Food drying is a local innovation that has existed for many years in Tanzanian communities and elsewhere all over the world. The purpose of food drying is to preserve and ensure that a certain type of food is available during the off-season (Wakholi et al., 2015). Thus, it is best to collect and dry these foods, even in the wild, during the growing season, to be used later to ensure food security and improve nutrition in the household.

Food drying is a very old, simple, and inexpensive way to conserve food. Insects, bacteria, fungi, and diseases cannot grow due to a lack of favorable conditions when food is properly dried down and stored. Drying food increases flavor and enables the preservation of nutrients. Drying and storing food is a very important component in ensuring food security.

Dry foods will last if they do not get wet; if they get moisture, bacteria grow faster and increase damage to foods. Thus, preservation principles are important to consider as well as principles of food drying (Leah, 2011).

Benefits of drying and storing food (fruits and vegetables)

• Drying helps to prevent vegetables from being damaged quickly.
• Drying vegetables and fruits helps reduce weight and quantities thereby simplifying storage and transportation, and avoiding post-harvest losses (Harrison and Andress, 2000).
• Storage and refining of vegetables can provide your family with a good diet for the whole year and may provide an alternative source of income.

Preparation

• Everything that will be used for drying should be very clean.
• Wash hands well and carefully before handling vegetables.
• Make sure fingernails are short and clean.
• Cover your head.
• Clean the working area and utensils used.
• Wash vegetables using clean water.
• After harvesting vegetables, sort them by quality to remove damaged produce. Poor quality fresh produce cannot become a quality product.

How to dry hard vegetables like orange flesh sweet potato leaves

Blanch vegetables to avoid enzymes that cause unwanted changes in vegetables, so as to preserve color and maintain vitamins. The following steps are used in blanching:

• Collect vegetables and sort them from damaged vegetables.
• Wash vegetables and dry them.
• Cut the vegetables into fine strips or cubes.
• Wash  again in filtered water
• Boil water and add salt (100 gm of salt per L of water or 10%).
• Put vegetables into boiling water and cover with a white cloth.
• Boil for 2-3 minutes. This kills enzymes and retains the green color of fresh leafy vegetables. Remove and strain the leaves immediately in the inverted white cloth.
• Put vegetables on a cloth spread over a drying tray.
• Let them dry for 1 – 2 days in a dryer, less time if the sun is hot, up to 3 days if there are too many clouds. If there is rain, dry them inside. To avoid molds, they should be crisp-dried within 3 days.

This method helps preserve nutrients and colors. Even without blanching, we can still have good results.

For best solar drying of fruits and vegetables, it helps to have strong sunlight. If the sun is not enough it will lead to dried produce to take longer to dry. Ideally greens should dry within 3 days and fruits in 4 days. Slow drying risks molding, and can cause the produce to change color. This is a challenge as the vegetables are widely available in the rainy season. One way of solving this is to take the trays of drying produce indoors to a warm kitchen during the rainy season, but this can lead to drying time taking longer than desired.

How to check if vegetables or fruits have dried adequately

After 1 or 2 days vegetable leaves will begin to break easily. Fruits will bend like leather after 3 – 4 days. Ways to check whether vegetables are dried adequately are the following:

• If you take a small sample, put it in your hands and crush, it should break and not bend; there should not be signs of any moisture.
• An overly-cooked vegetable will not dry well but will disintegrate and become too soft. Properly dried vegetables are light and fragrant.
• Test for dryness: Place vegetables in a clean nylon bag and leave overnight in a dry storage place.  If any moisture is found inside the bag, then the vegetables are not dry enough.After making sure they are well-dried, store them as described below. 

After making sure it is well-dried, store it as described below.

Vegetables and fruits can be stored in the following ways:

• A clean and dry container with a good sealing cover should be used. You can also use plastic buckets or other containers. Put the dried foods in a container and cover if it is a bucket. You can improve the seal by by covering the bucket with a nylon sheet tied with a string to limit moisture, air, and insects access.
• It is good to label containers with contents and date processed to remember what kind of food is within.
• After 3 days, open the container to check if the storage is in good condition with no moisture or odor in the container.
• If the vegetables are not dried or stored adequately they will smell bad.
• It is good for food to be stored in a dark room to protect the quality of vitamins. 

Dried foods can be stored in plastic bags and kept in a cold, dark place. Table 1 summarizes common problems in the drying and storage process for troubleshooting purposes.

How dried produce looks after proper drying

After a day or two dried leaves can easily be broken and dried fruits usually are less flexible, like leather. If you take a small amount of vegetables in your hand and press them by opening and closing, the vegetables will break into small pieces.

How to cook dried vegetables and fruits

If you decide to cook, you can soak for an hour then boil, and you can cook as you would non-dried vegetables or fruits. If you decide to prepare differently (to fry) you may soak for 5-15 minutes.

Shelf life

Dried foods can be used for one year from the day they were dried (for very hot or humid places the storage time may be reduced toonly six months).

Market and sale of dried vegetables and fruits

Dried vegetables or fruits can be sold in packets. For example, a packet containing 50 grams of dried greens can be sold for $0.50.

For all vegetables, we need a strong sun. If the sun is not enough it will lead to dried foods to change color. This is a challenge as the vegetables are widely available in the rainy season. One way of solving this is to take the plastics and put them in the house during the rainy season, but this will lead to drying for up to 4 days.

Key principles for the market and product quality:

• Choose fruits and vegetables that are equally mature
• Use clean and safe water every time, and keep it clean
• Cut the vegetables into the small same size
• Water boiling and salt solution to reach 2% of boiling water
• Drier should not be overloaded
• Check the temperature of the drier - not more than 60 ° C
• In the packaging, close the pair in the label
• Use a legally acceptable label
• Store in a clean, dry, cool place with no bright light.

References