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.

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”.

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DISPERSED SYSTEMS:

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

POLYMERS 101:

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

Transglutaminase

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.

Exploiting Jello’s elastic properties – Liz Hickok

Via “Chowhound‘s” Food Media

Liz Hickok makes sculptures of San Francisco in jello. This is Telegraph Hill shaking and wobbling.

You can see the whole “San Francisco in Jell-O” series on Youtube at her channel http://www.youtube.com/user/ehickok or with much more on her own website http://www.lizhickok.com/

Of course if you were at MIT you could simulate Jello for a class project but it seems much easier to just make the jello !

Christine Joly-Duhamel and colleagues in 2002 * suggest that the basis of jello (an all gelatin gel) elasticity is the extent and size of the triple helix regions – and therefore I infer, not the entropic contribution of the highly flexible coils separating them. An entropic contribution would come from the coiled regions being straightened out on deformation. Straightening the coils would make them more ordered, thus decreasing entropy, and so there would be a restorative force “seeking” to return to the higher entropy (more disordered) state. Although never purely entropic, polypeptide gels have been considered more entropic than enthalpic (Rheology of fluid and semisolid foods – M. A. Rao page 326), but Joly-Duhamel’s model suggests a more enthalpic type gel for gelatin than was thought previously. Enthalpic restorative forces in gel elasticity come from the energetics of bending and otherwise straining bonds in relatively stiff chains – a model considered valid for many polysaccharide gels.

*All Gelatin Networks: 2. The Master Curve for Elasticity. Christine Joly-Duhamel, Dominique Hellio, Armand Ajdari, and Madeleine Djabourov. Langmuir, 2002, 18 (19), 7158-7166• DOI: 10.1021/la020190m • Publication Date (Web): 27 July 2002

Hopefully some food chemistry came to life…

There are many elements needed to create a good and compelling class – good material, a willing instructor, but the essential element is enthusiastic and dedicated students.  It is a circular argument: enthusiastic students generate enthusiasm in the instructor, which generates enthusiasm in the students, and around we go again.

I was privileged to have an almost uniquely good natured, good humored, and hard-working group who were willing to participate in this experiment in teaching food chemistry. Of course not everything that was tried worked flawlessly – but no good thing was ever perfect the first time around. And we were not having enough fun…

The key structural element of the class that I believe led to our moderate success was the use of case studies to highlight many of the basic elements of food chemistry. The two more successful ones were bread making and espresso.

Breadmaking was viewed as a system both in narrow and broad senses. In the narrow sense: a matrix of interacting components in the dough and in the finished product. In the broader sense; as the progress of a variable agricultural raw material through its intermediate processing steps (e.g. milling) through to final processing, storage, and consumption.

In the narrow sense we were able to incorporate elements of…

Polymer Science (entanglements, glassy and rubbery states and their responses to changing temperature and plasticization [water])

Rheology (viscoelasticity)

Starch behavior (gelatinization, susceptibility to attack by amylases, & retrogradation [junction zone nucleation and growth] and staling)

Maillard reactions (the effects of water activity, temperature, pH [mostly with the pretzel lab], and the contribution of fermentable reducing sugars from damaged starch)

Foams and foam stability (dough gas cells as a solid/liquid foam stabilized by proteins and lipid-based surface active components, the foam to sponge transition from dough to bread)

Enzymatic activity and thermostability (mostly amylases:  the increasing susceptibility to hydrolysis of undamaged and damaged starch granules and finally gelatinized starch; the different windows of opportunity for extensive hydrolysis of gelatinized starch during baking by fungal, cereal, and bacterial amylases )

In the broad sense we were able to observe elements of…

Genetics (the interaction with genetically determined kernel hardness and subsequent starch damage during milling, fermentable sugar production by amylases, and Maillard development of crust color; the genetics of gluten protein variability and its effects on gluten and dough viscoelasticity),

Rheology/Polymer science (fracture mechanics of kernels, polymer entaglements – stress build up and subsequent relaxations as vital steps in the transformation of flour, water, salt, and leavening [yeast or sourdough] to bread)

Espresso was also viewed in these two ways.

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In the narrow sense we were able to incorporate elements of…

Rheology – the contribution of particulates to viscosity, the contribution of polymer size to viscosity and to the persistence of espresso crema as expressed by changes in foam drainage related to viscosity

Maillard (of course) – during roasting, the delay while the beans dry out, the increasing darkness, the formation of aromatic volatiles, the production of carbon dioxide, and the role of carbon dioxide in the formation of the cream foam.

Microstructures and inhomogeneity – the idea of espresso as a polyphasic colloidal system (e.g. Piazza, L; Gigli, J; Bulbarello, A (2008). Interfacial rheology study of espresso coffee foam structure and properties. Journal of Food Engineering 84 (3) 420-429. )

In the broad sense we were able to incorporate elements of…

The idea of coffee as an agricultural product; variability in composition related to species, region of growth, the fact that it needs intermediate processing before it can be roasted (allowing an opportunity to explore cell wall polysaccharides in detail  – particularly the pectin in the cherry mucilage).
Of course there was much more – but this is just a summary.

And of course student engagement is vital. The following pictures tell the story, and I need to express tremendous thanks the class for their collective contribution to a successful term !!!

Starch lab

Pretzel lab

Coffee day

Starch again

Meat lab

Baking lab

Intelligent molecules – yeah right ! – more like silly putty on steroids.

Forwarded from a student in this winter’s class- Tangential to food chemistry per se but not to the polymer science parts of it.

Military use new gel that hardens on impact

To quote the article “The substance relies on “intelligent molecules” that “shock lock” together to absorb energy and create a solid pad”. Seems to me they don’y need to be too “intelligent” just big enough and entangled enough that they can’t pull apart (disentangle) on the imposition of a high speed deformation, like a bullet impact. Silly putty on steroids. It is cool stuff nonetheless.

Aah- Finally a quote from the inventor “Richard Palmer, the inventor of this gel said “When moved slowly, the molecules will slip past each other, but in a high-energy impact they will snag and lock together, becoming solid … In doing so they absorb energy.” http://www.daxii.com/articles/d3o_the_magic_shock_absorbent_gel.aspx

Image From Telegraph.co.uk

Vision of d30 in action here…

http://splodetv.com/video/reactive-d3o-gel

and here

http://www.youtube.com/watch?v=8EBWGbhsuws

image via http://thegearjunkie.com