TECHNICAL PAPER # 60
PRESERVATION OF FRUITS
DRYING AND CURING
Joel M. Jackson
George G. Schultz
1600 Wilson Boulevard, Suite 500
Arlington, Virginia 22209 USA
Tel. 703/276-1800 . Fax: 703/243-1865
Understanding Home-Scale Preservation of
Fruits and Vegetables
Part II. Drying and Curing
[C]1988, Volunteers in Technical Assistance
This paper is one of a series published by Volunteers in
Assistance (VITA) to provide an introduction to specific
state-of-the-art technologies of interest to people in
countries. The papers are intended to be used as guidelines
help people choose technologies that are suitable to their
situations. They are not intended to provide construction or
implementation details. People are urged to contact VITA or
similar organization for further information and technical
assistance if they find that a particular technology seems
meet their needs.
The papers in the series were written, reviewed, and
almost entirely by VITA Volunteers technical experts on a
voluntary basis. Some 500 volunteers were involved in the
production of the first 100 titles issued, contributing
5,000 hours of their time. VITA staff included Margaret
Crouch as project manager, Suzanne Brooks handling
layout, and graphics, and James Butty as technical
The author of this paper, VITA Volunteer Eric P. Rusten, a
Peace Corps Volunteer to Kenya and Nepal, is a graduate
at Washington University in St. Louis, Missouri. The
are also VITA Volunteers. William G. Schultz is a mechanical
engineer and has specialities in food processing
George Rubin is a product developer with Dell Products
in New Jersey, having retired as manager of the Welch
Foods Inc. in Westfield, New York; Joel Jackson is a food
scientist with Food Preservation Systems in Windsor, Maryland.
VITA is a private, nonprofit organization that supports
working on technical problems in developing countries. VITA
offers information and assistance aimed at helping
and groups to select and implement technologies appropriate
their situations. VITA maintains an international Inquiry
a specialized documentation center, and a computerized
roster of volunteer technical consultants; manages long-term
field projects; and publishes a variety of technical manuals
Preserving the surplus food that is often available at
time helps ensure a continuous supply of food throughout the
year. There are several methods of food preservation,
canning, freezing, pickling, drying, and curing (smoking or
All these preservation methods aim to prevent or at least
slow down spoilage. Careful attention to the proper
preserving and storing also helps ensure that the food stays
nutritious as possible.
This paper, the second of a two-part series, discusses
of drying and curing (smoking or salting) fruits and
at home, for home use. The preceding paper looked at the
of canning and freezing. Guidelines are given to help
select the best possible method of preserving the produce
they have available.
Drying, smoking, salting, and pickling have been used for
of years to keep food from spoiling. Canning or jarring to
preserve food is much more recent. It was first developed in
by Nicholas Appert, a French chef who learned that food
in sealed containers would keep for extended periods of
Appert, like his predecessors, did not know why food
spoiled or why their technique worked, this early method was
quite successful and has changed little since it was
Today, it is one of the most popular methods of preserving
In the early twentieth century, freezing became a popular
for short-term preservation of food, but its high cost has
it from becoming as common as canning in many parts of the
II. FOOD SPOILAGE
WHY FOODS SPOIL
The rotting of fruits and vegetables has four major causes.
of these--molds, yeasts, and bacteria--are microorganisms
in great numbers in the air, soil, and water. They are the
causes of food spoilage. Enzymes, the other major cause of
food spoilage, are complex chemical substances found in all
cells, including the skins and flesh of fresh fruits and
vegetables. All preservation methods are aimed at preventing
these four agents from acting upon the food being preserved.
Molds are fungi that grow in warm, moist food. As the mold
it slowly consumes the food matter and brings about changes
the character of the food. This promotes the growth of other
microorganisms, eventually leading to complete food
The ideal temperature for mold growth is between 10 and
But at a temperature of 90[degrees]C or more, all molds and
yeasts are destroyed, except for a few rare, heat-resistant
Yeasts are another type of fungi. They act upon starches and
sugars to produce alcohol and carbon dioxide in the process
fermentation. The ability of yeasts to bring about fermentation
makes them very valuable organisms for the production of
beer, and wine. But they can cause food to ferment even when
is not desired, making the food unfit for consumption. This
of food spoilage can be prevented by reducing the moisture
of the food and raising or lowering the temperature beyond
the point required for yeast growth.
Bacteria are microscopic organisms that exist almost
Some bacteria are beneficial in that they help in the
of certain foods. For example, cheeses are made by the
certain bacteria on milk. Yet others are harmful because
contribute to food spoilage or produce poisons that can
serious illness and even death when ingested.
Some spoilage-causing bacteria can be killed at the same
that destroy yeasts and molds. Others must be heated to
temperatures as high as 116[degrees]C (240[degrees]F) for as
long as 20 minutes.
Keep in mind that cooking time lengthened as altitude
Where food preservation is concerned, the most dangerous of
bacteria is the one that causes botulism, a disease that is
fatal. Botulism-causing bacteria are naturally found in the
They thrive at moderate temperatures between 21[degrees] and
and 120[degrees]F) and can be easily introduced into food
utensils, soiled hands, or polluted water.
Botulism-causing bacteria can be destroyed by heating them
temperatures above boiling, at least 116[degrees]C
(240[degrees]F), for up to 20
minutes. It is important to note that this type of bacteria
survive, grow, and reproduce only in moist environments at
temperature, and in the absence of air. These are the exact
present in cans or jars where food is preserved by the
Properly canned food should be safe from botulism poisoning,
since both the poison and bacterium are destroyed by boiling
15-20 minutes. But if canned food should ever smell bad when
opened, it should be discarded to avoid being eaten.
Enzymes are organic compounds classified as proteins. They
as chemical catalysts in the cells of plants and animals and
are essential for normal growth and development. However,
fruit or vegetable is picked, its enzymes slowly stop
in their normal constructive way and start to break down the
plant tissue. If this action is not slowed or halted, the
will start to decompose and eventually spoil. It is
necessary to slow or stop the action of enzymes if fruits
vegetables are to be preserved successfully.
Enzyme action requires specific environmental conditions
the cell. These include narrow ranges of temperature,
and acidity. If any of these conditions is significantly
the action of the enzyme can be altered. For example, enzyme
action slows down at lower temperatures and increases at
slightly higher than normal. Some enzymes are destroyed
when plant tissue is heated above 54[degrees]C
(130[degrees]F). But many, including
some that contribute to browning of foods, may not be
at temperatures less than 90[degrees]C.
Besides temperature and moisture, two other factors affect
actions of food spoiling agents. The first is cleanliness,
act of working with food only under sanitary conditions.
involves cleaning all foods thoroughly before preserving
keeping hands and work area clean, and washing all equipment
in the preservation process in boiling water. If proper care
taken to keep everything very clean, food that is preserved
should keep for many months, remaining tasty and nutritious.
The second factor in controlling food spoiling agents is the
level of acidity of the food being preserved. Many of the
that bring about spoilage are very sensitive to acidity
and cannot live in highly acidic environments. These
agents can be controlled by increasing the acidity of the
Some fruits and vegetables are naturally acidic and
therefore are easier to preserve. Foods with acidity
of 4.5 or higher are considered to be low in acid. Beans,
mushrooms, pumpkin, white potatoes, etc., are some examples
common low-acid fruits and vegetables. On the other hand,
with acidity measurement of below 4.5 are regarded as strong
acid content. Some examples of high acid fruits and
are lemons, grapefruits, oranges, tomatoes, pineapples, etc.
is important to remember that varieties of the same food
have different ratings, as will identical varieties grown
III. FOOD PRESERVATION METHODS
The major methods of fruit and vegetable preservation are
pickling, drying, freezing, and curing (smoking or salting).
Whatever method of preservation you choose, keep in mind
that preserved food is only the next-best alternative to
food, not a replacement. Whenever a fruit or vegetable is
some of the food's nutritional value is lost, along with
some of its natural flavor, color, and aroma. For this
only the freshest and best quality fruits and vegetables
be used for preservation.
DRYING FRUITS AND VEGETABLES
Drying fruits and vegetables to retard or prevent spoilage
been practiced in many parts of the world for thousands of
Sometimes known as sun drying, this process involves laying
out in the sun until it becomes suitably dry, and then
it in containers for later use.
The basic principle behind drying fruits and vegetables is
remove between 80 to 90 percent of the water from the
thereby creating an environment that cannot support
life. Also, as water is removed from the plant's tissues,
sugar, protein, and other solutes increase in concentration.
is an additional factor that prevents the growth and
of microorganisms that may cause spoilage.
Several factors are important when considering drying as a
method for preserving fruits and vegetables.
o Dried fruits
and vegetables taste different from fresh,
frozen produce, even when they are reconstituted
by adding water
before they are eaten. People who are
not in the
habit of eating dried produce may need some
time to get
used to the different tastes.
o Exposing fruits
and vegetables to sunlight and heat will
result in the
loss of some vitamins. The longer the
the greater the loss of nutrients. This
partial loss of
vitamins from the produce can be reduced
pretreatment before drying and during the
o The various
nutrients in dried produce are highly concentrated
because of the
removal of most water from the
tissues of a
fruit or vegetable. In other words, 500 grams
of fresh apples
will have less nutritive content than 500
grams of dried
o Some fruits and
vegetables are easier to dry than others.
apples, apricots, coconuts, dates, figs,
plums are fruits that dry quite easily, while
bananas, breadfruit, and grapes are more difficult
to dry. Most
legumes are easily dried, as well as
potatoes, cassava root, onion flakes, and
the leaves of
various herbs and spices. On the other
asparagus, beets, broccoli, carrots, celery, various
pumpkin, squash, and tomatoes are more difficult
successfully. If done with the help of solar energy,
the drying of
fruits and vegetables is the least
food preservation methods.
o Produce that
has been dried sufficiently and stored in
containers stays fresh for about six months to a
on the storage containers used and the
type of produce
Methods of Drying
There are essentially three different ways to dry fruits and
vegetables. First and most basic is simple sun drying, where
produce is simply laid out in the sun to be dried. There is
pretreatment, and no special devices are used to assist the
process. The second method, solar drying, again makes use of
the sun's energy to help dry the fruits or vegetables.
this method, the produce is usually pretreated to prevent
and retard vitamin decomposition, and housed in a
special structure to aid the drying process. In the third
the produce is pretreated, and placed in a special drying
that uses commercial energy as its source of heat. All of
methods, although similar in some respects, do require
different materials and equipment, and therefore each will
Sun Drying. To sun-dry fruits and vegetables, you need a
flat surface, plenty of sunlight, and warm, dry air. This
has been used for thousands of years. But there are several
First, it takes a significant amount of time to completely
dry the fruit or vegetables. Second, while the produce is
it is exposed to airborne pollutants so that the final
will most likely not be very clean.
Solar Drying. On the other hand, solar drying overcomes
difficulties by placing the prepared produce on trays made
non-metal material, and then placing the trays in a
covered with glass or plastic. An example of a simple solar
is shown in Figure 1. Since a solar dryer depends upon
it costs essentially nothing to operate. However, solar
can be used only when sunlight is intense and the air
dry. Depending upon the types of fruits and vegetables being
dried and the temperature and humidity of the air, it can
from one to three days to completely dry produce.
Convection Drying. Both of these problems--the need for sunlight
and the slow drying time--can be overcome by using a
dryer, which does not depend on sunlight to dry the produce.
using a commercial source of energy such as electricity,
kerosene, the amount of heat entering the dryer can be closely
regulated and maintained at an optimum level
(30-60[degrees]C or 86-140[degrees]F),
thereby keeping drying time to a minimum. Moreover, since
fruits and vegetables are not exposed to sunlight during the
drying process, they retain more of their vitamins. A
kerosene-heated dryer is shown in Figure 2. One of the
of drying produce in a convection dryer is the high cost
of the energy required to operate the dryer.
Each of the preceding methods requires that the fruits and
undergo some form of preparation before being dried.
The equipment and materials needed to prepare produce depend
partially on the type of produce being processed, but
on whether pretreatment against discoloration, vitamin loss,
contamination is carried out. If the produce needs only to
dried so that it can be stored for a few months and the
the dried fruit is of little concern, very little equipment
be needed other than knives to slice and peel the produce.
On the other hand, if you want to store dried produce longer
one or two months, and you also want to prevent
retard vitamin loss while the produce is being dried, more
and materials will be needed. Such equipment includes:
o A medium to
large cooking pot (between 4 and 8 liters in
which to blanch the produce if needed;
o A large basin
or plastic bucket (about 10 to 20 liters in
which to soak the produce in an anti-discoloration
o Another large
basin or plastic bucket in which to soak the
produce in a
sulfite solution to combat vitamin loss and
o A wooden fume
box in which to sulfurize the produce, if a
method against vitamin loss is desired;
o Some sublimed
sulfur (99.5 percent pure) or a powdered
compound such as sodium bisulfite or potassium
if the produce will be sulfurized. However,
been found to cause allergic reactions in a
percentage of people and should be used with care.
o Some ascorbic
acid (vitamin C) or lemon juice to make the
anti-discoloration solution, if the produce will be pre-treated
containers (glass jars with tight-fitting lids
sturdy plastic bags also work well).
It is not difficult to construct a fruit and vegetable
care must be taken in selecting the construction materials. Be
sure to choose a wood that will not discolor the produce or
an off flavor to it. A local carpenter could probably advise
on most suitable woods. In addition, it is important never
any metal materials for dryer parts that will come in contact
with the fruits or vegetables. The acidic juices from some
and vegetables will corrode many metals, resulting in the
loss of the produce being processed and the slow
of some dryer parts.
The Drying Process
For most fruits and vegetables, drying is accomplished by
the air temperature to between 33[degrees]C and 60[degrees]C
to stimulate evaporation. This temperature is also the
ideal temperature for the growth and reproduction of many
microorganisms. As a result, both spoilage and loss
of vitamins may occur. To avoid this, it is essential to dry
produce as quickly as possible.
The rate at which fruits and vegetables dry depends on three
major factors. First, drying time is lengthened if the
has a very high water content, a small surface area, or a
skin. Second, drying time is increased if the relative
humidity of the air is high. In other words, if the air
holds nearly all the water it possibly can, it will be
take on much more, and the fruit will not be able to lose
moisture to become dehydrated. Third, as water evaporates
piece of fruit or vegetable, the air surrounding the food
saturated with water, causing the rate of evaporation to
down and eventually stop. To prevent this from happening and
keep the rate of evaporation as high as possible, it is
that air be kept in constant motion near the fruit to carry
the moisture-laden air. so, to increase the rate at which
and vegetables dry, force warm, dry air over produce being
to enhance the evaporation of water.
As with other preservation methods, it is essential to dry
fresh, undamaged fruits and vegetables. Following this rule
reduce the chances of spoilage during drying and storage.
the best produce is selected, it must be cleaned thoroughly
in most cases sliced, peeled, and cored, if necessary. Water
from produce during drying causes the produce to shrink
As a result, most fruits and many vegetables should not
be sliced too thinly. The best procedure for each type of
or vegetable can be determined either by the trial-and-error
method, or better yet, by following drying instructions for
specific fruit or vegetable as outlined in a drying guide
Pre-Treatment. Before placing fruits or vegetables on drying
trays, you may want to preheat them. In general, fruits and
make a better product if they undergo one or more of the
following pre-drying treatments: anti-discoloration,
sulfurization. Choice of pretreatment method, if any,
whether the benefits outweigh the costs.
The flesh of many fruits and vegetables turns a rusty, brown
color when exposed to air. To prevent sliced produce from
during drying, you need to soak the produce in an
solution. This solution can be prepared either by
dissolving one to three teaspoons of pure ascorbic acid
C) in about one cup of water, or by squeezing the juice from
several lemons into a cup of water. The amount of ascorbic
or the number of lemons needed for a specific type of fruit
vegetable can be determined by trial-and-error. This
should then be sprinkled over the produce soon after it has
peeled, pitted, and sliced. An alternative method is to pour
concentrate into a shallow basin half-filled with water. The
produce can then be soaked in the solution.
The skins of some fruits such as cherries, figs, grapes,
and other berries are not only relatively tough, they are
covered by a thin wax-like coating that inhibits drying. If
skins are not weakened and their wax coatings removed, the
rate will be significantly retarded. Both of these problems
be solved by quickly dunking the fruit first in boiling
then in cold water.
The final pretreatment process is sulfurization. Pretreating
fruits and vegetables with sulfur preserves their color. In
addition, it helps retain vitamins A, B1, and C and inhibits
growth of microorganisms in the produce during the initial
of the drying process. Note, however, that sulfurization is
since food safety depends mainly on how successfully the
produce is dried. There are two ways to sulfurize produce.
first method, which is relatively easy and quick, involves
the prepared fruit in a sulfite solution. To make the
add between 1.5 and 3.5 teaspoons (about 5-10 grams) of
sodium sulfite, sodium bisulfite, or potassium metabisulfite
four liters of water. Then, soak the produce in the solution
about 15 to 30 minutes.
The second method, which involves sulfurizing produce in a
box (Figure 3), is considered by some experts to produce
results. In this method,
a small amount of
pure powdered sulfur---about
(approximately 3 grams)
for every 500 grams of
produce--is burned in
the bottom of a large
fume box containing
stacked trays of fruits
and vegetables. Once
the sulfur has completely
vent holes in the box
should be sealed.
The produce remains inside the box for at least 20 or 30
before it is removed for drying. When removing the produce
the box, it is a good idea to stand so that the wind blows
from the box, thereby blowing the sulfur dioxide fumes away
you. The trays of produce should then be loaded directly
dryer for drying.
Care of Dried Foods. Each fruit and vegetable has a
appearance and texture when it is thoroughly dried.
fruit is sufficiently dried if no moisture is visible when
fruit is cut. Most recipe instructions for drying specific
and vegetables include a test to determine whether the
After the produce is dried, it should be left to cool (if
on the trays. Pour the dried produce into a large, open
container, preferably plastic or enameled metal. Cover the
with a porous cloth so that air can circulate, then place
the container in a warm, dry area with good air circulation.
Leave the produce in the container for at least 10 days,
at least once a day. This process, called conditioning, is
to distribute the remaining moisture evenly in the produce,
reducing the chance of spoilage, particularly from mold.
dried fruits and vegetables can be added to the container,
only during the first few days of conditioning.
After the produce is completely dried, it can be packaged
stored. It is important to let the produce cool completely
placing it in either plastic bags or glass jars. No special
are needed to store dried fruits or vegetables, but
lids are essential if the produce is to be kept in good
for any length of time.
The complete process of drying fruits and vegetables can be
into two major activities: (1) produce preparation and
pretreatment, and (2) drying. Produce preparation and
is more labor-intensive, but it can be done by one or two
people, if only a moderate amount of produce (10-50
processed. To reduce the amount of time and effort involved
this activity, all equipment and materials must be cleaned
the preparation and pretreatment of the produce begin. Since
several stages in this activity involve letting the fruit or
vegetables either soak in a solution or sit on a tray, it
be possible to set up an assembly line preparation system,
sufficient personnel and drying space were available. This
make the best use of the equipment and time available, and
enable a large amount of produce to be processed in a
short period of time.
Once the produce is in the dryer, relatively little work
be done, except to clean all the preparation equipment. If
produce is being dried with a solar dryer, it may be
periodically adjust the placement of the dryer to take
of the sun's position. If a convection dryer is used, it may
be necessary to periodically check the setting of the
element. It will also be necessary to check the contents
periodically (no matter which dryer is used) to see how the
is progressing. It may also be necessary to shift the trays
around in the dryer so that all the produce dries evenly.
Aside from blanching (quickly heating produce in boiling
both sun-drying and solar dryers use no commercial energy.
makes them not only inexpensive but useful in areas where
sources of energy are either very costly or not available.
Unlike solar dryers, convection dryers do require commercial
energy. The quantity needed depends upon the amount and type
produce being dried and the relative humidity of the
air. Generally, convection dryers either run on commercial
or they are heated by means of a stove or portable heater,
using gas or kerosene. Although the temperatures required to
dry fruits and vegetables are low, a significant amount of
will be consumed because of the long time required to heat
dryers. Convection dryers should probably be used only if
is an inexpensive and reliable supply of energy available.
The principal advantage of sun-drying is that it costs
since it uses solar energy, a free, limitless energy source
is also non-polluting. Food dried in the open, however, may
exposed to animals and insect pests unless, it is covered
some sort of cloth net (e.g., cheesecloth) or a fine-mesh
Although no costs are associated with the operation of a
dryer since it also uses energy from the sun, the principal
is the cost of either buying or building such a device.
This may be expensive initially, but since it can be used
after year with little need for repairs or maintenance, the
lifetime expense should be very low.
Compared to open sun-drying, solar dryers use the sun's
more efficiently, making it possible to dry produce in a
period of time.
If a convection dryer is used, there is the added
having to pay for the commercial energy required to run the
dryer. Energy costs may be offset, however, because the
does not require sunlight; it can be used at night or in
The only other probable expense, except for storage
will be the purchase of chemicals required to pretreat
This cost should be relatively low, however, since only
amounts are needed to process a fairly large quantity of
Advantages and Disadvantages
In general, drying fruits and vegetables is a very effective
to preserve produce. Dried produce has the advantage of
very light in weight and low in volume and therefore easy to
carry and store. The majority of dried fruits need no
preparation since they can be eaten in the dried state.
they are a highly concentrated source of nourishment and
since most of the water has been removed. Preparing dried
that can be eaten straight from the jar is usually a simple
of either adding boiling water and stirring, or cooking the
dried food until it is soft. This reconstituted produce can
be eaten as is or mixed with other foods.
The difference in taste between fresh and dried fruits and
may be a slight disadvantage in some cases, but in most it
should not be a problem. In fact, some dried fruits may be
flavorful than fresh fruit.
The time required to dry fruits and vegetables properly and
resulting loss of vitamins pose two major disadvantages that
to be carefully considered. Another important factor to
is the relative complexity of the pretreatment procedures
in preparing fruit and vegetables for drying. Some people
may also find it difficult to purchase the chemicals needed
this stage, and some may actually find it difficult to
or build a solar dryer. one final disadvantage of solar
that you are at the mercy of the weather. Successful outdoor
drying is possible only in regions with prolonged sunshine
Convection dryers have one major advantage over solar dryers
sun-drying and that is, drying can be carried out
for days. Unlike solar dryers, convection dryers are not
subject to daily and seasonal weather variations.
But convection dryers are not without any problem. The fuels
burned in convection dryers may cause other problems. Use of
may contribute to problems of deforestation. Coal may cause
fossil fuels are becoming increasingly expensive and are
not always available.
The equipment used to dry fruits and vegetables requires
more than simple cleaning. This maintenance task should not
ignored since clean equipment will reduce the risk of
the produce being dried. Special care should be taken with
the cleaning of the dryer. As fruits and vegetables are
their juices will undoubtedly drip onto the drying trays and
other parts of the dryer. If the trays are not cleaned after
use, microorganisms will quickly start to grow and multiply.
may contaminate any new produce placed on the trays. In
the corrosive nature of some juices may contribute to the
of the trays and dryer.
Maintaining a solar dryer involves checking the parts
for wear and tear. For example, make sure that vents are
not blocked. Plastic sheeting may need to be replaced once a
because it scratches easily and tends to become brittle and
cloudy from prolonged exposure to sunlight. The wooden
a homemade solar dryer will also need to be painted
to prevent the wood from weathering.
If a convection dryer is used, follow the maintenance
provided by the manufacturer. This will ensure that the
dryer remains in good working order for many years.
Alternatives to Home-Scale Drying
Forming a food-drying cooperative is a good way to defray
costs of processing fruits and vegetables. Such a
could possibly have several dryers built and then work as a
to dry everyone's surplus produce. This should allow more
to benefit from preserving fruits and vegetables and permit
drying of greater quantities of produce for each member.
A food-drying cooperative could easily become part of an
farmers' cooperative or women's organization. If successful,
cooperative could even rent its drying services to other
of the community, and in doing so pay for the equipment used
prepare and dry the produce.
If surplus fruits and vegetables cannot be preserved by
drying, or freezing, they most likely can be preserved by
This method of food preservation uses salt (either dry or
into a brine solution), vinegar, oils, and/or smoke to
environment that retards or prevents the growth of
Salt is the primary ingredient used in the curing process.
the ability to draw water out of the food, and when used in
concentrations inhibits the growth of many living organisms.
small concentrations, it provides the conditions that
growth and reproduction of lactic-acid-producing bacteria.
numbers of these bacteria increase, the amount and
of the acid they produce also rise. Eventually, the level of
acidity exceeds the tolerance of not only all harmful
but also the lactic-acid formers themselves.
Along with drying, curing is one of the oldest methods of preserving
produce. But cured produce, especially salted or brined
foods, can be preserved and stored for longer periods of
Although some fruits can be preserved by curing, this method
most commonly reserved for vegetables, since the flavor of
vegetables is fairly compatible with salt and vinegar. For
reason, this section of the paper will refer primarily to
curing of vegetables.
Curing is a relatively easy method of preserving produce,
since it does not require a lot of equipment or supplies, it
also rather inexpensive. Most cured vegetables are stored in
jars similar to those used in canning, and in some cases,
vegetables are heated in a water-bath canner to assure their
Equipment and Materials Required
Since it is easier to cure relatively large quantities of
it is helpful to have several large stoneware crocks or
some other large container that can hold at least 20 liters
material and that is unaffected by the action of salt or
acids. Since vegetables may be soaked in a brine solution,
will be necessary to have something to cover the vegetables
like a plate or a latticed wooden cover. A heavy weight will
also be needed to hold the vegetables under the brine
It may also be helpful to cover the crock with a large piece
cheesecloth to keep insects from fouling the curing
Standard kitchen implements will be needed to prepare the
for processing. The following items should be kept on
hand: measuring cups and spoons, knives, a cutting board,
spoons, large glass or enamel pans or bowls, a piece of
for straining, and a scale to weigh the vegetables. once
the curing process is finished, the produce will need to be
stored in jars similar to those used in canning. Some cured
vegetables also need to be boiled in a water-bath canner, so
these you will also need a large kettle.
If the vegetables are to be smoked, it will be necessary to
either buy or build a smoke box in which the vegetables can
hung and exposed to the thick curing smoke.
Each curing method and recipe will require different
and spices. For example, a fine-grained, iodine-free
salt will be needed for salt curing, while vinegar with an
acid concentration of between 4 and 5 percent will be needed
pickling, and wood and wood chips for smoking.
As with all preservation methods, only fresh undamaged
should be used in curing.
Once selected, it should be carefully
cleaned and either left whole or cut into the desired sizes
There are three main methods of curing produce:
Salting. Salting is the process of curing vegetables in
which inhibits the growth and action of spoilage-causing
Vegetables are salt-cured in one of two ways:
(salt plus juice drawn from the vegetables by the salt)
or brining (salt plus water).
The amount of natural juice in the
vegetables determines whether they need to be dry-salted or
Vegetables are brined whenever they do not release enough
natural juice to form the sufficient amount of liquid
Vegetables with plenty of natural juices, like corn,
green snap beans, greens, or cabbage, can be dry-salted.
Vegetables such as cabbage or white turnips are often
to give them a slightly sour flavor.
If you want to cure your
vegetables this way, simply use one-tenth the quantity of
needed for salting.
This comes to about 300 grams of salt for
each 12.5 kilograms of vegetables, although the ratio may
depending on the recipe being followed.
The smaller quantity of
salt stimulates the growth of the lactic-acid-producing
that not only cause fermentation but also prevents the
activity of harmful bacteria.
To increase the storage life of vegetables, pack them into
canning jars, and boil in a water-bath canner.
Pickling. Pickling generally makes use of vinegar in place
along with salt to cure vegetables, although some pickle
call for just brine or vegetable oil.
The procedure for pickling
is quite similar to brine-curing, with specific recipes
special spices, varying quantities of vinegar or salt, and
slightly different instructions.
Smoking. Although smoking is used primarily to cure meats
fish, it can also be used to preserve vegetables.
vegetables have a unique flavor and may be mixed with other
or eaten plain. The
easiest way to smoke vegetables is to slice
them if needed, tie the pieces together on a long piece of
string, and hang the vegetable braid over an open fire.
open fire is convenient only if the fire is also used to
keep the house warm.
Otherwise, it would be better to build a
simple smoke box (Figure 4) for outdoor use only.
Some vegetables need to be oiled, spiced, and slightly
before being smoked; others need no pretreatment.
After they are
smoked, they can be stored in cloth bags or glass jars.
You can build a simple smoke box from a barrel.
Dig the fire pit
at least 10 inches from the barrel and connect the two with
pipe or tile trench.
Curing is one of the easiest preservation methods to perform
because it requires a small amount of time and effort.
or two people are needed to preserve a relatively large
of produce. If all
the necessary materials are on hand, the
vegetables can be prepared, packed in crocks, and set aside
little as three to five hours, depending upon the quantity
this first stage of the process is completed,
it is necessary to examine the curing vegetables
remove any scum that may have accumulated.
Also, if the cured
produce will be kept for long periods of time, it will be
to pack the vegetables in jars and process them further by
heating them in a water-bath canner.
Besides being relatively quick and easy to do, curing also
very little, if any, commercial energy.
In the first stage of the
salt and pickling processes, only the blanching of the
consumes any energy.
If the cured vegetables are packed in jars
and processed in a water-bath canner, a little more energy
be needed. Finally,
if vegetables are cured by smoking, fuelwood
will be needed, but if the vegetables are hung over a fire
being used for another purpose no additional energy will be
used. Only a small
amount of wood is needed to run a smoking box,
since only a small smoldering fire is used.
After all is considered,
curing is one of the least energy-intensive preservation
The economic advantages of curing vegetables are essentially
same as those for other preservation methods.
may be one of the best methods to preserve a temporary
vegetables for a few months.
The raw materials needed are usually
inexpensive and can be easily acquired, and the process is
quick and easy to accomplish.
If the objective is to do
more than just cure vegetables--that is, if you want to put
vegetables through the canning process in the interest of
their storage life--the costs will rise because of the
energy use and the need for canning equipment and storage
Advantages and Disadvantages
Curing fruits and vegetables has four primary
advantages: it is
relatively inexpensive; it is quick; it is easy to do; and
turn an otherwise bland-tasting product into something more
addition, it is a viable alternative for people
who may not have the money or equipment to preserve fruits
vegetables any other way.
A major disadvantage of salt-cured vegetables is the need to
the salt out of them before they can be eaten.
Also, too much
salt in one's diet is not healthy, especially if other
problems exist. It
may also be difficult or even impossible for
people living in warm tropical regions to keep the curing
pickling crocks in a relatively cool place.
Because curing is a relatively simple preservation method,
is very little maintenance required other than routine
of all equipment.
For salt and brine curing, there is the need to
periodically remove the scum from the surface of the curing
and the replacement of the covering cloth whenever it
soiled. If the cured
produce is canned as necessary, jar lids
will need to be replaced as necessary, and the jars
inspected for any chips or cracks.
Alternatives to Home-Scale Curing
If fruits and vegetables are to be smoked, it might be less
expensive and more convenient for a group of people to build
smoke box that everyone could use rather than for each
build its own.
Additionally, some money may be saved if people
purchased supplies and materials in large quantities as a
instead of buying smaller quantities as individuals.
IV. CHOOSING THE
PRESERVATION METHOD RIGHT FOR YOU
Because of the vast variety of fruits and vegetables grown
one locality, it is unlikely that only one of the four
techniques--canning, freezing, drying, or curing--would be
the only suitable method.
Therefore, a food preparation system
should be developed that matches your particular
a system should consist of a combination of methods that are
appropriate for the different types of fruits and vegetables
be preserved. It
should also meet the available resources and the
specific needs of the individuals involved.
The two most dominant constraints affecting the type of
system that can be used are the availability of capital
and the cost and availability of a constant supply of
constraints essentially group the four different
preservation methods into three primary systems:
commercial energy and money are readily available,
comprising all four methods, can be used.
sufficient energy but only a moderate supply of
available, system two, comprising canning,
curing, can be used.
3. Where energy is
either lacking or very expensive, and
money is in
short supply, system three, comprising drying
and curing, can
Secondary constraints are also important for determining
preservation method or methods can be used.
For example, the
following questions should be addressed in deciding which of
four methods or systems to use.
The brief discussion following
each question points out many factors that must be
before a decision can be reached.
o How long will
the food need to be preserved? If relatively
preservation is desired (six months to a year),
preparation is an important concern, then
freezing may be
the best choice.
o How much food
needs to be preserved? If only a relatively
small amount of
food needs to be preserved, then freezing
may be the best
choice. On the other hand, if
to be preserved
are larger than the space available in the
canning, drying, or curing may be better choices.
o Are the proper
jars for canning available along with other
equipment? If so, and large quantities of food
need to be
preserved, then canning may be the best choice.
o What fruits and
vegetables need to be preserved? Some
vegetables respond better to specific preservation
Some may turn to mush if frozen; canning may
have the same
effect on others. To decide which
be most suitable for a specific vegetable,
it is best to
consult one of the books listed in the
or seek help from the government agricultural
office, a high
school, or a university.
o Is a special or
unique taste treat desired? If so, then
or pickling may be the best choice, since
both are used
to make specialty foods.
o How much
previous experience with food preservation do you
have? If the
answer is little or no previous experience,
then maybe the
least complicated method should be tried
It is a good idea to master this method
more complicated and difficult procedures.
o What is the
weather like during peak harvest time? If it
is sunny, dry,
and windy, then preserving with a solar
dryer may be a
good choice, provided it also meets all
o How many people
are available to help with a large
fruits and vegetables? If only one or two
will be involved in food preservation, it
might be best
to select a method, like freezing or curing,
that can be
done in the shortest amount of time with the
preservation method do you like best? Trying out
methods on a variety of fruits and vegetables
will enable you
to develop your own preferences. At
point, it is
important to note that determining a preservation
careful consideration of many variables
that make up a
situation. In most cases, though,
there is a
significant amount of leeway open to the individual
the appropriate preservation method.
Anderson, Jean. The
Green Thumb Preserving Guide. New York:
& Company, Inc., 1976.
The Complete Food Preservation Book. New York:
Company, Inc., 1978.
Burch, Joan, and Burch, Monte.
Home Canning and Preserving.
Virginia: Reston Publishing Company,
Central Food Technological Research Institute.
Preservation of Fruits and Vegetables."
The Wesley Press, 1981.
Hertzberg, Ruth; Vaughan, Beatrice; and Greene, Janet.
Brattleboro, Vermont: The Stephen
Preserving Summer's Bounty. New York:
and Company, Inc.,
Levinson, Leonard Louis.
The Complete Book of Pickles and
York: Hawthorn Books, Inc., 1965.
Schuler, Stanley, and Schuler, Elizabeth Meriwether.
the Fruits of the
Earth. New York: The Dial Press, 1973.
Stoner, Carol Hupping, Editor.
Stocking Up: How To
Foods You Grow,
Naturally. Emmaus, Pennsylvania: Rodale
Groppe, Christine C., and York, George K.
"Pickles, Relishes, and
Quick, Easy, and Safe Recipes."
Leaflet No. 2275.
California: University of California,
Etchells, John L., and Jones, Ivan D.
"Preservation of Vegetables
by Salting or
Brining." Farmers' Bulletin No.
U.S. Department of Agriculture, 1944.
"Canning and Bottling as Methods of Food Preservation
Food Preservation in Bangladesh. Dacca,
Women's Development Programme, UNICEF/DACCA,
Stiebeling, Jazel K.
"Solar Food Preservation."
Illinois Institute of Technology, 1981.
U.S. Department of Agriculture.
Human Nutrition Research
"Home Canning of Fruits and
D.C.: U.S. Department of Agriculture,
VI. SUPPLIERS AND
Dixie Canner Equipment Company
786 East Broad Street
P.O. Box 1348
Athens, Georgia 30601 USA
Food Preservation Systems
P. O. Box 188
New Windsor, Maryland 21776 USA
National Drying Machinery Co.
2705 N. Hancock Street
Philadelphia, Pennsylvania 19133 USA
Proctor & Schwartz, Inc.
251 Gilbralter Road
Horshan, Pennsylvania 19044 USA