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Nano-EGCG could take tea benefits into clear beverages

By Stephen Daniells , 24-Sep-2010

Modified whey protein may nano-encapsulate the green tea compound EGCG and slow its rate of degradation 3.2-fold, thereby offering nano-encapsulation potential for formulators, says a new study.

Thermally modified beta-lactoglobulin, the major protein in whey, was found to nano-encapsulate EGCG and produce particles smaller than 50 nanometers. Such particles would have good transparency and could be added to clear beverages, report Israeli researchers in Food Hydrocolloids.

Talking to NutraIngredients, lead researcher Dr Yoav Livney at the The Technion, Israel Institute of Technology, Haifa said: “As far as we know, this is the first paper reporting nano-encapsulation of EGCG intended for food application. It is apparently the first EGCG nanoencapsulation method based on natural ingredients only. Moreover, the extremely small nanoparticles developed (<50nm) enable the enrichment of clear beverages."

Dr Livney added that their proposed nanotechnology would allow the addition of EGCG to mineral water, ready-to-drink tea beverages, soft drinks, fruit juices, and dairy beverages. In addition, sport drinks would be a great application for this technology, as many of them are also enriched with protein, particularly whey proteins.

"It is of particular interest in clear beverages, where the nano-size of the particles serves to protect the EGCG without causing turbidity, thus maintaining the sensory properties of the product," added Dr Livney.

Tea facts

The majority of science on tea has looked at green tea, with benefits reported for reducing the risk of Alzheimer's and certain cancers, improving cardiovascular and oral health, as well as aiding in weight management.

Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent. Oolong tea is semi-fermented tea and is somewhere between green and black tea. The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.

The success has translated into a booming extract market, valued at a around $44m (€29.7m), according to recent report from Frost & Sullivan. The market is expected to grow by more than 13 per cent over the next seven years. Key players include DSM, Taiyo, and Tate & Lyle. Innovation in delivery has also seen companies like Maxx Performance release an encapsulated green tea extract for bakery applications.

Study details

Despite the potential health benefits of EGCG, “its sensitivity to oxidation limits its enrichment in the diet for preventive medicine”, wrote Dr Livney and his co-workers.

The researchers therefore looked at the potential to use thermally modified milk protein to produce nano-vehicles for EGCG. The whey protein was heated to 85 °C to denature the structure and produce a thermally modified protein with an association for the tea polyphenol 3.5 fold higher than the unmodified protein.

In terms of their ability to protect the polyphenol from oxidation, Dr Livney and his co-workers report that the initial degradation rate was 33-fold lower for the nano-encapsulated EGCG, compared with unprotected EGCG. Over the course of eight days, the degradation rate was 3.2-fold slower, they added.

“Based on our results we proposed the following mechanisms of protection. The heat-induced unfolding of the protein exposes some of the inner and more non-polar domains in the protein. EGCG binds to those exposed domains, apparently by a combination of hydrophobic interactions and H-bonds, causing the formation of visible microfibrilar structures,” said the researchers.

Dr Livney added that it is important to note that these visible structures were only formed when samples were gently shaken, whereas high shear is applied in the nanoparticle formation process.

“Steric shielding, immobilization and antioxidative properties of available free thiols seem to explain the protective effect of the co-assembled beta lactoglobulin–EGCG nanoparticles against degradation of this health-promoting green tea catechin,” they added.

The next step

Dr Livney confirmed that work was continuing in this area with the researchers "working on extending the pH of possible products and planning to assess the biological effectiveness, and bioavailability of the nano encapsulated particles compared to the unprotected EGCG".

Source: Food Hydrocolloids
Volume 24, Issue 8, Pages 735-743
“Thermally-induced protein–polyphenol co-assemblies: beta lactoglobulin-based nanocomplexes as protective nanovehicles for EGCG “
Authors: A. Shpigelman, G. Israeli, Y.D. Livney

Disclaimer: This article has been updated following additional clarifications from Dr Y. Livney.

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