Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Food chemistry

7,666 views

Published on

Published in: Education, Technology, Business
  • Hello,
    How are you doing and how is life down there in your Country? I guess you are having good time. My name is Cordelia . I would love to be communicating with you for a mutual and well established friendship. I am really consumed by your profile, giving me the impression that you will be a type i desire to have as a friend. Pleas i will like you to write me back on my email address(ask4pretycordelia@hotmail.com) so that we can share our photos and experience of life and every other things in common with each other. I will wait to hear from you.

    Take care of yourself.
    Cordelia
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here

Food chemistry

  1. 1. FOOD CHEMISTRY STEREOCHEMISTRY IN FOOD By: AZHAR AIZAT
  2. 2. INTRODUCTION• Chiral carbon atoms - carbon atom that is bonded to four different groups – which bring about two distinct spatial arrangement of molecule, called enantiomers.Similarity• Enantiomers are mirror image of each other, have identical physical and chemical properties
  3. 3. Differences One of them will rotate the plane of polarization of plane polarized light in a clockwise direction This enantiomer is said to be dextrorotatory (+ or d) and has a positive specific rotation value. Another enantiomer will rotate the plane of polarization of the plane polarized light in an anticlockwise direction. It is said to be laevorotatory (- or l) where it has negative specific rotation value.
  4. 4. F9.1: Explain the three differentconventions used for naming the differentenantiometric forms1) D, L notation• An older convention used for sugar and amino acids.• The absolute configuration of other sugars about each chiral centre is then named by analogy: o If the C=O pointed away, the –OH group on the right then it is a D-isomer. o And if the C=O pointed towards you , the –OH group on the left then it is a L-isomer
  5. 5. • The D,L system is also applied to amino acids.• Using the “CORN” rule, the “COOH”, “R-side chain group”, “NH2” are around the Carbon atom.• CORN rule: o Molecule is viewed with the C-H bond pointed away from the observer (same as in the R,S system) o Made up of COOH, R and NH2 arrange around the carbon atom.  If it is arranged clockwise – D-form  If anticlockwise – L-form
  6. 6. • Almost all naturally occurring amino acids are the L-form and are usually tasteless.• Synthetic D-amino acids taste sweet and most naturally occurring sugars are D-form.• Enantiomers that does do not occur naturally cannot be metabolized by our body.• SUGARS  contain an aldehyde or ketone, and all carbons which do not have it is attached to an alcohol.• Amino acids  contain carboxylic acid (COOH), Hydrocarbon chain (R) and amino group (NH2)
  7. 7. 1) R,S system (CIP system) Cahn, Ingold & Prelog• Used for other groups of compounds.• Involve 3 steps: i. Atom bonded to the chiral carbon are ranked in order of increasing atomic number – most common would be  (H<C<N<O<F<Cl<Br) ii. When 2 @ more atoms have the same atomic no. (eg: -CH3 & -COOH) , the 2nd atoms are used to rank the substituents (so –COOH >CH3, since atomic no of 3xH < O) . And if the 2nd atom is also the same, then move on the next atom and so on. (remember that double bond count as double - COOH = 3O, since one of O have double bonds. iii. View the double molecule with the lowest ranking is pointing away from you, other three substituent must either decrease in order in a clockwise direction (R-enantiomer) @ in an anti clockwise direction (S-enantiomer)
  8. 8. F9.2: DISTINGUISH BETWEEN THEPROPERTIES OF ENANTIOMERIC FORMSOF STEREOISOMERS FOUND IN FOOD
  9. 9. • Enantiomers may be similar but different enantiomeric forms of molecule have different taste smells and toxicity.• This is because biological systems are much more sensitive to the shape of molecule• E.g.:  Carvone:  R-form= Laevorotatory= has smell and flavour of spearmint.  S-form= Dextrarotatory= has the smell and flavour of caraway seeds.  Limonene:  +(d) = Smells of oranges  -(l)= Smells of lemons
  10. 10. • Sometimes, a natural flavour is a pure enantiomer, because it is biosynthesis tends to stereo specific.• Synthetic equivalence is often a racemix mixture  mixture of equal amounts of the enantiomers . (easier to synthesis)• E.g.:  alphaionone in raspberries.• As for toxicity it can varies tremendously between the different enantiomer, as become tragically apparent in the Thalidomide disaster.
  11. 11. Template Provided By www.animationfactory.com500,000 Downloadable PowerPoint Templates, Animated Clip Art, Backgrounds and Videos

×