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The definition of the term “sample” is expressed as “a portion of the whole, selected in such a way as to be truly representative of the whole.” Some additional explanations for this definition include: (a) no sample truly represents all the respects of the whole consignment or population; (b) the sample is always different from the whole consignment, even for the parameters of interests; (c) the sample will only be adequate for the determination of certain elements; and (d) the sample will only be adequate for some analytical techniques (Smith and James, 1981). The sole objective of sampling is to reduce the mass of a target material without significantly changing its other properties, either by taking increments from flowing streams of a material or by splitting when the whole lot of the material can be handled (Gy, 1998).

Particle characterization, i.e., description of primary properties of food powders in a particulate system, underlies all work in particle technology. Primary particle properties such as particle shape and particle density, together with the primary properties of a fluid (viscosity and density), and also the concentration and state of dispersion, govern secondary properties such as settling velocity of particles, rehydration rate of powders, resistance of filter cakes, etc. It could be argued that it is simpler, and more reliable, to measure the secondary properties directly without reference to primary properties. Direct measurement of secondary properties can be carried out in practice, but the ultimate aim is to predict secondary properties based on primary properties, as when determining pipe resistance to flow from known relationships, feeding in data from primary properties of a given liquid (viscosity and density), as well as properties of a pipeline (roughness). Since many relationships in powder technology are complex and often are not yet available in many areas, particle properties are mainly used for qualitative assessment of the behavior of suspensions and powders, for example, as an equipment selection guide. Since a powder is considered to be a dispersed two-phase system consisting of a dispersed phase of solid particles of different sizes and a gas as the continuous phase, complete characterization of powdered materials is dependent on the properties of a particle as an individual entity, the properties of the assembly of particles, and the interactions between those assemblies and a fluid.

Food powders can be classified into different categories according to their handling properties. The bulk properties of food powders are a function of physical and chemical properties of the material, the geometry, size and surface characteristics of the individual particles, as well as the history of the system as a whole. This chapter introduces someways to evaluate food powder failure properties, such as angle of wall friction, effective angle of internal friction, failure function, cohesion, flowability, compressibility and other mechanical properties. These mechanical properties can be combined with environmental conditions such as moisture, temperature, particle size and chemical composition in order to condense physical and chemical issues related to the powder during manufacturing and distribution. Shear testers are used for bi-dimensional stress quantification that leads to the calculation of these properties. Other direct measurement methods for failure properties are also introduced. Handling properties such as angle of repose, angle of slide, conveying angle and angle of spatula are provided with some relevant reference methods, and new methods such as rapid methodologies are utilized for evaluating drainage, flow or conveying capabilities. Powders are classified according to handling in dispersion systems or according to their dynamic or static conditions during transport or storage.

In the food and related industries there are some particulate systems, such as grains or pulses, which may be stored outdoors in large piles unprotected from the weather. When being taken for processing, such materials may be removed by dragline or tractor shovel and delivered to a conveyor. Space allowance can be done by estimating the volume of the pile through aerial or ground surveys and multiplying by the bulk density of the material. Since bulk food materials are able to deteriorate with outside ambient conditions such as moisture, there is a need to provide protection for these piled particulate systems. Several alternatives have been used such as domes and cylindrical structures with conical tops, which are normally known as silos. Some of these structured forms of storage have been termed according to a particular application, such as corrugated-wall structures known as grain silos. The dome silo storage system has been successfully used to store salt and different kinds of grains. The reclaiming systems for these types of silos are similar to those used in outdoors storage, e.g., draglines, scraper reclaimers, bucket wheel reclaimers, etc. Outdoor and structured storage systems are useful when huge amounts of materials need to be in inventory, but direct connection to feed processing lines is somewhat difficult.

Materials handling in the food and processing industries is concerned with movement of materials in different cases, such as from supply point to store or process, between stages during processes, or to packing and distribution. The movement of materials is a crucial activity that adds nothing to the value of the product, but can represent an added cost if not managed properly. For this reason, responsibility for materials handling is normally vested in specialist handling engineers, and many food manufacturers adopt this procedure. If a company does not have a specific department in charge of materials handling, the responsibility for efficient handling of materials falls on the production manager and his/her staff. It is important, therefore, for production executives to have a sound knowledge of the fundamentals of good handling practice.

In many food processes it is frequently necessary to reduce the size of solid materials for different purposes. In this case, size reduction may aid other processes such as expression and extraction, or may shorten heat treatments such as blanching and cooking. Comminution is the generic term used for size reduction and includes different operations such as crushing, grinding, milling, mincing, and dicing. Most of these terms are related to a particular application, e.g., milling of cereals, mincing of beef, dicing of tubers, or grinding of spices. The reduction mechanism consists of deforming the food piece until it breaks or tears. Breaking of hard materials along cracks or defects in their structure is achieved by applying diverse forces.

The term “size enlargement” includes a number of processes that purposely combine small particles into large permanent masses in which the initial primary units are still identifiable. Applications in food processing are surprisingly numerous and are becoming increasingly important as more “structured” foods are developed. Size enlargement operations are used in the process industries with different aims such as improving handling and flowability, reducing dusting or material losses, producing structural useful forms, enhancing appearance, etc.

In the past, a wide range of food products were technically not feasible for manufacture but are possible today through the development and design of encapsulated ingredients. Such formulations derive from processes that totally envelop the active material in a coating or “capsule,” thereby conferring distinct physico-chemical capabilities compared to the original non-encapsulated ingredients. Encapsulation can be defined as a process where a continuous thin coating is formed around solid particles, liquid droplets, or gas cells that are fully contained within the capsule wall (King, 1995). In particular, food processing encapsulation is directly related to the coating of minute particles of ingredients (e.g., acidulants, fats, and flavors), as well as whole ingredients (e.g., ground raisins, nuts, and confectionery products), by microencapsulation and macrocoating techniques, respectively (Shahidi and Han, 1993). Encapsulation is a topic of interest in a wide range of scientific and industrial areas, varying from pharmaceutics to agriculture and from pesticides to enzymes. Although the technology of encapsulation and controlled release is undoubtedly the most developed in the area of drug delivery systems, it has also revolutionized the food and fragrance industries (Greenblatt et al., 1993).

The unit operation in which two or more materials are interspersed in space with one another is one of the oldest and yet one of the least understood unit operations in process engineering. In agriculture and food processing, mixing operations are often used to blend ingredients. Particularly, mixing is used in the food industry with the main objective of reducing non-uniformities and gradients in properties such as concentration, color, texture, or taste between different parts of a system (Uhl and Gray, 1986). The degree of uniformity required may vary somewhat, but most of the time it is important to provide a nutritionally balanced and palatable feed mixture.

Separation techniques are involved in a great number of processing industries and represent, in many cases, the everyday problem of a practicing engineer. In spite of this, the topic is normally not covered efficiently nor sufficiently in higher education curricula of some engineering programs, mainly because its theoretical principles deal with a number of subjects ranging from physics principles to applied fluid mechanics. In recent years, separation techniques involving solids have been considered under the general interest of powder and particle technology, as many of these separations involve removal of discrete particles or droplets from a fluid stream.