Lab Cat

13 Mar 2011

Science on Sunday: Glycemic Index

Filed under: Health, Nutrition, Science — Tags: , , , — Cat @ 1:49 pm

One of the problems with science is how it is reported in magazines and newspapers.  Also how it is reported on the web can be a problem.  This problem came to light for me when I was reading the free magazine “Better Nutrition”.  In the February issue there was a short article on “The best weight management diet” which talked about a New England Journal of Medicine article which showed that high protein-low glycemic index diets were better for maintaining weight loss.  This sound realistic and was confirmed by reading the article, but what peeked my interest was the table of glycemic index values in the Better Nutrition article because apparently sourdough bread has a lower GI (54) than white bread (100).

This did not seem possible as sourdough bread is essentially made from the same ingredients as white bread with a different starter is added instead of yeast for proofing.  There is nothing in the process of making sourdough bread that should change the carbohydrates, which are from wheat flour.

So I looked up how glycemic index was measured.  What I found was that glycemic index (GI) ranks foods by how quickly they increase blood sugar (glucose) levels.  Foods that increase blood sugar rapidly after being consumed have a high GI.  For example, honey has a GI of 85 and sucrose, table sugar, has a GI of 70. Conversely foods which are slowly digested and absorbed have a low GI.    Examples of these foods are green vegetables (GI = 15) and dark chocolate with greater than 70 % cocoa solids (GI = 22).

GI is measured by feeding measured portions of the test food containing 10 – 50 grams of carbohydrate to 10 healthy people after an overnight fast.  Blood samples are taken at 15-30 minute intervals over the next two hours and used to construct a blood sugar response curve. The area under the curve (AUC) is calculated to reflect the total rise in blood glucose levels after eating the test food.  The results for a test food is divided by the results of the standard containing the same amount of carbohydrate, either glucose or white bread are used as standards, and multiplied by 100.  The result gives a relative ranking for each tested food.  There is some concern, firstly that the standards used are different and secondly two hours after a meal is too short.  Food is known to stay in the stomach for over 4 hours, so longer term blood glucose monitoring might be better.

The glycemic index was developed at the University of Sydney (Australia) originally to aid people with diabetes control their blood sugar levels.  Low GI diets are useful for people with diabetes as it allows them to regulate their blood sugar levels and this in turn helps with insulin levels and may reduce insulin resistance for people with Type II diabetes.

So the more I read, the less likely it seemed that sourdough bread could have a lower glycemic index than white bread, which by the way, in some measurements of GI is set as the reference with a GI of 100 and in others, where glucose is the reference, white bread has a GI of 70.  Yes, not even the measurements of GI are standardized.

Interestingly it seems that the reason the high protein/low glycemic index diets work is that protein fills you up and after eating a meal that is high in protein you are more satisfied.


Thomas Meinert Larsen, et al, Diets with High or Low Protein Content and Glycemic Index for Weight-Loss Maintenance N Engl J Med 2010; 363:2102-2113 doi:10.1056/NEJMoa1007137


21 Jul 2009

Non-Enzymatic Browning Introduction 2

Food tastes best when browned.

Food tastes best when browned.

Food in always complex unless you are studying something quite simple such as a beverage with few ingredients (vitamin water, anyone?).  Even sucrose has a complex chemistry, more of which I will share in a future post.  So individual NEB reactions cannot be isolated in food.  Quite often intermediates and products from one reaction become intermediates in another reaction, especially in the Maillard reaction. Thus, most food chemistry textbooks use Non-Enzymatic Browning (NEB) as synonymous with the Maillard reaction. However, the other NEB reaction cause browning in food without the use of enzymes.

Both caramelization and lipid oxidation cause browning in certain foods, i.e. sugar-based and fried foods, respectively. Ascorbic acid degradation is significant in food with a low pH (high acidity) especially in citrus juices.  The reaction of flavanoids is important in highly colored foods as the colorful anthocyanins degrade and lose their color.  The reaction of flavanoids may also be important in soy protein, but less because of a color change and more due to a lose of isoflavones.

NEB Intro Part 1

23 Jun 2009

Non Enzymatic Browning

My major interest in food chemistry is how food changes during processing and storage.  I am especially interested in how color changes take place.  The reactions I am interested in are called Non Enzymatic Browning reactions to differentiate them from the browning that occurs when you cut an apple or banana, which involves an enzyme.

Non enzymatic browning (NEB, non enzymic browning) reactions are the most important reactions in food, and, no, I am not biased.   Just image the aroma of melting chocolate, freshly baked bread or  a roasting leg of lamb, the golden color of a croissant, the dark amber color of a well brewed beer; caramels, toast.  These are all caused NEB reactions.

There are five different NEB reactions and I intend over the next few months to write about each of them:

  1. Caramelization – browning of sugar, especially sucrose
  2. Lipid Oxidation – the oxidation of fats and oils; including rancidity
  3. Break down of flavonoids – highly c0lored compounds can also lose their color
  4. Degradation of ascorbic acid (Vitamin C) – AsA is unstable even without oxygen
  5. The Maillard Reaction –  reaction between carbonyl compounds and amino acids

Numbers (3) and (4) are not typically on a list of NEB reactions, but I did my thesis on ascorbic acid browning and it definitely goes brown without oxygen and without enzymes.  The degradation of flavonoids is one I have added and came to me in flash of inspiration when at a conference.  I am sharing it with you now, so this is new even though I had the idea three or four years ago.

More later…

12 Mar 2009

Knitting Delays Dementia

Filed under: Science — Tags: , , — Cat @ 3:07 pm

Mum heard on the BBC World Service that knitting can reduce depression in older women:

Apparently physical therapists and doctors have noticed that old ladies (and perhaps men – not mentioned) who are in pain and depressed, improved a lot when they took up knitting.  They used less medication, were more cheerful and their  memories improved.

Doctors think it may be the movements in knitting that help to calm patients.  They also suggest that knitting groups overcome feelings of isolation and making nice things makes the ladies feel  less useless.

They are starting a proper research programme in Bath to sort out the different factors.

I did a quick search and all I could find was this on BBC Health, which is more about dementia than depression:

Those who had during middle age been busy reading, playing games or engaging in craft hobbies like patchworking or knitting were found to have a 40% reduced risk of memory impairment.

So pick up those needles and stop your mind from deteriorating.

28 Feb 2009

My Hero: Marie Curie

Conveniently the topic for the next Scientiae Carnival, Role Models of Women Making History, dovetailed nicely with the next exercise for the Total Leadership process.  I found the examples in the book about Total Leadership hard to follow on from as they were both about family members that had overcome adversity and personal challenges. These stories are very interesting, but while I admire my family greatly and I know they have undertaken personal challenges, to me a hero is someone who has done something beyond every day living.  So I chose Marie Curie.

Teaching chemistry to freshmen undergraduates makes me realize how white male dominated it was especially at the beginning of the twentieth century.  A few women stand out in my mind as having been successes despite the system – Dorothy Hodgkin and Rosalind Franklin are two from the mid to late twentieth century that come to mind.  Marie Curie (1867 – 1934) succeeded as a chemist and physicist at an earlier time than these two and from within the system.  I admire her because she dedicated her life to science to such an extent that she left her home country, Poland, to do research at a better institution in Paris.  This was definitely unusual for women at that time.  When she found her scientific niche, she carried out her research at the highest level winning two Nobel prizes.  Every scientist dreams of winning one, but two is outstanding.

The first Nobel prize was the prize for Physics awarded in 1903 to Marie Curie, Pierre Curie and Henri Becquerel

“in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena discovered by Professor Henri Becquerel.”

The second, the 1911 Nobel Prize in Chemistry, was awarded

“in recognition of her services to the advancement of chemistry by the discovery of the elements radium and polonium, by the isolation of radium and the study of the nature and compounds of this remarkable element.”

Marie Curie with her daughters

Marie Curie with her daughters

In addition to being a brilliant hardworking scientist she was also a wife and a mother.  Imagine Marie Curie, who discovered radiation, worrying about Pierre having holes in is socks or Irene getting enough fruit to eat*.

I connect to Marie Curie and see her as a role model because she gave her all to science despite the conventions and expectations of women at her time.

*I am sure she had governesses and housekeepers and was probably quite bourgeois, but still she did it.  She could have just stayed at home and done what every other middle class woman of the late nineteenth and early twentieth centuries was doing.


Wikipedia on Marie Curie

Susan Quinn (1995) Marie Curie – A Life, Heinemann, London

27 Jan 2009

Simple Sugars: Fructose, glucose and sucrose

Glucose, fructose, sucrose

Glucose, fructose, sucrose

Simple sugars are carbohydrates. Glucose and fructose are monosaccharides and sucrose is a disaccharide of the two combined with a bond.  Glucose and fructose have the same molecular formula (C6H12O6) but glucose has a six member ring and fructose has a five member ring structure.

Fructose is known as the fruit sugar as its make source in the diet is fruits and vegetables. Honey is also a good source.

Glucose is known as grape sugar, blood sugar or corn sugar as these are its riches sources. Listed in food ingredients as dextrose.

Sucrose is the sugar we know as sugar or table sugar. Typically extracted as cane or beet sugar. If sucrose is treated with acid or heat, it hydrolyzes to form glucose and fructose.  This mixture of sucrose, glucose and fructose is also called invert sugar.

Nutritionally, these sugars are the same as they all provide 4 Cal/g. This is true for starch and other digestible carbohydrates too. Of the three sugars, fructose is the sweetest and glucose the least sweet, so typically less fructose can be used than table sugar (sucrose) – if sucrose has a sweetness of one, fructose is 1.7 and glucose 0.74

Fructose is more soluble than other sugars and hard to crystallize because it is more hygroscopic and holds onto water stronger than the others. This means that fructose can be used to extend the shelf life of baked products more than other sugars.

Wikipedia has lots information on sugars, including information on the three I am interested in fructose, glucose and sucrose.

19 Jan 2009

SBC09: Blogging for High School Science Classes

High School Science Blogging

I just got back from the Science Blogging Conference and here is a photograph from the best session I attended. These High School Students (and teacher) told us what they were up to in their Biology classes. In particular I found it interesting how they use the internet to communicate with each other and with the teacher.

It has given me much food for thought for my classroom, but unfortunately I think I need to teach them how to use Word and Excel before starting with a Twitter discussion group. I am hoping that e-learning (Blackboard) will help with teaching this semester.

There are more pictures from the different sessions I attended on Flickr.

14 Jan 2009

Molecular Gastronomy is Part of Food Science

In a recent issue of Food Technology, the magazine for IFT members, Hervé This responds to the suggestion that molecular gastronomy is part culinary art and part science. He gives a very good summary of the differences between cookery/culinary, food science and food technology:

“Cooking is a technique (sometimes an art) and the objective is to make food.”

“On the other hand, molecular gastronomy is a science. It is performed in a laboratory.”

“Furthermore, science is not technology. Thus, applied science cannot exist. Application involves technology (from techne, doing, and logos, study). When examining mechanisms of phenomena, the goal is not to apply knowledge (application), but rather to produce it.”

He admits that he himself had problems during his thesis of separating out science from technology but he states very strongly that molecular gastronomy is science and molecular cooking is using the results from molecular gastronomy to create new food items or improve old ones. This’ Ph.D. thesis, on Physical Chemistry of Materials, was entitled Molecular and Physical Gastronomy or the equivalent in French.

The confusion between the science, art and technology of food is present in food science. That there does not appear to be a final definition of molecular gastronomy adds to this confusion, especially as chefs have taken over this term, rather than using This’ preferred Molecular Cooking. Khymos gives a good summary of the different definitions.

I do have problems with the fact that Molecular Gastronomy is so trendy and considered to be the saving of the world’s food supply.  [So I exaggerate? What’s the problem?] Many articles about Molecular Gastronomy and the restaurants that practice molecular cookery appear to have never heard of food science.  So I appreciated the fact that This states that molecular gastronomy is part of food science but I struggle to place it within the traditional subject areas of food science.  It overlaps mostly with food chemistry.  At least This’ part of Molecular Gastronomy is heavily physical chemistry based.  The research undertaken is more directly relevant to cooking and culinary arts than much of food chemistry.  For example, my research on the Maillard reaction has few direct practical applications, unless you are willing to mix amino acids and sugars together in your kitchen.  I still would not recommend eating the results of my research.

Within the article he gives an excellent summary of what science is – the idea of testing a hypothesis to give new information which increases our knowledge of a system.   I might even use some of these ideas for teaching.


Hervé This Molecular Gastronomy vs. Molecular Cooking Food Technology December 2008 (PDF)

24 Nov 2008

Music Monday: The World in Six Songs, Daniel Levitin, A Book Review

Filed under: Science — Tags: , , , — Cat @ 8:23 am

Can the World be described by six songs? If so, what would the topics be and why? The question Daniel Levitin tries to answer in his new book “The World in Six Songs” actually appears to be can songs be divided into six categories? He obviously thinks so and his six themes are Friendship, Joy, Comfort, Knowledge, Religion and Love. The book is more than that, as he also describes how music effects us, emotional and mentally. He, like many musicians, myself included, is convinced that music does have a positive effect on us:

For example, we know that singing releases endorphins (again, a “feel good” hormone) but why is not known; and this lack of causal understanding makes many scientists uncomfortable about the connection between singing and endorphins.

However, he accepts that this means that he has a bias when it comes to research:

Scientists are in the business of wanting proof for everything, and I find myself caught somewhere in the metaphysical middle on this issue. As a musician, I’m reminded on a daily basis of the utterly ineffable, indescribable power of music.

But unfortunately current research showing this effect of music just has not been done, or done badly if it has been done at all:

On the research front, many of the studies on the effectiveness of music therapy are not performed to rigorous scientific standards, and so their claims remain unproven.

In fact, he goes on to compare some of the music therapy research with research done with potential psychic sense and not positively.

His thesis is a continuation of the thesis first presented to us in his first book, “Your Brain on Music” in which he totally disagrees with Steven Pinker who refers to music as “auditory cheesecake” meaning that our appreciation of music is an enjoyable side effect of language development. When I first read this quote from Pinker I decided that Pinker must be tone deaf and obviously has never MADE music himself. So it seems that I share the same bias as Levitin.  Levitin does suggest that since neurochemical states in the brain motivate us to act and emotion and motivations evolved together; the fact that music makes us feel good it motivates us to… fall in love, feel happy, get more energy and go to work, learn tasks, follow religion and so on.

But how does this fit with songs?  What is a song? Anything sung, apparently:

By definition, “a song” is a musical composition intended or adapted for singing. One thing the definition leaves unclear is who does the adapting. Does the adaptation have to be constructed by a professional composer or orchestrator, as when Jon Hendricks took Charlie Parker solos and added scat lyrics (nonsense syllables) to them, or when John Denver took Tchaikovsky’s Fifth Symphony and added lyrics to the melody? I don’t think so. If I sing the intro guitar riff to “(I Can’t Get No) Satisfaction” by The Rolling Stones (as my friends and I used to do frequently when we were eleven years old), I am the one who has done the adapting, and even if separated from the vocal parts of that song, this melodic line then stands alone and becomes a “song”: by virtue of my friends and I singing it. More to the point, you can sing “As Time Goes By” with the syllable “la” and never sing the words – you may have never have seen Casablanca and you may not even know that the composition has words – and it becomes a song by virtue of you singing it.

He concentrates mostly on popular music because he is mostly interested in what music makes us tick:

I’m particularly interested in that portion of musical compositions that people remember, carry around in their heads long after the sound has died out, sounds that people try to repeat later in time, to play for other; the sounds that comfort them, invigorate them, and draw them closer together.

The discussion in the book was hard to follow as I lacked the depth of music knowledge required. It should have come with a CD. I have since discovered that clips of the songs are on the book’s website. Unfortunately, the book I read is back at the library. Perhaps when it comes out it paperback and I have time to read it leisurely, over the summer rather than during the first month of a new semester at a new college teaching new classes, I might try again and work through some of his arguments.

I enjoyed “This is Your Brain on Music” which was about the neuroscience behind our responses to music. It was fascinating. I tried to review it but found the detail overwhelming. I still have part 2 of my review in my drafts folder!

Other References

23 Oct 2008

Thirsty Thursday: Ingredients of Energy Drinks

Filed under: Food — Tags: , , , , — Cat @ 7:52 am

Since I cannot drink alcoholic beverages and unless it is really really cold, I do not really like hot beverages either*, I typically drink water, orange juice and the occasional can of fruit soda.  I am interested in finding out about new beverages available and have been very interested in the recent development and growth of energy drinks. For those of you unaware of energy drinks, like myself until I wrote this article, these are highly caffeinated, highly sugared sodas such as Red Bull, Monster or Rockstar**, which are advertised as improving performance and stamina. For example, Red Bull claims this:

Red Bull® Energy Drink is a functional beverage with a special formulation and combination of ingredients. It has been specially developed for times of increased mental and physical exertion. In addition, Red Bull vitalizes the body and mind.
Red Bull’s effects are appreciated throughout the world by top athletes, busy professionals, active students and drivers on long journeys.

Red Bull’s Ingredients include  taurine, glucoronlactone, caffeine, B vitamins, sugar (sucrose and glucose), water and acesulfame K or aspartame/sucrolose.

The biggest criticisms of energy drinks comes from their high caffeine levels.  Red Bull USA does not directly state the amount of caffeine in a can of Red Bull except to say:

The caffeine in one can of Red Bull equals that of one cup of filtered coffee.

According to CBC from an article published in 2005 this is 80 mg per 250 ml serving. In humans, caffeine is a diuretic and stimulant, and is probably the most highly consumed psychoactive substance.  Consuming caffeine can ward off drowsiness and general increase alertness.  There have been many studies into the benefits and harm of caffeine, but generally it is considered harmless is small doses.

Taurine is generally considered to be an amino acid, despite lacking a carboxylic acid group, and is produced during the metabolism of cysteine, a sulphur containing amino acid. It is present in Red Bull at 1000 mg/250 ml.  The effects of taurine on the body are varied and there is still on going research. Unlike other amino acids, taurine is not found in structural proteins but it typically present as a monomer.  It is found in high concentrations in the brain, where is it considered to act on the thalamus, a major regulartory area of the brain.  It may also act as an antioxidant and may aid with the detoxification pathway of some substance by binding with toxins to speed up their excretion. Interestingly in my studies with the reaction of amino acids and glucose, to measure browning, taurine was the second faster reacting amino acid after lysine.

Glucuronolactone is a carbohydrate that is produced during the metabolism of glucose.  It has a role in the detoxification process.

The final “health giving” ingredient in Red Bull is, according to their website, B-group vitamins.  I find this generalization annoying as B vitamins covers a wide range of metabolic functions. According to Wikipedia the UK version of Red Bull contains inositol, niacin, pantothenic acid, vitamin B6 and vitamin B12.  If I want to find out what B vitamins are in US Red Bull, I obviously have to buy my own.

There have been some concerns (1, 2, 3, 4) that mixing energy drinks and alcohol could be a problem as the caffeine masks the effect of the alcohol.  The drinker thinks are less drunk than they actually are. However, Pintaday justifies his Red Bull habit despite reading the CBC article referred in #3 above.  There is also concern that energy drinks may affect heart rate and blood pressure.  This may just come down to another coffee situation, which one moment is the deadliest drink ever and the next minute coffee is redeemed and considered beneficial.  Consumers beware?

I was going to make a pun about needing an energy drink to keep me going, but I am too tired to care.

*My Britishness has been questioned as I do not like tea or beer.  I used to joke that the reason I came to the States was because I was expelled due to my unBritish drinking habits, both alcoholic and nonalcoholic.  However, since I like coffee even less than tea that leaves me even lower in terms of American drinking habits.

**A complete listing of energy drinks, Wikipedia-style, is here.

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