Spray drying instant coffee

Spray drying instant coffee refer to a type of coffee that has been treated with a spray drying process that remove all the water from the coffee beans.

Spray dryers are rapid dryer, drying rate is high. Product quality can be controlled and maintained in drying process. Highly controllable drying systems flow of hot air, droplet speed and droplet temperature can be effectively controlled.

With spray-dried coffee, the texture of the coffee powder is usually very fine for most people. Coffee aroma consists of a complex mixture of volatile compounds, whereas non-volatile compounds contribute to flavors such as sourness, bitterness, and astringency.

Spray drying is achieved by spraying liquid coffee concentrate as a fine mist into very hot, dry air. The droplets are dried in very hot air (approx. from 80 to 180˚C) and evaporate leaving behind the coffee powder.

The spray drying process is very quick and uses high heat. Because of that, the process produces fine and small particles, which results as a powdered form.
Spray drying instant coffee

Food powder production by spray drying

Spray drying is widely used in the industry for conversion of a suspension or solution into a dry powder product.

The three stages that occurs in a spray dryer before drying is accomplished includes:
*Atomization
*Spray air mixing and moisture evaporation
*Dry product separation from the exit air

The process of spray drying consists of the transformation of a product in fluid form to the solid state in the form of powder. The spray-drying process reduces water activity of products, retards bacterial degradation and extends the product’s shelf life. All spray dryers employ atomizer or spray nozzle to disperse the liquid or slurry into a controlled drop size spray.

The process is done through the dispersion of droplets from the product inside a chamber, in contact with hot air. When the droplets and the heated gas come into contact, the solvent in the droplets evaporate, leaving a dry powdered product.

In this process, substances known as carriers or encapsulating agents can be added. Starch, modified starch, maltodextrin, solid corn syrup and gum Arabic etc., are kinds of high molecular weight carbohydrates commonly used as spray-drying carriers. The main functions of spray-drying carriers are to increase glass transition temperature of product, and reduce stickiness and wall deposition during spray-drying.

Spray drying results from application of energy, which acts on the liquid to the point of causing its rupture and disintegration, in order to divide it into millions of individual particles, thereby creating a mist or spray of droplets.

The development of spray drying equipment and techniques started in the 1870s. Spray drying has come of age ever since the technique was used during the World War II, because the idea to reduce the transport weight of foods and other materials became important.

Recently, the spray drying technique has been applied extensively for the production of functional foods, pharmaceuticals and nutraceuticals. Encapsulation using spray drying is highly preferred due to economic advantages compared to other encapsulation methods.
Food powder production by spray drying

Skim of low-fat milk

Dry milk was referred to as milk powder until the mid 1960s, when the designation was changed by the American Dry Milk Institute to dry milk in the United States.

Large quantities of skim of low fat milk are dried. This may be done by spraying atomized droplets of milk into chamber through which heated air is circulated (spray drying).

The atomizers used in this process include mainly rotary and pressure types. The final articles size of the dried powder produced by utilizing a rotary atomizer and the basic plant is greater than 1000 microns.

The milk also may dry by allowing it to flow over the surface of two heated metal drum that rotate toward each other.

A thin layer or film of product is dried over an internally steam-heated drum with steam pressure up to 620 kPa and 149 °C. Approximately 1.2 – 1.3 kg steam are required per kilogram of water evaporated.

The dried milk then is scraped from the drum surface, as they rotate, by metal scraper.

The operating variables for a drum dryer include condensation of incoming product in an elevator, temperature of incoming product, steam pressure in drum, speed of drum, and height of product over drum.

Dried milk (usually the spray dried type that contains about 5% of moisture) may be re-humidified to slightly higher moisture content after drying.

It has poor dissolving properties and where sold for domestic use is subjected to further instantisation, which agglomerates granules and leads to a faster dissolution time.
Skim of low-fat milk

Milk powder spray drying

Dried milk is manufactured from evaporated milk. In spray drying, the milk concentrate is finely dispersed in the spray tower by centrifugal atomization or by nozzle atomization and dried with hot air (150-220 °C). The final drying process reduces the water content to about 4%.

The removal of water by spray drying is an energy expensive process and even if it were not, spray drying would not normally be chosen as the only methods of water removal in milk powder production.

Spray dried powder consists of small, regular spherical particles, is light in color and had very little burnt taste.

In general, there are four stages in spray drying of drying milk powder, these are:
*Atomization of milk into a spray, at the top of the atomizing chamber
*Spray-air contact, mixing and flow
*Drying of spray droplets in flight
*Collection and separation process of milk powder from the air

Spray dried powder is generally considered to be of better organoleptic quality than roller dried.

Spray dried milk has poor dissolving properties and subjected to a further process, instantisation which agglomerates granules and leads to a faster dissolution time.
Milk powder spray drying

Processing of instant coffee

Instant coffee entails the extraction of ground coffee with warm water to form a concentrated liquid brew, followed by removal of the water from the brew by some method of dehydration. The residue which is left is instant coffee.

Instant coffee is produced after grinding and extraction by percolation. Instant coffee is prepared in either of the following way:
*By forcing an atomized spray of very strong coffee extract through a jet of hot air. This evaporates the water in the extract and leaves dried coffee particles, which are packaged as instant, or soluble, coffee. Most spray-dried instant coffees have been marketed in a granular form, rather than the small special spray-dried form, since the mid-1960s.

*By freeze-drying, which results in a product that looks somewhat like ground roasted coffee and retains some of coffee’s aroma. Freeze dried coffee has a longer shelf life than spray-dried coffee.

Spray and freeze fried coffee extract have generally lost their original volatile flavor and aroma compounds. The flavor of instant coffee can be enhanced by recovering and returning to the extract or finished dry products some of the natural aroma lost in processing.

The aroma constituents from the grinders, percolation vents and evaporators may be added directly or in concentrated or fractioned form to achieve the desirable product attributes.
Processing of instant coffee 

Spray drying of mango powder

Mango powder, mainly used as a beverage base or flavoring I prepared by drying mango puree. Spray drying is one of the most commonly used commercial process for drying fruit purees.

Immediately prior to spray drying, 5% liquid glucose and tri-calcium phosphate (0.5% as an anti-caking agent) are incorporated into the puree.

The mixture is then heated at 50 °C for 30 minutes, homogenized at 2,800 rpm, pumped to the atomizer (at 2,800 rpm) and spray dried at 165 °C inlet temperatures.

The dried powder falls into the bottom of the chamber.

If the proper feed formulation and process parameters are applied, spray-drying is an efficient and hygienic method for producing cheap but high quality mango fruit powder.

Mango powder can be stored up to 6 months in polyester or metalized polyester pouches at 27 – 32 °C.
Spray drying of mango powder

Processing of banana powder

Banana powder is a powder made from processed banana. It has a high sugar and low starch content and can be produced as a substitute for fresh banana in making cakes or their premixes as well as in the processing of banana snacks, crackers or crisps.

In the manufacture of banana powder, fully ripe bananas are peeled, pulped and converted into a paste by passing through a chopper followed by a colloid mill. Good quality paste with proper drying facilities produces good quality powder. Immature or overripe fruits should be excluded from the bulk.

A 1 or 2% sodium metabisulfite solution is added to improve the color of the final product.

Both spray and drum drying may be used; however, the latter is more favorable as it allows the recovery of all solids.

In case of using spray drying, milk solids are added at 10% level. Spray drying of food rich in inverts square is difficult because of their thermoplastic nature, which results in the adherence of the dried matter to the sides of the sprayer and necessities.

However, when milk solids are added, spraying becomes easy and the material does not stick to the walls of the sprayer.

The quality of banana powder is determined by the color, flavor, texture and moisture content.
Processing of banana powder

Spray dried flavors

Spray drying is the method of choice for powdered flavors. It remains the main approach for encapsulating flavors due to its low cost and equipment accessibility.

Various food flavors oils, essential oils, vitamins, useful bacteria, probiotics, butter oil, fish oil, vegetable oil and food colors can be encapsulated in a solid matrix during spray drying.

The flavor is typically emulsified in an aqueous gum solution, it is passed though atomization into hot air streams where evaporative cooling brings the inlets air temperature down from 200-325 °C to 80-90 °C. 

The resulting flavor is stronger and much more stable to evaporation and oxidation.

Encapsulated powders have found applications in cake mixes, biscuits mixed, ice cream mixes, oatmeal, instant beverages and a wide variety of snacks.

The main disadvantage to this method are the loss of volatiles, degradation of sensitive compounds and sometimes further need of fine powder processing.
Spray dried flavors

Spray drying processing

Spray drying is a common unit operation to convert liquid materials into powders for preservation, ease of storage, transport and handling and other economic considerations.

In principle, an aqueous dispersion of oil in water emulsion containing carrier material dissolved in the water phase is converted into a dry powder by spraying the feed into hot dry air resulting in moisture evaporation.

It is used for drying liquid solutions and suspension with the objective producing light porous powder. Now, spray drying is a common practice in the food and dairy industries to make powders for capturing bioactive components and nutrients for a longer period of time.

Spray drying normally contains the following stages: atomization, air contact, evaporation, and product recovery. Finely divided drops of liquid food are dried by direct contact with heated air in extremely short residence time of 3 – 30s, which results minimum heat degradation of dried product.

Liquid is transferred to fine drop by using their: 
*Rotary
*Pressure nozzle
*Pneumatic two fluid atomizing device

Spray drying is the accepted method for the production of milk and whey powders, coffee creamers, cheese powder, dehydrated yeast extract, instant coffee and tea, isolated soybean protein, enzymes, maltodextrin, egg powder and many other products in powder forms.

Spray drying processing