Liquid filtration in the food industry: example with steviol glycoside

The company specializes in the production and marketing of steviol glycosides, derived from a South American plant, Stevia rebaudiana Bertoni. This shrub contains molecules that give foods a sweet taste without adding color. The final product comes in the form of a white powder. To manufacture it, various filtration steps must be implemented throughout the production chain.

Since 2014, Pemflow had been supplying the company with 20 µm bag filters for the first filtration stage, specifically the filtration of Stevia leaves infused in hot water.

In 2015, as the company also needed filtration equipment for filtering the syrup used to sweeten certain sodas, they consulted our filtration experts for the supply of filter capsules in 5 / 0.45 & 0.2 µm, equipped with 1.5-inch Tri-Clamp connections.

The company’s CEO recently consulted us to implement a system providing filtration before chromatography. This step occurs at the end of the process, according to the following sequence:

• Infusion of Stevia leaves in hot water
• Filtration through 1000/500 µm mesh
• Liming to raise the pH to 10
• Centrifugation for sludge removal
• Production of a “clear” solution at 10% dry matter
• Passage through the chromatography column, equipped with a 20 µm mesh filter

The customer therefore wanted to insert a safety filtration step before the chromatography stage, in order to prevent clogging of the column’s mesh. Clogging occurred after only a few hours, after treating approximately 2 m³ of extract, whereas the daily volume to be treated was 5 m³. The extract to be filtered contained few particles but tended to precipitate during processing. Particle size did not exceed 10 µm. The chromatography column was fed by a centrifugal pump, installed in a skid.

The customer’s specification was as follows:

• stainless-steel housing on stand or support
• 1-inch clamp inlet/outlet connections
• pressure gauge on the inlet port
• flow rate: 1250 L/h
• pressure range: 0.4 to 0.8 bar
• temperature: ambient
• nominal rating: 10 µm

Given the service conditions, we selected a 20-inch single-cartridge stainless-steel housing, code 3. The chosen filter body features a molded head and a stainless-steel clamp closure. It is widely used in various industrial liquid-process applications.

We recommended installing a cartridge providing nominal depth filtration. Its density gradient ensures excellent retention capacity and low pressure drop thanks to its large void volume. This solution fully met the customer’s expectations.

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