Food powder (also called powdery food) is the most common format of dried solid food material that meets specific quality standards, such as moisture content, particle size, and particular morphology. [1] Common powdery food products include milk powder, tea powder, cocoa powder, coffee powder, soybean flour, wheat flour, and chili powder. [1] Powders are particulate discrete solid particles of size ranging from nanometres to millimetres that generally flow freely when shaken or tilted. The bulk powder properties are the combined effect of particle properties by the conversion of food products in solid state into powdery form for ease of use, processing and keeping quality. [2] Various terms are used to indicate the particulate solids in bulk, such as powder, granules, flour and dust, though all these materials can be treated under powder category. These common terminologies are based on the size or the source of the materials.
The particle size, distribution, shape and surface characteristics and the density of the powders are highly variable and depend on both the characteristics of the raw materials and processing conditions during their formations. These parameters contribute to the functional properties of powders, including flowability, packaging density, ease of handling, dust forming, mixing, compressibility and surface activity. [3]
Food powder may be amorphous or crystalline in their molecular level structure. Depending on the process applied, the powders can be produced in either of these forms. Powders in crystalline state possess defined molecular alignment in the long-range order, while amorphous state is disordered, more open and porous. Common powders found in crystalline states are salts, sugars and organic acids. Meanwhile, many food products such as dairy powders, fruit and vegetable powders, honey powders and hydrolysed protein powders are normally in amorphous state. [4] The properties of food powders including their functionality and their stability are highly dependent on these structures. Many of the desired and important properties of the food materials can be achieved by altering these structures.
Powder is a particulated food with a large interfacial area. Food is a composite mixture of mainly protein, carbohydrate, fat and minerals. These components can absorb water molecules in their active hydration sites. The amount and rate of water adsorption depends on the bulk and particles’ surface composition, total particle surface area (particle size), internal porosity and molecular structure. As the particulated foods (powders) have a larger surface area and broken chemical structure at the interface compared with the bulk food, water hydration rate and absolute hydration capacity is larger than in the bulk material of same species. [4]
Powder also has a composite surface with various sized capillaries and geometrical patterns which results in slow penetration of water. Powders with a high amount of low molecular weight carbohydrates or protein are hygroscopic (uptake moisture quickly), thus dissolve with ease. Crystalline powders are slow to dissolve because the dissolution needs to progress from outside to inside as the water molecules cannot penetrate quickly due to the tight molecular structure of crystals. [4]
In many processing situations, the powder forms are essential, such as in mixing and dissolution. Powder particles are created from bulk solid materials by dehydration and grinding.
Drying (dehydrating) is one of the oldest and easiest methods of food preservation. Dehydration is the process of removing water or moisture from a food product by heating at right temperature as well as containing air movement and dry air to absorb and carry the released moisture away. [5] Reducing the moisture content of food prevents the growth of microorganisms such as bacteria, yeast and molds and slows down enzymatic reactions that take place within food. The combination of these events helps to prevent spoilage in dried food.
The foods can be dried using several methods either in the sun or oven or even food dehydrator. However, sun dried method requires warm days of 29.4 °C or higher, low humidity and insect control while oven-baked is less efficient as it may destroy the nutrients of the food. [6] It is recommended to use electric hot air food dehydrator which is simple and easy to design, construct and maintain. [7] In fact, it is very affordable and has been reported to retain most of the nutritional properties of food if dry using appropriate drying conditions.
Grinding is the process of breaking solid food items into smaller particles including powders by using food processors.
Guar gum, also called guaran, is a galactomannan polysaccharide extracted from guar beans that has thickening and stabilizing properties useful in food, feed, and industrial applications. The guar seeds are mechanically dehusked, hydrated, milled and screened according to application. It is typically produced as a free-flowing, off-white powder.
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO2, commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant families of materials, existing as a compound of several minerals and as a synthetic product. Examples include fused quartz, fumed silica, opal, and aerogels. It is used in structural materials, microelectronics, and as components in the food and pharmaceutical industries. All forms are white or colorless, although impure samples can be colored.
Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing process used with metals, ceramics, plastics, and other materials. The atoms/molecules in the sintered material diffuse across the boundaries of the particles, fusing the particles together and creating a solid piece.
Spray drying is a method of forming a dry powder from a liquid or slurry by rapidly drying with a hot gas. This is the preferred method of drying of many thermally-sensitive materials such as foods and pharmaceuticals, or materials which may require extremely consistent, fine particle size. Air is most commonly used as the heated drying medium; however, nitrogen may be used if the liquid is flammable or if the product is oxygen-sensitive.
Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other liquids, or may be filled by gas or vacuum. In the last case, the material is properly called silica xerogel.
In materials science, the sol–gel process is a method for producing solid materials from small molecules. The method is used for the fabrication of metal oxides, especially the oxides of silicon (Si) and titanium (Ti). The process involves conversion of monomers in solution into a colloidal solution (sol) that acts as the precursor for an integrated network of either discrete particles or network polymers. Typical precursors are metal alkoxides. Sol–gel process is used to produce ceramic nanoparticles.
Drying is a mass transfer process consisting of the removal of water or another solvent by evaporation from a solid, semi-solid or liquid. This process is often used as a final production step before selling or packaging products. To be considered "dried", the final product must be solid, in the form of a continuous sheet, long pieces, particles or powder. A source of heat and an agent to remove the vapor produced by the process are often involved. In bioproducts like food, grains, and pharmaceuticals like vaccines, the solvent to be removed is almost invariably water. Desiccation may be synonymous with drying or considered an extreme form of drying.
Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials. This is done either by the action of heat, or at lower temperatures using precipitation reactions from high-purity chemical solutions. The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components and the study of their structure, composition and properties.
A dispersion is a system in which distributed particles of one material are dispersed in a continuous phase of another material. The two phases may be in the same or different states of matter.
Filler materials are particles added to resin or binders that can improve specific properties, make the product cheaper, or a mixture of both. The two largest segments for filler material use is elastomers and plastics. Worldwide, more than 53 million tons of fillers are used every year in application areas such as paper, plastics, rubber, paints, coatings, adhesives, and sealants. As such, fillers, produced by more than 700 companies, rank among the world's major raw materials and are contained in a variety of goods for daily consumer needs. The top filler materials used are ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, talc, and carbon black.
Dry lubricants or solid lubricants are materials that, despite being in the solid phase, are able to reduce friction between two surfaces sliding against each other without the need for a liquid oil medium.
Particle technology is the science and technology of handling and processing particles and powders. It encompasses the production, handling, modification, and use of a wide variety of particulate materials, both wet and dry. Particle handling may include transportation and storage. Particle sizes range from nanometers to centimeters. Particles can be characterized by diverse metrics. The scope of particle technology spans many industries including chemical, petrochemical, agricultural, food, pharmaceuticals, mineral processing, civil engineering, advanced materials, energy, and the environment.
Dynamic vapor sorption (DVS) is a gravimetric technique that measures how quickly and how much of a solvent is absorbed by a sample such as a dry powder absorbing water. It does this by varying the vapor concentration surrounding the sample and measuring the change in mass which this produces. The technique is mostly used for water vapor, but is suitable for a wide range of organic solvents. Daryl Williams, founder of Surface Measurement Systems Ltd, developed Dynamic Vapor Sorption in 1991; the first instrument was delivered to Pfizer UK in 1992. DVS was originally developed to replace the time and labor-intensive desiccators and saturated salt solutions used to measure water vapor sorption isotherms.
Granulation is the process of forming grains or granules from a powdery or solid substance, producing a granular material. It is applied in several technological processes in the chemical and pharmaceutical industries. Typically, granulation involves agglomeration of fine particles into larger granules, typically of size range between 0.2 and 4.0 mm depending on their subsequent use. Less commonly, it involves shredding or grinding solid material into finer granules or pellets.
Crystallization of polymers is a process associated with partial alignment of their molecular chains. These chains fold together and form ordered regions called lamellae, which compose larger spheroidal structures named spherulites. Polymers can crystallize upon cooling from melting, mechanical stretching or solvent evaporation. Crystallization affects optical, mechanical, thermal and chemical properties of the polymer. The degree of crystallinity is estimated by different analytical methods and it typically ranges between 10 and 80%, with crystallized polymers often called "semi-crystalline". The properties of semi-crystalline polymers are determined not only by the degree of crystallinity, but also by the size and orientation of the molecular chains.
Microcrystalline cellulose (MCC) is a term for refined wood pulp and is used as a texturizer, an anti-caking agent, a fat substitute, an emulsifier, an extender, and a bulking agent in food production. The most common form is used in vitamin supplements or tablets. It is also used in plaque assays for counting viruses, as an alternative to carboxymethylcellulose.
Instant noodles, or instant ramen, is a type of food consisting of noodles sold in a precooked and dried block with flavoring powder and/or seasoning oil. The dried noodle block was originally created by flash-frying cooked noodles, which is still the main method used in Asian countries; air-dried noodle blocks are favored in Western countries. Dried noodle blocks are designed to be cooked or soaked in boiling water before eating. Ramen, a Japanese adaptation of Chinese noodle soup, is sometimes used as a descriptor for instant noodle flavors by some Japanese manufacturers. It has become synonymous in the United States with all instant noodle products.
Caking is a powder's tendency to form lumps or masses. The formation of lumps interferes with packaging, transport, flowability, and consumption. Usually caking is undesirable, but it is useful when pressing powdered substances into pills or briquettes. Granular materials can also be subject to caking, particularly those that are hygroscopic such as salt, sugar, and many chemical fertilizers. Anticaking agents are commonly added to control caking.
A powder is a dry solid composed of many very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of granular materials, although the terms powder and granular are sometimes used to distinguish separate classes of material. In particular, powders refer to those granular materials that have the finer grain sizes, and that therefore have a greater tendency to form clumps when flowing. Granulars refer to the coarser granular materials that do not tend to form clumps except when wet.
Agglomerated food powder is a unit operation during which native particles are assembled to form bigger agglomerates, in which the original particle can still be distinguished. Agglomeration can be achieved through processes that use liquid as a binder or methods that do not involve any binder.