Coating foods with powders

25 Coating foods with powders S. Barringer, Ohio State University, USA

DOI: 10.1533/9780857098672.3.625 Abstract: Foods are coated with powders to improve flavor, color, and produce other desirable quality changes. The most common powder applied to foods is salt, though sweet and savory seasoning blends are also popular, as well as functional ingredients. Powder properties such as size, shape, flowability, density and solubility affect the powder coating process. The major types of equipment including screw fed tubes, scarf-plate feeders, roll dispensers, conveyor belts, tumble drums and electrostatic coating are discussed. Common problems, such as surging and clogging during coating, dustiness, adhesion and shelf life are also discussed. Key words: electrostatic, salt, particle size, adhesion, tumble drum.

25.1 Introduction The most common powder applied to foods is NaCl, or common table salt. The size of the salt greatly affects its functionality. Size affects salt’s flow characteristics, which affects its ability to produce an even, reproducible coating. Size also affects the time dependence of salt release in the mouth, and solubility, all of which affect the taste perception of salt. In a mixture, all of the powders must be a similar size and density. Powders can be coated onto foods by a number of methods. Most powder distributors use gravity to deliver the powder to the food. The powder is dispensed out of a tube, slides along a vibrating metal triangle known as a ScarfPlate Feeder or is picked up on rollers in a roll salter. The food may travel on a conveyor belt or in a tumble drum. A dust collector or recycling system may be used. Electrostatic systems can be used to charge the powder, producing a more homogeneous coating. Cohesiveness, clogging, and surging is frequently a problem. The best solutions are to decrease ambient humidity or add anticaking agents. Adhesion of

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626 Handbook of food powders the seasoning on the food is critical. Proper dispensing minimizes loss during coating. Conveyor belt design is critical to minimize vibrations that shake the powder off of the product. The surface must be tacky enough that the powder adheres to the surface. Dust in the plant must be minimized. Shelf life of the powder is also an issue. Flavors can be encapsulated and antioxidants added to extend shelf life. Packaging may include a light barrier, oxygen scavengers or nitrogen flushing.

25.2 Types of powders used as food coatings The success of many foods is due to the powdered coatings that are applied. Powders are added to a variety of foods because they add novelty, give an attractive appearance, define the product shape, improve taste, increase shelf life, or create texture. Powders are especially important in the snack food industry where the snack base (which frequently consists of items such as corn chips, popcorn, and extruded corn starch) often has an unattractive appearance and tastes bland or mealy. The secret to the popularity of these snacks is seasoning powders which give an appealing color and flavor. Other foods are powder coated to improve functionality such as adding antimicrobials or affecting texture. Salt is the most common powder applied to foods. The most popular seasonings for sweet snacks are powdered sugar, possibly with cinnamon or vanilla. The most popular seasonings for salty snacks include cheese, BBQ and sour cream and onion. Savory seasonings frequently combine salt, cheese, tomato, onion, garlic, and other ingredients which interact to produce the desired flavor.

25.2.1 Salt The most common powder applied to foods is NaCl, common table salt. Salt is so common because it accentuates the flavor of almost any food it is added to. Salt is frequently added by itself, as well as being the major ingredient in most seasoning blends. Up to 1.7%, the saltiness curve is ascending, then it plateaus (Burg, 1998). Thus, small differences in concentration can make a large difference in saltiness. In salted potato chips, 1.6% NaCl is the standard level of addition, though these levels have been dropping for decades as consumers continue to demand lower levels of salt in their food. KCl provides saltiness without sodium, so it is frequently used as a salt substitute, though it produces a bitter off flavor. NaCl can be substituted with up to 33% KCl without producing a noticeable off flavor, reducing the undesirable sodium content. Other approaches to reducing sodium content include altering particle size and use of other flavor potentiators. Most salt is mined, purified and the salt brines are evaporated. Based on how it is evaporated, different shapes and sizes are produced. If the brine is evaporated in a vacuum pan, it produces a concentric or cubic form of

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Coating foods with powders 627

Fig. 25.1

Cube (top), Star Flake® Dendritic Salt (middle) and grainer (bottom) salt (photo courtesy of Morton Salt Inc.).

crystalline salt (Fig. 25.1, top). If low levels of yellow prussiate of soda (YPS), or sodium ferrocyanide, is added, it interrupts crystal formation. Small cubes form, which aggregate into large cubes. These cubes have a porous structure with large surface area and good adherence, and are known as Star Flake® Dendritic Salt (Fig. 25.1, middle). A third shape of salt is produced by evaporating salt in the grainer, or modified Alberger process (Burg, 1998; Niman, 1997). Water evaporates from the surface of the brine, so that only the uppermost layer of the brine becomes saturated. The salt nuclei are formed only on the surface. As the crystals grow, they are held on the surface by surface tension but, being heavier than the brine, are partially immersed into it. Because

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628 Handbook of food powders crystallization proceeds at the surface, the crystals grow laterally, causing them to sink more deeply. The result is a hollow quadrilateral pyramid, floating inverted, with thin sides and a relatively heavy bottom point (Fig. 25.1, bottom). If the salt is formed with grinding rollers, it no longer has a regular shape (Kuntz, 1994). Salt is also available in a range of sizes. The salt is crystallized to the desired size, or can be screened into different size fractions. Larger sizes can also be reduced by grinding rollers. Size can be determined by laser diffraction, but it is most commonly sold based on sieve size. Generally, the percentage retained in each sieve of a series of sieves is reported, though in some cases a single sieve size is reported. When a single sieve size is reported, it is the sieve that stops at least 50% of the salt. The sieve size is the number of wires per square inch, thus the larger the sieve size, the finer the salt. Salt is available in a range of sizes from coarse or pretzel salt at a 20 sieve size, down to extra fine with a 325 mesh. The size of the salt affects a number of factors. If it is mixed with other powders, it must be a similar size or else the powder will stratify during handling, producing coating with variable salt content. The taste perception of salt is also affected by the size of the salt crystals. Fine salts dissolve quickly because they have a large surface area to weight ratio, creating an intense salty sensation, which then disappears quickly. Coarser salt particles provide a longer lasting salty perception because they dissolve more slowly (Burg, 1998). Fat decreases the intensity of saltiness, so in foods with a large amount of surface fat, small particles of salt become enrobed in fat, losing their intensity. For that reason, coarse salt is typically used on the surface of high fat snacks such as potato chips (Burg, 1998). Foods with less than 30% oil, such as crackers, work best with a small particle size such as flour salt because the fine salt has better adherence, more uniform distribution and high solubility. Since particle size effects flavor release in the mouth, separation with other ingredients and appearance, different sizes work best for different applications. Some of the applications for each particle size are given in Table 25.1. Table 25.1

Salt particle sizes used for different applications

Sieve size

Common applications

16–24 16–40 20–50 40–140

Pretzels or rolls Topping crackers and breadsticks Snack cracker dough before baking, nuts roasted in the shell Salting snack crackers after baking, croutons, bread crumbs, potato chips, popcorn, oil roasted nuts Mixing with wheat flour Low oil tortillas, dry air popped popcorn Coating chocolate, extruded puffs, microwave popcorn, dry roasted nuts

70 70–240 >200

Source: Adapted from Morton Salt Inc. (1995).

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Coating foods with powders 629 Size also affects salt’s flow characteristics. The ability of the salt to flow freely is crucial to produce efficient coating (Biehl and Barringer, 2003). Flowability is improved by low humidity in the environment, a free-flowing shape such as for cubic salt, and the use of anticaking agents, such as tricalcium phosphate or silicon dioxide. Finer salts can be more evenly applied, though this size benefit may be offset because finer salts are more cohesive and will clump readily unless an anticaking agent is used. As well as the particles being a similar size, the density of the salt should be similar to the other ingredients in a mixed seasoning blend. The density of salt can be decreased by the addition of sodium ferrocyanide to interrupt the crystal structure and produce a more porous structure. The more porous the structure and the more irregular the shape, the lower the bulk density. Since salt is denser than most food powders, the goal is typically to reduce the salt’s bulk density and match its size to the other powders to minimize stratification. The solubility of salt is important in some food systems because it determines if and how rapidly the salt will dissolve on the surface of the food system. When high solubility is desired, a porous structure, such as in dendritic salt, should be used. The irregular surfaces found in Alberger and pulverized salt also make them go into solution more rapidly than cube salt. In some cases, a lower solubility is desired. For example, coarse rock salt is frequently added to pretzels for visual appeal. However, the partially dissolved salt raises the local heat capacity, creating a weak spot in the dough. This is not a problem for large pretzels, but for small, thin pretzels, flake salt is used instead because it is less soluble, causing less of an increase in heat capacity and therefore is less likely to cause blisters (Burg, 1998).

25.2.2 Seasoning blends The most popular seasonings for sweet snacks are powdered sugar, possibly with cinnamon or vanilla. The most popular seasonings for salty snacks changes with time, but cheese and BBQ are always near the top of the list. Sour cream and onion, and ranch are also popular. These flavors are complex, and change across regions of the country and over the years as consumer preference changes. The seasoning frequently combines salt, cheese, tomato, onion and garlic, with salt being the most abundant ingredient. Monosodium glutamate, yeast extracts, disodium inosinate and disodium guanylate can be added to accentuate savory, salty flavors. Botanical extracts may also be added to boost savory notes, as well as acting as antioxidants. Maltol is often added as a sweetness enhancer, but it also enhances and modifies savory flavors, adds mouthfeel, increases creaminess and dairy notes and decreases bitterness. At low levels, salt enhances sweetness as well as rounding out flavors. Oil and silicon are added as processing aids to improve flowability. Bulking agents such as maltodextrin, whey powder, wheat flour, or corn flour are also added so that excess powder can be added

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630 Handbook of food powders to the coating system (Seighman, 2001). During processing, the extra coating falls off and leaves the food with a more uniform coating than would be possible if only the desired amount of seasoning was applied to the food initially. Typical seasoning levels are 8–10%, depending on the seasoning and snack base (Gould, 1994). Particle size is also an issue in seasoning blends. The increased flavor intensity as the particle size decreases is used in a number of applications, such as powdered sugar on donuts (van Osnebrugge, 1989). A range of particle sizes is frequently used in seasoning to create an initial flavor impact by the finer particles, followed by a lingering aftertaste from the coarser particles.

25.3 Principles and equipment for coating foods with powders The high temperatures involved in baking, frying and extruding drive out most volatile flavor compounds, making it important to apply flavors on the surface of many products after thermal treatment rather than mixing them in with the raw ingredients. Powder coatings are typically distributed by gravity onto foods on a conveyor belt or inside a tumble drum. The food items generally come directly out of the oven, fryer or extruder and are coated immediately to maximize the use of surface oil or moisture to adhere the powder. After the powder is applied, a top coating of oil may be sprayed on to hold the seasoning in place. 25.3.1 Powder dispensers Powders can be dispensed by several different types of distributors. Most systems use gravity to deliver the powder to the food. In one popular design, the powder is conveyed inside a tube by the flights of a rotating screw (Fig. 25.2). The powder may be dispensed only out of the end of the tube, or the tube may have small openings along its length, allowing powder to fall out over the whole length of the tube. The ‘curtain’ produced by the powder falling out of holes along the length of the tube can be seen in Fig. 25.3. When working correctly, powder is dispersed along the entire width of the food bed. However, under humid conditions the powder can clump and clog the holes, so that uneven distribution occurs. In another gravity based design, powder slides

Fig. 25.2 A screw-type seasoning dispenser (photo courtesy of Spray Dynamics, Inc.).

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Coating foods with powders 631

Fig. 25.3 Screw feeder with electrostatic attachment coating popcorn in a tumble drum.

Fig. 25.4

Scarf feeder inside a tumble drum, coating tortilla chips.

along a vibrating metal triangle known as a Scarf-Plate Feeder (Fig. 25.4). This feeder can dispense sticky or tacky coatings as well as free-flowing coatings. The vibration breaks up soft clumps and there are no holes to clog; however, surging can still occur. The diagonal edge causes powder to fall across the width of the food bed. Another gravity fed device is a roll dispenser or salter. The powder lies in a trough between one or two rollers. The grooves in the grooved rollers pick up the salt as they roll up and away from the center, and drop it off the far side onto the bed of food. Figure 25.5 shows a roll salter immediately after the fryer. This design minimizes clumping problems, but the flow rate can be affected by the salt bed depth and does not work well with very fine powders. Pneumatic seasoners, which are less common, use compressed air to blow powders across the bed of food items. The seasoning is frequently put on a load cell so the powder is delivered at a set rate by weight. Snack manufacturers may put 30–50% more seasoning than actually needed onto a product because of the expected waste (Anon,

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632 Handbook of food powders

Fig. 25.5

Roll salter over potato chips, immediately after the fryer.

1992). A recycling system is installed under some coating systems to capture the powder that falls off, remove the fines and clumps and reuse the rest of the seasoning. Because of the high cost of many seasoning powders, a recycling system can be economical. However, care must be taken to ensure the system is sanitary and does not become contaminated with food crumbs that can allow bacteria to grow. Most seasonings will not support microbial growth, but many food bases will.

25.3.2 Food conveying Powders can be applied over either a conveyor belt or inside a tumble drum. In a conveyor belt system, the powder is dispensed over the belt, so that only one side of the food is coated, unless there is a device to flip the pieces over. In some foods, such as potato chips, the chips may be layered two or three layers deep, so that more seasoning lands on the top layers. One study found that coating levels decreased from 60% on the top layer to 30% on the middle layer and 10% on the bottom layer (Gould, 1994). Thus, a conveyor belt system may not produce foods that are as evenly coated as a tumble drum, but requires less space. In some factories there is not enough ceiling height to allow for tumble drums to be installed, and so conveyor belts are used instead. In addition, some companies use conveyor belts because they want to apply seasoning to only one side of the food, such as for crackers. The crackers emerge from the oven and are seasoned while still hot, to improve adherence. If the snacks are only one layer deep and one-sided coating is desired, this method can give very even coating. However, more waste is typically produced if the food does not cover the entire surface of the belt. Many foods are coated in a tumble drum because the tumbling action mixes the product as the seasoning is being applied, producing even coating on all sides (Figs. 25.3 and 25.4). Tumble drums are horizontal cylinders with one end raised so that product flows from one end to the other. Flights are set inside the drum which lift the product, causing the product layers to be rearranged as

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Coating foods with powders 633 they move down the drum. As the layers of product slide over each other there is some transfer of powder, producing more even distribution. The powder dispenser is installed inside the drum. If the food does not have much surface oil, it may be sprayed with oil at the beginning of the drum, then coated with powder in the rest of the drum. Many foods are coated inside tumble drums, including pet food, potato chips, donuts, and even hams. A dust collector may be installed on tumble drums to minimize dust in the air and crossover contamination between lines (Fig. 25.6). While dust collectors do not remove all dust, concerns over allergens, such as milk powder, in seasonings has greatly increased their use. Rubber liners can also be used in tumble drums to speed clean up and changeover between seasonings. After seasoning, the food is dispensed into the package with a weigh filler (Fig. 25.7). Once considered too costly for all but the most expensive foods, weigh fillers have become the standard in the food industry. The food falls gently into individual hoppers, which are each weighed and a computer calculates

Fig. 25.6

Fig. 25.7

Dust collector on a tumble drum seasoning potato chips.

Snacks being conveyed to weigh fillers (photo courtesy of Heat and Control).

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634 Handbook of food powders which combination of hoppers will produce the closest weight to the label weight. The chosen hoppers open and fill the package below, producing a great cost saving by not giving away excess product.

25.3.3 Electrostatic coating In electrostatic coating, the powder is charged as it is dispensed. The powder is charged by going through a corona field or by tribocharging. The most common method used commercially is to create a negative corona discharge from a wire or point electrode that is charged to at least 25 kV. As the powder moves through the electric field, it picks up the free ions in the air and becomes charged. For tribocharging, the powder is blown down a tube of appropriate material and charge is transferred to the powder. The charged particles tend to separate from each other in the air so they fall over a wider area than if they were uncharged. Once the powder is charged, it is attracted to the food product, which is grounded through contact with the conveyor belt or tumble drum underneath it. The powder also distributes itself more evenly on the food item because charged powder already on a location repels incoming particles which move to uncoated areas. The charged powder coats not only the surface of the food facing upwards, but also the more difficult, hidden regions, due to the wraparound effect of the space-charge field (Bailey, 1998). Electrostatic attraction has been claimed to produce a more homogeneous coating even on difficult shapes, and reduce seasoning falloff because of more even coating. The attraction of the charged coating particles towards a ground also reduces dust that would otherwise be produced (Elayedath and Barringer, 2002). The use of electrostatics has been shown to increase transfer efficiency by an average of 68% and decrease dust by 65% (Ricks et al., 2002). It has also been shown to decrease the amount of colorant of mold inhibitor added because of the more even coating produced (Amefia et al., 2006). A labeled example of an electrostatic system is shown in Fig. 25.8.

Electrostatic wire

Powder applicator

Powder

Coated chips

Uncoated chips

Fig. 25.8 Electrostatic coating of tortilla chips (photo courtesy of Terronics Development Corp.).

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Coating foods with powders 635 A comparison of an electrostatic salter with a mechanical salter found that the electrostatic salter maintains uniform spacing of particles during dispensing by inducing a negative static charge on their surfaces, causing the particles to mutually repel each other and producing a more even distribution of salt (Strietelmeier and Reynolds, 1969). Other foods that are electrostatically coated include seasoning corn and tortilla chips (Anon, 1992), putting salt onto crackers and pretzels (Gorton, 1993), and flavors onto confections (Knechtel, 1969). The bactericide added to control pathogens on the meat surface can be reduced by as much as 90% using electrostatic coating because electrostatics improves coating evenness and eliminates overspray (Ahlberg, 2001).

25.4 Difficulties caused by powder coating and ways to resolve them Powder coating suffers from several problems that affect the quality of the final product. Cohesive powders are difficult to dispense evenly, and frequently cause surging in the dispensing system that results in uneven coating. Adhesion of the powder to the food can be a large problem, because frequently the powder does not stay on the food surface unless a large amount of oil or water are present. Dusty powders can cause explosions and health hazards. And finally, the shelf life of the powder may limit the shelf life of the food product.

25.4.1 Cohesiveness, clogging, and surging In most powder coating applications, the most efficient coating is produced by fine, free-flowing powders (Biehl and Barringer, 2004). Free-flowing powders produce a more reproducible flow rate and are more evenly distributed across the surface of the product. Smaller particles are more likely to be evenly distributed, and are less likely to fall off of the product; however, finer powders are more cohesive and tend to form clumps. If the powder is cohesive or ambient humidity is too high, powders clump, and coating uniformity decreases. This can be a major problem in gravity fed powder dispensers. Powders that have clumped may completely clog the system so that no powder gets delivered to the food. Surging occurs when the clumped powder partially blocks the dispenser, slowing the rate of powder flow. When the pressure builds up and forces the blockage loose, the powder surges forward, producing too much powder on the food. The process repeats, producing under- and over-coated items, but the average use rate of powder is constant so the problem may be hidden unless the seasoning level on the food is monitored directly. The most common solutions to clumping are to control the relative humidity in the coating room, and to add anticaking agents. Decreasing the relative

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636 Handbook of food powders humidity, though expensive, is common because of other benefits to the shelf life of the product. A low relative humidity is typically accompanied by decreased temperature. However, this is not always economical since it is desirable to coat the food immediately out of the oven or fryer to maximize adherence, and these rooms are typically very hot and humid. Since many flavor powders are very hygroscopic and agglomerate easily, anticaking agents are frequently added to keep powders free-flowing. The smaller the powder, the more cohesive it is (Adhikari et al., 2001), thus anticaking agents are especially important for fine powders. Even salt, when it is ground to the very small size of flour salt, becomes cohesive and anticaking agents must be added. Anticaking agents such as silicon dioxide or tricalcium phosphate are frequently added to fine or hygroscopic food powders to prevent clumping. These anticaking agents are very small powders that are added to another powder to inhibit its tendency to cake, improving the flowability (Peleg and Hollenbach, 1984). Most anticaking agents are insoluble in water but many of them can absorb considerable amounts of water as a result of their large surface area. The host particles become coated with a layer of these anticaking particles and are physically separated. Thus the points of contact are between anticaking particles, which are chosen primarily for their low attractivity. This prevents the rest of the powder from clumping. However, under very high or prolonged humidity, even anticaking agents can become saturated with water allowing the powder to clump.

25.4.2 Adhesion of the seasoning Powder can be lost in several locations: during coating, during conveying and in the package. Powder lost during coating is due to inefficiencies of powder dispensing onto the food. Powder lost on the conveyor belt and in the package is due to poor adhesion. Conveyor belt design is critical to minimize vibrations that shake the powder off of the product. Older vibratory conveyors were notorious for removing a majority of the seasoning from the food, while modern belts have been developed which produce almost no seasoning loss. Use of horizontal rather than vertical motion helps to minimize powder loss (Fig. 25.9). Since powder coating involves applying powders on the surface of the product, it is critical that the surface is tacky enough that the powder adheres to the surface for the entire shelf life of the food. For fried snacks, the snack goes straight from the fryer to the coating line so that the product is still hot and the surface of the snack is still wet with oil when the seasoning is applied. Thus, no additional tack agent is required. However, the surface oil content decreases rapidly once it is removed from the fryer. In tortilla chips, the surface oil dropped from 80% to 36% of the total oil during the cooling process (Moreira et al., 1997). On potato chips, the adherence decreases up to 40% as the temperature decreases (Buck and Barringer, 2007). Oil can be applied directly as a tack agent. The food is sprayed with oil, then seasoning is applied and adheres to the oil. Some products have very

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Coating foods with powders 637

Fig. 25.9 Horizontal motion conveyor system (photo courtesy of Heat and Control).

little surface oil to start with, such as popcorn. Other products, such as fried corn chips, absorb most of the surface oil after frying, so they may require a secondary spray of oil after the powder is applied, to hold the seasoning to the surface. A top coating of oil is also added to low or no fat snacks, to add palatability since without the surface oil, these products are unpleasantly dry in the mouth. While oil is probably the most common tack agent, other tack agents can also be used. Other tack agents include water, sugar water and hydrocolloid solutions. When an aqueous solution is used, a final drying step is frequently required, which may be undesirable because of the increased expense from the additional processing step. Adhesion is also affected by particle shape, size and composition. Flakes give better adhesion than cubes because of their larger surface area, but porous cubes can be better than either (Miller and Barringer, 2002; Sumonsiri and Barringer, 2011). For crackers especially, adhesion can be difficult because of their smooth surface. Crackers are frequently oiled then flake or dendritic salt is applied because they have the best adherence to the smooth cracker surface. Finer powders adhere better as do powders with high fat content or other composition that make them inherently stickier (Buck and Barringer, 2007).

25.4.3 Dustiness Powders that are fine and free-flowing, in other words the powders that produce the most even coating, also tend to be the dustiest. Dusty powders produce a number of problems. The powder floats around the coating room, coating the walls and other surfaces, increasing cleaning costs. Powders with a lot of spice are very irritating and may even create unhealthy conditions for the workers in the area who breathe in the dust all day. Finally, dust in the air creates an explosion hazard, and there have been many dust explosions in food plants which have resulted in loss of life.

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638 Handbook of food powders When a powder is very dusty, the first thing to consider is the amount of anticaking agent used. A slight excess in anticaking agent changes the powder from free-flowing to extremely dusty. Proper control of anticaking agent addition will minimize this problem. Coarser powders, and powders with higher fat content tend to be less dusty. Dust collectors are frequently used to minimize dust in the plant, as well as crossover contamination between lines (Fig. 25.6).

25.4.3 Shelf life Seasonings tend to lose flavor intensity quickly during storage, especially when exposed to oxygen and ultraviolet rays. Flavors can be encapsulated and antioxidants added to extend shelf life but this is not common due to the cost. Packaging frequently includes a light barrier. Oxygen scavengers and nitrogen flushing are also used but are less common because of the cost and the slowness of the nitrogen flush machine. Ultimately, many products are simply given short sell by dates as the best means to maximize quality.

25.5 Conclusion In powder coating, the particle size, density, and flowability are important to the final quality. Different dispensing systems are used depending on the properties of the powder. Screw fed tubes, scarf-plate feeders and roll salters all have different advantages for dispensing powder. The food can be coated in tumble drums or on a conveyor belt. Manufacturers are continuing to find methods to improve coating efficiency and evenness. Methods such as electrostatics, and improved dispenser and conveyor belt design decrease the over application and falloff of seasonings.

25.6 Sources of further information and advice There are many manufacturers of tumble drums and other powder coating equipment. A few of them are listed below: Heat and Control www.heatandcontrol.com/ FOODesign Machinery and Systems, Inc www.foodesign.com/ PPM Technologies www.ppmtech.com/ Machinery and Process Design www.mpd-inc.com/ Snack food processing Lucas EW, Rooney LW, eds. Snack foods processing. Lancaster, PA: Rooney Technomic Publishing Co. Matz SA. 1984. Snack food technology. Westport CT: AVI Publishing Co Inc.

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Coating foods with powders 639 Electrostatic coating Terronics, Inc. www.terronics.com/ Spray Dynamics www.spraydynamics.com/ Bailey AG. 1998. The science and technology of electrostatic powder spraying, transport and coating. J Electrostat 45(2):85–120. Hughes JF. 1997. Electrostatic particle charging: industrial and health care applications. Taunton, Somerset, England: Research Studies Press, Ltd.

25.7 References ADHIKARI, B, HOWES, T, BHANDARI, BR

and TRUONG, V. (2001) Stickiness in foods: a review of mechanisms and test methods. Int J Food Prop 4(1): 1–33. AHLBERG, P. (2001) Electrostatic coating may offer Listeria protection for meat products. Horsham, PA: Vertical Net LLC. 2001. Available from www.foodonline.com. Accessed 18 September, 2001. AMEFIA, A, ABU-ALI, JM and BARRINGER, SA. (2006). Improved functionality of food additives with electrostatic coating. Innov Food Sci Emerg Technol 7(3): 176–181. ANONYMOUS. (1992) Product profile. Snack Food 81(12): 14–16. BAILEY, AG. (1998) The science and technology of electrostatic powder spraying, transport and coating. J Electrostat 45: 85–120. BIEHL, H and BARRINGER, SA. (2004) Comparison of powder properties important to transfer efficiency and dust in different coating systems. Innov Food Sci Emerg Technol 5(2): 191–198. BIEHL, HL and BARRINGER, SA. (2003) Physical properties important to electrostatic and nonelectrostatic powder transfer efficiency in a tumble drum. J Food Sci 68(8): 2512–2515. BUCK, V and BARRINGER, SA. (2007) Factors dominating adhesion of NaCl onto potato chips. J Food Sci 72(8): E435–E441. BURG, JC. (1998) Salty snack sensations. Food Product Design 8(11): 127–143. ELAYEDATH, S and BARRINGER, SA. (2002) Electrostatic powder coating of shredded cheese with antimycotic and anticaking agents. Innov Food Sci Emerg Technol 3(4): 385–390. GORTON, L. (1993) Coating and topping-applying the finishing touch. Baking and Snack Aug: 45–48. GOULD, WA. (1994) Snack food manufacturing and quality assurance manual. Alexandria, VA: Snack Food Association. KNECHTEL, H. (1969) Processes for retention of candy flavors are examined. Candy Industry and Confectioners’ Journal 133(3): 9–14. KUNTZ, LA. (1994) The many benefits of salt. Food Product Design 3(10): 48–61. MILLER, MJ and BARRINGER, SA. (2002) Effect of sodium chloride particle size and shape on nonelectrostatic and electrostatic coating of popcorn. J Food Sci 67(1): 198–201. MOREIRA, RG, SUN, X and CHEM, Y. (1997) Factors affecting oil uptake in tortilla chips in deep-fat frying. J Food Eng 31: 485–498. MORTON SALT, INC. (1995) Morton salt food processing salt grade matrix. Chicago IL: Morton Salt. NIMAN, S. (1997) Salt is not just salt – considerable difference exist. Cereal Foods World 42(10): 809–811. PELEG, M and HOLLENBACH, AM. (1984) Flow conditioners and anticaking agents. Food Technol (5): 95–98. RICKS, NP, BARRINGER, SA and FITZPATRICK, JJ. (2002) Food powder characteristics important to non-electrostatic and electrostatic coating and dustiness. J Food Sci 67(6): 2256–5563.

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640 Handbook of food powders SEIGHMAN, J.

(2001) ‘Snack food seasonings’. In: EW LUSAS and LW ROONEY (Eds.), Snack foods processing. Lancaster PA: Rooney Technomic Publishing Co Inc., 495–527. STRIETELMEIER, DM and REYNOLDS, JW. (1969) On electrostatic salting. Snack Food 58(9): 46–48. SUMONSIRI, N and BARRINGER, S. (2011). Effect of sodium chloride and target properties on nonelectrostatic and electrostatic coating. J Electrostat 69: 578–586. VAN OSNEBRUGGE, W. (1989) How to flavor baked goods and snacks effectively. Food Technol 43(1): 74–82.

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