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”.

>>><<<

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

Science outreach summer

So far this summer I have given two short workshops using wheat, flour, bread,  and baking as a way of bringing food chemistry to life.

The First group was the

Oregon Farm Bureau’s  Summer Agriculture Institute

on the theme of Grain-Gluten-and Great bread. And started with the quote from Henri Fabre a 19th C French entomologist.

“History celebrates the battlefields whereon we meet our death,
but scorns to speak of the plowed fields whereby we thrive;
it knows the names of kings’ bastards
but cannot tell us the origin of wheat”
.

We worked through H.E. Jacob’s “Rivalry of the grasses” from “6000 Years of Bread” on the theme that wheat was ascendant partly because it made risen products with palatable textures as a result of the unique properties of gluten proteins [their stubborn insolubility, the ability of the large glutenin molecules to cross-link into enormous (by molecular standards) elastic networks, and the viscous contribution of the gliadins leading to the viscoelasticity of wheat flour dough].

We looked at the fracture properties of grain during milling and how these are related to a single gene that determines if wheat kernels are soft or hard. Then through the genetics of gluten diversity and finally to experiencing some of this in breads and doughs. it was a lot of fun, and we had great bread to eat as well.

sai01

sai02

sai03

The Second Event was the…

Apprenticeships in Science & Engineering (ASE) Mid-Summer Conference

workshop for high school juniors and seniors.

This year we went with the TSoB (the science of baking) workshop again. But this time enhanced with hands-on dough mixing, and sprinkles of…

Polymer chemistry – dough and gluten properties
Physical chemistry – dough hydration and mixing
Physics/Rheology – fracture mechanics in milling, dough properties, bread texture
Organic chemistry – Maillard browning reactions
Physics – the gas laws & rising bread
Biochemistry – fermentation
& Genetics

All the students were remarkably engaged with the topic, helped along by a bribe of very fresh baguettes. The teachable moments were abundant but it seemed the most effective were;

-to experience the relationship between weak and strong dough and dough elasticity by rolling out dough  by hand.

-to hand mix a dough from scratch and to experience the rate of hydration and to feel gluten devlopment and to get to understand why we need air in dough (an aqueous phase saturated in CO2 cannot spontaneously create gas bubbles, they need to be prenucleated in the dough).

-to experience the relationship between water activity and crust browning.

We had a lot of fun and are looking forward to next year.

I don’t have clearance yet to show faces, but even the hands tell a great story about student engagement !

We have one more workshop planned this summer for the K-12 science and math teachers of Lincoln County Oregon.

0lbap08

0lbap07

0lbap10

video-6-01m-53s

More silly putty science via Mike the Mad Biologist at ScienceBlogs

We use silly putty in class, both the Food Systems Chem and my graduate Food Polymer Science classes,  to get a handle [literally] on aspects of non-linear visco-elasticity of materials. Mike the Mad Biologist at ScienceBlogs linked to this video story at 30threads.

It pays to know your raw materials

Don’t mix up your mung beans and poppy seeds.  From Science Punk

Wine Authorities: Rosé from the Friday Fermentable

Terra Silligata

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.

311

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