Ultrasonic extraction is a non-thermal process and thereby preferred for the extraction of polyphenols such as catechins from tea. Ultrasound increases the efficacy of extraction process at lower temperature so that a degradation of the healthy components is prevented. High temperature extraction often leads to degradation of polyphenols and increase protein and pectin extraction which interfere with the organoleptic quality of tea by cream formation. The ultrasonically assisted cold brew method provides a tea beverage with better sensory attributes as it can be carried out at low temperature avoiding the evaporation of volatile components and the degradation of temperature sensitive of biomolecules (e.g. antioxidants). Studies have also shown that the ultrasonic method gives a higher extraction yield of polysaccharides than the conventional method with boiling water. Polysaccharides are health-beneficial like antioxidants, providing hypoglycemic, anti-HIV, anti-cancer, anti-blood coagulant, anti-radiation, and hepatoprotective impact.

Tea is an aromatic beverage, commonly prepared by pouring hot or boiling water over cured leaves. Cold brew is the process of steeping tea leaves in room temperature or cold water for an extended period (approx. 10-15 hrs.). Cold brewed tea can be prepared by placing loose tea (or tea bags) in cold water and leaving the container for a number of hours. This is very time-consuming and the extraction is often incomplete. The ultrasonic cold brew method speeds up the infusion process drastically, transferring the ingredients (caffeine, phenolics, catechins etc.) of the tea leaves into the water. Since the tea is not brewed with boiling water, the ultrasonic cold brew results in a smoother flavor.

Cold brew tea is rapidly made by sonication. The UP400St extracts flavour and health-promoting compounds from the tea leaves within seconds without applying heat.

Cold Brew Tea

While most tea is prepared using (boiling) hot water, it is also possible to brew a tea infusion from tea leaves using room temperature or cooled water. This requires a significantly longer steeping time to extract the active ingredients and flavor. To intensify the extraction of the key components and to accelerate the process, power ultrasound is the perfect tool. Besides a more complete extraction in a very short time results the ultrasonic cold brew in a different flavor profile.

Advantages of Ultrasonic Cold Brew Process

The conventional cold brewing has some disadvantages compared to the steeping in hot water. During a conventional cold brewing less active compounds (e.g. catechins, polyphenols, caffeine etc.) are extracted resulting in a lack of the nutritional and healthy benefits of tea.

Advantages Of Ultrasonic Cold Brew

rapid

mild process

high extraction yield

energy saving

simple & safe operation

low costs

Ultrasonic Cold Brew for Industrial Production

Whether you want to produce small, medium or large volumes for the commercial production of cold brew tea – Hielscher has the suitable ultrasonic equipment for your purposes. Whilst small to mid-size volumes can be processed in batches, for larger volumes is a sonication in continuous mode recommended. Various ultrasonic processors with capacities from 500W to 16,000W and a broad range of sonotrode, flow cell reactors and accessories allow for the optimal process settings.

Click here to read more about our powerful industrial ultrasonicators!

Ultrasonic Cold Brew Tea Recipe

For feasibility tests and the preparation of smaller volumes (500 – 1000 mL), the ultrasonic cold brew can be easily carried out with an UP200Ht or UP200St. Find the instructions below:

Pick a suitable vessel. The size of the glass beaker or plastic vessel should match the volume (do not choose a too big vessel).

For 1L of tea, add 10 – 15gr (approx. 2-3 Tbs) of whole tea leaves.

Fill with cold (filtered) water.

Sonicate for approx. 30 – 60sec. Longer time extracts stronger flavor and more caffeine. White teas will brew the quickest, followed by green teas and twisted/flat oolongs, allow most time for rolled oolongs, pu-erhs, herbal infusions and black teas.

Use a tea strainer to separate the tea leaves from the beverage. Serve according to taste (e.g. pure, over ice cubes, with sugar or milk) or store in the refrigerator.

Ultrasonic Cold Brewed Coffee

Similar to the ultrasonic tea extraction and cold brew, coffee can prepared in cold water under sonication. Power ultrasound is also used for the extraction of caffeine and phenolics from coffee beans. Click here to learn more about the ultrasonic caffeine extraction!

Literature/References Banerjee, S.; Chatterjee, J. (2014): Efficient extraction strategies of tea (Camellia sinensis) biomolecules. Food Scientists & Technologists 2014.

Shalmashi, A. (2009): Ultrasound-Assisted Extraction of Oil from Tea Seeds. Journal of Food Lipids 16; 2009. 465–474.

Saleh, I.A.; Kamal, S.K.; Shams, K A.; Abdel-Azim, N.S.; Aboutabl, E.A:; Hammouda, F.M. (2015): Effect of Particle Size on Total Extraction Yield and Silymarin Content of Silybum marianum L. Seeds. Research Journal of Pharmaceutical, Biological and Chemical Sciences 6/2; 2015. 803-809.

Venditti,E.; Bacchetti,T.; Tiano, L.; Carloni, P.; Greci, L.; Damiani, E. (2010): Hot vs. cold water steeping of different teas: Do they affect antioxidant activity? Food Chemistry 119/ 4; 2010. 1597–1604.