Food & Beverage Concentration

Food concentration means removing part of solvent from liquid food for better production, preservation and transportation. It could be categorized to evaporation and freeze concentration.

Evaporation Concentration

Evaporation works on the basis of volatile differences between solute and solvent. When the volatility of the solute in the solution is small and the solvent has obvious volatility, the solvent is vaporized by heating to concentrate the solution. The food solution to be concentrated is placed in an evaporator and heated by an external heat source. As the temperature rises, the solvent (water) in the solution will be converted into vapour, because the boiling point of water is relatively low and it is easy to vaporize.

During the evaporation process, the solvent vapour escapes continuously, while the solute (such as sugar, protein, minerals, vitamins, pigments and other non-volatile or difficult-to-volatile components) remains in the remaining solution due to its higher boiling point and lower volatility. The evaporated solvent vapour is then collected and cooled through a condenser to convert it back into liquid form. This process can recover some energy and reduce energy consumption. The condensed water can be recycled or discharged.

The original solution is concentrated into smaller volume after evaporation and condensation as the increasing concentration of solute. The concentrated food solution can be used for subsequent processing, such as further drying, candies, jams, juices, or as an intermediate raw material for food production.

Multi-stage or multi-effect evaporation and concentration system are often used in practical industrial production. According to the needs of specific production processes, food concentration needs to be accurately measured in real time to ensure stable product quality and improve concentration efficiency. Contact Lonnmeter, an online concentration meter supplier, for more online concentration meter solutions.

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Main Features of Evaporation and Concentration

Heating temperature and time should be considered seriously in food and beverage evaporation. “Low temperature and short time” is mainly to ensure food quality as much as possible, while “high temperature and short time” is mainly to improve production efficiency.

Excessive heating will cause degeneration, charking and caking of proteins, sugars and pectin. The processed material contacting closely with the heat transfer surface is prone to scale for the highest temperature, compared with surrounding temperature of material. Once scale is formed, it will seriously affect the heat transfer efficiency and even cause safety problems. The positive measure to solve the scaling problem is to increase the liquid velocity. Experience has shown that increasing the liquid velocity can significantly reduce the formation of scale. In addition, electromagnetic anti-scaling and chemical anti-scaling methods can be taken to prevent potential scaling.

Viscosity

Many foods feature rich protein, sugar, pectin and other ingredients with high viscosity. During the evaporation process, the viscosity of the solution increases with the concentration as fluidity decreases, which hinders the heat conduction significantly. Therefore, for the evaporation of viscous products, circulation or stirring measures forced by external force are generally adopted.

Foamability

Food materials with more protein have greater surface tension. When evaporating and boiling, there are more and more stable foams, which easily cause the liquid to enter the condenser with the steam, causing the liquid to lose.Foam formation is related to interfacial tension. Interfacial tension occurs between steam, superheated liquid and suspended solids, and solids play a core role in the formation of foam. Generally, surfactants can be used to control the formation of foam, and various mechanical devices can also be used to eliminate foam.

Corrosiveness

Some acidic foods, such as vegetable juice and fruit juice, are prone to corrosion of the evaporator during evaporation and concentration. For food, even mild corrosion often causes contamination that makes the product unqualified. Therefore, the evaporator used for acidic foods needs to be made of corrosion-resistant and thermally conductive materials, and the structural design should be easy to replace. For example, the concentration of citric acid solution can use impermeable graphite heating tubes or acid-resistant enamel sandwich evaporators.

Volatile components Many liquid foods contain aromatic and flavor components, which are more volatile than water. When the liquid evaporates, these components will escape along with the steam, affecting the quality of the concentrated product. Although low-temperature concentration can reduce the loss of flavor components, a more perfect method is to take recovery measures and then add them into the product after recovery.

Freeze Concentration

Food raw material liquid (such as juice, dairy products or other solutions containing a large amount of water) is cooled in a low temperature environment. When the temperature drops below the freezing point, the water molecules in the solution will precipitate in the form of ice crystals. This is because water reaches solid-liquid equilibrium at a specific temperature and pressure. Below this temperature, excess free water will freeze first, while solutes (such as sugars, organic acids, pigments, flavors, etc.) are not easy to freeze with water due to different solubility, but remain in the unfrozen concentrate.

Separation of Ice Crystals

The formed ice crystals are separated from the concentrate by centrifugation, filtration or other physical methods. This process does not involve the evaporation of solutes, so it can effectively prevent the degradation of heat-sensitive ingredients and the loss of aroma. The concentrate after separating the ice crystals is the frozen concentration product, which has a significantly higher solute concentration than the original solution, while retaining the original color, taste, nutritional value and flavor of the food to the greatest extent.

Controlling Freezing Conditions

During the freeze concentration process, factors such as freezing rate, freezing temperature and time need to be precisely controlled to optimize ice crystal size, morphology and separation from the concentrate to ensure the quality of the final product. Freeze concentration technology is particularly suitable for heat-sensitive foods and beverages, such as fresh fruit and vegetable juices, biological products, pharmaceuticals and high-end condiments. It can maximize the natural quality of raw materials and has the characteristics of energy saving and high efficiency. However, this method also has certain limitations. For example, the concentration process cannot be effectively sterilized and may require additional sterilization treatment. In addition, for some solutions with high viscosity or containing special ingredients, the difficulty of separating ice crystals from the concentrate may increase, resulting in reduced concentration efficiency and increased costs.

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