Lab Cat

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…

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6 Comments »

  1. My mom is an absolute genius in the kitchen. I’ve heard of people having trouble keeping their pesto from browning in the hour or so between food prep time and serving it on the table. My mom’s pesto never goes brown. She told me the secret is to put the lemon juice into the blender first before any of the other ingredients. That way when the basil leaves start getting torn up, they’re immediately covered in lemon juice and don’t get a chance to discolor.

    Your sock summit socks look divine!

    Cheers,
    Josie

    Comment by Josie — 25 Jun 2009 @ 11:00 am

    • Josie,

      Thanks for your comment.

      The browning that basil leaves undergo when chopped up caused by enzymes and lemon juice is doubly good because the acid reduces the enzyme activity and the ascorbic acid (vitamin C) reverses the reaction converting the brown pigment into something not colored.

      Comment by Cat — 26 Jun 2009 @ 9:51 am

  2. […] NEB Intro Part 1 Possibly related posts: (automatically generated)Book Review: In Defense of Food. Part 1: IntroductionThe Scientific MethodLet’s organize things and make science! Leave a Comment […]

    Pingback by Non-Enzymatic Browning Introduction 2 « Lab Cat — 21 Jul 2009 @ 7:37 am

  3. the book will be of great help to me in my research work

    Comment by Ikegwu, Theophilus M. — 29 Sep 2009 @ 6:32 am

  4. why amla juice turns brown and how can we prevent it by not disturbing the nutrient content of the juce?

    Comment by shivam — 23 Jul 2010 @ 3:06 am

  5. Would this issue I have with strawberry wine not holding its colour in the weeks after fermentation be the result of this reaction? Or is it a case of very unstable anthocyanins? Also,I have noted that if a batch has a particularly high level of volatile acidity, the colour is not lost at the same rate.

    Comment by Wayne — 13 Oct 2010 @ 6:51 am


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