ACS Spring meeting a feast for food chemists

The Spring meeting of the American Chemical Society (ACS) has highlighted a bunch of interesting studies related to food.

The first one to grab my interest was the report by scientists Dr Iain Brownlee and Prof Jeff Pearson of Newcastle University about the potential of alginates to reduce fat uptake by up to 75% !!! They used an artificial gut to do the experiments and the artificial gut gained no weight during the experiment. For the life of me I can’t think of a specific reason why alginates may be better at reducing fat absorption than other polysaccharides.  If it is charge there are LM pectins, chitosan, and carrageenans that may also be effective. If it is size & viscosity, then barley and oat beta-glucans  should be effective. Brownlee and co-workers wrote in a 2005 review**

“Evidence suggests that the intake of dietary alginates results in a number of potentially beneficial physiological effects, such as reduced intestinal absorption, increased satiety, reduced damaging potential of GI luminal contents, modulation of colonic microflora, and elevation of colonic barrier function. Alginates have all these properties, whereas other fiber types have previously been reported to have some but not all of these effects. Similar effects have also been noted for other dietary fibers. A direct comparison of the physiological effects of alginate to those of other dietary fibers is not always possible, since relatively few studies have considered the potential of alginate as a dietary fiber”.

**Alginate as a Source of Dietary Fiber. I.A. Brownlee et al. Critical Reviews in Food Science and Nutrition, Volume 45, Issue 6 September 2005 , pages 497 – 510

The press release is certainly short on specifics, particularly on the mechanism. I cannot find yet a refereed article on this specific study, I await it with relish, thickened of course with alginate!

Alginate is a co-polymer mannuronic and glucuronic acid residues – here is the structure courtesy of the FAO

alginate

Dark-roasted coffee may be easier on the tummy

In another presentation at the ACS meeting Veronika Somoza, Ph.D. from the University of Vienna in Austria, and Thomas Hofmann, Ph.D. from the Technische Universität München in Germany, reported the that an increase in N-methylpyridium in darker roasted coffee was associated with reduced acid production by stomach mucosal cells.  In their words…

Our data show, for the first time, that caffeine, catechols and N-alkanoly-5-hydroxytryptamides are those coffee components that stimulate molecular mechanisms of stomach acid secretion in human stomach cells… We found out there’s no single, key irritant. It is a mixture of compounds that seem to cause the irritant effect of coffee.

“…one of the coffee components, N-methylpyridium (NMP), seems to block the ability of the stomach cells to produce hydrochloric acid and could provide a way to reduce or avoid stomach irritation. Since NMP is generated only upon roasting and not found in raw coffee beans, darker-roasted coffees contain higher amounts of this stomach-friendly coffee ingredient. Dark- roasted coffee can potentially contain up to twice as much of the ingredient as light-roasted coffees, but its levels can vary widely…”.

The scientists who conducted study are self-confessed coffee-lovers and were reported to be “very excited about this research.”

I think the press release may have the compound name wrong N-methylpyridinium is a known roasting product of the degradation of trigonelline [which is in green beans]. The other main outcome of roasting trigonelline is the production of nicotinic acid. The peak for N-methylpyridinium comes at higher roast temperatures as shown by Stadler et al in 2002***.

***Alkylpyridiniums. 1. Formation in Model Systems via Thermal Degradation of Trigonelline. Richard H. Stadler,, Natalia Varga,, Jörg Hau,, Francia Arce Vera, and, Dieter H. Welti. Journal of Agricultural and Food Chemistry 2002 50 (5), 1192-1199.

trigonelline

Figure with permission ACS

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.

chairs

“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

untitled

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.

MTGase links – Cooking Issues

http://cookingissues.wordpress.com/2009/10/08/transglutaminase-aka-meat-glue-primer/

MTGase primer

http://cookingissues.wordpress.com/primers/transglutaminase-aka-meat-glue/

This is the first time I’ve come across the Cooking Issues site/blog and it certainly looks interesting.

http://www.cookingissues.com/

It is the “tech n’ stuff”  blog of the French Culinary Institute in New York City

Other recognition

One of my graduate students has the most downloaded paper from the current issue of the journal of Cereal Chemistry…

Effect of Carbonate on Co-Extraction of Arabinoxylans with Glutenin Macropolymer. T. Kongraksawech,  A. S. Ross, and Y.-L. Ong. January/February 2010, Volume 87, Number 1: Pages 86-88.

Congratulations Teepakorn !

Glutenin macropolymer is the gel formed on the top of the pellet after very high force centrifugation of a wheat flour slurry that has been mixed with dilute sodium dodecyl sulfate [a detergent]. Glutenins are the larger of the gluten polymers that form large “macro” or “super” polymeric networks that contribute the elastic component of dough behavior. There is still discussion in the literature  about the molecular level mechanisms of glutenin chemistry, but we won’t go into that here.

Our research group is interested in alkaline processing of wheat doughs, as in some noodle products. Alkaline doughs made with sodium carbonate are stiffer than normal doughs made with salt [all other things being equal] but there is little understanding of the molecular level events that contribute that. This was part of  a research effort aimed at finding that mechanism. Our hypothesis is that the alkali redistributes the proportion of the arabinoxylan [fiber: AX] portion of flour that is soluble, leading to more water absorption in the aqueous dough phase and a change in dough properties. Our results showed that some AX is entangled with the glutenin macropolymer gel and the concentration increases under the alkaline conditions used in this experiment.

We have published other work in this research effort.

Glutenin Macropolymer in Salted and Alkaline Noodle Doughs. Y. L. Ong,  A. S. Ross, and D. A. Engle. January/February 2010, Volume 87, Number 1: Pages 79-85.  DOI:10.1094/CCHEM-87-1-0079

NOODLES2 poster