Taste and Flavour Facts

Taste and Flavour Facts

Sulekha Rani.R,PGT Chemistry,KV NTPC kayamkulam

Recent scientific research has revealed just how complex our sense of flavour really is. There is no single sense that defines flavour - although we perceive the flavour of food in our mouths, it is our brains that determine flavour. When humans evolved, we had to take whatever food we could - we ate berries and leaves or, when we could kill an animal, raw meat. It was essential to our survival to detect what food was safe, so we honed and evolved our senses to ensure we liked foods that were safe to eat and disliked those that were dangerous.

Our tongues have five different types of sensors (taste buds) - sweet, sour, salt, bitter, and umami (this last has only recently been recognised as a separate taste sensation - the taste of mono sodium glutamate, MSG - found in tomatoes, parmesan cheese and soy sauce, etc.). These are crucial. When we put food in our mouths, we need to decide whether to eat it or spit it out - this can be a life or death decision and needs to be made quickly. We need sugar as a source of energy - so we like sweet tasting foods - if all we taste is sweetness we will eat the food. We need salt to survive - salt has many essential roles - salt affects the electrical conductivity through the body - it governs how our hearts beat, how signals are transmitted along our nerves and in our brains, and controls many other processes.

Glutamic acid is one of the essential amino acids that form the building blocks of proteins - so recognising foods that provide it is important. It therefore not surprising that our "Umami" taste receptors are particularly attuned to the sodium salt of glutamic acid (mono-sodium glumate). Sourness often accompanies foods as they are going off due to bacterial action - think of sour milk - so recognising sourness helps us decide not to eat some foods. Most poisonous berries are taste bitter, so we need to recognise and dislike bitter foods. If we eat a bitter food we will not only spit it out, but follow that up by vomiting to get rid of any trace that may accidentally have got into our digestive systems.

But taste is just the last line of defence - we use all our other senses first - and these affect how we react to different tastes. First we look at the food - is it the "right" colour? Next we touch it - is it firm or soft? At the same time, we listen to how it sounds when we break it - is it crisp or soggy? Then we sniff it - are there any unpleasant odours? All these impressions tell us what to expect when we put food in our mouths. If we are eating berries, we will be looking for sweetness, combined with "fresh" and "tangy" aromas; if it is meat we will be looking for saltiness without any sour "off" aroma. The type of food and our memories of similar foods tell us the key aromas and tastes to look for in the "flavour". All this complex information is processed by our brains and interpreted as the "flavour" and is tasted in our mouths.

Our sense of smell is much more discriminating than our sense of taste. The organ we use to detect aromas is the olfactory bulb, located at the back of our noses near the middle of our heads. Inside the olfactory bulb, we have at least 700 different types of sensor and can use them to distinguish many millions of different molecules. It is not surprising that wine tasters sniff the wines first - their noses are attuned to look for a range of aromas that give clues to the grape variety and region, etc.

But how we use all this information is greatly influenced by the other senses. For example, if you taste a wine you will be influenced by its colour. Indeed, a recent experiment, fooled all the experienced wine tasters. In this experiment, the tasters were asked first to taste six white wines and describe the flavour. They described the flavours using words like "refreshing", "strawberry" and "citrus" to identify different notes in the aroma - these are words frequently used to describe white wines. Then when asked to identify the wines, the tasters were able to correctly identify the grape and the region - some even giving the exact vineyard and vintage.

Next a trick was played - the same six wines were served again, but this time with a little inert red food dye added. This time the tasters used completely different language to describe the flavour - "woody", "tannic" and "powerful" - all words associated with red wines. Then when asked to identify the wines, all plumped for red grape varieties and a few ventured opinions on actual wines they believed they had just tasted. However, when the experiment was repeated again - this time with the tasters blindfolded - they once again got the answers correct.

But there is much more to flavour perception than just the sum of all the different inputs from the eyes, mouth and nose. Our brains, it seems, respond much more to changes in which molecules are in the nose and mouth than they do to what is actually there, for example - if you chew a piece of gum, the flavour will disappear after a few minutes, as your brain gets "bored" by the aroma in the nose - but there is virtually no reduction in the amount of flavour molecules in the nose. However, if you simply change the input from your tongue, by, for example - taking a sip of sweetened water - the full flavour will be instantly restored. The area of flavour perception is one of the most exciting areas for scientific research - it holds out the promise of helping us find ever better ways to produce truly wonderful food.

article ...DCI,... Peter barham....

Hydrogen Opens the Road to Graphene ... and Graphane

Hydrogen Opens the Road to Graphene ...

and Graphane

Sulekha Rani.R , PGT Chemistry, KV NTPC Kayamkulam

Reaction of single-walled carbon nanotubes (SWNTs) with hydrogen gas. (Credit: Image courtesy of Umeå University

An international research team has discovered a new method to produce belts of graphene called nanoribbons. By using hydrogen, they have managed to unzip single-walled carbon nanotubes. The method also opens the road for producing nanoribbons of graphane, a modified and promising version of graphene.

A thin flake plain carbon, just one atom thick, became world famous last year. The discovery of the super material graphene gave Andre Geim and Konstantin Novoselov the Nobel Prize in Physics 2010. Graphene has a wide range of unusual and highly interesting properties. As a conductor of electricity it performs as well as copper. As a conductor of heat it outperforms all other known materials.

There are possibilities to achieve strong variations of the graphene properties for instance by making graphene in a form of belts with various width, so called nanoribbons. Nanoribbons were prepared for the first time two years ago. A method to produce them is to start from carbon nanotubes and to use oxygen treatment to unzip into nanoribbons. However, this method leaves oxygen atoms on the edges of nanoribbons, which is not always desirable.

In the new study the research team shows that it is also possible to unzip single-walled carbon nanotubes by using a reaction with molecular hydrogen. Nanoribbons produced by the new method will have hydrogen on the edges and this can be an advantage for some applications. Alexandr Talyzin, physicist at Umeå University in Sweden, has over the past decade been studying how hydrogen reacts with fullerenes, which are football-shaped carbon molecules.

"Treating the carbon nanotubes with hydrogen was a logical extension of our research. Our previous experience has been of great help in this work," says Alexandr Talyzin.

Nanotubes are typically closed by semi-spherical cups, essentially halves of fullerene molecules. The researchers have previously proved that fullerene molecules can be completely destroyed by very strong hydrogenation. Therefore, they expected similar results for nanotube end cups and tried to open the nanotubes by using hydrogenation. The effect was indeed confirmed and they also managed to reveal some other exciting effects.

The most interesting discovery was that some carbon nanotubes were unzipped into graphene nanoribbons as a result of prolonged hydrogen treatment. What is even more exciting -- unzipping of nanotube with hydrogen attached to the side walls could possibly lead to synthesis of hydrogenated graphene: graphane. So far, graphane was attempted to be synthesized mostly by reaction of hydrogen with graphene. This appeared to be very difficult, especially if the graphene is supported on some substrate and only one side is available for the reaction. However, hydrogen reacts much easier with the curved surface of carbon nanotubes.

"Our new idea is to use hydrogenated nanotubes and unzip them into graphane nanoribbons. So far, only the first step towards graphane nanoribbon synthesis is done and a lot more work is required to make our approach effective," explains Alexandr Talyzin. "Combined experience and expertise from several groups at different universities, was a key to success

Underground River Below the Amazon River

Underground river below the Amazon River

Sulekha Rani.R , PGT Chemistry, KV NTPC Kayamkulam

The Amazon river is known to be the second longest in the world, shorter only than the Nile

Scientists led by an Indian-origin researcher have discovered a huge underground river which they believe is flowing some 13,000 feet beneath the mighty Amazon River in Brazil.

The researchers at Brazil's National Observatory believe the subterranean river is about 6,000km long, about the same length as the Amazon on the surface.

Dr Valiya Hamza, from the BNO, said the discovery of the underground river came from studying temperature variations at 241 inactive oil wells drilled in the 1970s and 1980s by Brazil's state-run oil company, Petrobras.

He said the 'thermal information' provided by Petrobras allowed his team of researchers to identify the movement of water 13,100ft under the Amazon River.

Their findings were presented in Rio de Janeiro at a meeting of the Brazilian Geophysical Society.

Computer simulations presented by doctoral student Elizabeth Pimentel, found the groundwater flow is mostly vertical to about 6,500ft deep, but changes direction and becomes almost horizontal at greater depths.

The apparent underground river has been named after Hamza, honouring the scientist who was the head of the research team that found the signs of the flowing water.

Researchers decided to name the Underground river the hamza,in tribute to the Scientist of Indian origin VALIYA MANNATHAL HAMZA , who has been studying the region more than four decades

It is believed to start in the region of Acre, flow through the basins of Solimoes, Amazona and Marajo and reach the sea at Foz do Amazonas. This would explain why large pockets of the sea in this area have low salinity.

The average flow of the newly discovered 'Rio Hamza' is just two per cent of the Amazon, but this puts it on par with the San Francisco river in California.

The average flow of the Amazon River is estimated at about 133,000 m3 / s, while the flow of the Rio Hamza is far slower at an estimated at 3090 m3 / s.

Dr Hamza said the existence of an underground river that also flows west to east would mean that the Amazon rain forest has two drainage systems - the Amazon and Hamza rivers.

He stressed that the studies examining the underground river were still in their preliminary stage but added that he expected to confirm the subterranean flow by the end of 2014.

Bacteria that can convert carbon into food

Bacteria that can convert carbon into food

Sulekha rani.R, PGT Chemistry,KV NTPC kayamkulam... ....................................................article from timesofindia

WASHINGTON: Scientists have identified some mysterious organisms in the dark depths of the ocean which they believe are converting carbon dioxide into a form useful for life. The bugs, which the scientists call "twilight" microbes, could be the missing link of global carbon cycle as they are found turning inorganic carbon into useable food some 2,625 feet below the ocean surface , LiveScience reported.

(Michael Sieracki and Jane Heywood at an inFlux fluorescence-activated cell sorter, a device used to separate out individual microbial cells at Bigelow Laboratory Single Cell Genomics Center. Researchers at Bigelow separated out single cells from ocean samples, contributing to research on carbon-capturing microbes in the deep ocean.

CREDIT: Dennis Griggs, Bigelow Laboratory Single Cell Genomics Center

The job of capturing carbon — crucial to sustaining life on Earth — is usually carried out by plants that use sunlight as energy. But light doesn't penetrate below 656 feet of ocean, so plants can't do this job. To survive, living cells must convert carbon dioxide into molecules that can form cellular structures or be used in metabolic processes , the scientists said.

Simple, single-celled organisms called archaea that often live in extreme conditions were thought to be responsible for much of the dark ocean's carbon fixation. But there was evidence that archaea could not account for the total amount of carbon fixation going on there.

Tiny Oxygen Generators Boost Effectiveness of Anticancer Treatment

By Sulekha Rani.R, PGT Chemistry, KV NTPC kayamkulam

Researchers have created and tested a miniature device, seen here, that can be implanted in tumors to generate oxygen, boosting the killing power of radiation and chemotherapy. The technology is designed to treat solid tumors that are hypoxic at the center, meaning the core contains low oxygen levels. The device (right) fits inside a tube (left) that can then be inserted into a tumor with a biopsy needle. (Credit: Birck Nanotechnology Center, Purdue University

Researchers have created and tested miniature devices that are implanted in tumors to generate oxygen, boosting the killing power of radiation and chemotherapy.

The technology is designed to treat solid tumors that are hypoxic at the center, meaning the core contains low oxygen levels.

"This is not good because radiation therapy needs oxygen to be effective," said Babak Ziaie, a Purdue University professor of electrical and computer engineering and biomedical engineering. "So the hypoxic areas are hard to kill. Pancreatic and cervical cancers are notoriously hypoxic. If you generate oxygen you can increase the effectiveness of radiation therapy and also chemotherapy."

The new "implantable micro oxygen generator" is an electronic device that receives ultrasound signals and uses the energy to generate a small voltage to separate oxygen and hydrogen from water ╨ a chemical operation called water electrolysis.

"We are putting these devices inside tumors and then exposing the tumors to ultrasound," Ziaie said. "The ultrasound energy powers the device, generating oxygen.

The devices were created at the Birck Nanotechnology Center in the university's Discovery Park. Purdue researchers are working with Song-Chu (Arthur) Ko, an assistant professor of clinical radiation oncology at the Indiana University School of Medicine.

Researchers have tested the devices in pancreatic tumors implanted in mice, showing they generated oxygen and shrunk tumors faster than tumors without the devices. The devices are slightly less than one centimeter long and are inserted into tumors with a hypodermic biopsy needle.

"Most of us have been touched by cancer in one way or another," Ziaie said. "My father is a cancer survivor, and he went through many rounds of very painful chemotherapy. This is a new technology that has the potential to improve the effectiveness of such therapy."

Findings are detailed in a research paper appearing online this month in Transactions on Biomedical Engineering. The paper was written by research assistant professor Teimour Maleki, doctoral students Ning Cao and Seung Hyun Song, Ko and Ziaie.

"The implantable mini oxygen generator project is one of 11 projects the Alfred Mann Institute for Biomedical Development at Purdue University (AMIPurdue) has sponsored," Ziaie said. "AMIPurdue has been instrumental in providing the development funding of roughly $500,000 on this project. And beyond funding, the AMIPurdue team has also helped us with market research, physician feedback, industry input, as well as intellectual property and regulatory strategy. We have been able to accomplish a great deal in a short time due to the collaborative effort with AMIPurdue."