Handling and
Preservation of Perishable Crop Produce
By Juliet
Danboyi Lassa
Definition and characteristics of
Perishable
Any product that degrades in quality over a short time is
considered perishable. Perishable goods need to be handled in a timely, careful
and efficient manner; they need to get from producer to consumer while still in
useable condition. Any business dealing in perishables needs a cost-effective
method of transporting perishable products before they spoil.
The term perishable
products as applied in this paper will focus on only on fresh fruits and
vegetables. These items need to be shipped under strictly-controlled
temperature and storage conditions. Dried, canned or otherwise preserved foods
are not considered perishable and therefore do not require such strict shipping
and handling conditions. They can be stored for longer periods of time and at
warmer temperatures since there is low risk of spoilage. Some shipping
companies will handle live plants and animals as perishable goods as well.
Harvesting and pre-processing
When the vegetable are maturing in the field they change,
their form day to day. There is a time when the vegetable will be at peak quality
from the stand-point of color, texture and flavor. After the vegetable is
harvested it may quickly pass beyond the peak quality condition. In –produce
heat is generated when large stockpiles of vegetables are transported or held
prior to processing. Since the heat further deteriorates the vegetables and catalysis
of micro-organism growth, the harvested vegetables must be cooled if not
processed immediately. However, cooling only slows down the rate of
deterioration, it does not prevent it. Each vegetable has its optimum cold
storage temperature which may be between about 0-10oC (32-50oF). The
continual loss of water by harvested vegetables due to transpiration,
respiration and physical drying of cut surfaces result in wilting of leafy
vegetables, loss of plumpness of fleshy vegetables and loss weight loss.
A 10°C
increase in temperature will cause fruit and vegetables to deteriorate twice as
fast, as well as encouraging disease organisms to grow twice as fast as well.
This is why it is important to remove field heat from the produce as quickly as
possible after harvest. In many processing plants it is a common practice to
process vegetables immediately as they are received from the field. Cooling of
vegetable in the field is common practice in some areas. Liquid nitrogen-cooled
trucks are best used for providing transportation of fresh produce to the
processing plant or directly to market.
|
Products
|
temperature
range(oc)
|
Approximate
storage life(weeks)
|
Approximate
post-storage life (days) at 21o to 34oc.
|
|
Bananas
|
11-13
|
3
|
2-4
|
|
Mango
|
5-7
|
4-6
|
2-4
|
|
Green
beans
|
0-2
|
7
|
2-4
|
|
Lettuce
|
0-2
|
12
|
6
|
|
Pineapple
|
8-10
|
6
|
4-6
|
|
Guava
|
8-10
|
4
|
3
|
|
Oranges
|
5-6
|
18
|
4-6
|
|
Onion
|
0-2
|
2
|
4-6
|
|
Tomatoes
|
6-7
|
3
|
4-6
|
|
Peppers
|
2-3
|
2
|
6
|
Preservation methods for perishable
goods
Ø
Freezing:
Freezing is an excellent way to preserve fresh vegetables at
home. Freezing does not sterilize food; the extreme cold simply retards growth
of microorganisms and slows down changes that affect quality or cause spoilage
in food. The quality of frozen vegetables depends on the quality of the fresh
products and how they are handled from the time they are picked until they are consumed.
It is important, also, to start with high quality vegetables because freezing
will not improve the product's quality. Fruits
and vegetables are best kept at low temperature but not directly in contact
with the cooling surface. They should be packaged before placement in the
freezer. They can be blanched and stored in air tight containers before placement
in the freezer.
Selecting Freezer Containers
Before preparing vegetables for
freezing, appropriate containers should be provided. The selection of
containers depends on the vegetable being frozen. Containers should be
moisture-vapor resistant, durable, easy to seal and should not become brittle
at low temperatures. Containers suitable for freezing vegetables include
plastic freezer containers, flexible freezer bags and their protective
cardboard cartons, or glass canning jars. Some household containers are not
recommended for freezing. Regular (not canning) jars break too easily at
freezer temperatures.
Preparing the Vegetables
Use vegetables at peak flavor and
texture for freezing. Wash vegetables thoroughly in cold water, lifting them
out of the water as grit settles to the bottom of the washing container. Sort
according to size for blanching and packing.
Types of Pack
Two
basic packing methods are recommended for frozen vegetables
· dry pack and tray pack.
Dry Pack
– Place
the blanched and drained vegetables into meal-size freezer bags or containers.
Pack tightly to cut down on the amount of air in the package. Leave 1⁄2-inch
headspace at the top of rigid containers and close securely. For freezer bags,
fill to within three inches of the top, twist and fold back top of bag; tie
with a twist or rubber band about 1⁄2- to 3⁄4-inch from the food. This will
allow space for the food to expand.
Provision
for headspace is not necessary for foods packed tightly in containers.
Tray Pack
– Place
chilled, well-drained vegetables in a single layer on shallow trays or pans.
Place in freezer until firm, then remove and quickly fill bags or containers. Close
and freeze immediately. Tray-packed foods do not freeze in a block, but remain
loose, so the amount needed can be poured from the container and the package
reclosed.
Pre-freezing
Handling of Vegetables
|
Vegetable
|
Preparation
|
Blanching Time
|
|
Spinach
|
(in boiling water unless
otherwise stated)
|
|
|
Green Beans
|
Select young tender beans. Wash or wax and remove ends. Leave whole,
slice or cut into 1-inch to 2-inch lengths. Blanch, cool and drain. Package,
seal and freeze.
|
3 minutes
|
|
Peppers:
|
Hot Wash and remove stems. Package, seal
and freeze.
cut in half, remove stems and
Halves,
cut into 1⁄2-inch strips or
rings
For
Use in Uncooked or Cooked Foods
Package, seal and freeze.
|
3 minutes
2 minutes
Do not blanch
|
|
Tomatoes
Quarter ripe tomatoes.
|
Cut into quarters or
eighths. Cool, package, seal and
freeze.
Remove stems, Cover and cook until tender).
Cool, package, seal and freeze.
|
5 to 10 minutes.
10 to 20 minutes
|
Ø Salting
One simple relatively low cost
method of preservation of fruits & vegetables is by pickling. It is a
process of fermentation, using brine (salt in water).
PICKLING
PROCESS
Pickles should be preserved in sterilised glass jars. Sterilisation of glass jars by boiling can easily be carried out at household level as follows:
B. Selection and preparation of vegetables
and fruits
Crispiness is highly desirable in
pickles. This is achieved by using high quality fresh crops. Green vegetables
or fruits can be pickled singly or assorted.
· Select green fruits or fresh vegetables
which are in good condition.
· Vegetables & fruits may be kept whole,
grated or cut into pieces as desired.
· Wash them thoroughly. They can be scrubbed
with a soft brush or rubbed with the palms of the hands. However care should be
taken to avoid bruising.
· Dry them with a clean cloth or kitchen
tissue paper. It is important to use dry produce.
C. Fermenting medium:
Brine (salt solution)High % brine is suitable for preservation of large quantity of vegetables and fruits which can be processed into value added products such as sauces and other processed foods. Low % brine pickling are suitable for vegetables and fruits which can be used in stews, fried rice noodles, gravies, sweet and sour sauces, salads and similar recipes. These are usually preserved in small quantities and are not stored for long period.
Pickling in brine
Pickling can be carried out in: -
(a) Low percentage (3 - 5%) brine
(b) High percentage (10%) brine
|
Brine
|
||||
|
|
Low % brine
|
High
% brine
|
||
|
Period of
fermentation process
|
1 week
|
3-4 weeks
|
2-3 days
|
1 week
|
|
Suitable
crops
|
Bananas Eggplant Green
beans Lettuce Pineapple Cucumber Oranges Spinach Tomatoes Peppers |
Bananas Eggplant Green beans Lettuce Pineapple Cucumber Oranges Spinach Tomatoes Pepper |
Bananas Eggplant Green
beans Lettuce Pineapple Cucumber Oranges Spinach Tomatoes Peppers |
Bananas Eggplant Green beans Lettuce Pineapple
Cucumber Oranges Spinach Tomatoes Peppers |
|
Shelf life
in months
|
3-4
|
6-8
|
12
|
6-8
|
(a) Pickling in low percentage (3 - 5%) brine
Ingredients:
1 kg of
vegetables or fruits
30 - 50 g
of salt
1 L of
water (boiled and cooled)
Once produce to be pickled has been prepared as at (B)
(i) Pack vegetables or fruits into a wide mouth sterilised container such as a glass jar or stainless steel container leaving a head space of 7 to 10 cm.
(ii) Prepare a 3 - 5 % salt solution by dissolving 30-50 g of salt in one litre of water. When the salt is completely dissolved, cover the produce with the brine solution. Place a heavy object (e.g a glass plate) on top to weigh down the vegetable below the brine level to ensure complete fermentation.
(iii) Cover the jar with a thin cloth for aeration and to prevent contamination.
(iv) Allow the preparation to ferment for a week in a moderately warm room (21 - 27ºC). Bubble formation indicates fermentation. Check for bubbles by tapping on the side of the container. If no more bubbles rise to the surface, fermentation has been completed.
(v) Remove any scum formed on top of the brine as it would affect its acidity and cause the product to spoil.
(vi)Once fermentation is completed, remove the cloth and close tightly the container.
(b) Pickling in high percentage (10%) brine.
Ingredients:
1 kg of vegetables
100 g of salt
1 L of water
The same procedures as above should be followed with the following modifications:
The concentration of the salt solution in step (ii) is higher and is prepared by dissolving 100g of salt in 1 litre of water.
The preparation in this case is left overnight to ferment. In the morning, another 100g of salt is added to every kg of vegetables/fruits used to maintain the salt solution at 10% concentration.
After one week and thereafter every week, 50g of salt is further added. This process can last 3 - 4 weeks until complete fermentation.
Note: Before use, pickles can be desalted through several washing or by soaking in plenty of water if desired.
Ø Drying Fruits and Vegetables:
· Step
1- Begin by washing and drying your
fruit or vegetable of choice. Thoroughly dry and slice your produce;
fruits and veggies that are cut into uniform thin slices dry best. A sharp
knife and steady hand is fine for this, but you may also find a mandolin slicer
or food processor useful. Make sure to discard any stems and woody or rotten
portions.
· Step
2 for Fruits- In place of a coat of sulphites, the
fruit slices still need something that is going to help preserve them and
extend their shelf life. I find what works best is a dip in ascorbic acid.
This is much safer, since ascorbic acid simply comes from vitamin C. Immerse
your fruit slices and let them soak for 3 minutes before removing them and
patting them dry with paper towels.
· Step
2 for Vegetables- Drying veggies is different from
drying fruits because dried fruits obtain a leathery texture, whereas dried
veggies become crisp. They contain less acid than fruits, so in a dried state
they become brittle instead of chewy. To prepare veggies to be dried, they
need to be blanched. This stops the enzyme action that causes loss of colour
and flavour during storage. Move
immediately onto the next step, as it is best to complete step #3 while the
veggies are still warm to the touch.
Crops and required blanching time
|
Suitable crop
|
Required
time for blanching
|
|
Tomatoes
|
1 min
|
|
Green beans
|
3 mins
|
|
Cucumbers
|
3 mins
|
· Step
3- Create your own drying trays by placing
cake cooling racks (the ones that look like little metal grids) on top of some
cookies sheets. These racks will allow for sufficient air flow, which is
imperative. Next, set your oven to 140 degrees. This is likely the lowest
setting your oven has. During the entire drying process, you will need to keep
the door to your oven ajar (open).
· Step 4- It will take between 4 and 12 hours for your
fruits and vegetables to dry, depending on what you are drying and how thinly
it is sliced. Check them after 4 hours. Dried fruit is done when it feels
dry and leathery to the touch, but still flexible. Dried vegetables are
done when they are brittle, as they will shatter if you hit them with your
hand.
· Step 5 for Fruits- After being oven dried, vegetables can
simply be cooled and stored in an airtight container. However, fruits must be
conditioned. Remove your fruits from the trays and place them in a tight
sealing jar. They will need to remain in this jar for the next 10 days. Every
day, give the jar a good shake. This will help to distribute the remaining
moisture in the fruit, giving it the desired texture. After those 10 days, you
can remove your dried fruit from the jar to store or consume it.
- Waste arising from overproduction - Producers of perishable goods should plan production schedules and volume according to customers demand. Fruits and vegetables are also vulnerable to waste due to overproduction.
- Waste arising from defects – When receiving mango for production, it passes through a sorter. Each size category are priced differently, smallest having the cheapest price. Then it passes again on a long conveyor belt. A series of quality assurance staffs are lined and removing defective mangoes. Defective mangoes are not fit for processing (not always true). Those are just waste if not sorted out properly.
- Waste arising from delayed processing – Time is money so it should be spent wisely. Office hours are 8am-12pm and 1pm to 5pm. A dishonest worker usually works under-time or takes a long rest during break-time. Every hour unwisely spent is considered as waste from operation. If the expected output of one employee is 500 pieces, then skipping work hours can reduce it down to 300. The 200 pieces deficits are losses. Delay causes spoilage of vegetables.
- Waste arising from transport – the nature of our Nigerian roads makes it very difficult to transport perishable goods such as tomato, oranges, mango from one part of the country to another. Other losses caused by transport are inadequate handling, improper packaging, damaged shelves and lack of cold feature.
- Waste arising from processing – There are natural losses in processing. Examples: peels of mango, pineapple and banana. Waste product can still be used. For example, converting banana peels to wine and vinegar.
Health Factors to Be
Considered During Handling and Preservation of Fruits and Vegetables
The following actions are not allowed in food processing
area:
1) Talking
2) Coughing and sneezing
3) Spitting
4) Eating, drinking and
5) Leaving the post of duty.
Insisting on doing the
mentioned actions could result in product contamination and spoilage
Conclusion
Handling and Preservation of fruits and vegetables to maintain its nutrients and
flavors are simple but difficult if the processes are not known and followed
strictly. Such information should be disseminated to women of all classes and
levels to improve the quality and hygiene of preserved fruits and vegetables.
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