and Its Derivatives
September 1997 -- Applications
By: Ronald C. Deis, Ph.D.
No doubt about it. Today's consumers are watching their fat and calories. But they still like their sweets. Last year's candy and gum sales climbed nearly 7% over the previous year, according to the latest "State of the Industry" report from Snack and Bakery Foods.
While many new types of products were introduced to accelerate sales, time-tested, but hard-to-change methods produce many favorite candies. Confectionery is still largely an art; most changes in ingredient technology accommodate the need to increase line speed. Starch and its derivatives comprise an integral part of this, controlling the effects of moisture migration during processing and shelf life.The confectionery industry represents a broad array of products, characterized or differentiated by: use of chocolate, method of cooking, percentage of moisture, agitation, forming methodology, crystallization of sugars, use of stabilizers, types of coatings, and more. The products can be broadly placed into four categories:
Gelled candies. These include jellies, gummy bears, licorice, gum drops, jelly beans and pastilles. Products in this category contain a gelatinizing agent, such as starch, gelatin, pectin or gum arabic.Aerated and/or grained confections. These include fondants, taffy, marshmallow, nougats and cremes.
Caramels, fudge and toffees. These are boiled confections, grained or non-grained.Compound coatings. These encompass a wide array of products, such as glazes, icings, frostings, panned confections, pastels, etc.
Within confections, starch and its derivatives see use in a broad range of functionalities, including use as: sweeteners, texture stabilizers, gelling agents, crystallization inhibitors, thickening agents, film formers, dusting agents, glazing agents, adhesives, flow agents, moulding agents, and foam stabilizers.To impart this range of functionalities, starch from several native sources may be used, and a number of chemical and physical modifications of the starch granule are employed. Corn starch is used most often, but rice, potato and tapioca starches also are used.
"The bulk of starch used for confectionery is for moulding and dusting," says Carl Moore, senior research scientist, A.E. Staley Manufacturing Co., Decatur, IL. That makes corn preferable for economic reasons, he points out, since corn starches are relatively inexpensive.
Setting the stageStarch is deposited as a reserve carbohydrate in plants, where it occurs naturally in granules, which have distinct shapes and sizes, depending upon the plant source. Rice starch granules are polygonal and small (3 to 8 microns); corn starch granules are more rounded (5 to 25 microns); tapioca granules are rounded, but truncated at one end (5 to 35 microns); and potato granules are more oval as well as being the largest granules available commercially (15 to 100 microns).
Within these granules are two distinct molecular types of starch, amylose and amylopectin - polymers of glucose. Amylose is a linear polysaccharide composed of up to 10,000 glucose residues connected by alpha-1,4 glucosidic bonds. Amylopectin is a larger, extremely branched molecule with short alpha-1,4 linked chains connected by alpha-1,6 glucosidic bonds.The ratio of amylose to amylopectin varies according to starch source, and plays an important role in starch functionality. Amylose contributes little viscosity on heating in solution, and its linear structure results in tight association - commonly called "retrogradation," which contributes to a firm gel or "set-back." Amylopectin, on the other hand, can bind much more water in solution, resulting in higher viscosity, lower solids and weaker gels. The amylose content in native starches commonly used in confectionery is: common corn starch, 28%; waxy corn starch, 0%; high-amylose corn starch, 55% to 70%; and tapioca starch, 18%. Within the framework of starch as a functional confectionery ingredient, starch products can be broken out into some broad categories:
Unmodified starches and physically modified starches. This group includes moulding starch, dusting starch, and re-dried starches for use in jelly candies, licorice and marshmallows. This also would include genetic modifications, such as high-amylose starch.
Modified cook-up starches. These are produced by chemically modifying starch by thin-boiling; cross-linking for acid shear and heat stability; and/or further modification (esterification or etherification) for control of retrogradation.Pregelatinized starches. These are cold water swelling starches produced by traditional hot-rolling or extrusion processes to disrupt granular structure.
Granular instant starches. These are produced by a unique physical process to instantize the starch within its granular structure. The granules swell while maintaining their integrity, producing different textures than traditional pregelatinized starches.
Down to the basicsStarch polymers also can be hydrolyzed with acid and enzymes to produce corn syrups, maltodextrins and dextrose, all extremely useful ingredients for creating candy. In terms of functionality, sweetness comes first to mind, but corn syrups also control sugar crystallization, and serve as a critical control ingredient for moisture retention. They also control viscosity; increase or decrease browning; and limit microbial spoilage.
To produce any of the range of hydrolysate products, a starch suspension is treated with acids and/or enzymes to reduce molecular weight. By varying the extent of conversion and the degree of acid (random cleavage of glucosidic bonds) or enzyme (more controlled cleavage) hydrolysis, a wide range of products can be produced. These are commonly differentiated by dextrose equivalent (DE), defined as the percentage of reducing sugar calculated as dextrose on a dry weight basis.Dextrose has a DE of 100, and starch is essentially zero. Hydrolysate products are further differentiated by the percentage of the saccharides contained within them, known as degree of polymerization (DP). A breakdown of at least DP1 (dextrose), DP2, DP3 and DP4+ can be obtained from suppliers. Within this zero to 100 DE range, all of the hydrolysate products can be found: corn syrups, high-maltose corn syrups, corn syrup solids, and maltodextrins.
More than sweet thingsMoving away from starch and increasing the DE, we first reach a range of products known as maltodextrins. Maltodextrins can be derived from several different cereal sources: primary on the market are corn maltodextrins (waxy and common), followed by potato, rice and tapioca. Maltodextrins range in DE from 1 to 19, and so are comparatively much less sweet than corn syrup and less hygroscopic. Because of their low level of reducing groups, they contribute less to browning. In candies, they contribute chewiness, viscosity due to high solids in solution, and binding properties. Like corn syrup solids and corn syrups, maltodextrins are amorphous, and tend to inhibit sugar crystallization. Due to their excellent binding properties, they help accelerate the panning process and are an excellent tabletting aid in direct compression products.
An extremely important ingredient in candies, corn syrup assumes a much broader role than mere "sweetener." Corn syrup controls crystallization of sucrose-inhibiting "graining," moisture retention, viscosity development, browning inhibition, and microbial spoilage."Most confectionery products use a combination of corn syrups and sugar in varying ratios," says Moore. "It dilutes the sugar out to the point where it doesn't crystallize. For example, a packaged marshmallow: it's soft, resilient. When you bite into it, you do not want to get a crystalline grit. On the other hand, a circus peanut is what we call a grained marshmallow - same ingredients, but you increase the sugar content and force the sugar to crystallize out. That produces a short, breaking, crystalline texture."
Technically, corn syrups and their dried forms, corn syrup solids, can be found in a DE range of 20 to 95. The lower the DE, the lower the hygroscopicity, but also the higher the viscosity. The lower-DE syrups can prove difficult to handle, but they may be effective in decreasing moisture pickup or development of stickiness in candies. Corn syrups as low as 36 DE are commonly found in the industry.Confectioners use 42 DE corn syrup as a more multipurpose ingredient than the other corn syrups. It possesses good flow properties. It also combines well with invert sugar or sucrose to control moisture in soft candies, and to reduce tackiness in hard candies.
High-maltose syrup is used to some degree, because it contains a minimum amount of dextrose. This translates into increased color stability by reducing browning, and a lowered hygroscopicity in hard candies.High fructose corn syrup (HFCS) has seen increasing use in the candy industry as an invert-sugar replacement. It is important to keep in mind that the "42" and "55" designations associated with HFCS refer to percentage of fructose, not DE. High fructose corn syrups also commonly contain lower solids (approximately 70%) than many corn syrups, which typically occupy the 80% range. HFCS may replace 5% to 50% of the sucrose, primarily in soft confections. In addition to sweetness, HFCS also contributes humectancy, solids, control of osmotic pressure, and crystallization control. High conversion syrups, primarily to 62 DE, contribute humectancy, solids, crystallization control, and viscosity, primarily in soft candies. They often are used in situations in which drying-out is a problem, resulting in adverse texture changes. A proper balance of invert sugar to corn syrup is important; over-use of high conversion syrups can result in a sticky product.
In gums and jellies, corn syrup may contribute 35% to 100% of the sweetener solids. Marshmallows may contain 35% to 80% of the sweetener as corn syrup (while fondants, creams, and fudges contain 10% to 40%). Blends of corn syrups and sucrose, dextrose, invert or HFCS are common, available from ingredient suppliers or mixed in-plant.Completing the spectrum through DE, we end up with dextrose as the basic unit of starch. Dextrose finds some utility in confections as a sweetness reducer (approximately 80% sucrose sweetness). Dextrose also gets utilized for its negative heat of solution, noted in the mouth as a cooling effect. This cooling effect creates interesting flavoring effects, notably enhances fruit flavors and "rounds out" other flavors. Dextrose also balances the effects of sugar-free or reduced-calorie products. Its flow properties and compressibility also are useful in tabletted items. Confectioners generally use dextrose in its monohydrate form. In its anhydrous form, which actually contains 0.5% water, dextrose helps adjust flavor and sweetness of compound coatings.
Moulding, not moldyCorn starch, as a polymer, assumes three major roles in confections: ingredient, moulding agent or dusting agent. In its simplest application, starch is used as a dusting agent for marshmallows or other sticky products. These starches are generally "redried" corn starches, dried to 3% to 9% moisture. Modified hydrophobic starches also are available. The dusting agent ties up sufficient moisture at the product's surface to prevent sticking to packaging or equipment.
The use of moulding starches is well-known, and not much has changed over the years. Manufacturers use moulding starches as a medium to form deposit-candy impressions in starch trays. Utilized for many years, this process takes the name "Mogul process." In general, the process consists of a tray destacker, which places finished deposit products - jellies, for example - on a chain-driven tray conveyor. Trays are emptied, and product is separated from starch. Empty trays are re-filled with conditioned starch, smoothed, then stamped with plaster stamps. A piston depositing system delivers molten candy into the moulds. The trays are stacked, then the product is staged to a drying room. After drying, the product separated from starch is finished (sugar-sanded, oiled, etc.), then packaged.The expected function of moulding starch is to form a well-defined impression to shape a toffee, fondant, fudge, or starch-, pectin-, or gelatin-based jelly or hard gum. It also absorbs moisture from the product and promotes "set." These functions are not well-matched in starchless systems.
The identity of moulding starch is simple: it typically consists of an unmodified common corn starch, supplemented with a white mineral oil or high-stability vegetable oil. Mineral oil sees the widest use, due to its stability; up to 0.30% may be used, but 0.05% to 0.10% is most common. No-oil varieties also have become available due to demand.Oil amount can prove critical, according to Eric Shinsato, application specialist, Cerestar, USA, Hammond, IN. Too little oil may result in impressions in the moulding tray which crumble. And too much oil might lead to cracking of the impression, resulting in malformed pieces.
Since the starch is re-used, it must be "conditioned" - sifted to remove candy pieces and starch agglomerates; dried to the proper moisture for the product to be moulded; cooled to 90° to 160(F; and properly buffered because many fruit candies are acidic. Starch moisture and temperature ranges are recommended for each candy type so the rate of moisture migration out of the product can be controlled. For example, gums and jellies require 5% to 7% moisture starch at 120° to 160(F; cream centers require 6% to 8% moisture starch at 90° to 115(F; and soft marshmallows require 5% to 7% moisture at 90° to 100(F. Starch manufacturers can supply information for the type of product desired.The most serious problems, according to Shinsato, can be caused by dextrinization of the starch during the repeated drying and cooling cycles. Since dextrinization increases the solubility of the starch, the starch may begin to stick to the confection. As the starch is conditioned, new starch is commonly exchanged in to control this gradual breakdown.
Forming a gelStarch serves many purposes in a candy, a major use being a gelling agent in jellies and hard gums. Typically, two types of starches have been used for this application. One group consists of the high-amylose starches, derived from hybrid corn. These contain 55% to 70% amylose. This high percentage of amylose imparts high-set gelling properties and excellent film-forming, due to the retrogradation of amylose. Blended with the second type of starch (thin-boiling starches), high-amylose starches aid in reducing drying time. The commonly used term, "thin boiling," refers to the low hot-paste viscosity developed when starches are acid-thinned. This low hot viscosity allows high solid sugar/starch solutions to be rapidly cooked and deposited. The thin-boiled starches provide a firm gel over 48 to 72 hours. However, this can be rapidly accelerated by blending with a high set-back starch, like a 55% to 70% amylose variety, to 16 hours or less.
Thin-boiled starches are designated further by "fluidity" - the inverse of viscosity. This means that an unmodified starch has a "zero" fluidity. Further thinning results in a "60," then a "65," "72," "75" or a "90" fluidity. As starches are acid-thinned, viscosity decreases, and gel strength decreases, but at a slower rate. A "90" fluidity starch has the lowest viscosity of the acid-thinned starches, as well as the lowest gel strength. Thin-boiling starches with lower fluidities will boil with a heavy viscosity, and produce a short texture; gel strength decreases as hydrolysis continues. Higher-fluidity starches boil thinner, but produce a more stringy texture and a weaker gel.Blending in unmodified starches increases chewiness and body in fudges and caramels. High-amylose starches can be blended (for example, using a 30:70 ratio) with a thin-boiling starch to increase gel rate and strength. However, when high-amylose starches are blended with thin-boiling starches, certain precautions must be taken. High-amylose starch requires a much higher cooker temperature, 330° to 340(F vs. 285(F for thin-boiling starches. Gel strength can dramatically increase, causing product "tailing" at too high a level. Speed of gelling, as well as overall viscosity, also must be monitored to maintain proper texture.
"For deposited jelly candies, you want a thin hot viscosity," says Moore, "followed by quick gelling properties once you get it into the mold. In the case of high amylose starch, the gelling speed and the final gel strength are related."High-amylose starches are available as 50%-to-55% amylose and 70% amylose varieties from National Starch and Chemical Co. and Cerestar USA. National Starch also offers a line of patented quick-setting starches for high-speed gels in eight to 10 hours, as well as patented, low-cooking-temperature, quicksetting starches. Batch cookers typically can handle lower fluidity starches, but higher fluidity starches are generally preferable in continuous operations.
Thin-boiling and high-amylose starches and blends of these are used generally in hard gum candies and soft jellies. Hard gums, such as some jujubes, pastilles and cough drops, require about 20% to 30% starch, creating a tough, melt-away texture that is not chewable. Soft jellies, such as jelly bean centers, orange slices, gum drops and spearmint leaves, possess a soft, jelly-like texture with a clean-cut bite. These products require much less starch, generally in the 9%-to-14% range.
New! Improved!Relatively new starches, made available in the last 15 years, can produce quick-setting jellies at lower cooker temperatures. These are the patented "cold-water swelling" starches (referred to earlier as granular instant starches), developed by Staley. One line of products, developed from a common corn or potato starch base, can be used in extruded candy centers or gelatin candies. Another line, produced from common corn, functions as low-temperature (250° to 260°F) and low-usage (2% to 4%) starches for licorice extrusion, wire-cut fondants, caramel, nougat and slab taffy. These products are produced by a unique process and possess features different from other available confectioner starches. Naturally, if the jelly can be deposited cold, volatile natural flavors can be better preserved, and higher levels of acids, such as citric or malic, can improve flavor.
"With cold-water-swelling starch technology, you can develop formulations that will gel in the mould without cooking," explains Moore. "You disperse it into a liquid corn syrup - it has to be primarily high fructose - mix it cold, and there is a certain length of time where the starch doesn't have enough moisture available to gel, so you can deposit it. Then, in a short length of time it will gel. This gel varies from a classic short-textured starch candy to a more resilient gelatin-like candy."Gelatin supplementation or replacement also represents an area of high interest for starch or similar ingredients, according to an industry source. Gelatin forms very clear, relatively stable gels, especially well-suited for marshmallows and gummy candies. In marshmallows, gelatin acts as a foam stabilizer and whipping agent. High-bloom gelatins produce high gel strength, good transparency and neutral taste. The industry uses low-temperature starches to provide additional heat stability, preventing melting during shipping, and lower costs in gelatin candies. In addition, interest is high in a reasonably priced gelatin replacement for kosher products.
Confection coatingNew products for planned confections also currently capture industry interest. Panned confections are products formed by another process to prepare a hard or soft "center," then coated with successive layers to provide a separate outer texture. Various confections fall into this group: hard-coated (jawbreakers, nonpareils, sugar-coated chewing gum, sugar-coated lozenges); chocolate-coated (malted milk balls, raisins, caramels, nuts); and soft-cooked (jelly beans, marshmallows, jelly eggs, Cinnamon Imperials, Boston Baked Beans).
The panning process coats candies by rotating them in a coating material in a revolving pan. Hard-coated products start with a center, such as a sugar pellet or a nut, then panned in sugar/corn syrup blends. Layers are panned on, then dried successively until enough layers are applied to reach the proper size. Color can be introduced in any layer(s). Once the last coating has been applied, the product is "polished" with a wax and/or confectioner's glaze. In certain products, such as nonpareils, dusting starch between layers prevents sticking and whitens the product. Hard coatings are applied with heat and air for drying.Soft-panned products do not require air and heat during panning. Instead, an adhesive solution is applied to the centers. Then, the centers receive a sugar coating. This process of adhesive and sugar is repeated to build the layers to the correct size piece. Flavor and color can be added to the coating layers. After coating, jellies are conditioned in an air-conditioned room (approximately 50% relative humidity for about two days). The pieces are finished with a sugar/syrup mixture, then polished with a liquid polish, such as carnauba wax.
Both hard- and soft-panned centers are commonly pre-coated with gum arabic, a low-viscosity, highly soluble exudate gum that serves as a binder, thickener, crystallization inhibitor, film former and emulsion stabilizer. As much as 10% to 40% gum arabic can be used as a binder in some products. Gum arabic has displayed seasonal variations in quality, availability and cost, so starch suppliers have focused on its replacement for some time. Several starch products have been developed that can be used in this application.According to Mike Kramer, applications scientist at Grain Processing Corporation, Muscatine, IA, the company has a line of modified food starches that can be used as an undercoat in panned candies or as a surface shine on chocolate. Preparations of 15% to 25% in water (cooked at 180(F for 10 minutes, then cooled) are required, with maltodextrin, sugar, and/or corn syrups added to increase solids and facilitate drying. Lower DE maltodextrins combined with these starches produce stronger, more opaque films, and higher DE maltodextrins adhere flavors more effectively. "Plasticizers, such as sodium citrate, propylene glycol or glycerin, increase the pliability of the film while raising the gloss," Kramer says.
Starch can also help the bottom line by shortening process time. "Gum arabic can be replaced as a pre-coating on sugar-free gum," says Cerestar's Shinsato. The company has developed a product that "considerably lowers coating time, since the viscosity of this acid-thinned, hydroxypropylated tapioca starch is low, even at 50% of the total layer amount, vs. a maximum 40% concentration for gum arabic. This results in less layers required, resulting in lower coating time."National Starch also offers a range of confectionery adhesive starches derived from tapioca and waxy maize. These have a range of viscosity and gelatinization temperatures for different applications.
Most of the more recent product improvements seem to have occurred in this area: replacement of higher-priced, less-available hydrocolloids with lower-cost starch alternatives. Although product types have not changed radically in the past 25 years, understanding of starch-application technology has helped the category grow. Much of the emphasis has concentrated on starch and starch products as film-formers, adhesives, glazes and gelling agents. These are the types of starch-based confectionery ingredients that we are likely to see evolving in the future.
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