Department:Agriculture

Solar drying of fruit and vegetables


AP Mnkeni, P Soundy and MO Brutsch


Contents

Solar drying of fruit and vegetables

This publication is about

Advantages of solar drying

Methods of drying

Advantages of solar dryers

The drying process

Packaging and storing

Specific products

Fruit

Vegetables

Recipes for dried fruit and vegetables

 



Solar drying of fruit and vegetables

For thousands of years people have sundried fruit and vegetables to preserve for leaner times. New technologies brought changed techniques, but at present the increasing demand for healthy, low-cost natural foods and the need for sustainable income, are bringing solar drying to the fore as a useful alternative for surplus products.

Save for tomorrow what you do not need today!







This publication is about



Advantages of solar drying

Food in the cupboard for later use increases household food security.

It creates employment opportunities and a sustainable income.

  • Dried products improve family nutrition because fruit and vegetables contain high quantities of vitamins, minerals and fibre.

  • For diabetics dried fruit prepared without adding sugar is a healthy choice instead of desserts.

  • Dried fruit can be used in stews, soups and casseroles or enjoyed as snacks. It can also be added to cereals for breakfast or used in making ice cream and baked products.

  • It improves the bargaining position of farmers. Sometimes farmers sell at very low prices during the harvest season because they cannot store or preserve their surplus products.

  • People are encouraged to establish their own gardens.

Methods of drying

Sun drying

Drying in the sun is very economical. You only have to spread the produce on a suitable surface and let it dry in the sun.

Disadvantages

Somebody has to stay at home throughout the drying period to chase off domestic animals, to remove the produce when the weather becomes too windy and dusty, or when it rains.

The dried product is often of poor quality as a result of grit and dirt.

The product is often unhygienic as a result of microorganisms and insects such as flies.

 

Solar drying

The technology and capital required to dry fruit and vegetables by solar dryers is basic and the entire operation can be completed in most kitchens. The structure can be very basic, e.g. a box frame covered with plastic sheeting.

Advantages of solar dryers

The drying process

Precautions

  • Cleanliness and hygiene are very important in the processing of dried fruit and vegetables.

  • To minimise the possibility of contamination, any person who is unwell or has infected wounds or sores, is ill with a gastric disorder or suffering from diarrhoea MUST BE EXCLUDED from the processing operations.

  • All cuts have to be covered with waterproof dressing.

  • Raw materials contaminated by moulds must not be used in processing.


Predrying treatments

Selection

Washing

Blanching

Before drying, all vegetables should be blanched in steam to halt the action of enzymes. However, blanching of fruit is optional. Steam blanching is recommended because it prevents the loss of some nutrients and the products being dried from adhering to each other. Do not underblanch, because the enzymes will not be inactivated totally and the dried vegetables will deteriorate during storage.

Procedure

Pour several centimetres of water into a large cooking pot that has a close-fitting lid. Heat the water to boiling and place over it, high enough to keep clear of the water, a wire rack or basket holding a layer of the vegetables (not more than 5 cm deep). Cover and let the vegetables steam for half the required time, then test to make sure all pieces are reached by the steam.

A sample from the centre of the layer should be wilted and feel soft and heated through when it has been properly blanched.

Peeling

Cutting and slicing


Dryers

A basic box-type low-cost solar dryer can be constructed at home or by village artisans. It is made of wire-mesh trays in a wooden framework surrounded by a clear plastic sheet. The solar cabinet dryer type has a surface of 10 m2 and is capable of drying 20 to 35 kg of fresh produce (depending on commodity) over a period of 3 to 4 days. Smaller portable models of the dryer can be constructed depending on available funds for the dryer, construction and the purpose of drying (home consumption or marketing).

 

For further information
available on solar drying
contact
Mr MD Brutsch at the University of Fort Hare
Tel: (040) 602 2131
Fax: (040) 653 1730
E-mail: mbrutsch@ufh.ac.za





Tray loading

Dryer loading

 


It is important to keep flies and other insects from
entering the cabinet and off the fruit because of the risk of contamination.

Drying

Unloading the dryer

Packaging and storing

Packaging should be carried out immediately after unloading and cooling because the dried slices will reabsorb moisture and be susceptible to attack by insects and other pests.

Proper storage should take place in the absence of moisture, light and air.

Specific products

Fruit


Mangoes

Select firm, ripe mangoes
Wash with clean water
Peel
Cut into slices (2
- 3 mm thick)
Arrange on trays for loading into the dryer
Test for dryness: slices should be pliable, without sticking together

 

Pineapples

Select firm, ripe fruit
Wash
Cut off the top and base
Peel
Cut into slices (2
- 3 mm thick)
Arrange on trays ready for loading into dryers
Test for dryness: slices should be pliable, without sticking together

 

Bananas

Select good-quality fruit
Wash
Peel and remove the 2 tips
Slice into pieces (5 mm thick)
Arrange on trays for loading into dryer
Test for dryness: slices should be pliable, without sticking together

 

Apples

Select good-quality fruit
Wash
Peel
Split
Core
Cut into regular slices (2 - 3 mm thick).
As you cut, dip the slices into lemon juice to retain the colour temporarily
Steam blanch for 5 minutes and remove excess moisture
Arrange slices on trays ready for drying
Test for dryness: leathery, no moisture when cut and squeezed



Cactus pears (prickly pears)

Select large ripe fruit
Using a clean cloth remove the glochids, dust and dirt
Wash and cut away both ends
Peel as thinly as possible
Remove the soft peel and keep to one side
(It is easier to remove if the fruit is cut in half) 
Juice the flesh and sieve
(This can be done by using a blender or a mixer)
Boil the juice
Add the soft peel into the juice together with sugar, lemon juice and salt. Cook for about 1 hour





For 1 kg peel, you need 750 g sugar, 65 ml lemon juice and a pinch of salt
Pour onto a sieve and allow to drain
Allow to cool
Arrange the pieces on trays and load into the dryer
Test for dryness: slightly sticky


 



Vegetables

Pumpkin leaves

Select fresh, tender leaves
Peel off the hairy outer skin
Wash in clean water
Steam blanch for 3 to 5 minutes
Place on trays ready for drying
Test for dryness: crumble easily

 

Tomatoes

Select fresh ripe fruit
Wash in clean water
Slice into regular pieces (vertically)
Arrange the pieces on the tray for drying
Test for dryness: a handful will spring apart after squeezing

 


Cabbage

Peel off the outer leaves
Wash in clean water
Cut the cabbage in two
Core
Chop into thin strands
Steam blanch for 5 to 8 minutes
Arrange on trays for drying. Spread evenly, not more than 1,5 cm deep.
Test for dryness: extremely tough ribs, the thin edges crumble.

Amaranthus sp.

Select young, tender and crisp leaves
Wash
Place loosely in a steaming basket and steam for 3 to 5 minutes or until well "wilted"
Spread sparsely on drying trays, keeping overlaps to a minimum
Test for dryness: crumble easily



Sweet potatoes

Select firm, smooth potatoes
Wash
Steam in small quantity of water until the potatoes are just tender (30-40 minutes)
Peel
Slice into pieces (3-5 mm) or shred
Arrange the pieces on trays for drying
Test for dryness: slices extremely leathery, not pliable, shreds are brittle


Carrots

Choose crisp, tender carrots without woodiness
(Not necessary to peel good, young carrots)
Steam until cooked through but not mushy (about 15-20 minutes depending on size)
Remove whiskers, tails and crowns
Cut into rings (2-3 mm) or shred
Arrange on trays for drying
Test for dryness: slices very tough, but can be bent. Shreds are brittle



Beetroot

Choose small ones without woodiness
Leave 1 cm of the tops (they will bleed during precooking if the crown is cut)
Steam until cooked through (20-30 minutes)
Cool, trim roots and crowns and then peel
Shred with a coarse blade of a vegetable shredder (slices are not recommended because they take a long time to dry)
Spread thinly on trays for drying
Test for dryness: shreds are brittle

Pumpkin

Deep orange varieties with thick solid flesh make the best product
Cut in half (manageable pieces for peeling) and remove seeds and all pith
Shred with the coarse blade of a vegetable grater
Place in shallow layers in the basket, steam for 6 minutes
Arrange shreds on drying trays ready for drying
Test for dryness: shreds are brittle






Green beans

Select young and tender stringless beans
Wash thoroughly
Steam for 2 to 3 minutes
Cut into short pieces or lengthwise
Arrange on trays for drying
Test for dryness: extremely tough ribs, the thin edge crumbles



Herbs

This category includes celery leaves as well as other aromatic herbs such as parsley, basil, sage, tarragon, etc. All these should be dried at temperatures not exceeding 40 C. (If it exceeds this temperature oils valued for flavour will be lost)

For best products

Water the herbs well the night before harvest.

Harvest on a sunny morning soon after the dew has dried and choose plants that are reaching flowering stage.

Harvest with sufficient stem, then strip off tougher leaves growing lower than 10 cm on the stalk.

Hold in small bunches by the stem and swish the leaves through cold water to remove any dust or soil.

Shake off the water and lay on absorbent towelling to allow all surface moisture to evaporate.

Cut off the handle stems and spread the leafed stalks one layer deep on the drying trays.

Put the dryer under a shade and cover the unventilated sides with a cloth to reduce the light on the herbs.

Turn the herbs several times to ensure even drying.

Test for dryness: crumble readily.




Recipes for dried fruit and vegetables

Cooking of dried vegetables

Water removed during drying must be replaced either by soaking, cooking or a combination of both. Root, stem and seed vegetables should be soaked for half an hour to 2 hours in sufficient cold water (only cover) until nearly restored to their original texture. Never supply more water than they can take up and always cook in the water they have been soaked in. Greens, cabbage and tomatoes do not need to be soaked. Add only sufficient water to keep covered, then simmer until tender.

 





Amaranthus (morog) croquettes

100 g amaranthus
4 tablespoons gram flour or bread flour
1 tablespoon masala
2 eggs, beaten
salt
pepper

Mix the amaranthus with gram flour or bread flour, masala, egg and seasoning
Leave in a cool place to firm up a little (preferably a refrigerator)
Form the firm mixture into cakes or croquettes, roll in the flour and fry briefly both sides until uniformly golden

 



Amaranthus or cabbage relish

100 g dried amaranthus or cabbage
1 large onion (chopped)
1 large tomato (chopped) or 1 tablespoon tomato paste
1 green pepper (seeded and chopped)
1 carrot (grated)
2 tablespoons cooking oil
cup coconut milk or skim milk
salt
pepper

  • Heat the cooker plate or coil until hot

  • Add onions and fry until glazed

  • Add the carrots and green pepper and stir for 2 to 3 minutes

  • Add the tomatoes or paste and keep stirring for another 2 to 3 minutes

  • Add the amaranthus or cabbage and coconut milk or skim milk. Allow to simmer at low heat for 5 minutes, stirring occasionally

  • Add salt and pepper to taste

  • Allow to simmer for 2 to 3 minutes while stirring occasionally and then remove from heat

  • Serve with stiff porridge or rice


Pumpkin fritters

1 cup dried pumpkin
125 ml ( cup brown bread flour or wholewheat flour
10 ml (2 tablespoons) baking powder
60 ml ( cup) brown sugar
2 eggs, beaten
pinch of salt

  • Soak pumpkin in enough water to cover and let stand for 1 hour

  • Mash the pumpkin well

  • Mix pumpkin, flour, baking powder, salt and pepper together

  • Stir in beaten eggs and drop spoonfuls onto a light-oiled pan, over medium heat

  • When bubbles appear, turn and cook on the other side

  • Serve with a sprinkling of cinnamon and sugar



Banana walnut loaf

200 g chewy banana chips
pinch of salt
1 level teaspoonful bicarbonate of soda

50 g soft margarine
1 egg, beaten
50 g walnut, chopped
250 g selfraising flour
teaspoon vanilla essence

  • Put banana chips, salt, bicarbonate of soda and soft margarine into a bowl

  • Pour over 2 cups of boiling water to melt the margarine and allow to cool, then blend roughly

  • Mix the egg, walnut, flour and vanilla essence and add the banana mixture and mix to a smooth malleable consistency

  • Bake the dough in a greased 1 kg-loaf tin in the centre of the oven at gas mark 4 (180 C) for approximately 50 minutes

  • Once out of the oven allow to cool for 10 minutes before turning over

  • Serve slices buttered or toasted


Pineapple and chicken wings

150 g sundried pineapple
1
/3 cup butter or margarine
cup tomato sauce

1 small clove of garlic (crushed)
1,5 kg chicken wings separated
1 cup fine, dry breadcrumbs
1
/3 cup syrup
1 tablespoonful of lemon juice
teaspoon ground ginger
1 tablespoonful of Worcestershire sauce

  • Soak the pineapples in 1 cup water for 1 hour and cut them into small chunks

  • Heat oven to 200 C

  • Put butter or margarine in a large shallow baking pan and set in an oven to melt

  • Combine tomato sauce and garlic. Brush the mixture on separate wings, then roll in breadcrumbs to coat all sides

  • Place in the baking pan turning them over in the butter

  • Bake for 30 minutes

  • Remove pan from oven and turn the chicken wings

  • Drain pineapples, measuring the juice (about a 1/3 cup liquid is required)

  • Combine the liquid with syrup, lemon juice, ginger and Worcestershire sauce and pour over wings

  • Bake for about 30 minutes or until chicken is very tender, adding pineapple chunks in the last 5 minutes

  • Remove from oven and serve with rice

Sundried mango ice cream

100 g sundried mango
White wine or tropical juice
3 eggs, separated
140 g castor sugar
l double cream, lightly whipped

  • Soak mango in white wine or, for non-alcoholic alternative, in a tropical juice

  • Use enough liquid to cover the fruit. After hour of soaking, puree fruit with soaking liquid

  • Whisk egg whites until stiff, then whisk in half of the castor sugar

  • Whisk the cream

  • Using a bowl, whisk the egg yolk and remaining castor sugar until thick

  • Add the pure of mangoes

  • Fold in the whipped cream and finally the egg whites

  • Freeze



Pumpkin cookies

1/3 cup shortening
1 cup sugar
2 eggs
1 tablespoonful vanilla essence
1 teaspoonful lemon extract
1 cup dried pumpkin
2 cups flour
4 teaspoonfuls baking powder
teaspoonful salt
teaspoonful ginger
teaspoonful nutmeg
1 cup seeded raisins
cup chopped nuts

  • Soak pumpkin in enough water to cover for about hour

  • Mash the pumpkin well

  • Cream shortening and sugar, beat eggs in well

  • Stir in the vanilla and lemon extract

  • Put pumpkin through a sieve and add into the mixture above, mixing well

  • Sift dry ingredients and add to the mixture

  • Add the raisins and nuts. Mix thoroughly

  • Drop teaspoonfuls onto a greased cookie pan and bake for about 15 minutes in a 190 C oven (makes 4 dozen)

Dried-fruit patties

  • Select equal parts of dried fruit (e.g. cactus pear, peaches, pineapples, raisins, prunes, etc)

  • Run them through a food chopper using a coarse blade

  • Add chopped walnut or pecans

  • Mix well and form into small balls the size of walnut

  • Press lightly between the palms of the hands to flatten

  • Roll in powdered sugar and place in the refrigerator to chill

  • These patties can be used as substitutes for sweets or cookies for picnics, deserts, snacks, etc

Dried apple fruit cake

3 cups dried apples
3 cups light syrup
1 cup raisins
3 cups flour
1 cup softened shortening
3 eggs, beaten
1 teaspoonful baking soda
1 teaspoonful cinnamon
teaspoonful nutmeg
teaspoonful cloves

  • Soak apples overnight in enough water to cover

  • In the morning, cut apples quite fine, add syrup and cook until apples are very tender

  • Add raisins and cook for another 5 minutes

  • Remove from heat and cool

  • Add shortening and eggs

  • Sift dry ingredients together and add to the mixture above

  • Blend well, then pour into 2 standard size bread tins lined with waxed paper

  • Bake in a 180 C oven for 1 hour or until a knife poked in the centre comes out clean

  • Cool on a rack


Acknowledgements

We would like to thank the National Research Foundation (NRF) of South Africa for providing the senior author with financial support in the form of Post Doctoral Fellowship and the Fort Hare/Norwegian Linkage Project for financial support in the research of which this booklet is one of the outcomes. We are grateful to the National Department of Agriculture for facilitating the production of the booklet.

REFERENCE

BRETT, A, COX, D.R.S., SIMMONS, R. & ANSTEE, G. 1996. Producing Solar Dried Fuit and Vegetables for micro and small-scale Rural Enterprise Development: Handbook 3: Practical Aspects of Processing. Chatham, UK: Natural Resources Institute.

 


For further information contact:
Department of Agronomy
University of Fort Hare
Private Bag X1314, Alice 5700
Tel: (040) 602 2069
Fax: (040) 653 1730
E-mail: amnkeni@yahoo.com or mbrutsch@ufh.ac.za

or

Resource Centre of the Department of Agriculture
Tel: (012) 319 7141/7085

2001

Printed and published by Department of Agriculture
and obtainable from Resource Centre, Directorate Communication,
Private Bag X144, Pretoria 0001, South Africa

Illustrations and DTP by Ronelle Stoltz



University of Fort Hare
Information provided by
Department of Agronomy
University of Fort Hare
Private Bag X1314, Alice 5700
Tel: (040) 602 2069 Fax: (040) 653 1730
E-mail: amnkeni@yahoo.com or mbrutsch@ufh.ac.za