Temperature, humidity affect health benefits of green tea powders

The beneficial compounds in green tea powders aren't as stable as once thought, according to a Purdue University study that will give industry guidelines on how to better store those powders.

"People drink green tea for health benefits, so they want the catechins to be present," said Lisa Mauer, a professor of food science. "The instant powder beverages are becoming more popular for consumers, and it's important to know how storage can influence nutrition of your products."

Catechins are the source of antioxidants thought to fight heart disease, cancer, diabetes and other health problems. Green tea powders are often used as ingredients in products that are flavored like green tea or tout the health benefits of the tea. U.S. imports of green tea increased more than 600 percent from 1998 to 2007, according to the U.S. Department of Agriculture.

Mauer found that increased temperature ? and humidity, to a smaller degree ? speed catechin degradation. She said it had been believed that the powders were stable below the glass transition temperature, the temperature at which an amorphous solid changes from a rigid, glassy state to a rubbery, viscous state. In that rubbery state, compounds may start reacting with each other faster due to increased molecular mobility, leading to significant chemical degradation.

But Mauer's findings, reported in the early online version of the Journal of Agricultural and Food Chemistry, showed that green tea powder degrades at lower temperatures, even below the glass transition temperature.

"Tea powders are not infinitely stable below their glass transition temperature. They degrade more slowly below that temperature, but they can still degrade," Mauer said.

Catechin concentrations were tracked using high-performance liquid chromatography. The method involved dissolving the green tea powder into a solution, which then passed through a column. Compounds moved at different rates and could be measured.

More than 1,800 powder samples were stored at varying temperature and humidity combinations for up to 16 weeks and then measured for catechin loss. Those at the highest temperatures and humidities lost the most catechins.

From those results, models were built to predict the rates at which catechins would be lost at different storage conditions. Mauer said those in the food industry could use the models to predict the amount of catechins ? and the likely health benefits ? in green tea powder at the time it is used.

"Knowing what's happening to the ingredients is extremely important for understanding the quality of a food or beverage product," she said.

Mauer said she would next look at what the catechins become once they degrade and how those new compounds affect nutritional qualities.

More information: Degradation Kinetics of Catechins in Green Tea Powder: Effects of Temperature and Relative Humidity, by Na Li, Lynne S. Taylor and Lisa J. Mauer

ABSTRACT
The stability of catechins in green tea powders is important for product shelf life and delivering health benefits. Most published kinetic studies of catechin degradation have been conducted with dilute solutions and, therefore, are limited in applicability to powder systems. In this study, spray-dried green tea extract powders were stored under various relative humidity (RH) (43–97%) and temperature (25–60 °C) conditions for up to 16 weeks. High-performance liquid chromatography (HPLC) was used to determine catechin contents. Catechin degradation kinetics were affected by RH and temperature, but temperature was the dominant factor. Kinetic models as functions of RH and temperature for the individual 2,3-cis-configured catechins (EGCG, EGC, ECG, and EC) were established. The reaction rate constants of catechin degradation also followed the Williams–Landel–Ferry (WLF) relationship. This study provides a powerful prediction approach for the shelf life of green tea powder and highlights the importance of glass transition in solid-state kinetics studies.

Provided by Purdue University (news : web)

Discovery of cis-4-Hydroxy-L-proline, a material of pharmaceutical, cosmetic products

 Discovery of the new enzyme, available for manufacturing of cis-4-Hydroxy-L-proline, a material of pharmaceutical and cosmetic products.

Prof. Kuniki Kino (Department of Applied Chemistry, Faculty of Science and Engineering) and Dr. Ryotaro Hara (Research Institute for Science and Engineering) have discovered New Enzyme, which contributes establish an innovative new industrial manufacturing method for cis-4-hydroxy-L-proline, an amino acid derivative.

cis-4-Hydroxy-L-proline is a kind of amino acid which is hydroxylated in the 4-position of L-proline and it is believed to have potential as a raw material for pharmaceutical and cosmetic products. trans-4-Hydroxy-L-proline , a cis-4-hydroxy-L-proline stereoisomer , has been used for a broad range of applications since an efficient fermentation production method was established by KYOWA HAKKO BIO CO., LTD. in 1997. cis-4-Hydroxy-L-proline, however, could only be manufactured through a complex chemical synthetic procedure, and due to the high costs involved, usage has been limited.

Using a new enzyme that positionally and stereoscopically hydroxylates L-proline discovered by Prof. Kino and Dr. Hara, KYOWA HAKKO BIO has established an efficient industrial production method for cis-4-hydroxy-L-proline. As a result, they are now able to steadily supply highly pure cis-4-hydroxy-L-proline at a low cost. Further, they now have the technology to cheaply produce a variety of highly pure proline derivatives.

Waseda University, as a “Research University”, keeps contributing to the development of industry through promoting Research collaborations.

Provided by Waseda University

Liquid crystal droplets discovered to be exquisitely sensitive to an important bacterial lipid

 In the computer displays of medical equipment in hospitals and clinics, liquid crystal technologies have already found a major role. But a discovery reported from the University of Wisconsin-Madison suggests that micrometer-sized droplets of liquid crystal, which have been found to change their ordering and optical appearance in response to the presence of very low concentrations of a particular bacterial lipid, might find new uses in a range of biological contexts.

Detecting endotoxin, a lipid-polysaccharide combination that is found in the outer membranes of many types of bacteria, is a standard way to establish the presence of bacterial contamination in a wide range of drugs, medical supplies and equipment. The current technology is based on a complex mixture of proteins isolated from the blood of a horseshoe crab, says Nicholas Abbott, a professor and the chair of chemical and biological engineering at UW-Madison.

Abbott, an expert in surfaces of soft materials, knows that liquid crystals have highly useful properties. "An unusual characteristic of a liquid crystal is that information travels through it over long distances. Many past studies have shown that events at a surface of a liquid crystal, which might affect just one layer of molecules, can trigger a change in the ordering of the liquid crystal that propagates as deep as 100,000 molecules away from the interface."

In a paper published on May 20, in Science, Abbott and colleagues showed that concentrations of endotoxin in the picogram/milliliter range were enough to trigger a change in the appearance of liquid crystalline droplets visible in a light microscope. "When we investigated the behavior of endotoxin with the liquid crystalline droplets, we were surprised to find that we could decrease the concentration of endotoxin to extremely low levels and still see that change in the ordering of the liquid crystals."

Abbott initially thought that the changes in the liquid crystalline droplets would be due to the adsorption of the endotoxin to the surfaces of the droplets, but the concentration was too low to justify this explanation. So Abbott and his graduate students I-Hsin Lin and Dan Miller along with colleagues in the NSF-sponsored UW-Madison Materials Research Science and Engineering Center determined that "the transition was not driven by adsorption of endotoxin over the surface of the liquid crystalline droplet, but instead by localization of the endotoxin at defects in the liquid crystal droplets."

The localization of impurities to defects is "ubiquitous" in material science, Abbott says, "and it appears that a similar phenomenon is occurring here, which then triggers the transition in the liquid crystal droplet. This is a fundamentally different mechanism that gives rise to a level of sensitivity which is 10,000 to 100,000 higher than surface-driven transitions seen in past studies of liquid crystalline systems, and it suggests the basis for a very high level of sensitivity in detection." Abbott also comments that "defect-driven ordering transitions in liquid crystalline systems have not been reported previously, and it is also highly surprising that it is so specific to the particular structure of endotoxin."

The defect-driven phenomenon that Abbott found could be more broadly applicable than endotoxin, but he says "endotoxin in itself is pretty important. Endotoxin comes from the outer membrane of Gram-negative bacteria, and is considered a key indication of bacterial infection." Animal immune systems themselves are tuned to respond to endotoxin, Abbott says, and the Food and Drug Administration requires testing for endotoxin on equipment used to make vaccines, drugs, intravenous fluids and many other devices and materials.

The current FDA-approved test for endotoxin is based on the blood of horseshoe crabs, which have evolved to combat infection by clotting their blood in the presence of endotoxin. Horseshoe crabs are captured, bled and then returned to the water. The horseshoe crab test is the "gold standard assay" for endotoxin, Abbott says, "but our system so far seems a bit more sensitive and does not involve any biological components. The change in optical appearance of the droplets is quite striking, and it occurs within a minute."

The discovery could be the start of a long road to commercialization, but Abbott cautions, "We have found a fundamental phenomenon, but it's a long path to have a validated technology that can replace the horseshoe crab assay."

Horseshoe crabs are some of the most primitive multicellular organisms surviving on Earth, but Abbott believes they would still appreciate not having to donate blood quite so often.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by University of Wisconsin-Madison. The original article was written by David Tenenbaum.

Journal Reference:

I-Hsin Lin, Daniel S. Miller, Paul J. Bertics, Christopher J. Murphy, Juan J. De Pablo, and Nicholas L. Abbott. Endotoxin-Induced Structural Transformations in Liquid Crystalline Droplets. Science, 19 May 2011 DOI: 10.1126/science.1195639

Do microbes swim faster or slower in elastic fluids? Research answers long-standing question

A biomechanical experiment conducted at the University of Pennsylvania School of Engineering and Applied Science has answered a long-standing theoretical question: Will microorganisms swim faster or slower in elastic fluids? For a prevalent type of swimming, undulation, the answer is "slower."

Paulo Arratia, assistant professor of mechanical engineering and applied mechanics, along with student Xiaoning Shen, conducted the experiment. Their findings were published in the journal Physical Review Letters.

Many animals, microorganisms and cells move by undulation, and they often do so through elastic fluids. From worms aerating wet soil to sperm racing toward an egg, swimming dynamics in elastic fluids is relevant to a number of facets of everyday life; however, decades of research in this area have been almost entirely theoretical or done with computer models. Only a few investigations involved live organisms.

"There have been qualitative observations of sperm cells, for example, where you put sperm in water and watch their tails, then put them in an elastic fluid and see how they swim differently," Arratia said. "But this difference has never been characterized, never put into numbers to quantify exactly how much elasticity affects the way they swim, is it faster or slower and why."

The main obstacle for quantitatively testing these theories with live organisms is developing an elastic fluid in which they can survive, behave normally and in which they can be effectively observed under a microscope.

Arratia and Shen experimented on the nematode C. elegans, building a swimming course for the millimeter-long worms. The researchers filmed them through a microscope while the creatures swam the course in many different liquids with different elasticity but the same viscosity.

Though the two liquid traits, elasticity and viscosity, sound like they are two sides of the same coin, they are actually independent of each other. Viscosity is a liquid's resistance to flowing; elasticity describes its tendency to resume its original shape after it has been deformed. All fluids have some level of viscosity, but certain liquids like saliva or mucus, under certain conditions, can act like a rubber band.

Increased viscosity would slow a swimming organism, but how one would fare with increased elasticity was an open question.

"The theorists had a lot of different predictions," Arratia said. "Some people said elasticity would make things go faster. Others said it would make things go slower. It was all over the map.

"We were the first ones to show that, with this animal, elasticity actually brings the speed and swimming efficiency down."

The reason the nematodes swam slower has to do with how viscosity and elasticity can influence each other.

"In order to make our fluids elastic, we put polymers in them," Arratia said. "DNA, for example, is a polymer. What we use is very similar to DNA, in that if you leave it alone it is coiled. But if you apply a force to it, the DNA or our polymer, will start to unravel.

"With each swimming stroke, the nematode stretches the polymer. And every time the polymers are stretched, the viscosity goes up. And as the viscosity goes up, it's more resistance to move through."

Beyond giving theorists and models a real-world benchmark to work from, Arratia and Shen's experiment opens the door for more live-organism experiments. There are still many un-answered questions relating to swimming dynamics and elasticity.

"We can increase the elasticity and see if there is a mode in which speed goes up again. Once the fluid is strongly elastic, or closer to a solid, we want to see what happens," Arratia said. "Is there a point where it switches from swimming to crawling?"

Arratia and Shen's research was supported by the National Science Foundation.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by University of Pennsylvania.

Journal Reference:

X. Shen, P. Arratia. Undulatory Swimming in Viscoelastic Fluids. Physical Review Letters, 2011; 106 (20) DOI: 10.1103/PhysRevLett.106.208101

.