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Microwaving tea the best way to brew and extract health benefits

Cup and teabag in the microwave
Microwaving tea extracts all the healthy components.

ABC Radio Central Coast

The microwave is now a standard in most kitchens, used to heat up leftovers or even make a pavlova — if you feel adventurous.

But zapping your food has the potential to unlock many more culinary and health benefits as food scientist Dr Quan Vuong has found during years of research.

Dr Vuong, who works at the University of Newcastle on the New South Wales Central Coast, specialises in finding ways to "add value" to natural products by extracting bioactive compounds with antioxidant capacities.

His 2012 research on extracting compounds in tea has recently garnered much interest across ABC Radio.

The discussion followed online outcry from UK audiences of TV drama Broadchurch last month, when actor David Tennant microwaved his cup of tea.

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In Dr Vuong's study though, to extract, isolate and purify the important components of green tea and black tea, he found that the following method activated 80 per cent of the caffeine, theanine and polyphenol compounds, and generated the best taste.

  1. Put hot water in the cup with your teabag.
  2. Heat in the microwave for 30 seconds on half power.
  3. Let it sit for a minute.

Polyphenols are antioxidants which are linked to good health properties like lowered cardiovascular disease and lower cholesterol, hypertension and diabetes.

Theanine is an essential amino acid that promotes relaxation and can be found in tea, some other plant foods and mushrooms.

"In food products, people are concerned with health benefits but also with food quality and shelf life," Dr Vuong said.

Dr Vuong said the health benefits are linked to high consumption or equivalent to more than three cups of tea a day.

The method can apply to herbal teas and loose tea leaves, he said.

What else can you microwave?

Since his tea study, Dr Vuong has investigated how microwaving other household or industrial food products to recover bioactive compounds could be further utilised by the food industry and reduce waste.

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In 2016, he found that microwaving lemon pomace — the leftover skin, pulp and seeds after a lemon is squeezed — for five minutes at 480 watts enhanced the total phenolic content, flavonoids, proanthocyanins and total antioxidant activity.

Flavonoids and proanthocyanins are groups of phenolic compounds that are linked to health benefits.

"Lemon or apple pomace which is coming from the food factories, they still have antioxidants, so if we can recover the benefits from this waste, we can make more functional food products," Dr Vuong said.

Dr Vuong also successfully recovered properties in macadamia nut skins.

Macadamia nut
The inner kernel of the macadamia is the edible part of the nut.

ABC TV

The optimal microwave settings were 4.5 minutes, power of 30 per cent or 360W with a sample to water ratio of five grams/100ml.

"We are world number one in macadamia production," Dr Vuong said.

"The skin and the husk is normally sent to waste and has no value. But the skin is actually high in phenolic compounds.

"The phenolic compounds could be used in functional food production in the food industry. They are linked with anti-cancer and cardiovascular disease and potent antioxidant properties."

Extracting Australian natives

Dr Vuong's next project is to investigate the benefits of native flora.

He has so far tested the optimal microwave settings for extracting bioactive compounds from eucalyptus robusta leaf (three minutes, 600W power and two g/100ml sample-to-solvent ratio.)

Dr Quan Vuong in the lab
Dr Quan Vuong is exploring the benefits of a diverse range of natural products,

Supplied: Dr Quan Vuong

Eucalyptus oil is used in cosmetic and pharmaceutical products and the aromatic and non-volatile compounds have high antioxidant properties linked with lowering pancreatic cancer in-vitro and killing cancer cells.

Only eight to 10 species of eucalyptus are currently used and exported, although there are some 800 different species which Dr Vuong said are yet to be studied.

His upcoming research student is set to study the beneficial compounds of Kakadu plum.

"We mainly dry this product and export to US but it has one of the highest levels of vitamin C in the whole fruit kingdom," he said.