Another term of delicious food chemistry – some of our activities…
Ever wondered about the chemistry behind a great Thanksgiving dinner? Here’s your chance to dazzle your friends with your knowledge of the esoteric and the practical chemistry of this national favorite.
The webinar is presented by Harold McGee and is part of the American Chemical Society’s “Joy of Science” Food Chemistry Series [link].
The series has included these topics
- Advanced Beer Chemistry and Brewing
- Cheers! The Chemistry of Wine
- The Chemistry of Cheese and Why We Love It
- Advanced Culinary Chemistry – Sizzles for the Summer
- Advances and Innovations in Wine Chemistry
- The Chemical Keys to Thanksgiving Dinner [you can register here]
with - Top Five Chemistry Tips for the Kitchen to come Feb 16 2012.
The older webinars in the series are available for viewing on the Food Chemistry Series web page
The Thanksgiving presentation will cover…
- The pros and cons of brining your turkey
- The two kinds of turkey muscle and how they’re best cooked
- How heating rates affect the flavor of sweet potatoes
- Why traditional persimmon pudding is almost black, and how to make it persimmon-colored
- And much more…
I don’t need ANY bad news about my espresso coffee!
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.
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.
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
Our 2011 FST 425 “Bringing Food Chemistry to Life” pretzels ready for the acid, neutral, and pH 8, 10, and 14 dips.
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!
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.
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.
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.
Final lab session of our Food Chemistry class this year.
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.
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.
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.
This is the first time I’ve come across the Cooking Issues site/blog and it certainly looks interesting.
It is the “tech n’ stuff” blog of the French Culinary Institute in New York City
Work on sensor arrays has great potential in food quality control.
The original work seems to have been for detection of toxic gases and has been around for while, but aren’t aromas just fragrant volatiles?
Work has been published in Nature and very recently in Chemical Communications.
A colorimetric sensor array for identification of toxic gases below permissible exposure limits
Liang Feng, Christopher J. Musto, Jonathan W. Kemling, Sung H. Lim and Kenneth S. Suslick, Chem. Commun., 2010
So, author Suslick’s son has published this little interesting missive in “Analytical Chemistry”
In this work the sensors are able to discriminate without ambiguity 10 different commercial coffees and coffees at various stages of roasting, as the excerpted figure shows.