Drying fruits and vegetables is one of humanity's oldest food preservation techniques. The earliest mentions of the process date back to a recipe from 1700 BCE, written on a clay tablet from Mesopotamia. However, there’s evidence that ancient humans used this technique several thousand years before. Traditional methods used the sun or wind tunnels to dehydrate fruits and vegetables. While preserving food, it produced lower pH and water content and retained natural antimicrobial compounds in dried fruit and vegetables, making them safer and stabler.
Though the primary purpose of this process was preserving food, today, the dehydration process also maintains the nutrition of dehydrated vegetables and fruits. This process translates to lower costs for storing, packaging, and transporting produce, as it reduces the weight and volume of end products. Contemporary society’s focus on eating convenient and instant foods is now juxtaposed against the health food industry’s emphasis on eating whole fruits, vegetables, greens, and superfoods. Powder and other supplements from this dehydrated produce retain the high nutritional value of freshly harvested plant foods. Using modern processing techniques, manufacturers can now produce quality nutritional products from dehydrated produce.
Using Dehydrated Fruits and Vegetables to Supplement Diets
The whole food movement has encouraged higher consumption of fruits, vegetables, greens, and superfoods. Powdered supplements and food additives are now common in many people's diets in developed countries, not just because of the added nutrition of dehydrated vegetables and fruits but also because they enhance the taste of foods and beverages.
Powders made from dehydrated produce offer a more practical solution for supplementing foods. These powders have longer shelf lives than fresh, refrigerated, or frozen produce while retaining more nutrients. New processing methods are also being developed to ensure that these powders maintain both the color and flavor of the raw foods from which they’re made. These methods ensure superfood powders derived from dehydrated fruits and vegetables are properly processed, extracted, and stored.
Types and Benefits of Dehydrated Fruits and Vegetables
Just about any type of fruit or vegetable can be dehydrated, reduced to a powder, and added to various processed foods.
Widely used dehydrated fruits and vegetables (along with fungi) include:
- apples
- beets
- blueberries
- broccoli
- carrots
- cherries
- coconuts
- cranberries
- oranges
- shiitake mushrooms
- spinach
- strawberries
- tomatoes
- watermelon
Dehydration keeps the nutritional value of these fruits, fungi, vegetables, greens, and superfoods intact. Powders derived from these often make their way into various food and drink products, supplementing processed food with their nutrients.
Nutrition of dehydrated vegetables and fruits offers the following benefits:
- Eliminating moisture greatly reduces the danger of bacterial, fungal, and other contamination.
- Contains no supplementary preservatives, sweeteners or other additives.
- Helps reduce waste by preserving produce for longer.
- Made from raw produce, so retains antioxidants, enzymes, essential fatty acids, fiber and minerals, and most vitamins.
- Offers excellent nutrition for those on vegetarian or vegan diets.
These foods also maintain their nutritional content for much longer than fresh produce or even that which is preserved by freezing. For example, fresh produce refrigerated for only a few days can lose as much as half of some nutrients.
Why Process Dehydrated Fruits and Vegetables Further?
As about a third of fresh produce goes to waste, dehydrating fruits and vegetables contributes to greater availability and more stable markets for high-nutrient foods. With the development of new drying methods, processing dehydrated fruits and vegetables will assist with feeding a burgeoning world population.
The introduction of this dehydrated produce into processed foods also gives it the nutritional value of these vegetables, fruits, greens, and superfoods. Powders, additives, and supplements then make these packaged foods more nutritious.
Processing Dehydrated Fruits and Vegetables
Further processing of dehydrated produce is required to turn it into additives or supplements that are then made into powders, extracts, and concentrates. By including the nutrition of dehydrated vegetables, fruits, and greens, makers of processed food can increase nutritional content and improve the flavor of their products. Some of these nutrient-dense foods allow consumers to get a day’s worth of nutrients in a single meal or even an individual product. Methods such as air drying, spray drying, vacuum-belt drying, drum drying, and freeze-drying are currently used to dehydrate produce.
Drying Methods for Fruits and Vegetables
Techniques for making vegetables, fruits, greens, and superfoods into powders are complex, with numerous issues depending on the type of produce used. Fruits with high sugar content are difficult to process as they stick to surfaces and burn when heated, even at lower temperatures.
Leafy greens and herbs are prone to decay, making them difficult to handle. To get around these problems, food processors must optimize harvest times; processing produce within short time frames to prevent spoilage. Often this involves technology like infrared lighting, which is used to destroy pathogens while preserving natural colors, nutritional value, and texture.
Air Drying
Used primarily for herbs and other ingredients added to foods, air drying is a low-tech yet cost-effective method for dehydrating produce. However, its disadvantages include a higher microbial presence and poorer quality end products that also pose a greater risk of contamination. The drying process is more difficult to control with this technique, and making powdered products from air-dried materials generates more waste.
Spray Drying
A method often used for fabricating finer powders, it’s used for ready-to-make and ready-to-drink powdered supplements. Spray drying offers a means to preserve nutrition and taste, which involves carefully controlled conditions like air temperature at inlets and outlets, relative humidity in the air, and speed of the atomizer. It’s used mainly for fruit juices to minimize drying problems.
The process consists of three basic steps:
- atomization
- droplet-hot air contact
- moisture evaporation
Powdered fruit juices made via spray drying include banana, bayberry, guava, mango, orange, pineapple, and other fruits.
Vacuum-Belt Drying
A gentler process than spray drying, vacuum-belt drying uses lower temperatures. It reduces pressure in the chamber to assist with moisture evaporation, thus eliminating oxidation. The practice protects unique characteristics inherent in the raw foods while also helping to maintain antioxidants, essential amino acids, minerals, and vitamins in the final product. Vacuum-belt drying further results in crispier products with better mouthfeel while preserving aroma, color, and flavor. It also helps prevent a burnt taste and is used to produce highly soluble powders in cold liquids.
Drum Drying
Drum drying results in a high-quality product with low microbial activity. It involves pureeing the produce, then running it over a heated drum. This material is then allowed to dry into thin sheets, creating different textures. Heat degrades nutrients but can temper this by using low temperatures over long periods.
Freeze Drying
Retaining the natural color, shape, and vital nutrition of dehydrated vegetables and fruits is a prime benefit of freeze-drying. It’s used for many dietary supplements and functional foods, preserving the taste of raw foods. Products made via freeze-drying minimize exposure to moisture and oxygen, and it’s a good processing technique for certain produce that requires a bit of moisture to inhibit browning and microbial growth. However, freeze-dried produce is insoluble in water, resulting in grainy or chewy textures when used in liquid products. Additionally, it tends to remove some aromas and subtle flavors in end products.
Prater Machines for Processing Dehydrated Fruits and Vegetables
Prater Industries manufactures several machines for processing dehydrated vegetables, fruits, greens, and superfoods, powdering them into supplements and additives. After drying, produce requires certain types of machinery to help moderate amalgamation, reduce particle size and grind fruits and vegetables into powders for additives and supplements. Prater’s lump breakers, hammermills, and fine grinders all work well for processing dehydrated fruits and vegetables.
Lump Breakers: Moderating Amalgamation
Also known as lump crushers or flake breakers, lump breakers help break down clumps in material. Fed agglomerated dehydrated produce from the top of the unit, they utilize rotating blades to crush larger clumps before passing through a set of comb-like, stationary blades, discharged below the unit once they’re reduced sufficiently. Lump breakers are used with materials like dehydrated fruits and vegetables that naturally agglomerates during processing, storage, or transporting.
Hammermills for Particle Size Reduction
Prater’s hammermills work well for production lines that run at high capacity while also delivering uniform particle size distribution. Operationally efficient, hammermills condition agglomerated blends of material, and are particularly good at breaking down organic material. They’re commonly used in particle reduction applications that require high throughput capacity.
Fine Grinders for Encapsulated Powders
Fine grinding is a critical stage for many manufacturers who process dehydrated fruits and vegetables. Prater’s highly efficient fine grinder designs are built to grind free-flowing materials, using high-speed impact on raw dehydrated produce to break down individual particles. Using a metered feed, raw material is introduced into the mill’s center, where rotor blades create impact and shear with help from stationary screens and jaws. As the stationary surfaces cause particles to decelerate, the differential in impact speed occurs as product rebounds back into the path of the rotor blade. Once particles reach the right size, they’re pulled through apertures in the screen and transported on to the next processing stage.
