified as the closest genotypes. According to PCA analysis, the first two principal components (PC1 and PC2) were able to explain 73% of total variation among the genotypes. While PC1 axis included projected area (vertical), equivalent diameter (vertical), and length, PC2 axis included L*, a*, b*, sphericity, roundness (vertical), and elongation (vertical). Among the present machine learning algorithms, RF yielded the best performances in mass estimation of bean seeds. It was concluded that machine learning techniques increased the efficiency of related machinery and helped to save time and labor.
... The surface area is closely related to evaporation from the seed surface. George et al. (2007) stated that drying rates increased with the increasing surface area of the seed. Similar to the present findings, Kibar et al. (2014) reported the average surface area of bean seeds as 200.62 mm 2 in non-irrigated areas and 239.99 mm 2 in drip-irrigated areas. ...
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Chickpea is an important edible legume that can be grown in rain fed conditions. Image analysis and machine learning could be used for rapid and non-destructive determination of seed physical attributes and such techniques yield objective, accurate and reliable results. In this study, size, shape, and area attributes of 26 different chickpea cultivars were determined by image processing method, and color properties were determined by chromametric method, and machine learning algorithms (Multilayer Perceptron-MLP, Random Forest-RF, Support Vector Regression-SVR, and k-Nearest Neighbor-kNN, were used for mass prediction of chickpea seeds. Ilgaz and Çakır cultivars had the highest size and shape values, while İzmir and Sezenbey cultivars had the highest color attributes. Compactness (in horizontal orientation) had a positive correlation with the equivalent diameter (in vertical orientation) and elongation (in vertical orientation) (r = 0.99 for both parameters). Besides, a* had a high correlation with b* (r = 0.97). According to Euclidean distances, Akça–İnci and Damla–Işık cultivars were identified as the closest cultivars in terms of physical attributes. In PCA analysis, PC1 and PC2 explained 73.17% of the total variation. The PC1 included length, geometric mean diameter, volume and surface area, and the PC2 included roundness (in horizontal orientation), thickness, elongation (in horizontal orientation) and sphericity. RF and ML had successful results with the values of 0.8054 and 0.8043 for train-test split, and 0.8231 and 0.8142 for k-fold cross validation, respectively. Present findings revealed that texture image processing and machine learning could be used as an effective and inexpensive discrimination tool for chickpea seeds.
... The surface area to volume ratio (SA/Vol) values which are 0.481 and 0.698 mm -1 for fruit and kernel, respectively, indicates that the drying (George et al., 2007) of kernel will require less time than fruits. ...
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s. Thevetia peruviana J. is a potential biofuel crop with cosmopolitan distribution and ensuring fruit-harvest almost throughout the year. Different physical properties of fruit and kernel such as, dimensions, 1000-unit mass, surface area, spheri-city, bulk density, true density, aspect ratio and angle of repose has been determined for ease in designing structures and equipments for handling, transportation, storage and processing. The shell has higher moisture content than kernel and fruit. Oil content in the kernel is as high as 62.14% (w/w) while other parts of fruits bear negligible amount of oil. The frequency distribution of size and weight for fruit and kernel has been evaluated. The sphericity of kernel is 10.14% more and the surface area is 77.12% less than that of fruit. Bulk densities of fruits and kernels are 591.70 and 657.73 kg m-3 ; the corresponding true densities are 1106.68 and 942.05 kg m-3. The porosity of fruit and kernel are 46.51% and 29.82% respectively. The angle of repose of fruit is 1.75% higher than kernel.
... The surface area of agricultural products is closely related to evaporation from the product surfaces. George et al. (2007) reported that drying rate increased due to increased surface area of the product. ...
Full-text available
Hazelnut is one of the most popular nuts consumed by people; it has different cultivars in Turkey. The aim of the current study was to characterize some physicomechanical characteristics, shape features, color, and biochemical properties of 6 standard and 3 local hazelnut cultivars grown in Turkey. The shape and size properties of the samples were determined using image processing techniques as an alternative to conventional measurement methods. Additionally, principal component analysis (PCA) was used to classify the hazelnut samples in terms of the biochemical parameters of the hazelnut cultivars. According to the findings, the highest crude oil (63.25%) and lowest protein contents (13.63%) were observed in the Kalınkara cultivar. Oleic and linoleic acids were the major fatty acids for all hazelnut samples. While local Devedişi and standard Çakıldak cultivars had the highest oleic acid levels, the highest linoleic acid level was observed for the Dağ fındığı cultivar. The cultivars of Foşa had the highest Zn and Mn, while the highest Cu was found in the Tombul cultivar. The greatest surface and projected areas were calculated for the Kara fındık and Dağ fındığı samples, while the greatest hardness value was measured for the Devedişi cultivar. PCA revealed some positive and negative correlations between the physicomechanical and biochemical parameters. The present analyses revealed significant correlations between hardness and internal shell b* values and between Cu content and internal L*. Such correlations should be taken into consideration in food processing applications and machine design for these hazelnut cultivars.
... The inlet conditions of the tray were assumed as equal to the inlet conditions of the dry drying chamber (George 2007). In addition, the outlet conditions of trays were assumed as equal to the outlet conditions of the drying chamber (Darvishi et al. 2018). ...
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Abstract The traditional vegetable drying (open-air/sun drying) method of harvesting of tomato, potato and onion in the Fogera District in Amhara regional state, Ethiopia, leads to loss of product, reduction in the quality of product and economic loss for the poor farmers. So, this experiment aimed to show the effectiveness of solar dryer technology by increasing the quality of the product in tomato, potato, and onion in Fogera district Northwest Ethiopia, 2018. A simple solar vegetable dryer is experimentally analyzed to alleviate the problem associated with vegetable processing in Woreta city. The first law of thermodynamics energy analysis was carried out to estimate the amount of useful energy gained from solar air dryer and energy utilization ratio of the drying chamber and the energy through drying box. The magnitude of the exergy inflow, outflow and exergy losses in the drying chamber during the drying process was determined by applying the second law of thermodynamics. The average solar drying efficiency was found to be 75.01% to 86.70% for tomato, 75.70% to 87.90% for potato and 58.7% to 85.5% for onion. Regrading the drying period, it took 33 h for tomato, 27 h for potato and 44 h for onion during the experimental test.
... The natural convection solar dryer was developed; the drying and thermal analysis were done and tested to obtain some performance evaluation parameters. An experimental study was done for investigation of performance of a solar drying system and a system with an auxiliary heater as a supplement to the solar heat [4][5][6][7][8][9][10][11][12][13]. We constructed a portable solar dryer of indirect type working on forced convection. ...
... When any agricultural product is dried, beneath controlled condition at specific humidity in addition to temperature, it offers speedy superior exceptional of dry product [2]. Drying entails the application of heat to vaporize moisture and some means of casting off water vapor after its separation from the food products [28]. It is for that reason a blended and simultaneous heat and mass switch operation for which power need to be supplied [3]. ...
Full-text available
Solar drying is one of the applications of solar energy. Drying means moisture removal from the product. Drying is helpful in preserving food product for long time; it prevents products from contamination. Direct sun drying, oblique solar drying, and blended mode solar drying are special solar drying techniques. Previously open to the solar or direct solar drying approach was used. However, it has many disadvantages. These disadvantages can be removed by use of solar green house dryer which are used for drying products as utility of sun power. In this paper, discussion about open sun drying, various green house dryers has been reported.
... Hence, Mohseni and Peters (2016) reported that an increasing ratio of 360% at the surface area of a particle caused the drying rate to be enhanced by more than twice. George et al., (2007) reported that the drying rate was accelerated due to increased surface area of the product and recommended a surface area to volume ratio of 12 cm -1 for the optimal ratio of surface area to volume for thin-layer drying of breadfruit with sun drying. Dursun (2001) indicated that the projected area of a product is a crucial engineering parameter for classification and clearing with regard to the principles of hydrodynamic and aerodynamic. ...
Full-text available
Size and shape data of agricultural crops provide great sources for food processing technologies. The physical attributes of different fruits should be known for the design, developing and innovation of food technologies. In this study, the size and shape distinctions of fifteen national and international walnut cultivars (Midland, Sütyemez-1, Serr, Maraş-18, Maraş-12, Sütyemez-2, Kaman-1, Kaman-5, Pedro, Howard, Chandler, Şebin, Şen-2, Bilecik and KR-1) were determined using elliptic Fourier and multivariate approaches. Firstly, the gravitational features of walnut cultivars were determined, and their dimensional, area and shape attributes were revealed by image processing. Cluster analysis was used to designate the walnut cultivars. Elliptic Fourier descriptors obtained from walnut outlines provided the comparisons among walnut cultivars in shape. The shape index indicated that Serr, Sütyemez-2, Midland and Şen-2 cultivars were oval-shaped, and the others were spherical. The cluster analysis divided the walnut cultivars into four subgroups. Elliptic Fourier descriptors perfectly distinguished the walnut cultivars according to shape.
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Chickpea is an important edible legume consumed worldwide because of rich nutrient composition. The physical parameters of chickpea are crucial attributes for design of processing and classification systems. In this study, effects of seven different irrigation treatments on size, shape, mass, and color properties of chickpea seeds were investigated, and machine learning algorithms were used to estimate mass and color attributes of chickpea seeds. The results showed that Multilayer Perceptron (MLP) had the greatest correlation coefficients for mass (0.9997) and chroma (0.9997). The MLP yielded better outcomes than Random Forest for both mass and color estimation. In terms of physical attributes, the best results were obtained in I1 (rainfed) and I5 (irrigation at 50% flowering and 50% pod fill) irrigation treatments. Additionally, single or couple irrigations at different physiological stages instead of full irrigation treatment might be sufficient to improve the physical attributes of chickpea.
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RGI International Journal is an interdisciplinary journal which was started by Radharaman Group of Institutes, Bhopal in the year 2011. Research Papers are invited for further issues. Publication in the journal is free of cost.
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Preface Food preservation is an action or a method of maintaining foods at a desired level of properties or nature for their maximum benefits. In general, each step of handling, processing, storage, and distribution affects the characteristics of food, which may be desirable or undesirable. Thus, understanding the effects of each preservation method and handling procedure on foods is critical in food processing. The first edition of this book was the first definitive source of information on food preservation. It was well received by readers and became a bestseller and was also translated into Spanish by Acribia, Spain, in 2003. Appreciation from scientists, academics, and industry professionals around the globe encouraged me to produce an updated version. This edition has been developed by expanding the previous one with the addition of new chapters and updating most of the chapters of the first edition. The 25 chapters in the first edition are now expanded to 44 chapters. The processing of food is no longer as simple or straightforward as in the past. It is now moving from an art to a highly interdisciplinary science. A number of new preservation techniques are being developed to satisfy current demands of economic preservation and consumer satisfaction in nutritional and sensory aspects, convenience, absence of preservatives, low demand of energy, and environmental safety. Better understanding and manipulation of these conventional and sophisticated preservation methods could help to develop high-quality, safe products by better control of the processes and efficient selection of ingredients. Food processing needs to use preservation techniques ranging from simple to sophisticated; thus, any food process must acquire requisite knowledge about the methods, the technology, and the science of mode of action. Keeping this in mind, this edition has been developed to discuss the fundamental and practical aspects of most of the food preservation methods important to practicing industrial and academic food scientists, technologists, and engineers. Innovative technology in preservation is being developed in the food industry that can extend shelf life; minimize risk; is environment friendly; or can improve functional, sensory, and nutritional properties. The large and ever-increasing number of food products and new preservation techniques available today creates a great demand for an up-to-date handbook of food preservation methods. This book emphasizes practical, cost-effective, and safe strategies for implementing preservation techniques and dissects the exact mode or mechanisms involved in each preservation method by highlighting the effect of preservation methods on food properties. The first edition was divided into four parts. Part 1: Preservation of Fresh Food Products encompassed the overview of food preservation and postharvest handling of foods. Part 2: Conventional Food Preservation Methods presented comprehensive details on glass transition, water activity, drying, concentration, freezing, irradiation, modified atmosphere, hurdle technology, and the use of natural preservatives, antioxidants, pH, and nitrites. Part 3: Potential Food Preservation Methods detailed new and innovative preservation techniques, such as pulsed electric fields, ohmic heating, high-pressure treatment, edible coating, encapsulation, light, and sound. Part 4: Enhancing Food Preservation by Indirect Approach described areas that indirectly help food preservation by improving quality and safety. These areas are packaging and hazard analysis. The second edition is divided into five parts. The grouping of Parts 2 and 3 in the first edition could not be a clear approach since it was not easy to separate the conventional and the potential methods. In the second edition, a better rational approach is used for grouping. The basis of grouping is the mode of preservation method. Part 1: Preservation of Fresh Food Products encompasses the overview of food preservation and postharvest handling of foods, which includes physiology of fresh fruits and vegetables; handling and postharvest treatments of fruits and vegetables; and postharvest handling of grains and pulses, fish and seafood, red meat, milk; and also minimal processing of fruits and vegetables. This part can be read independently for those who want a basic background in postharvest technology for foods of plant and animal origin. It also gives valuable background information on the causes of food deterioration and classification of food preservation methods with the mode of their action. Part 2: Preservation Using Chemicals and Microbes presents comprehensive preservation methods based on additives of chemical or microbiological nature, including fermentation, antimicrobials, antioxidants, pH-lowering agents, and nitrides. Each chapter covers the mode of preservation actions and their applications in food products. Part 3: Preservation by Controlling of Water, Structure, and Atmosphere details preservation methods based on physical nature, including modified-atmosphere packaging; glass transition and state diagram; membrane technology; stickiness and caking; drying, including osmotic dehydration; water activity; surface treatment and edible coating; encapsulation and controlled release. Part 4: Preservation Using Heat and Energy describes preservation methods based on thermal and other forms of energy, including pasteurization, canning and sterilization, cooking and frying, freezing, freezing–melting (or freeze concentration), microwave, ultrasound, ohmic heating, light, irradiation, pulsed electric field, magnetic field, and high pressure. In addition, chapters on hurdle technology (or combined methods) that uses a combination of preservation techniques are also included. Part 5: Enhancing Food Preservation by Indirect Approach presents the approaches that indirectly help food preservation by improving quality and safety. These techniques are packaging, hygienic design and sanitation, hazard analysis and critical control point (HACCP), good manufacturing practice (GMP), and commercial considerations of managing profit and quality. Packaging is an integral part of food preservation and it has very wide scope. In this edition, packaging techniques are presented in three chapters. This second edition will be an invaluable resource for practicing and research food technologists, engineers, and scientists, and a valuable text for upper-level undergraduate and graduate students in food, agriculture/biological science, and engineering. Writing a book is an endless process, so the editor would appreciate receiving new information and comments to assist in future compilations. I am confident that this edition will prove to be interesting, informative, and enlightening to readers.
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Freshly harvested rosehips (Rosa canina L.) were dehydrated in a parallel flow type air dryer at six air temperatures (30, 40, 50, 60, and 70°C) at air velocities of 0.5, 1.0, and 1.5 m/s. Drying air temperature and velocity significantly influenced drying time and energy requirement. Minimum and maximum energy requirement for drying of rosehips were determined as 6.69 kWh/kg for 70°C at 0.5 m/s, and 42.46 kWh/kg for 50°C, 1.5 m/s. In order to reduce drying energy consumption, it is recommended that the drying air velocity must not be more than 0.5 m/s and drying air temperature should be 70°C. In addition, the influence of drying air temperature and air velocity on the color of dried rosehip has been studied. Hunter L, a, b values were used to evaluate changes in the total color difference (ΔE) on dried rosehips. 70°C drying air temperature and 1 m/s air velocity were found to yield better quality product.
The tools and technique used in the Design of Experiments (DOE) have been proved successful in meeting the challenge of continuous improvement over the last 15 years. However, research has shown that applications of these techniques in small and medium-sized manufacturing companies are limited due to a lack of statistical knowledge required for their effective implementation. Although many books have been written in this subject, they are mainly by statisticians, for statisticians and not appropriate for engineers.Design of Experiments for Engineers and Scientists overcomes the problem of statistics by taking a unique approach using graphical tools. The same outcomes and conclusions are reached as by those using statistical methods and readers will find the concepts in this book both familiar and easy to understand. The book treats Planning, Communication, Engineering, Teamwork and Statistical Skills in separate chapters and then combines these skills through the use of many industrial case studies. Design of Experiments forms part of the suite of tools used in Six Sigma.Key features: Provides essential DOE techniques for process improvement initiatives Introduces simple graphical techniques as an alternative to advanced statistical methodsâ reducing time taken to design and develop prototypes, reducing time to reach the market Case studies place DOE techniques in the context of different industry sectors An excellent resource for the Six Sigma training program This book will be useful to engineers and scientists from all disciplines tackling all kinds of manufacturing, product and process quality problems and will be an ideal resource for students of this topic.Dr Jiju Anthony is Senior Teaching Fellow at the International Manufacturing Unit at Warwick University. He is also a trainer and consultant in DOE and has worked as such for a number of companies including Motorola, Vickers, Procter and Gamble, Nokia, Bosch and a large number of SMEs.
Conference Paper
The seeded breadfruit (Artocarpus altilis) commonly known as breadnut, is a popular fruit of the Caribbean and known for its deliciously boiled or roasted mature seeds. The fruit in its partially immature form is sometimes used as a vegetable. The thin-layer drying characteristics within a temperature range of 35°C to 80°C and a flow rate of 1.2 m/s were investigated for pretreated (cooked in salted water for 35-40 min at 100°C) and untreated in-shell mature seeds. The results indicated that drying of the in-shell seeds took place exclusively in the falling rate period and can best be described by a two-term solution of the diffusion equation. Results also suggest the importance of the shell as a constraint to moisture transfer from the kernel.
Research and development work in solar drying conducted in Thailand during the past 15 years is reviewed. Technical and economic results indicate that solar drying for some crops such as paddy, multiple crops and fruit is feasible. However, both the farmers who accept solar drying and the places where it is accepted are still very few. This may be due to the long payback period and high initial investment cost. Research and development work on solar air heaters is also reviewed. Most of the solar air heaters developed in Thailand have used modifications to the roofs of buildings. Both bare and glass-covered solar air heaters have been found technically and economically feasible when compared to electricity but have not been able to compete with fuel oil. Further research and development work should be continued in order to reduce costs. A standard test for solar air heaters should also be developed.
A detailed description of a novel direct-mode solar dryer with a staircase design is presented. The temperature variation of the dryer compartments with time of day are plotted. Its efficiency values as a solar collector ranged between 0.26 and 0.65. Drying curves for various fruits and vegetables are shown.
In this study, a solar cabinet dryer consisting of a solar air heater and a drying cabinet, was used in drying experiments. Pumpkin, green pepper, stuffed pepper, green bean, and onion were dried in thin layers. Three different drying air velocities were applied to the process of drying to determine their effects on drying time. Fresh materials were dried by a natural sun drying method. In order to explain drying curves of these products different moisture ratio models were performed and evaluated based on their determination coefficients (R). Our results revealed that drying air temperature could increase up to about 46°C. Drying air velocity had an important effect on drying process. Drying time changed between 30.29 and 90.43 hours for different vegetables by the solar drying. This drying time was between 48.59 and 121.81 hours for the natural sun drying. Drying curves could be explained by determined thin layer drying models satisfactorily with very high determination coeffcients.
Solar drying, an energy-saving process, is an efficient food conservation solution for countries that often have only sun as an energy source. Decreased energy requirements for a drying and improved dewatering process result from lower moisture fraction. This investigation focuses on the study of water behaviour inside the product to be dewatered in the particular case of a tunnel drier, and on the evolution of water content during the whole process starting from evaporation and ending with evacuation of the humid air. The mass transfer of water was respectively studied, analysed and simulated as to apprehend better the mechanisms governing drying and to build a real simulation tool to help in the design and automation of tunnel industrial driers. Space and time profiles of water content led to the assessment of drying velocity during the different phases and consequently to the comprehension of quantitative analysis. The kinetics obtained with the model under different working parameters (temperature, pressure, reactor time residence) and within various initial and boundary conditions show good agreement with those obtained experimentally.
A two-dimensional finite-element formulation and solution of a set of transient coupled heat and diffusive moisture transfer equations is presented. The solution procedure developed uses an alpha family of approximation for stepping in time for the solution of the coupled set of equations applied to simulate the stepwise convective drying behavior of banana slices. The model tested was validated with experimental data from different sources for stepwise drying of banana using a heat pump dryer (HPD) as well as continuous batch drying in both Cartesian and cylindrical coordinate systems. The maximum deviation of moisture content between experimental and simulation results was 0.05% wet basis (% w.b.). Good agreement of the simulated results with experimental data for stepwise as well as continuous convective drying of banana samples indicates the validity of the procedure and its incorporation in the optimization of drying processes.