dehydration

CHAPTER 1
The Problem and Its Background
Introduction
The earliest method of dehydration is by sun drying. It is a relatively simple and
inexpensive process. It is still the most common method of drying food products. However,
several problems are associated with sun drying, such as susceptibility to contamination and
subsequent spoilage as the product is exposed to elements. Sun drying is also considerably a long
process compared to modern methods and it requires a very large area of operation.
Dehydration of food is an effective weapon against microbial attack. Since the free water
in food is essential for the proliferation of bacteria, preservation of food by drying has been
practiced since the ancient times. But advances in food science and technology have created
wholly new forms, such as composed freeze – dried foods that resume their original shapes or
dehydration. Processed food by dehydration can now be found in the market. There are naturally
dehydrated foods such as nuts, grains and peas. These foods are often finished commercially
with artificial drying. Artificial drying helps in weight reduction b water loss. Water removal
occurs at high or low temperatures.
Statement of the Problem
This research is conducted to produce a low cost food dryer. Specifically, it aims to
answer the following questions:
1. How does the fabricated food dryer operate in terms of:
a. Costing?
b. Temperature?
c. Time?
2. How effective is the machine in drying foods in terms of efficiency in drying and
reliability?
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Hypotheses
The following are the basic assumptions of the researchers:
1. The fabricated food dryer is more efficient than sun drying in dehydrating foods such
as fruit, vegetables and others.
2. Lowering the cost of the food dryer is possible by substituting the dry bulb into a
heating coil as a heater.
Significance of the Study
Technological Aspect
A food dryer minimizes the large area used for sun drying food and shortens the long
procedure in sun drying. A food dryer is a very convenient way to dehydrate food.
Economic Aspect
Small entrepreneurs who cannot afford expensive food dryers can now avail one. Most
available food dryers are bulky because they are intended for mass production which makes them
reasonably expensive. Small entrepreneurs will benefit by using the fabricated food dryer since
with it, it takes shorter time to dry products than sun drying. Also, the process of drying would
not be delayed during calamities like rain storms which can result to loss of profit.
Health Aspect
Drying, as applied to food, is the removal of moisture so that the unfavorable
environment for yeast, molds and bacteria will not be obtained. The food dryer will achieve the
dehydrated state of a given product in the shortest time possible to minimize the chances of
spoilage.
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Scope and Delimitations of the Study
This study is only focused on the construction of a portable food dryer and its efficiency.
The product is visualized for the household level mainly as it can be used more efficiently and to
its full extent even in the simple confine of a house. The food dryer may be used in businesses
with performance developments but this aspect will not be discussed in this research paper.
The research took place at San Sebastian, Tarlac City and Tarlac Montessori School from
November 2008 to March 2009.
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CHAPTER 2
Review of Related Literature
This chapter deals with the related literature and studies of the portable food dryer.
RELATED LITERATURE
Food Preservation
Food preservation is the process of treating and handling food to stop or greatly slow
down spoilage (loss of quality, edibility or nutritive value) caused or accelerated by microorganisms.
Some methods, however, use benign bacteria, yeasts or fungi to add specific qualities
and to preserve food. While maintaining or creating nutritional value, texture and flavor is
important in preserving its value as food. This is culturally dependent, as what qualifies as food
fit for humans in one culture may not qualify in another culture.
Preservation usually involves preventing the growth of bacteria, fungi, and other microorganisms,
as well as retarding the oxidation of fats which cause rancidity. It also includes
processes to inhibit natural ageing and discoloration that can occur during food preparation such
as the enzymatic browning reaction in apples which causes browning when apples are cut. Some
preservation methods require the food to be sealed after treatment to prevent recontamination
with microbes; others, such as drying, allow food to be stored without any special containment
for long periods.
Common methods of applying these processes include drying, spray drying, freeze
drying, freezing, vacuum-packing, canning, preserving in syrup, sugar crystallization, food
irradiation, and adding preservatives or inert gases such as carbon dioxide. Other methods that
not only help to preserve food, but also add flavor, include pickling, salting, smoking, preserving
in syrup or alcohol, sugar crystallization and curing.
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Drying Foods
Drying or dehydration, the oldest method of food preservation, is particularly successful
in the hot, dry climates found in much of New Mexico. Quite simply, drying reduces moisture
necessary for bacterial growth that eventually causes deterioration.
Successful dehydration depends upon a slow steady heat supply to assure that food is
dried from the inside to the outside. Drying is also an inexact art. Size of pieces, relative
moisture, and the method selected all affect the time required to dehydrate a food adequately.
Methods of Drying
Foods may be sun dried with or without a solar dehydrator, in a gas or electric oven, or
with a portable electric dehydrator. Dehydrators with thermostats provide better control over
poor weather conditions and food quality than sun drying.
An effective solar dehydrator is the shelf above the back seat of a car. Clotheslines are
another popular drying rack for ears of corn and strips of jerky.
1. Sun drying
Prepared foods are placed on drying trays. Stainless steel screening and thin wood lath
are good materials for home-constructed drying trays. As aluminum screening reacts with acids
in the fruit, it is less desirable. Galvanized, copper, fiberglass, or vinyl screening should not be
used.
2. Freeze Drying
A freeze dryer works on the principle of sublimating ice from a frozen food product and
removing the vapor in partial vacuum of about 27 Pa pressure. At this pressure, the product is
below the triple point of water; hence, the vapor is removed without passing through the liquid
phase. The removal of moisture from within the product in the vapor form results in limiting the
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movement of soluble solids, maintaining the tissue structure and minimizing product shrinkage.
Sublimation can take place at temperatures below 0 degrees Celsius. Hence, below this, foods
can be dried without heat damage unlike other drying procedures. However, freeze drying is an
expensive process and is suited mainly for special types of dried products.
3. Solar Drying
Solar drying is an industrial process in many countries where outdoor temperatures reach
115°F or higher. In East Asia, spice crops and other exported plant materials are routinely solar
dried. Solar drying is different form “sun drying”. Solar drying uses equipment to collect the
sun’s rays in a unit designed to ventilate moisture. The temperature in the unit is usually 20° –
30° higher than in open sunlight.
4. Tray or Cabinet Dryers
Tray dryers are small-capacity dryers that use hot air as the drying medium. The products
being dried are often carried on trays that can be supported either by tray guides attached on the
walls of the drying chamber or by tray trucks that could be rolled into and out of the dryer.
Cabinet dryers are generally low-cost and easy to construct and operate. It is ideal for laboratory
drying experiments and other drying tests because of its small size.
5. Tunnel Dryers
Tunnel dryers consist of long drying chambers that can accommodate a train of carts
loaded with a number of trays. The drying medium moves from one end of the tunnel to the other
end in the process picks up moisture from the product. Auxiliary heaters are commonly installed
at certain sections of the drying chamber because the drying air temperature tends to drop along
the length of the tunnel. Tunnel dryers can also be designed for continuous operation by
providing means of moving the tray carts from one end of the tunnel to the other.
6. Drum Dryers
Drum dryers consist of rotating drums that are heated from within, generally by steam.
During its rotation, the heated drum surface is allowed to come in contact with a pool of liquid
material. The liquid immediately boils and sticks to the drum surface where it dries. The dried
film of food sticking on the surface is removed from the rotating drum with a stationary scraper.
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Drum dryers can provide high drying rates and economical use of heat. However, these are suited
only for liquid or slurry foods that can stand high temperatures for short periods ranging from
two to 30 seconds. In the food industry, therefore, drum dryers are used for milk, soups and baby
food.
7. Vacuum Shelf Dryer
Drying of heat-sensitive food products at temperatures below 100°C may be achieved
using vacuum dryers. These dryers consist of an air-tight chamber with food products on plates
heated at low pressures. The pressure ranging from 0.135 to 9.45 kPa allows evaporation of
moisture from the product at low temperatures. Drying cost using this system is relatively high
because additional work is needed to pull a vacuum within the drying chamber.
8. Bin Dryer
Cereal grains, as well as other relatively dry granular products, are commonly dried in bin
dryers. This type of dryer consists of a container bin with perforated flooring and drying air
plenum underneath. Hot air is forced from the plenum through the flooring and through the bed
of granular food product. Drying can take place only if the air can pass through the bed of goods
being dried.
Bin dryers generally require low capital and operating costs but they allow relatively low
drying rates.
9. Spray Dryer
Spray dryer are used mainly for drying liquid food products, such as milk and fruit juices,
into powdered form. This is accomplished by atomizing the feed through a nozzle at pressures
ranging from 3.6 to 48.4 MPa. The fine droplets produced are allowed to come in contact with
hot air which moves within the drying chamber. Due to the very large surface area of contact
between the droplets and the drying medium, very rapid rates are achieved.
10. Drying Times
Drying time varies widely because of the method selected and the size and amount of
moisture in food pieces. Sun drying requires the most time; an electric dehydrator requires the
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least. Vegetables take from 4-12 hours to dry; fruits take 6-20 hours. Meats require about 12
hours. Making raisins from grapes may require days/weeks when dried outside.
When testing foods for dryness, remove a piece from the center of the drying tray and
allow it to come to room temperature. Fruits and meat jerky should be leathery and pliable;
vegetables should be brittle.
Nutritional Value of Dried Foods
Dried foods retain their protein, mineral and vitamin A content fairly well if soaking
water is also consumed. Because they are concentrated into a small mass, dried foods can also be
high in calories.
RELATED STUDIES
Local Literature
Sun drying is the earliest method of dehydration of foods in the Philippines. It is
relatively simple and inexpensive, but it is still a common method in dehydration of foods.
Drying by exposure in the sun is also a considerable longer process compared to modern
methods of drying.
Sun drying requires a large area of operation. It can be very a very unreliable procedure
due to the intractability of weather conditions even during the dry season.
Several problems of sun drying are exposure to contamination and susceptibility,
subsequent spoilage as the product is exposed to the elements.
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CHAPTER 3
Research Methodology
This chapter explains the type of research design applied for this study. This chapter
includes the data gathering used by researchers and what processes were involved in forming the
final product. A part of this chapter is the procedures or experiments done to evaluate the final
product.
Research Design
This study made use of the experimental method of research. During this experiment,
researchers gained knowledge from a trial and error method. This is the most prestigious method
for advancing Science and Technology and for the Research and Development for the reason that
it is a production-oriented. Since this study is concerned with a portable food dryer, the
experimental method helped in determining its efficiency in drying time based on the different
products dried.
Experimental Procedure
I. Fabrication of the Portable Food Dryer
A. Conceptual Design
B. Materials
C. Assembly
II. Testing the Portable Food Dryer
First, gather all the materials to be dried. Weigh all the supplies using a measuring scale.
Now, the drying process can begin, starting off with the Saluyot leaves. Place 30 grams of
Saluyot leaves inside the Portable Food Dryer and set the timer to three minutes. After that,
weigh the Saluyot leaves again. This process will be repeated with each of the materials only
differing in the length of time in drying. The banana chips should be dried for seven minutes.
The sweet potato chips should be dried for four minutes. The shrimp should be dried for 12
minutes and the fish should be dried for 22 minutes.
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Research Paradigm
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INDEPENDENT
VARIABLE
Portable Food Dryer
DEPENDENT
VARIABLE
Dried Saluyot leaves,
banana chips, sweet
potato chips, shrimp and
fish at desired moisture
content.
CHAPTER 4
Presentation, Analysis and Interpretation of Data
This chapter focuses on the presentation, interpretation and analysis of data based on the
personal observations of the researchers upon experimentation and evaluation.
The research projects was carefully prepared and planned by the researchers to achieve
the desirable or expected outcome. After finishing the research projects, it was tested of its
functions and table 1 shows the results of the observations on the food’s sensory attributes after
drying.
Table 1: Dehydrated Products at using Fabricated Food Dryer
Product Initial Weight Drying Time Drained Weight
1) Dried Saluyot
leaves
30 grams 3 minutes 15 grams
2) Dried Banana
Chips
40 grams 7 minutes 20 grams
3) Dried Sweet
Potato Chips
25 grams 4 minutes 13 grams
4) Shrimp 50 grams 12 minutes 25 grams
5) Dried Bangus 75 grams 22 minutes 38 grams
Table 1 shows the length of time wherein the products’ weight would be reduced to
almost half of its original weight. For Saluyot leaves, it took about three minutes for 30 grams to
become 15 grams. For the banana chips, seven minutes were needed for the 40 - gram sample to
become 20 grams. For the sweet potato chips, it took four minutes for 25 grams to become 13
grams. On the other hand, for the 50 - gram shrimp, it took 12 minutes for it to become 25 grams
and 22 minutes for the 75 – gram Bangus to become 38 grams. (These observations were
perceived by the researchers while conducting the experiment).
CHAPTER 5
Summary, Conclusion and Recommendation
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Summary
The machine is effective in drying-up Saluyot leaves, Banana Chips, Sweet Potato,
Shrimp and Bangus. The weight of each of the product was reduced to half of its original weight.
The food dryer is more convenient than drying through sun. Using the food dryer is time
efficient especially in cooking.
Conclusion
Based from the experimentation done, we can conclude that drying of food in the
food dryer is more efficient and more convenient than sun drying since it requires less possible
time in dehydrating food and it minimizes the large area used for sun drying food. Dehydrating
of food in a food dryer is also more reliable than the process of sun drying. Sun drying can be a
very unreliable procedure due to the inconsistency of weather conditions. The food dryer is not
that costly since heating coils were used as the medium of heating. As for health concerns, drying
reduces the moisture needed for bacterial growth which causes deterioration. With sun drying,
another reason of its unreliability is that one of its problems is exposure to contamination and
succeeding spoilage as the product is exposed to the elements. On the other hand, food dryer
minimizes the chance of spoilage since the product will achieve its dehydrated state in the
shortest time possible.
Recommendation
For the betterment of the food dryer, the researchers recommend the following:
1. The screen, tray for the product, should be changed into screen with thinner
spaces so products put on the tray will not be dropped below the heating area.
2. Aside from Saluyot leaves, Banana, Sweet Potato, Shrimp and Bangus, next
researchers can also focus on other leaves to be dried.
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3. Further studies can also be conducted to improve the food dryer.
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