Ion exchange resins for the food and beverage industry

Depending on its origin, thin juice contains varying amounts of non-sugar substances, e.g., ash. During evaporation from 15 Brix to 65–70 Brix there is a risk of scale formation. To prevent scale forming in the evaporation station, to produce soft molasses, or to prevent precipitation of thick juices during storage, the alkaline earth ions can be removed with Lewatit^® cation exchange resins of differing acid strengths. Various methods can be used for this.

The color of sugar juice from beet and cane increases during the production process. Colorants such as caramel color bodies, melanoidins and melanin-polyphenol-iron complexes are formed. When producing refined sugar, various Lewatit^® adsorber resins based on styrene or acrylic polymers can be used to decolorize sugar syrups with more than 1,000 ICU to meet all quality requirements in the sugar industry.

If liquid sugar syrups only need to be desalinated to improve the quality of the sugar, inversion should be avoided if possible. This can be achieved by preventing the occurrence of H+ ions. The process can take place at temperatures up to 60°C, making it very suitable for tropical regions and farms where the dry matter is at least 60 Brix. A subsequent inversion is possible in individual cases.

The hydrolysis of polysaccharides and oligosaccharides is catalyzed by H+ ions. The splitting off of sucrose leads to a mixture of glucose and fructose, which turns polarized light to the left. This process is well known as inversion. The resulting mixture is invert sugar, which is processed into artificial honey and liquid sugar. Liquid sugar, in particular, has grown in importance as it is widely used to sweeten non-alcoholic soft drinks.

Nowadays, inulin is used as an ingredient in food production, for example in yogurt as a fat substitute and to improve the taste, texture, and mouthfeel. In sausages it is used to increase the fiber content. Inulin is one of the prebiotic food additives. It also serves as a base for the hydrolytic production of fructose and oligofructose. Inulin can be extracted from the beets of, for example, chicory and topinambur.

The salt-rich raw thin juices have to be demineralized by ion exchange resins. Mixed-bed arrangements with Lewatit^® resins are used for subsequent polishing of the fructose.

Lewatit^® MDS types are monodisperse ion exchange resins with a uniformity coefficient < 1.1 and a particle size ranging between 290 and 370 μm. The resins are commercially used in chromatographic separation processes with simulated moving bed equipment, e.g., sugar recovery from molasses, separation of glucose and fructose, size separation of sugar molecules, separation of organic acid, and separation of amino acids.

From raw materials such as corn, wheat, potatoes, rice, tapioca, etc., the starch industry uses enzymatic hydrolysis of starch to produce a variety of sweeteners. After the starch hydrolysis, Lewatit^® resins are used for processing, e.g., of glucose and maltose, by demineralization and decolorization of the syrup. Proteins and residues of by-products can be removed as well.

For syrups with a high dextrose equivalent, such as B. dextrose and fructose (after isomerization), and also syrups with a low dextrose equivalent, e.g., glucose and maltose, Lewatit^® resins are used in co-current or counter-current systems, preferably in double-pass/merry-go-round systems.

Sugar alcohol from various nickel-catalyzed hydrogenated mono- and di-saccharides is of enormous commercial interest for sweetening a wide range of products because it has low calorific value and does not cause dental caries. After hydrogenation, the raw polyol solution is decolorized and demineralized with ion exchange resin. Various arrangements can be used.

Citric acid is the most important organic acid produced in tonnage and is extensively used in food and pharmaceutical industries. It is produced mainly by submerged fermentation from different sources of carbohydrates, such as molasses and starch-based media. Lactic acid is an organic acid occurring naturally in the human body and in fermented foods. It is used in a wide range of food, beverages, personal care, healthcare, cleaners, feed and pet food, and chemical products as a mild acidity regulator with flavor-enhancing and antibacterial properties.

The commercial production of lactic acid is typically done by fermentation from different sources of carbohydrates. Food acids such as citric and lactic acid need to be demineralized after fermentation, mainly to eliminate sulfuric acid and sulfate ions. Effective resins for the demineralization of food acids are strong acid, gel-type Lewatit^® S resins combined with weak base anion Lewatit^® S resin.

Pectin is usually extracted from citrus peel by nitric acid. The acidic thin juice contains approximately 1% pectin, 2% nitric acid, and 300–400 ppm calcium ions. Calcium ions impair the quality of pectin so the concentration of such ions needs to be reduced by ion exchange. Calcium ions can easily be removed with Lewatit^® ion exchange resin.

Gelatin and collagen hydrolysates are pure collagen protein, which is obtained from animal raw materials from pigs, cattle, or fish. This raw material is collagen-rich tissue from animals, which has been approved for human consumption and which meets the requirements of gelatin and collagen production. The polypeptides contained in the raw material are treated with a gentle, enzymatic process until the desired molecular weight of the peptides is reached.

Depending on the enzymes and hydration conditions, the final product can deviate more strongly with regard to the distribution of the molecular weight or other parameters. In contrast to classic gelatin, collagen peptides or collagen hydrolysates have no gelling ability.

In order to meet the requirements of the food, pharmaceutical, and cosmetics industries, desalination and decolorization in combination with polishing with Lewatit^® ion exchange resins may be necessary.

Alongside large amounts of interfering salts, whey contains valuable proteins and lactose. The recovery and processing of these substances is becoming more and more important. However, the whey has to undergo suitable treatment in order for the protein and lactose to be extracted and used. Effective resins for the demineralization of whey are strong acid, gel-type Lewatit^® S resins combined with weak base anion Lewatit^® S resins.

The production of grape most requires extensive decolorization and demineralization to prevent the salts overriding the typical taste of the reduced sugar content (15–20%). Refined most can be added to wine most before fermentation to produce high-quality wine. It is also used to blend fruit drinks, wine supplements, and carbonated soft drinks. Non-functionalized adsorber resins are used to reduce polyphenolic colors, while conventional SBA types are used for non-selective color removal.

Apple and pear juice are used as blending juice in carbonated soft drinks. The juice contains approximately 12% sugar as di- or mono-saccharides. Apple and pear juices also contain polyphenolic color components, which are formed enzymatically during extraction. They can be removed with adsorber resins. Afterwards the clarified juice is demineralized with ion exchange resins. These juices are passed through a weakly anionic resin prior to demineralization because of their high free acid content.

Pineapple juice, primarily from waste trimmings, contains roughly 10% sugar and extremely high quantities of citric acid and nitrogenous components. To allow use as canning syrup, demineralization and partial decolorization are necessary. In view of the high concentration of acid and salts, double-pass filtration is recommended.

Orange juice, either freshly extracted or reconstituted juice, is neutralized using weak anion resins. The resin reduces free citric acid as well as more weakly dissociated acid such as ascorbic acid and folic acid. To recover valuable ascorbic and folic acid, it is advisable to “overload” the resin in order to ensure displacement by the stronger citric acid.
Another specific application for adsorber resin is debittering of orange juice. Orange juice contains 20–30 ppm bitter components like limonin or hesperidin, which could otherwise be tasted.