Lab Cat

18 Aug 2009

Tasty Tuesday: Sugar Chemistry

I really should just sent you to Exploratorium which has an excellent section on sugar chemistry, but sugar chemistry is so cool, that I have share it with you myself.  In fact sugar chemistry is so interesting that it supports a whole sector of the food industry.  I am, of course, talking about candy.  Food Scientists typically divide the candy industry into chocolate and non-chocolate candy and most of the non-chocolate candy is made from different forms of sucrose.

If you remember sugar is the common name for sucrose, which has the very confusing chemical name of β-D-fructofuranosyl-α-D-glucopyranoside which is a fancy way of saying that it is made up of glucose and fructose.  In this post, I will interchange the words sugar and sucrose, but in chemistry sugar refers to saccharides which  are considered to be small carbohydrates.

The most important property of sucrose is its high solubility over a wide temperature range.  The different sugar candies are made by heating a sugar-water solution, as the heating time increases water evaporates.  This increases the sugar concentration and the temperature of the solution increases.  The temperature of the solution is dependent on sugar concentration:

Effect of Sucrose Concentration on Temperature

Effect of Sucrose Concentration on Temperature

Candy technologists not only control the sugar concentration by heating the sugar-water mixture to a predetermined temperature, they also control the final physical arrangement of the sugar molecules by the other ingredients added and by the way they treat the sugar-water mixture while it is cooling. This determines whether the solution sets in a crystalline form or not.  The non-crystalline form is also known as amorphous.  Thus sugar candies are divided into crystalline and amorphous.

Crystalline candies include fudges, fondant and rock candies. Amorphous candies include cotton candy, hard candy and brittles, where the sucrose has been set into a glass, and caramel and taffy, which are chewy rather than hard.

References

For Figure:

Wikipedia Candy#Sugar Stages

Harold McGee On Food and Cooking 2nd Edition p681

Advertisements

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…

27 Mar 2009

Food Labeling

The March issue of Food Technology arrived and as always I turned to the last page, which is Perspectives*. This month Joe Regenstein has a very good comment about labeling and hiding information from the consumer is hurting the industry.  As he says:

The irony is that the activist community has had much more success in attacking the food industry for not labeling products than it really has had in convincing consumers that the technology is bad for them.

He goes on to protest about the misleading labeling, that really has no meaning:

And finally, what about all those terms we’re sticking on our labels (and in our advertising) that are sometimes justified but just as often plainly misleading?  For example: free range, natural, local. When these words are misused, we  not only cheapen the words,  but we cheapen the entire food industry.

So get with the act, food industry folks and tell what is really in our food.

*It is online too, but as a pdf file

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.

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.

References

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

2 Sep 2008

Tasty Tuesday Science Snippet: Flavor Boosters

In the last issue of New Scientist (issue 2671; 30 Aug 08) there is an article (p22) in the technology section about molecules we can add to food that will enhance the flavor.  These molecules are flavorless themselves but increase the sweetness or saltiness of the food.  There are also molecules that will block the bitter taste of foods such as grapefruit.

These molecules are being developed by testing them against cell lines of taste receptors.  These receptors have been altered to glow flourescent green when responding to the taste in question.  These cell lines have also been useful in furthering sensory research – finding new taste receptors for compounds such as calcium chloride.

The cell lines are obviously not as good as the human tongue and can only respond to the taste that they are programmed for, typically sweet, salt, sour, bitter or umami.  Hence, when a flavor enhancer has been developed, shown to be safe for consumption, it has to go through a human sensory trial.

My concerns with flavor enhancers are several:

1) We get habituated to levels of flavor. So adding a sweet flavor enhancer may make us used to a high level of sweet tastes.  This is already true in the US, where food is much sweeter than that found in Europe.

2) This is pandering to the American preference of bland tasting food. In the article they were looking for bitter blockers for the after taste of soy but Asians and I (and probably many other vegetarians) do not find soy bitter.  Do people really dislike the idea of strong tastes so much, what about sweet and sour sauces?

3) I would prefer to see companies using more natural ingredients, especially herbs. Surely these new compounds are no cheaper than herbs?  I cook without adding any salt but I use a lot of herbs.  My Dad, who typically adds salt to everything does not do this to food I have cooked.  The herbs make up for the absence of salt.  Admittedly if I did use salt I could reduce the amount of herbs added to get the same flavor effect as salt enhances flavors.

1 Feb 2008

Berries and Cancer

Dig those blackberries from last summer. Any excuse to reuse my photos! We all know we should be stuffing our faces with lots of fruits and veggies, but what is the evidence and which ones are the best?

In a recent article (1), Seeram reviewed the evidence that berries prevent cancer. This review was a little frustrating to follow, and I started wondering if it was a rewritten introduction to a grant application. For an article published in the Journal of Ag. and Food Chem., I personally could have done with a better overview. Some of the detail, while may be necessary in a cancer journal, lost me without careful concentration and then I lost myself in the acronyms. You may realize this from the discussion below. To be fair, they did explain quite a bit of the science and the subject knowledge might be all over the place with different researchers studying different berries and cancers.

In the USA, commonly consumed berries include blackberries, black and red raspberries, blueberries, cranberries, and strawberries. The active ingredients in berries includes Vitamins A, C, E and folic acid; calcuim and selenium; phytosterols; and phenolic molecules such as anthocyanins, flavonols and tannins.

So how good are berries at preventing and reversing cancer?

In vitro studies, with cell lines, have shown that berry phenolics in addition to being potent antioxidants, they also:

“[…]exhibit anti-inflammatory properties, are able to induce carcinogen detoxification (phase-II) enzymes, and modulate subcellular signaling pathways of cancer proliferation, apoptosis and tumor angiogenesis […].”

Coo. That sounds good, but as I am not a cancer researcher the details of the reviewed studies were difficult for me to follow. Raspberry, cranberry and lowbush blueberry juices showed the strongest inhibition of cell growth, which is good as we do not want cancer cells to grow. A red raspberry extract treated so it went through conditions that mimicked the digestive system decreased the number of colon cancer cells and protected against DNA damage induced by hydrogen peroxide. Blueberries induced apoptosis (cell death) of cancer cells and may influence prostate cancer cells [I assumed to the good]. Cranberry extracts inhibited the growth of human breast cancer.

Animal studies showed that rats fed berries and fruit juices showed a significant reduction in AOM-induced aberrant crypt foci, which is a leading indicator of colon cancer. AOM is azoxymethane and acts as a carcinogen to trigger colon cancer in rats and mice.

As for human studies:

Increased fruit and vegetable consumption has been associated with the decreased risk of a number of cancers of epithelial origin, including esophageal cancer.

As an aside, I prefer the British spelling for oesophagus, the oe looks more dignified and I do say “oh-sophagus” or “oo-sophagus”

It is hard to know how much bioactives we are consuming. This is partly, as this article reports, because the amount of phytochemicals present in foods is not known and changes dramatically depending on growing conditions. Organic strawberries had a greater effect on human colon and breast tumor cells than conventionally grown strawberries. Organic berries were more effective probably because they contain more secondary metabolites than conventionally grown fruit.In addition:

Studies have shown a high variability in phenolic intake based on variations in individual food preferences. A high daily intake of fruits and vegetables is estimated to provide up to 1 g of phenolics.

Unfortunately, “high daily intake of fruits and vegetables” is not defined in the article.

Even if we know how much of the bioactive compounds we consume, we still do not know how bio-available these phenolics in berries or other fruit.

I find it amusing that articles always end up with a statement which in effect says “more research is needed, I am the best person to do it and I need funding now“. In this article the concluding paragraph goes:

In conclusion, it is strongly recommended that this area of research for berry fruits continue to be explored, as this will lay the foundation for the development of diet-based strategies for the prevention and therapy of self types of human cancers.

My conclusion?

Eat lots of berries, now and forever more. Fortunately, I have lots in my freezer. Yum.


Reference:

(1) Seeram, N.P. (2008). Berry Fruits for Cancer Prevention: Current Status and Future Prospects. Journal of Agricultural and Food Chemistry DOI: 10.1021/jf072504n

ResearchBlogging.org

29 Jan 2008

Wine Color

Filed under: Food, Food Science or Molecular Gastronomy — Tags: , , — Cat @ 10:00 am

A recent article (1) in the Journal of Agriculture and Food Chemistry discusses the relationship between young red wine color and grape phenolics. On reading, the first question I asked is how is wine made? So, of course, I checked with Wikipedia.

The most important difference between red and white wines is the fact that red wine is made from red or black grape pulp together with the grape skins (must), whereas white wine is made from white grape juice. However, white wines can be made from red grape juice as long as the skins are not present. Grape skins contain anthocyanins and tannins, which contribute to both the color and the strong flavor of red wines. Merlot wine, for example, has a high tannin content which is why it is strongly astringent.

For red wine, the must undergoes a 5 – 14 day maceration during which the ethanol content increases due to natural (?) fermentation and anthocyanins and tannins are extracted from the grape skin. As the ethanol content increases, more of these polyphenols are extracted. The degree of extraction varies depending on time and temperature of maceration and fermentation, concentration of ethanol, and other winemaking conditions. During fermentation, when the yeast is converting the grape sugar to ethanol and carbon dioxide, and during maturation, these polyphenolic compounds further react.

The hypothesis of the article was:

It may be possible to predict the wine color from the levels and the profile of grape phenolics.

For this study they consider young red wines. Presumably they did not have enough time to mature the wines for years. Young wines were fermented for fourteen days at 25 oC ; they do not appear to have been matured in any way.

So how do you measure wine color?

Color should be measured so that the wines all have the same pH and should be filtered to remove any solid particles. Boulton’s color assay (also) can determine the total wine color and the color caused by copigmentation, anthocyanins and polymeric pigments. Color intensity and tonality can be measured using a UV/Visible spectrophotometer at wavelengths 420 and 520 nm.

When the polyphenolic content of grapes and wine were compared to the total wine color, there was good positive correlation for both grape and wine anthocyanins, despite the fact that anthocyanins were only responsible for ~50% of the color of the wine. It is possible that this correlation would decrease with wine maturity as polymeric pigments and copigmentation would increase.

All in all, the level of anthocyanins in the grapes could be used to predict red wine color.

Reference

1) Jensen, J.S., Demiray, S., Egebo, M., Meyer, A.S. (2008). Prediction of Wine Color Attributes from the Phenolic Profiles of Red Grapes (Vitis vinifera). Journal of Agricultural and Food Chemistry DOI: 10.1021/jf072541e

ResearchBlogging.org

14 Jan 2008

Books: In Defense of Food Science

Filed under: Books, Food, Food Science or Molecular Gastronomy — Tags: , , — Cat @ 9:49 pm

I took a break from reading new to me fiction, as part of NaJuReMoNoMo or whatever it is called, to read Michael Pollan’s new book In Defense of Food. I will review it in a few days but now I have this burning desire to defend my vocation, food science. When I wrote this original post, food science needed introducing to people not defending. There still seems to be confusion as to what is food science. In the last month, I have read articles or books that malign food science unjustly.

Over Christmas in The Best American Science and Nature Writing 2007 I read Patricia Gadsby’s Cooking for Eggheads which had originally been published in Discover magazine. It is a great article about Hervé This and Molecular Gastronomy. She ably describes molecular gastronomy. Gastronomy is part of the title evoking the spirit of Brillat-Savarin and the molecular part was added by This and Kurti to evoke the chemical units that make up food. In addition:

Molecular had a dynamic, modern ring to it, perfect for ushering gastronomy into a new era. Besides, molecular gastronomy sounds so much more fun, sophisticated, and cultured than plain old “food science”, a field with which it somewhat overlaps but is largely geared to the mass-market needs of the food industry

This last week, I read Pollan’s new book, which is a great read despite, or perhaps because of, the fact that he claims that the problem with our food, in the US, is caused by the twin evils of nutritionism and the food industry. He concentrates more on the former than the later and when it comes to food science he gets confused been food science and food technology. for example:

Very often food science’s efforts to make traditional foods more nutritious make them more complicated, but not necessarily any better for you. (p153)

Today foods are processed in ways specifically designed to sells us more food by pushing our evolutionary buttons – our inborn preferences for sweetness and fat and salt. These qualities are difficult to find in nature but cheap and easy for the food scientist to deploy, with the result that processing induces us to consume much more of these ecological rarities than is food for us. (p 149-150)

This is the problem is with both essays. Food science is another academic subject; like biology or physics, just slightly (ahem) more applied. It cannot be blamed for the mass production of food any more than physics is to blame for the development of the nuclear bomb. Neither can food science be praised for producing the flavorful fast foods. Food scientists may have been instrumental in developing shelf-life extenders and flavors so that food could be mass produced and taste good* at the same time.

Molecular gastronomy is a part of food science; in the same way that food technology is part of food science. They are branches off the main trunk. Molecular gastronomy is more concerned with chemical changes, including rheology and flavor; and food technology is more concerned about engineering and processing. Food science, plain and old, includes both these and food safety as well.

As with other sciences, food science is not to blame for the reduced quality of the American diet. Scientists may have developed low fat yogurts and no-carbohydrate pastas; but a science cannot be blamed for that. As a food scientist I am interested in what happens when food is processed by any means – home, factory, restaurant. I am, admittedly, an academic and have the luxury of being able to ask why.

I do not deny that there is a problem with the American (and perhaps the British) food supply chain. We, as consumers, have moved too far away from production. This will be solved in many different ways, but I will be surprised if food science is not part of the solution.

*Tasting good needs a rejoiner. It would be great if mass produced food tasted as good as home cooking but it has some way to go. I still hope that one day we can have healthy tasting mass produced food.

Older Posts »

Create a free website or blog at WordPress.com.