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This post was last edited by Qingfeng Xuchi on 2022-3-3 at 10:54. 1. The current situation in the sugar industry: As people’s living standards improve, their expectations regarding food quality also increase. Syrup is a sweet treat commonly found in our daily lives, and it has become an essential ingredient in our daily routines. Since it is made from plant juices, it is relatively safe to consume. However, as technology has gradually advanced, some people use additives in production in order to gain certain benefits. Syrups produced with these additives, if consumed over a long period of time, can have an adverse effect on human health, particularly by contributing to obesity. Most of the syrups available on the market today are made by mixing concentrated sugar solutions with flavors and colors. rather than real fruit syrups, and these syrups are sometimes diluted with water to be sold as juices. In recent years, as restrictions on the use of food additives have been imposed in our country, most syrups used in the food industry are now made from potatoes or wheat, rather than from more expensive sources such as sugarcane. As a result, the syrup prepared in this way contains some starch and proteins, as well as a high amount of non-sugar impurities; therefore, it must be decolorized. 2. Classification and description of syrup decolorization methods. Traditional syrup decolorization techniques in China currently include: activated carbon decolorization and ion exchange resin decolorization. 1. Activated carbon decolorization: Activated carbon is an amorphous form of carbon with a highly developed pore structure and a large specific surface area. Due to its lack of exchange capacity, activated carbon cannot remove ionized dyes. Pigment substances tend to ionize easily under alkaline conditions; therefore, activated carbon has a stronger adsorption capacity in acidic solutions and a weaker one in alkaline solutions. Its aromatic ring structure enables activated carbon to effectively adsorb aromatic compounds and organic substances with three or more carbon atoms; it also has a strong adsorption capacity for non-charged substances, especially showing the best effect in removing phenols. 60% of the pigments in sugar solutions are ionic in nature; therefore, using only activated carbon for decolorization does not yield good results. It is necessary to combine it with other decolorizing agents capable of removing ionic substances in order to achieve better outcomes. In the production of refined sugar, it is usually used in conjunction with anion exchange resins. Activated carbon used for sugar processing is generally one that contains a high proportion of mesopores, and its adsorption capacity is typically measured by the caramel adsorption value. Activated carbon adsorption results in high consumption and a large amount of solid waste; it can generally only be used in continuously operating systems, not in batch operations. 2. Decolorization using ion exchange resins: Ion exchange resins are polymer compounds with a network structure that contain functional groups. Ions with opposite charges on these functional groups can exchange with each other, and they can also exchange with ions from the outside environment that carry the same charge. In sugar production, most pigments are in an ionized state and carry a negative charge; they can exchange with anions, which is why anionic resins can be used for sugar decolorization. In sugar production both domestically and internationally, large-pore anion resins are generally used for adsorption-based decolorization. These large-pore adsorption resins are highly effective in decolorizing syrups, particularly in removing colloidal substances and pigments. They also possess excellent regeneration properties: fast adsorption speed, mild elution conditions with good selectivity, easy regeneration process, and a long service life. The principle behind using ion exchange resins for the decolorization of sugarcane juice is that most colorants exhibit good selectivity for strong-base anion (SBA) resins. Furthermore, it is very simple and convenient to remove these components from the resin using a salt solution (usually 10% NaCl). There are two types of SBA resins that can be used—acrylic resin and styrene resin. Acrylic resins are more resistant to impurities and are typically used for \"dirtier\" juices, generally achieving 60-70% decolorization. Styrene resin has a high decolorization rate (70-80%), but it has poor resistance to long-term contamination by impurities; therefore, it is typically used in \"cleaner\" fruit juices. The carbonated and filtered sugarcane juice is decolorized in a refining plant. Similar to the beet/corn decolorization process, due to the high color load of the raw pulp, adsorbent-type resins can be considered for syrup decolorization. 3. Sugar refining and decolorization process flow: To ensure the automatic and efficient operation of the resin units, a new system design concept has been adopted. The small resin columns are placed on a turntable, and switching between them is achieved through the rotation of this turntable. The material flow is controlled by an automatic rotating distribution mechanism, which divides the resin columns into functional areas such as exchange, washing, regeneration, and rinsing. When a resin unit reaches a designated area, the corresponding processing step is carried out. This allows each process to be executed independently while maintaining continuous operation of the entire process. Starch ----- Slurry preparation ----- Saccharification ----- Neutralization ----- Decolorization ----- Filtration ---- Resin treatment ----- Evaporation ----- Isomerization ------ Decolorization ----- Resin treatment ----- Evaporation Sugar holds the most unusual position among all consumable foods around the world. Sucrose is produced from sugarcane or beets; in fact, most refined sugar comes from sugarcane (about 75%), with the remainder coming from beet sugar. All sugars can be roughly divided into raw sugar or refined sugar. Raw sugar: Raw sugar is produced directly from sugarcane, through purification processes that do not involve the use of phosphoric acid; only a minimal amount of calcium oxide is used during the purification of the juice, thereby yielding raw sugar from sugarcane. Such sugar is brown in color and is rarely used directly. Refined sugar: Refined sugar is obtained by processing raw sugar, and it has a shiny white color. Most sugar mills purchase/import raw sugar and then process it to produce refined sugar. 4. Comparison of decolorization processes: Compared with the traditional activated carbon method, ion exchange resins have certain advantages, as clearly stated above; compared with the activated carbon method, resin treatment technology offers numerous advantages. Therefore, it is an inevitable trend for sugar mills to use ion exchange resins, with the main application being the decolorization of syrup using DuPont-grade ion exchange resins. 5. Applications and advantages of Tulsion resins in syrup decolorization. Thermax has developed two ion exchange resins that are highly suitable for syrup decolorization: Tulsion® A-72 MP and Tulsion® A-30 MP. Tulsion® A-72 MP is a large-pore styrenic strongly basic anion exchange resin, supplied in the form of chloride ions. Tulsion® A-72 MP can be effectively used in high-temperature environments (60–70°C), which are common in sugar mills. This type of resin is generally used for the decolorization of sugar solutions with a Brix value of 200–700 ICUMSA. Tulsion® A-30MP is a large-pore acrylic strongly basic anion exchange resin, supplied in the form of chloride ions. This resin can be effectively used for syrup decolorization in high-temperature (70 degrees) environments. Due to its acrylic matrix and high porosity, this resin is used for the decolorization of dark sugar syrups with a Brix value of 800–2000 ICUMSA. Unlike the macroporous styrenic resin Tulsion® A-72 MP, this resin, although it has a lower affinity for colored substances, can be easily regenerated after treatment with sodium chloride. The typical resin characteristics of Tulsion® A-72 MP and Tulsion® A-30 MP are shown in Appendix 1. Selection of Dussmann resin for syrup decolorization: The choice between a one-stage, two-stage, or three-stage treatment process is determined by the concentration of colorants in the melted sugar. The table below can be used as a reference for selecting resins: Syrup Color / Melt Color / Resin Combination. Feed colour: < 200 – ICU A-72 MP; Raw material color: 200–400 – ICU A-72 MP followed by A-72MP; 1000–2000 – ICU A-30 MP – A-30 MP – A-72 MP. Note: The use of one or two units is determined by the quality of the processed syrup. If two units are used consecutively, the decolorization results can be further improved. The first unit is mainly for cleaning, while the second unit is for polishing. The application of Dusheng resin in syrup decolorization involves multiple steps for the decolorization of sugar using this resin. Each step is as follows: · Service Cycle · Sweetening off · Backwash · Regeneration · Sweetening on during the next service cycle. Service Cycle: The sugar solution that needs to be decolorized (with a sugar concentration of 60–65%) is passed through the resin bed at a temperature of 700°C at a flow rate of 2–4 BV/hr; the flow rate through the resin bed depends on the quality level desired for the sugar solution. If the flow rate is high, it may result in very little adsorption of colored substances, and fine particles may also form, ultimately leading to a decrease in the pressure in the resin bed. An increase in color leakage or reaching a predetermined amount indicates the end of the service cycle. Decolorization using DuSheng ion exchange resin: Formation of colorants in syrups: The color in raw sugar is mainly due to coloring that occurs during the concentration of sugarcane juice; the main reasons for this are: · Heating the sugar during concentration leads to the formation of caramel. ·Formation of melanoid-type impurities. These are all reaction products of reducing the sugar content (glucose and fructose) in glycosamines (such as glutamate). ·The formation of melanin is a pigment produced by the melanin polyphenol iron complex. Principle of decolorization using ion exchange resins: The ion exchange resins used in sugar production are large-pore, strongly basic anion exchange resins of type I, which exist in the form of chloride ions. The principle of color removal through ion exchange can be expressed as: RN+ (CH3)3 Cl- + CA → RN+ (CH3)3 A- + CCl. The resins used for sugar decolorization have a high porosity, which ensures the adsorption of high-molecular-weight colorants. In addition to functional groups and structure, the properties of polymers play an important role in resin decolorization. Over the past 30 years, the ion exchange resins produced by Thermax have been widely used in the water treatment industry in India and abroad. However, these technical-grade resins intended for water treatment are not suitable for the food industry, such as the sugar industry, as this industry has very strict requirements regarding operating conditions and the purity of the final products. Sweetening Off and Other Operations: The procedure for each of the steps mentioned above is as follows: Sweetening off and backwashing of the resin are carried out using hot water (50–55°C) to remove suspended particles and restore the resin particles. Regeneration is usually carried out at high temperatures (50–55°C) using a basic salt solution of 2 BV at 10% w/v containing 0.5% to 1% sodium hydroxide. After a few cycles, it is recommended to treat it regularly with 5% hydrochloric acid to thoroughly clean the resin. Properties of Tulsion® Resins for Sugar Decolourization Application: Figures 1 and 2 show the decolourization performance and leakage characteristics of Tulsion® A-72 MP and Tulsion® A-30 MP resins (test conditions are provided below). 1. Resins used: Tulsion® A-30 MP, Tulsion® A-72 MP2. Service traffic: 3 BV/hour3. Temperature: 70°C4. Dried substance: 58-60° Brix, sugar content of 5. Feed color: ICUMSA 6 values of 350, 650, and 2000 for international sugar colors. Regeneration level: 200 g/L sodium chloride and 20 g/L sodium hydroxide (10% + 1% W/V). It can be seen from the data that by selecting an appropriate combination of resins, it is possible to obtain syrups with a colority of less than 100 ICUMSA. When this syrup is evaporated and crystallized, sugar with a chroma of 30 or less will be produced. As mentioned earlier, resin treatment also reduced the levels of sulfuric acid and phosphates in the syrup. This in turn helps to improve the clarity and whiteness of the finished sugar.