Sulzer Technical Review Issue 1 / 2020
TWICE™ — an ice-cold process for highest food concentration
When it comes to food, we all have different tastes and needs. But we all want our food to taste fresh, look good, have the best nutritional content, and be healthy.
To meet all these requirements, food companies invest considerable efforts in research and development and marketing. And they all rely on process technologies to produce and develop new products that will enable them to satisfy their existing consumers and gain new ones. As a proactive and committed technology and process solutions supplier, Sulzer applies its expertise to support food companies in meeting their ambitious and exciting challenges.
At Sulzer, we design innovative food processing technologies and equipment. We understand the market and provide appropriate solutions to meet its needs. In our ultramodern test center, our skilled engineers have developed a new process to produce highly concentrated liquid foods that present unequaled nutritional and organoleptic properties. Organoleptic properties are the aspects of food, water or other substances that are experienced using the senses — including taste, sight, smell and touch.
With the following white paper, Sulzer presents TWICE™, a cutting-edge liquid food concentration process. It offers a viable alternative to evaporation and produces the finest quality with high concentration levels. This new concept will provide food companies new product development opportunities to ensure and strengthen their position on the demanding and rapidly changing liquid food market. It is now possible to overcome challenges that were insurmountable before with the help of this ingenious process.
Severine Dette, Sales Engineer, Crystallization, Winterthur
Dr. Severine Dette, Sulzer Chemtech, Winterthur, Switzerland
Lucas Maetz, Sulzer Chemtech, Winterthur, Switzerland
First presentation as Sulzer White Paper, December 2019
The global liquid food industry is expected to reach an estimated USD 1.9 trillion by 2021 . Growing urbanization and disposable income are the major drivers for the growth of this market. According to the United Nations, 68% of the world population will live in urban areas by 2050, compared with 55% today . Urban lifestyle and higher disposable income have led to a growing interest in sports and a healthier way of eating and drinking . Indeed, consumers are paying more attention to nutrition and its impact on their health and environment. This results in strong market demand for premium quality, fortifying products and healthy liquid foods [4, 5, 8]. All product categories (ready-to-drink tea and coffee, juices, nutraceuticals, beer, wine, etc.), as well as all the ingredients used to produce these drinks, are affected by this general market trend.
Liquid foods concentration has been used for decades. The technique is extensively used in the liquid food industry because its scope of application is broad, and its economic benefits are substantial. The main goal is to reduce the volume of water in a product so that the relative amount of the product increases. This provides multiple advantages. The process reduces the volume and weight of the product, it facilitates storage, handling and transportation and lowers the related costs. The product’s shelf life is also substantially longer. Concentrates can be easily reconstituted by adding water. Orange juice is a notable example of liquid food concentration. The global success of this juice results mainly from this process. Brazil is, by far, the world’s leading producer and exporter of orange juice . Once the fruit is harvested, it is squeezed, then concentrated through evaporation, and later frozen. The frozen concentrate is stable and can, therefore, be shipped around the world and stored before it is sold. Thanks to these concentration and freezing processes, consumers enjoy Brazilian orange juice all year long with constant quality at a reasonable price.
With all available concentration technologies our clients can save storage and distribution costs. With a focus on high-quality and value-added products, freeze concentration has a wide spectrum of applications. Products such as fruit and vegetable juices, coffees, teas, herbal and algae extracts, as well as beer, wine and many more are concentrated successfully with best-in-class nutritional and sensorial qualities.
- Guarantee of aroma, flavor and color in the product — only pure water is removed
- Low operating temperature — concentration of heat-sensitive products
- No filters (no fouling) and no centrifuges
The filling step starts with the piston at the highest position. As the piston moves downward, the space that is created above the piston is filled with an ice slurry consisting of a mixture of crystals and concentrated juice from the circulation loop. At the same time, the space below the piston decreases and pushes the concentrated juice either back to the circulation loop or out of the process as the final product. The filling stroke ends with the piston at the lowest position.
The space between the piston and the crystal bed is filled with ice crystals and concentrated juice. The piston then moves upward, and concentrated juice flows through the filter screen above the piston to the space below the piston. The ice crystals cannot pass through the filter screen and, thus, they remain in the wash column where they are compressed into a bed of crystals within the cylinder. The piston has not reached the highest position yet.
A small overpressure from the melting loop forces pure water (ice molten in the melter in Fig. 1) downward through the filter screen thereby washing the crystal bed. The wash front gets displaced and moves downward.
The fourth step starts by activating the rotating disk equipped with scraping knives . The piston continues to push against the crystal bed and moves it upward as the scraper knives shave pieces from the ice crystal bed. The scraping step is finished when the piston has reached its highest position and the rotating disk has been switched off.
Freeze concentration with separation of washed ice crystals has been used for more than 30 years. Commercial units are in operation around the world. The technology is every much appreciated, and results achieved with it exceed customers’ expectations. Despite these strengths, freeze concentration with crystal suspension shows its limits at concentration levels higher than 45 Brix (°Bx)* . To overcome this challenge, Sulzer developed TWICE™, a new two-step crystallization process.
Freeze concentration faces separation difficulties with higher concentrated products due to the increasing viscosity at the freezing point. Consequently, separating the ice crystals from the remaining liquid concentrate turns to be a challenge. The viscosity at freezing point is an important parameter. Sulzer’s engineers observed that when the viscosity exceeds 20 centistokes (cSt), the separation of ice crystals in the wash column becomes critical. Therefore, viscosity is the limiting factor of freeze concentration technology. Figures 3 and 4 illustrate multiple juices and coffee extracts. When the concentration level exceeds 40 °Bx, the concentrate surpasses the viscosity of 20 cSt.
Sulzer developed a new cold crystallization process — which combines suspension freeze concentration (Fig. 5) and static layer crystallization (Fig. 6) — called TWICE™.
So far, high concentrated liquid food concentrates (> 60 °Bx) have only been produced using evaporation technology. However, evaporation has associated drawbacks such as loss of aroma, flavor and color. The combination of suspension freeze concentration and layer crystallization, named TWICE™, can increase the concentration of various juices up to 61 °Bx (Fig. 7). That is equivalent to results achieved by evaporation but without the associated drawbacks.
TWICE™ is a new liquid food concentration process. This process is based on the combination of two crystallization technologies offered by Sulzer, namely, suspension freeze concentration and static layer crystallization. The synergy of these two processes enables food engineers to produce liquid food concentrates with unparalleled organoleptic and nutritional qualities. The revolutionary procedure has proven the ability to reach concentration levels up to 60 °Bx for juice applications and up to 40 wt% for coffee extract applications.
 Lucintel [Internet]. Growth Opportunities in the Global Beverage Market. February 2017.
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