Why certain flavor combinations melt in your mouth

British chef Heston Blumenthal is credited with originating the "food pairing hypothesis" which posits that foods that form pleasing flavor combinations -- from strawberries and chocolate to the more unexpected caviar and white chocolate -- do so because they share numerous chemical compounds responsible for flavor.

A study published in Scientific Reports examines this hypothesis, concluding that for some cuisines it holds true, including North American and Western European food, but that for others, including East Asian food, it is false. The researchers examined the relationships between individual ingredients with the techniques of network theory, which is often used to investigate the organization of complex systems.

"It's really natural to think in terms of networks because the food pairing hypothesis is really about making connections between different ingredients," said Yong-Yeol Ahn, a statistical physicist at the University of Indiana in Bloomington and a member of the research team.

Flavor is a crucial element of food pairing. But what is it? Flavor is different than taste. The tongue recognizes tastes -- the familiar sensations of salty, sour, bitter and sweet, as well as savoriness, called umami. Flavor encompasses much more of the sensory experience of eating.

"Eighty percent of our eating experience is determined by the nose," said Bernard Lahousse, the science director of Sense For Taste, a research company that supplies information to chefs, bartenders and food companies.

Rounding out the eating experience are texture, sound, and more. Although scientists understand some of the basics, much mystery remains.

"Odor is fascinating," said Jeff Potter, the author of "Cooking for Geeks". Whereas taste is simple to describe … We have a hypothesis for a model of how we think our nose smells things."

The Experiment

To find out what foods people actually enjoy in combination, Ahn and his team went online. With the 56,000 recipes they gathered from three databases, two in English and one in Korean, they began building their analysis of the food pairing hypothesis.

The researchers compared the combinations found in the recipes to a flavor network they created based on the presence of flavor compounds in different ingredients. The comparison revealed the relative popularity of different food combinations and enabled them to compare the tendencies employed by different cuisines .

This "Food Pairing Tree" displays several of the foods whose flavors most closely align with the flavors of lobster. Credit: ? Foodpairing.com, 2011 All rights reserved

They found that the most common ingredients in North American and Western European foods were milk, butter, eggs, wheat, and vanilla. The recipes contained pairs of ingredients with many common flavors at a rate much higher than random chance. They also reported in their study that for East Asian foods, "the more flavor compounds two ingredients share, the less likely they are to be used together."

Ahn noted that his research in this area was in its early stages and that his team is working to improve the quality of their data and analysis. Other researchers dispute their approach.

Flavor's Nuance

Lahousse criticized Ahn's model because it does not filter out what he considers the unimportant flavors that comprehensive chemical analysis identifies.

"Each flavor molecule has its own flavor threshold," said Lahousse. "You really have to look at what are relevant flavors, how can they react with the flavors of other products."

Lahousse, a bioengineer by training, and his company have also researched the relationships between ingredients and their use in recipes. He said that their own analysis of a different dataset of 180,000 recipes showed different results than Ahn's, especially for Japanese food, which he called "the biggest success story we have with food pairing."

Some of their flavor-pairing insights are available online in a tool (see below) endorsed by many highly-regarded chefs. The application highlights foods that share common tastes and is designed to help identify unexpectedly tasty combinations. However, much of their work has not been made available to scientists for scrutiny. Ahn said he was unable to compare his approach to that of Sense for Taste because the methods the company uses are not fully disclosed. Lahousse said he understands this criticism, but that the company balances the amount of information made public against its efforts to run as a business.

Beyond Flavor

Lahousse also admitted that there many unanswered questions about how food is experienced.

"You cannot explain everything by looking at food pairing because a recipe is more than flavor alone," he said. "It's much more complex."

Sometimes, despite mixing ingredients that should form agreeable flavor combinations, a dish does not work. Often, a chef may need to add ingredients that introduce additional elements for reasons of balance. For example, a dish may be calling for an additional taste of sweetness, or perhaps a bit of lemon to add a sour note to round out the dish. But the chef is not necessarily making those adjustments because of the flavors that element brings.

Ahn believes that even if an ingredient is applied this way, solely for the benefit of taste to the tongue, its contribution to overall flavor should still be analyzed. Lahousse believes that this is where careful analysis of a food's most important flavors pays off. For example, he said, garlic and onions add flavor, but also sweetness. They also influence the browning of meat as it is cooked.

Eggs are another popular ingredient, especially in baking. Lahousse said they are not added for their flavor profile, but for their contribution to texture.

Ahn said it is important to consider eggs' flavor contribution, because even though they influence a food's structural properties, that recipes evolve, and if the flavors were not pleasing to those who ate it, the recipe would change over time to reflect flavor preferences as well as those of texture.

Finding Harmony

Even if the flavor notes of two foods line up, a deft hand may still be required to make a combination sing.

The visualization of lobster's most closely-related foods hosted on Lahousse's website, clearly highlights the crustacean's affinity to strawberry. But, he said, many factors influence how those items are best combined and balanced, including the culture of those eating the dish and even the qualities of the individual lobster and strawberries.

"If you start to add strawberry to lobster you have to be a very good chef," said Lahousse. "The chance is very high that you will add too much sweetness to this dish. You have to be able to make a really good balance."

Potter likened the combination of flavors to notes or chords on a piano. Some will join together in a more pleasing way than others. Two wildly differing sets of odor molecules might not mesh if they didn't have any accompaniment. He pointed again to lobster, and to chocolate as its pairing.

"That's not to say that a really talented chef couldn't make lobster and chocolate work," said Potter. "I'm sure there's a combination with an appropriate set of ingredients where those dissonant chords do actually produce a pleasing sound."

For home cooks facing a nearly empty refrigerator and a lack of inspiration, Potter recommends taking inventory and Googling a list of your seemingly mismatched ingredients to identify opportunities to create your own culinary innovations.

"I'm a huge fan of experimentation; there's no single better way to learn how to cook than to go into the kitchen and try doing something," said Potter.

Provided by Inside Science News Service (news : web)

Graphene grows better on certain copper crystals

New observations could improve industrial production of high-quality graphene, hastening the era of graphene-based consumer electronics, thanks to University of Illinois engineers.

By combining data from several imaging techniques, the team found that the quality of graphene depends on the crystal structure of the copper substrate it grows on. Led by electrical and computer engineering professors Joseph Lyding and Eric Pop, the researchers published their findings in the journal Nano Letters.

"Graphene is a very important material," Lyding said. "The future of electronics may depend on it. The quality of its production is one of the key unsolved problems in nanotechnology. This is a step in the direction of solving that problem."

To produce large sheets of graphene, methane gas is piped into a furnace containing a sheet of copper foil. When the methane strikes the copper, the carbon-hydrogen bonds crack. Hydrogen escapes as gas, while the carbon sticks to the copper surface. The carbon atoms move around until they find each other and bond to make graphene. Copper is an appealing substrate because it is relatively cheap and promotes single-layer graphene growth, which is important for electronics applications.

"It's a very cost-effective, straightforward way to make graphene on a large scale," said Joshua Wood, a graduate student and the lead author of the paper.

"However, this does not take into consideration the subtleties of growing graphene," he said. "Understanding these subtleties is important for making high-quality, high-performance electronics."

While graphene grown on copper tends to be better than graphene grown on other substrates, it remains riddled with defects and multi-layer sections, precluding high-performance applications. Researchers have speculated that the roughness of the copper surface may affect graphene growth, but the Illinois group found that the copper's crystal structure is more important.

Copper foils are a patchwork of different crystal structures. As the methane falls onto the foil surface, the shapes of the copper crystals it encounters affect how well the carbon atoms form graphene.

Different crystal shapes are assigned index numbers. Using several advanced imaging techniques, the Illinois team found that patches of copper with higher index numbers tend to have lower-quality graphene growth. They also found that two common crystal structures, numbered (100) and (111), have the worst and the best growth, respectively. The (100) crystals have a cubic shape, with wide gaps between atoms. Meanwhile, (111) has a densely packed hexagonal structure.

"In the (100) configuration the carbon atoms are more likely to stick in the holes in the copper on the atomic level, and then they stack vertically rather than diffusing out and growing laterally," Wood said. "The (111) surface is hexagonal, and graphene is also hexagonal. It's not to say there's a perfect match, but that there's a preferred match between the surfaces."

Researchers now are faced with balancing the cost of all (111) copper and the value of high-quality, defect-free graphene. It is possible to produce single-crystal copper, but it is difficult and prohibitively expensive.

The U. of I. team speculates that it may be possible to improve copper foil manufacturing so that it has a higher percentage of (111) crystals. Graphene grown on such foil would not be ideal, but may be "good enough" for most applications.

"The question is, how do you optimize it while still maintaining cost effectiveness for technological applications?" said Pop, a co-author of the paper. "As a community, we're still writing the cookbook for graphene. We're constantly refining our techniques, trying out new recipes. As with any technology in its infancy, we are still exploring what works and what doesn't."

Next, the researchers hope to use their methodology to study the growth of other two-dimensional materials, including insulators to improve graphene device performance. They also plan to follow up on their observations by growing graphene on single-crystal copper.

"There's a lot of confusion in the graphene business right now," Lyding said. "The fact that there is a clear observational difference between these different growth indices helps steer the research and will probably lead to more quantitative experiments as well as better modeling. This paper is funneling things in that direction."

Lyding and Pop are affiliated with the Beckman Institute for Advanced Science and Technology at the U. of I. The Office of Naval Research, the Air Force Office of Scientific Research, and the Army Research Office supported this research.

Story Source:

The above story is reprinted from materials provided by University of Illinois at Urbana-Champaign.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Joshua D. Wood, Scott W. Schmucker, Austin S. Lyons, Eric Pop, Joseph W. Lyding. Effects of Polycrystalline Cu Substrate on Graphene Growth by Chemical Vapor Deposition. Nano Letters, 2011; : 111004083339002 DOI: 10.1021/nl201566c

Scientists develop algorithm to understand certain human diseases

 Patricia Clark, the Rev. John Cardinal O’Hara, C.S.C. Associate Professor of Chemistry and Biochemistry at the University of Notre Dame, and Bonnie Berger, professor of applied mathematics at the Massachusetts Institute of Technology, have published a paper on the development of a computer algorithm that can accurately predict which parts of protein sequences help prevent the proteins from aggregating.

Their article, the second published by the interdisciplinary research team, was submitted to the journal Proceedings of the National Academy of Sciences. The experimental work was completed at Notre Dame in Clark’s laboratory with Berger testing the computational predictions in her lab.

Protein aggregation occurs when the long linear sequence of a protein misfolds and begins to interact with copies of itself, thus preventing it from performing its essential functions in the cell.

Clark and Berger found that aggregation-resistant proteins tend to possess “capping” structures at either end of their correctly folded structure. However, if a “cap” is removed, the remaining protein aggregates quickly.

Proteins known to be highly prone to aggregation do not contain said capping structures, a finding that could help predict which proteins along with which genetic mutations will likely lead to aggregation.

Misfolding and aggregation can lead to numerous diseases ranging from juvenile cataracts to cystic fibrosis and cancer. Aggregated proteins can also form toxic structures known as amyloid fibers, which are linked to Alzheimer’s, Huntington’s, Lou Gehrig’s and other neurodegenerative diseases.

The two hope that by studying the mechanisms that can lead to aggregation as well as the structural features that some proteins possess that help avoid aggregation, strategies can be discovered to help treat aggregation diseases.

Provided by University of Notre Dame (news : web)

'Impossible' feat: Certain materials can exhibit ferromagnetism and superconductivity at same time

 It actually seems impossible: Scientists from the Helmholtz-Zentrum Dresden-Rossendorf and the TU Dresden were able to verify with an intermetallic compound of bismuth and nickel that certain materials actually exhibit the two contrary properties of superconductivity and ferromagnetism at the same time. A phenomenon that had only been demonstrated around the globe on a small number of materials and which might provide highly interesting technological opportunities in future.

Just in time for the 100th anniversary to commemorate the discovery of superconductivity by the Dutch physicist Heike Kamerlingh Onnes on April 8, 1911, scientists from the Helmholtz-Zentrum Dresden-Rossendorf and the TU Dresden published their research results in the journal Physical Review B.

Headed by Dr. Thomas Herrmannsdörfer, the team from the HZDR's High Magnetic Field Laboratory (HLD) examined a material consisting of the elements bismuth and nickel (Bi3Ni) with a diameter of only a few nanometers -- which is unique since it has not been achieved elsewhere so far. This was made possible through a new chemical synthesis procedure at low temperatures which had been developed at the TU Dresden under the leadership of Prof. Michael Ruck. The nano scale size and the special form of the intermetallic compound -- namely, tiny fibers -- caused the physical properties of the material, which is non-magnetic under normal conditions, to change so dramatically. This is a particularly impressive example of the excellent opportunities modern nanotechnology can provide today, emphasizes Dr. Thomas Herrmannsdörfer. "It's really surprising to which extend the properties of a substance can vary if one manages to reduce their size to the nanometer scale."

There are numerous materials which become superconducting at ultralow temperatures. However, this property competes with ferromagnetism which normally suppresses superconductivity. This does not happen with the analyzed compound: Here, the Dresden researchers discovered with their experiments in high magnetic fields and at ultralow temperatures that the nanostructured material exhibits completely different properties than larger-sized samples of the same material. What's most surprising: The compound is both ferromagnetic and superconducting at the same time. It is, thus, one of those rarely known materials which exhibit this unusual and physically not yet completely understood combination. Perhaps bismuth-3-nickel features a special type of superconductivity, says Dr. Herrmannsdörfer. The physicist and doctoral candidate Richard Skrotzki, who has just turned 25, is making a vital contribution to the research results and describes the phenomenon as "the bundling of contrary properties in a single strand."

The TU Dresden and the HZDR are partners in the research alliance DRESDEN-concept which pursues the objective of making visible the excellence of Dresden research.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Helmholtz Association of German Research Centres, via EurekAlert!, a service of AAAS.

Journal Reference:

T. Herrmannsdörfer, R. Skrotzki, J. Wosnitza, D. Köhler, R. Boldt, M. Ruck. Structure-induced coexistence of ferromagnetic and superconducting states of single-phase Bi_{3}Ni seen via magnetization and resistance measurements. Physical Review B, 2011; 83 (14) DOI: 10.1103/PhysRevB.83.140501