Today’s molecule – furan

I don’t need ANY bad news about my espresso coffee!

From FECYT – Spanish Foundation for Science and Technology, via “Eurekalert

Here is their press release…

“Coffee in capsules contains more furan than the rest”

Coffee in capsules contains more furan than the rest, although the levels are still within safe health limits.

“Preparing a coffee in a drip coffee maker is not the same as making one in an espresso machine or from capsules, because these give rise to differing levels of furan”, Javier Santos, a professor at the Department of Analytical Chemistry at the University of Barcelona and lead author of the study, tells SINC.  Concern has risen over recent years about the presence of this compound in foods, because of its toxic and carcinogenic effects in animals, as well as the fact that the International Agency for Research on Cancer has listed it as a possible carcinogen in humans.

“The results, published online in the Journal Food Chemistry, reveal that higher concentrations are found in espresso (43‐146 nanograms/mililitre) than in coffee made in drip coffee makers, both in the case of normal coffee (20‐78 ng/ml) and decaffeinated coffee (14‐65 ng/ml).  The levels of these toxic products were “slightly lower” (12‐35 ng/ml) in instant coffee, but a great deal higher in those made from the capsules of a well-known brand, which showed up higher levels (117‐244 ng/ml).”

“The reason for these higher levels is due to the fact that hermetically-sealed capsules prevent furan, which is highly volatile, from being released, while the coffee makers used to brew this coffee use hot water at higher pressures, which leads to the compound being extracted into the drink”, says Javier Santos. The longer that coffee is exposed to the air in cups or jugs, meanwhile, the more the furan evaporates. ”

“Different values, but not dangerous: The researcher stresses that, in all these cases, the levels of the substances found are within the limits considered to be “safe” to health. In fact, the team has estimated the amount of furan ingested as a result of coffee consumption in Barcelona, obtaining values of 0.03‐0.38 micrograms/kilogram of body weight, which is less than the maximum acceptable level (2 μg/Kg of body weight). In order for furan ingestion to exceed the maximum acceptable values, a person would have to drink at least 20 cups of capsule coffee or 30 espressos per day (for the brands with the highest furan content), or 200 instant coffees. These estimates were made on the basis of 40 ml cups and an average body weight for coffee drinkers of around 70 Kg.”

“The study also shows that furan concentrations are lower if coffee is roasted at low temperatures over a longer time (140ºC for 20 minutes) than in coffee roasted under usual conditions (200‐220ºC for 10-15 mins).”

Furan, like acrylamide, is one of a group of carcinogenic substances that can form when foods and drinks are subject to heat treatment. They are the result of a reaction, known as the Maillard reaction, between carbohydrates, unsaturated fatty acids and ascorbic acids or its derivatives.”


M.S. Altaki, F.J. Santos and M.T. Galceran. “Occurrence of furan in coffee from Spanish market: contribution of brewing and roasting”. Food Chemistry 126 (4) 1527, June 2011 (Available online December 2010). Doi: 10.1016/j.foodchem.2010.11.134.

Food Science [sort of] in action

Once again food gums come to the rescue of our building project.

This time – sodium alginate.

Here an I applying a slurry of a 2% (w/w) alginate solution containing peat moss, compost, and grass seeds to a newly exposed cut at the back of our driveway.

The alginate forms a gel slowly in-situ using the Ca2+ from the soil, and we found out, from the peat moss. It seems to bind the soil  and retains moisture for the seeds.

The alginates gel more strongly if there are more “G” or guluronate blocks than “M” or mannuronate blocks based on a variant of the ion-mediated “egg-box” junction zones of a similar nature to those found in low- methoxy pectins.

Other polysaccharides with ability to bind soil exist, possibly the most unusual one being the gums of  a “new” polysaccharide complex from the seeds of  “Artemisia sphaerocephala” in the family Asterceae. A sphaerocephala is thought to have pectin-like polymers with arabinogalactan side chains and the putative presence of a 4-O-Methyl glucuronoxylan which is considered to be bioactive (Batbayar et al., 2008).

In contrast Zhang et al. (2007) reported onlythe presence of arabinose, xylose, lyxose, mannose, glucose, and d-galactose but no acidic monosaccharides.

The reported ability of A sphaerocephala gum to improve chewing quality and elasticity in noodles (Xing et al., 2009) may suggest an anionic polymer with gelling capabilities similar to alginate or low-methoxy pectins. A sphaerocephala gum is reputed to be effective against diabetes and has a clinical record in animal studies to support that conjecture (e.g. (Xing et al., 2009).

Soil? A sphaerocephala gum also has the interesting property of being able to aggregate sandy soil (Batbayar et al., 2008).

BATBAYAR, N., BANZRAGCH, D., INNGJERDINGEN, K. T., NARAN, R., MICHAELSEN, T. E. & PAULSEN, B. S. 2008. Polysaccharides from  Mongolian plants and their effect on the complement system:  I.  Polysaccharides from plants of the Asteraceae family. Asian Journal of Traditional Medicines, 3, 33-41.

ZHANG, J., WU, J., LIANG, J., HU, Z., WANG, Y. & ZHANG, S. 2007. Chemical characterization of Artemisia seed polysaccharide. Carbohydrate Polymers, 67, 213-218.

Inspiration: The Kitchen Chemistry Sessions

Congratulations to Subha Ranjan Das an Assistant Professor in the Department of Chemistry @ Carnegie Mellon University


The Kitchen Chemistry Sessions


The taste of Chemistry

Lots of inspiration and resources available through these links

Chemistry in the Kitchen

a forum

The Kitchen Chemistry Sessions

A Facebook page

CMU’s Magazine

Our 2011 FST 425 “Bringing Food Chemistry to Life” pretzels ready for the acid, neutral, and pH 8, 10, and 14 dips.

A winter of food chemistry instruction

Can’t show the students for administrative reasons, but we had a good and educational time once again.

Bringing you highlights from the second iteration of  “BRINGING FOOD CHEMISTRY TO LIFE”.



Mayonnaise and egg white foams, and ways of messing them up that were instructive for the chemistry lesson.


Using the Brookfield viscometer to show how viscosity changes with molecular weight @ equivalent w/w concentration, and how it changes with w/w concentration @ equivalent molecular weight. The Brookfield with the helipath stand was also good for demonstrating how the viscosity of the mayonnaise decreased with increasing shear rate [shear thinning]. The helipath stand makes sure the sensor is going through an as yet unsheared region, taking time-dependent thixotropic behaviors largely out of play.

Fun with spherification whilst experiencing the gel forming capabilities of biopolymers with different gelling mechanisms [alginates, glucomannans, methylcellulose].

COFFEE WEEK: browning reactions, & foam and emulsion production and stability in espresso as related to roast degree [and therefore  the interplay between arabinogalactan peptide, and maybe galactomannan, extractability [during hot water extraction] and thermal degradation [during roasting] in determining the stability of the espresso crema]

Prepared for a cupping [monsooned, versus washed arabicas, versus robusta]

Color versus roast degree via tri-stimulus color meter.

How fun to have an espresso machine as part of the lab equipment! And coffee roasters too.

The instructor/barista hard at “work”

STARCH WEEK: not just formal viscometric studies, but also hands on experience of the different gelatinization temperatures and pasting behaviors of a variety of starches [e.g. potato versus wheat].

The instructor/starchista hard at work.

Using freshly made noodles as a way of bringing to life the profound  functional influence of differences in starch amylose content on food texture.

MEAT WEEK: As a plant scientist I find this work really hard to clean up because of all the fats!

Water holding capacity, gelation with salt and heat, transglutaminase, effect of pH and nitrites on color


More on sugar structural representations… Isn’t the internet wonderful?

These 2 comments were posted regarding the recent post on glycosidic bond representation.

Almost since the year dot sugar chemists have indulged themselves in bond representations with right angle bends in them and ever since I started teaching on the BSc Food science course at London South Bank University in the 1970s undergraduates have, at first, found them difficult. In the earlier editions of my food chemistry textbook* I experimented with bonds having a smooth bend but these are only a partial solution and very difficult to render neatly with packages such such as ChemDraw. The best solution is to move as quickly as possible from Tollens and Haworth structures to actual chairs. Purist organic chemists often insist that you can’t teach chairs (and boats and planes) until you’ve done many hours on the thermodynamics of cyclohexane derivatives etc. but this is nonsense. Sugar behaviour in food is very much easier to understand from a chair. “

Tom Coultate —

Dr Coultate is the Author of the excellent “* “Food: the Chemistry of its Components” 5th edition, publ. Royal Society of Chemistry, 2009”.

That comment prompted this response From SteveB – “Dr. Coultate is right on the mark when he makes the suggestion of moving quickly to the use of chair conformations to graphically represent sugar molecules. Not only do chair representations deal quite nicely with the graphically messy ‘right angle bond’, but they also better represent the steric and electronic interactions of whatever axial and equatorial functionality is present“.

I though it worthwhile then to show representations of typical chair conformations when I came across yet another fabulous and credible resource on the internet.

It is…

Structural Basis of Glycan Diversity by Carolyn R. Bertozzi and David Rabuka

in Essentials of Glycobiology 2nd Ed via The National Center for Biotechnology Information.

Editors – Richard D. CummingsJeffrey D. EskoHudson H. FreezePamela StanleyCarolyn R. BertozziGerald W. Hart& Marilynn E. Etzler.

Thankfully, as the information was created by or for the US government, the site is within the public domain, and so content is reproducible with appropriate attribution.

A great resource are the downloadable powerpoint teaching slides of all their diagrams !

So here is an example pertinent to the 2 comments reproduced above showing the conversion from the Haworth projection of β-D-glucose and in the chair conformations, also showing the predominance of the 4C1 chair where all -OH groups are equatorial and as far away from each other as possible.


“FIGURE 2.8. (a) β-D-Glucose in Haworth projection and in its 4C1 and 1C4 chair conformations; (b) envelope and twist conformations for a five-membered ring structure”.

We can now see the value of this in rendering the glycosidic bond fee of ambiguity in this example showing maltose and gentiobiose. Of course maltose is salient to our original discussion of the representation of D-glucose in starch, sharing the same α1→4 glycosidic linkage.

chairs maltose

Pretzel logic

Final lab session of our Food Chemistry class this year.

20100311 AR pretzel ANNOT

An experience of the effects of pH on browning reactions.

We make a variant of traditional soft pretzels, using a rather leaner formula than often used [for us no milk or eggs]. The loss of lactose from the milk and glucose from the egg might have contributed to our failure to get the same level of color development we saw last year when we used a full rich formula with egg and milk.

20090312 pretzels

Still it is a great way to experience the effect of pH shift on the color and aroma generated by primarily Maillard browning, allthough at pH 14 in the 4% NaOH, other reactions are very likely.

2010 formulation


2009 formulation

untitled 2009

A poolish is a 50:50 mixture of flour and water BY WEIGHT with about 0.1% of the flour weight as dried [instant] yeast [NO SALT] that is allowed to ferment around 16 hours before being added to the final dough.

Teapots, fluid dynamics, and baked potatoes – but what are we to do with the buttery taste?

Beating the teapot effect

(Submitted on 17 Oct 2009)

Cyrill Duez’s team show that superhydrophobic surfaces stop the tea from wetting the inner surface of the spout and pretty much stop the dripping.

Richard Alleyne, science correspondent for the UK Telegraph newspaper, says this backs up the old adage that putting butter inside the spout stops the drip.

But no-one is saying what we should do with the buttery taste – maybe get used to it like the Tibetans have with tsampa (toasted barley flour, green tea, and yak butter) – see picture on the last page of the linked PDF file

Of course all this leads to some interesting side trips on the internet, this time to the web page of Lydéric Bocquet an the Liquids @ interfaces’ group at the Laboratoire de Physique de la Matière Condensée et Nanostructures, Université Lyon 1, and a link to a paper of his from The American Journal of Physics from 2007 called “Tasting edge effects“. The paper  backs a hypothesis that, to quote him, “the baking of potato wedges constitutes a crunchy example of edge effects” .  He goes on to say in the abstract- “A simple model of the diffusive transport of water vapor around the potato wedges shows that the water vapor flux diverges at the sharp edges… This increased evaporation at the edges leads to the crispy taste of these parts of the potatoes“.

All I can say is, thank goodness this happens and that baked potatoes have extra tasty edges, all a function of increased drying rates that speed Maillard browning.

FotoosVanRobin via Flickr

Coffee stains explained

And an hour later  – even more interesting things – like the paper 12 years ago in “Nature” that explained the nature [pardon the unintentional but awful pun]  of the rings in coffee stains via a flow from the interior of the liquid to the exterior, bringing suspended material with the flow and depositing it at the edge of the drying droplet. And coffee is a good example because oft he amount of dispersed but not dissolved material in the cup. It would be interesting to see if the effect is more pronounced with espresso than drip filter given the far higher level of suspended solids in an espresso cup.

Capillary flow as the cause of ring stains from dried liquid drops”  Robert D. Deegan et al

Nature 389, 827-829 (23 October 1997) | doi:10.1038/39827 – even folks without a full text subscription should be able to access the abstract via this link .

Who’da thought Nature would be interested in coffee stains – still,  the journos and editors, they probably live on coffee.


Fabulously fun, but serious thought has gone into this…

[See the BFCTL August24 post “Spot the deliberate error” for a commentary on the method]

From The Science Creative Quarterly at the Univ. of British Columbia.

click here…


By Andrew Thaler

About the post author “Andrew Thaler is a graduate student studying deep-sea biology. When not in the lab, he spends his time out on the water, usually swearing at his boat while simultaneously sacrificing some important tool to Poseidon in a desperate attempt make the motor start. He is also a recreational beer brewer, and these two hobbies have melded together to create this handy guide for when emergency rations run out. He writes at”




Thanks BarleyWorld

Well – maybe ?

Plant cell wall engineering

The amazing structural properties of plants” – “Via “ScienceWise”  at the Australian National University.

I came across this when I was searching for the strategies used by other people and institutions regarding efforts to expand the public awareness of science. It’s a little old, from February 2008, but I thought it of interest.

Plant cell walls are incredibly important in all sorts of places in foods: from the texture of fruits and vegetables, and how texture softens during ripening, often due to concerted action by enzymes like pectinases, to the efficacy of extraction techniques where plant cell walls that need to be degraded for access to the internal contents e.g. wine grape crushing. Plant cell walls also soften under the impact of enzymes produced by post-harvest microbial growth. Any one who has experienced the effects of Erwinia carotovora soft rot on potatoes or carrots has seen first hand what the concerted effects of pectinases, cellulases, and xylanases can do to the integrity of the plant tissue. Cell walls  are important in cereal processing as well. Depending on their solubility arabinoxylans (AX) in wheat can be beneficial or detrimental to baking properties of flour, and AX create a second elastic polymer network in cookies that can limit their spread. Soluble beta-glucans [closely related to cellulose] are a benefit as soluble fiber in oats and barley, but can be a nightmare  for brewers trying to drain a mash tank.

Daniel J. Cosgrove, of the Department of Biology at Penn State University, got it right when he wrote;

Without cell walls, plants would be pliant piles of PROTOPLASM, more like slime moulds than the stately trees and other greenery that grace our planet“.

(Cosgrove DJ. 2005. Growth of the plant cell wall. Nature Reviews Molecular Cell Biology 6, 850-861 | doi:10.1038/nrm1746)

Anyone who has mistakenly grabbed a Erwinia rotted potato has experienced what the whole plant kingdom would feel like, and what its TEXTURE would be, without the cell walls – YEECH!

One problem about plant cell walls is their complexity. It has been hard to model their fine structure, and even harder to define the sequence of events in their synthesis.

In the article “Mixing cell biology with mechanical engineering” Shankar Kalyanasundaram, Hung Kha and Richard Williamson, biologist and engineers team up to model primary cell wall structure.

Williamson is quoted…

The mechanical properties of any material always reflect its underlying structure” of course for food scientists the mechanical properties are also the properties we perceive as texture when we eat the material.

Dr Kalyanasundaram reported; “… biologists might be able to test the individual components that make up the structure of the cell wall, but they don’t have the expertise to model the various components as a system.. How the structure of a cell wall gives rise to its mechanical properties is an important research area, and we need this understanding if we are to better understand cell expansion and the role it plays in plant growth“.

This is entirely aligned in its strategy with  the systems approach to understanding plant cell walls published by  Chris Somerville and colleagues from Stanford in 2004

(Somerville et al. 2004. Toward a Systems Approach to Understanding Plant Cell Walls.  Science 24: Vol. 306. no. 5705, pp. 2206 – 2211. DOI: 10.1126/science.1102765)

The abstract of Kha et al can be found here –  —  —  —  Kha H, Tuble S, Kalyanasundaram S, Williamson RE. (2008) Finite element analysis of plant cell wall materials. Advanced Materials Research 32: 197-201.

Permian dietary fiber

On Nova Science Now on PBS last night they reported about work studying the contents of small liquid inclusions in New Mexico’s Saledo salt beds that were  laid down in the Permian era 250 million years ago.

The report showed fascinating electron micrographs of mats of cellulose in the inclusions – hi-fiber salt  no less!

The cellulose was identified by it resistance to hydrolysis in 0.5 N NaOH and it susceptibility to hydrolysis by beta 1-4 specific cellulase enzymes.

So cellulose is not only the most abundant organic molecule on the earth, it is now the oldest identified macromolecule. Not bad for a bunch of glucose.

Secrets in the Salt…

can be seen  in its entirety at this link.

The researchers, Jack D. Griffith, Smaranda Willcox, Dennis W. Powers, Roger Nelson, & Bonnie K. Baxter published the work in Astrobiology in April 2008 (Griffith et al 2008 Astrobiology 8 (2): 215-228. doi:10.1089/ast.2007.0196.  Discovery of Abundant Cellulose Microfibers Encased in 250 Ma Permian Halite: A Macromolecular Target in the
Search for Life on Other Planets

No image – because the copyright holders want to charge a USD$86.50 fee for use of ONE image from the paper just in A SINGLE  email, let alone what they’d charge for a blog, notwithstanding the free advertising they’re getting.

You need to go to the PBS site for the electron micrographs.