Ultrasonically Cold Brew Tea
- Power ultrasound is a proven method for intense extraction of flavors, polyphenols and active ingredients from plants.
- Cold brewed tea offers many benefits, including more intact active ingredients for the health benefits as well as a smoother flavor.
- As a non-thermal extraction method, ultrasound intensifies the extraction / infusion without degradation of the biomolecules.
- By sonication, teas and infusions can be cold brewed – without long processing time.
Benefits from Ultrasonic Cold Brew Tea
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.
Why ultrasonic cold brew?
- non-thermal extraction
- avoiding the degradation of temperature sensitive biomolecules
- avoiding volatile component evaporation
- improved extraction of aroma components and glycosidic aroma precursors
- less bitterness
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.
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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
- 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!
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Literature / References
- Md. Afroz Bakht, Mohammed H. Geesi, Yassine Riadi, Mohd. Imran, Md. Imtiyaz Ali, Mohamed Jawed Ahsan, Noushin Ajmal (2019): Ultrasound-assisted extraction of some branded tea: Optimization based on polyphenol content, antioxidant potential and thermodynamic study. Saudi Journal of Biological Sciences, Volume 26, Issue 5, 2019. 1043-1052.
- Shalmashi, Anvar (2009): Ultrasound-assisted extraction of oil from tea seed. Journal of Food Lipids. 16. 465 – 474.
- 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.
General Information about Tea
Tea is after water the second mostly consumed beverage and is known for many beneficial effect on human health.
Tea leaves contain diverse polyphenols, including flavonoids, epigallocatechin gallate (EGCG) and other catechins, which function as strong antioxidants. Other ingredients are caffeine, theobromine and theophylline.
Caffeine constitutes about 3% of tea’s dry weight, translating to between 30 mg and 90 mg per 8oz / 250mL cup depending on type, brand, and brewing method. Tea also contains small amounts of theobromine and theophylline, which are stimulants and xanthines similar to caffeine. A study found that the caffeine content of 1 g of black tea ranged from 22 to 28 mg, while the caffeine content of 1g of green tea ranged from 11 to 20mg, reflecting a significant difference. Regarding nutrition and health benefits, polyphenols are the most important components. Tea leaves contain diverse polyphenols, including flavonoids, epigallocatechin gallate (commonly noted as EGCG) and other catechins. Polyphenols appear to be responsible for the many health benefits attributed to tea, which prevent degenerative diseases. They show antimutagenic, antidiabetic, anti-inflammatory, antioxidant, antimicrobial effects as well as cancer-preventive activities to prevent cardiovascular diseases. Polyphenols are antioxidants and they function as radical-scavenger, modify signal transduction pathways, work as cell cycle checkpoints, suppress apoptosis, and influence enzymatic induction.
Green and black tea is an important dietary source that provides plant polyphenols and several studies are suggesting that polyphenols from tea may protect against diseases such as cancer, obesity or Alzheimer’s disease. Epigallocatechin Gallate (EGCG) is counted as one of the most powerful active ingredients that gives green tea its strong medicinal properties.