The present invention relates to sugar products and, in particular, to a new structural forms of sugar and edible composition made with this form of sugar.
Crystallization is one of the oldest industrial chemical transformation processes known. Vast quantities of crystalline substances are produced for commercial purposes, i.e., in excess of 100 million (10%) metric tons per year. One of the most common products prepared by crystallization is sugar.
Crystallization of sugar is a complex process. The growth of crystals involves simultaneous transfer of heat and mass in a multi-phase, multi-component system. While the coexistence of these conditions alone presents complex control problems, fluid and particle mechanics and thermodynamic instability create further complications.
Conventional wisdom in the science of sugars teaches crystallization by supersaturation. Supersaturation requires removal of water from a solution to increase solute concentration beyond that characteristic of equilibrium. Cooling, evaporating, and precipitating are used. Manufacturing procedures for crystallizing sugar are heat and energy intensive. Moreover, nucleation of sugar crystals during supersaturation is relatively uncontrollable. Consequently, the size and shape of the resulting crystals are unpredictable.
The drawbacks of known sugar manufacturing procedures are especially manifested when preparing sugar having reduced-size crystals. Reduced-size crystalline sugar product is referred to herein as microcrystalline sugar. Individual particles of microcrystalline product are typically no greater than 50 micrometers (.mu.m).
Classification of crystallizers known in the industry follows the methods by which supersaturation is achieved. The technical aspects of procedures used for sugar crystallization are well documented, and they are generally high-energy procedures.
For example, one method of manufacturing reduced-size crystals involves grinding and sieving crystalline sugar. Grinding is energy intensive. Moreover, fracturing sugar results in a wide distribution of sizes of ground sugar crystals. The large crystals must be reground and sieved. Much of the product is lost as fines. Thus, grinding and sieving is expensive and inefficient.
U.S. Pat. No. 3,981,739 to Dmitrovsky et al discloses preparation of crystalline sugar from solution by (1) concentrating a solute in the presence of seed crystals added thereto, followed by (2) further removal of solvent through heating and evaporation of the stream resulting from the first stage concentration. This energy intensive procedure produces sugar crystals having an average size in the range of 325-425 .mu.m. The Dmitrovsky et al '739 disclosure is a solution process that relies on nucleation by addition of seed crystals while concentrating by high heat and vacuum evaporation. The same procedure is disclosed in U.S. Pat. No. 4,056,364 to Dmitrovsky et al.
U.S. Pat. No. 4,159,210 to Chen et al describes a method for preparing crystallized maple sugar product by (1) concentrating maple syrup to a solids content of about 93-98 weight percent (wt%) in the presence of heat and partial vacuum, and (2) impact heating until transformation and crystallization of the syrup occur. The product may then be cooled, milled and screened to a suitable size range. The Chen et al '210 procedure is energy intensive, relies on "beating" to induce nucleation of the crystals, and calls for subsequent milling to obtain reduced-size crystals.
In U.S. Pat. No. 4,362,757 to Chen et al a crystallized sugar product and a method of preparing same are described. The method disclosed in the Chen et al '757 reference includes concentrating sugar syrups to a solids content of about 95 wt % to about 98 wt % by heating to a temperature of about 255.degree. F. to about 300.degree. F. The resulting concentrated syrup is maintained at a temperature of about 240.degree. F. in order to prevent premature crystallization. A premix consisting of an active ingredient (e.g., a volatile flavor, an enzyme, an acidic substance such as ascorbic acid, a fruit juice concentrate, or a high invert sugar substance) is mixed with the concentrated sugar syrup. The combination is subjected to impact heating until a crystallized sugar product made up of fondant-size sucrose crystals and the active ingredient is formed that has a moisture content of less than 2.5 wt %. The Chen et al '757 process required heat intensive concentrating and heating for nucleation.
U.S. Pat. No. 3,365,331 to Miller and U.S. Pat. Nos. 4,338,350 and 4,362,757 describe a process for crystallizing sugar which involves impact beating a sugar solution to provide nucleation. The process involves input of a considerable amount of energy and has problems directly related to temperature control.
Other disclosures include British Patent Specification No. 1 460 416 and U.S. Pat. No. 3,972,275 (Tate & Lyle Limited), which disclose a continuous process wherein a syrup solution is catastrophically nucleated and discharged into a crystallization zone. Catastrophic nucleation is achieved by subjecting the solution to shear force that can be applied in apparatus such as a colloid mill or homogenizer. The solution is discharged onto a moving band where the water must be boiled off by maintaining the material at a relatively high temperature. A related process has been disclosed in British Patent Specification 2 070 015 B and U.S. Pat. No. 4,342,603, which is used for crystallization of glucose. In the disclosed procedure a supersaturated solution is subjected to shear force and allowed to crystallize on a belt. Both the sucrose process and the glucose process require solution processing at high temperatures and are, consequently, energy intensive.
U. K. Patent Specification GB 2 155 934 B of Shukla et al discloses a method for crystallizing sucrose or glucose from a solution. Shukla et al subject a sugar solution to evaporation to produce a supersaturated sugar solution. The supersaturated solution is then subjected to shear in a continuous screw extruder to induce nucleation. The retention time of the syrup is below 25 seconds (on the average) at a temperature of 155.degree. C. to 145.degree. C. (239.degree. F. to 293.degree. F.) for sucrose, and 100.degree. C. to 135.degree. C. (215.degree. F. to 275.degree. F.) for glucose. After the syrup is subjected to progressive nucleation, Shukla et al pass the syrup onto a moving band to permit crystallization to continue at a gradual rate at a relatively high temperature. The Shukla et al process requires maintenance of the solution at temperatures that do not drop below the boiling point of water.
U.S. Pat. No. 3,615,671 to Shoaf discloses a method of producing food products by encasing dry particular food particles within a casing of spun sugar filaments. In order to enhance (1) shaping of the fibers and particles and (2) the tendency of the fibers to stick to each other with a minimum of compression, Shoaf uses a humectant in the sugar mix to be spun and controls the relative humidity of the gases surrounding the filaments as they are spun. The humectants described as useful are as follows: invert syrup or corn syrups and polyhydric alcohols, e.g., sorbitol, glycerol and pentahydric alcohols, e.g., xylitol. Shoaf is concerned with preventing crystallization of the spun sugar in order to enable the manufacturer to encase dry food particles by wrapping and compressing filaments of the spun sugar around the particles.
More recently, a trade brochure provided by Domino Sugar Corporation, Industrial Products, entitled "Co-Crystallization" (undated) describes a product in which microsized crystals form aggregates having a second ingredient disposed over the surface of each aggregate. The process for producing this new product requires that all starting materials must be in a liquid state. Therefore, solvent must be driven off by heat and/or vacuum in order to concentrate the syrup for crystalline growth. As in other solution processes, energy is required to transform the sugar to microsized crystals.
Inherent in the procedures set forth above, as well as other procedures known in the art, is the technical philosophy of dehydration to promote crystallization. Supersaturation, pan drying, and nucleation by agitation or chemical reaction depend on the principle of eliminating water to form crystals. A common difficulty with crystallization based on this technical underpinning has been lack of control over crystalline growth.
Another method of making microcrystalline sugar is disclosed in U.S. Pat. No. 5,518,551 and 5,601,076 to Battist et al. This method requires the addition of amorphous sugar to a large volume excess of a liquid that is mostly a liquid in which sugar is not soluble. This liquid preferably contains a solvent for the sugar, i.e., water, which is said to contribute significantly to the formation of crystals. The resulting produce is distinctively spheroidal wherein smaller crystals are arranged in a "helical" pattern. This method produces a viable product with small crystals, but the method requires relatively large amounts of organic liquids such as ethanol or xylene, which can be problematic to handle both with respect to flammability and environmentally acceptable disposal. Moreover, removal of the large quantities of these organic liquids consumes large amounts of time and energy, and the use of such liquids adds material costs to the process. Even despite such efforts, it can sometimes be difficult to remove trace amounts of the organic liquid, with residual amounts capable of interfering with taste when the crystal product is used in foods.
Thus, it would be a significant advance in the art of crystallization to provide a mechanism for crystal formation which departs from traditional dehydration and that provides a low energy means for producing a crystalline sugar product.
Accordingly, it is an object of the present invention to enable the artisan to make a sugar product which has a predictable and uniform crystal size without energy-intensive procedures. Other objects and surprising new sugar/crystal technology are disclosed in the remainder of the specification.