Green tea flavonoids: Anti-browning additives for dairy?

By Stephen Daniells

- Last updated on GMT

Related tags: Green tea

Scientists in the US are looking into the potential of green tea
polyphenols to stop the Maillard reaction in thermally processed
dairy to prevent dark colours and off-flavours.

The research is one of the few studies that look beyond the health benefits of green tea extracts and reports a food formulation application for the polyphenols.

The potential health benefits of tea, which have mainly focused on green tea, have been receiving considerable levels of study, with scientists reporting a wide range of effects, including a lower risk of certain cancers, improved heart health, weight loss, and protection against Alzheimer's.

But new research from Gerry Schamberger and Theodore Labuzathe from the University of Minnesota, report that the polyphenols may also have a role in food formulation.

"The reported use of catechins as food additives is limited,"​ they wrote in the journal LWT Food Science and Technology​ (doi: 10.1016/j.lwt.2006.09.009).

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.

The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin (EC).

The new research focussed on the ability of green tea flavonoids EGCG and EC to control Maillard browning during the UHT milk.

The Maillard reaction is also known as non-enzymatic browing. The carbonyl group of the sugar reacts with the amino group of the amino acid to form N-glycosylamine, which is unstable and, via the "Amadori rearrangement"​, produces ketosamines.

These so-called Amadori compounds are involved in a cascade of further reactions that can eventually result in the formation of dark colours, off-flavours and a loss of nutritional content.

"The ability to inhibit Maillard browning in UHT milk and other food products would be useful to prevent the development of flavours unacceptable to consumers,"​ said the researchers.

Schamberger and Labuzathe added EC and EGCG (0.l and 1.0 millimoles per litre) to milk that was subsequently thermally processed (up to 140 degrees Celsius).

The researchers used front-face fluorescence spectroscopy (FFFS) to monitor the levels of furosine and lactulose (markers of the Maillard reaction) in UHT milk, and found that the control milk (no green tea extract additives) when stored at 35 and 45 degrees had almost double the fluorescence after 150 days. Addition of 0.1 millimoles of EC and EGCG is reported to have reduced Maillard fluorescence, compared to the control milk.

When added at the 1.0 millimole per litre level, Schamberger and Labuzathe report that fluorescence in the UHT milk was negligible.

"Throughout shelf-life testing, these compounds reduced Maillard associated fluorescence in milk,"​ they said.

The control milk and milk with added tea extract were subsequently tested by 80 consumers to evaluate their liking, and therefore acceptance, of the product.

"Consumer sensory testing analysis found the green tea milk samples were liked as well or better than the control milk samples,"​ report the researchers.

"These flavonoids may be of use to the food industry to control Maillard browning,"​ they concluded.

The research was funded by Dairy Management Inc. and partly by a grant to the Center for Food Protection and Defense, University of Minnesota.

Only recently the potential of green tea as a luxury flavour was reported by FoodNavigator.com. Japanese firm, Aiya, was at HIE in Frankfurt recently to promote its range of macha tea ingredients, which it believes has huge potential in a number of food categories.

The Japanese firm, which has its European head office in Vienna, was promoting macha primarily as a luxury tea flavour, or in other words a premium food and beverage ingredient.

Macha, which is used in Japanese tea ceremony and has been drunk for centuries, is different from traditional tea in that it is not infused but ground. It is also grown differently, and is noticeably more expensive.

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