Advanced food chemistry Lecture notes
Inhoud
Lipids 1 ..................................................................................................................................................... 2
Lipids 2 ..................................................................................................................................................... 5
Lipids 3 ..................................................................................................................................................... 9
Phenolics 1............................................................................................................................................. 13
Phenolics 2............................................................................................................................................. 17
Phenolics 3............................................................................................................................................. 21
Carbohydrates 1 .................................................................................................................................... 27
Carbohydrates 2 .................................................................................................................................... 31
Carbohydrates 3 .................................................................................................................................... 33
Protein 1 ................................................................................................................................................ 38
Protein 2 ................................................................................................................................................ 41
Protein 3 ................................................................................................................................................ 44
1
,Lipids 1
• Definition: Any molecule that is not soluble in water. Short chain fatty acids (these however
are soluble in water).
• Lipids classification:
• Green = contain glycerol. Purple = saponifiable (know breaking of an ester bond)
• In nature most fatty acids have double bonds in cis conformation, which induces a bend in
the molecule.
• Nomenclature: You should be able to give the short notation.
• Chemical characterization: (3.5)
1. Analysis of fatty acid composition with GC-FID
Gas chromatography combined with FID: Flame ionization detector.
Conversion reaction (burn the molecule), measures how much carbon is present. You
need a volatile molecule, but lipids are not so a preparation step is necessary.
Triglycerides are hydrolysed and methyl esterified with the help of methanol and a
strong base/acid.
Peak identification: Retention time compared to a pure fatty acid standard. Are of the
peak is proportional to the concentration of the fatty acid. Longer carbon chain is longer
retention time. Also more saturated is longer retention time. A longer column will allow
a better separation (even isomers)
2. Analysis of Iodine Value with titration method
AOCS method with Wijs reagent (ICI). IV is the number of grams of iodine reacted with
100g of oil.
more saturated fatty acids = low IV. IV not only dependent on the fatty acid, but also on
the type of molecule, TAG and FAME have different IV’s.
2
, 3. Analysis of TAG composition with HPLC (ECN: Equivalent carbon number)
Reversed phase HPLC: Hydrophobic stationary phase. ELSD detection or Mass
spectrometry. Elution order based on Equivalent Carbon number. The bigger the ECN,
the longer the retention time.
Oleic acid, linoleic acid and linolenic acids.
Calculation:
with the calculation above:
4. Analysis of oil quality (hydrolysis and lipid oxidation)
Hydrolysis:
Measured by titration with NaOH.
Oxidation:
• Difference between seed and pulp oil:
Seed oil is extracted from Endosperm, low water content, small oil bodies surrounded by
proteins and phospholipids.
Pulp oil is extracted from Mesocarp, higher water content, large oil bodies and almost no
proteins.
• Th effect of high water content of stability during storage of seeds and pulp: Higher aw is a
link to a lower stability. Increase in 3 type reaction: Increase lipid oxidation and lipolysis (non-
3
, enzymatic), increase of enzymatic activity (lipase and lipoxygenase), higher spoilage by
bacteria which grow faster and better with high aw.
• New sources of oils and fats(3.6). Different sources of fat: Vegetable and animal. Difference
between seed oil and pulp oil and interest for new source of oils.
• Extraction steps of seed oils: (3.7-3.9) Cleaning:
• Dehulling: Size reduction:
• Conditioning: Pressing:
4
Inhoud
Lipids 1 ..................................................................................................................................................... 2
Lipids 2 ..................................................................................................................................................... 5
Lipids 3 ..................................................................................................................................................... 9
Phenolics 1............................................................................................................................................. 13
Phenolics 2............................................................................................................................................. 17
Phenolics 3............................................................................................................................................. 21
Carbohydrates 1 .................................................................................................................................... 27
Carbohydrates 2 .................................................................................................................................... 31
Carbohydrates 3 .................................................................................................................................... 33
Protein 1 ................................................................................................................................................ 38
Protein 2 ................................................................................................................................................ 41
Protein 3 ................................................................................................................................................ 44
1
,Lipids 1
• Definition: Any molecule that is not soluble in water. Short chain fatty acids (these however
are soluble in water).
• Lipids classification:
• Green = contain glycerol. Purple = saponifiable (know breaking of an ester bond)
• In nature most fatty acids have double bonds in cis conformation, which induces a bend in
the molecule.
• Nomenclature: You should be able to give the short notation.
• Chemical characterization: (3.5)
1. Analysis of fatty acid composition with GC-FID
Gas chromatography combined with FID: Flame ionization detector.
Conversion reaction (burn the molecule), measures how much carbon is present. You
need a volatile molecule, but lipids are not so a preparation step is necessary.
Triglycerides are hydrolysed and methyl esterified with the help of methanol and a
strong base/acid.
Peak identification: Retention time compared to a pure fatty acid standard. Are of the
peak is proportional to the concentration of the fatty acid. Longer carbon chain is longer
retention time. Also more saturated is longer retention time. A longer column will allow
a better separation (even isomers)
2. Analysis of Iodine Value with titration method
AOCS method with Wijs reagent (ICI). IV is the number of grams of iodine reacted with
100g of oil.
more saturated fatty acids = low IV. IV not only dependent on the fatty acid, but also on
the type of molecule, TAG and FAME have different IV’s.
2
, 3. Analysis of TAG composition with HPLC (ECN: Equivalent carbon number)
Reversed phase HPLC: Hydrophobic stationary phase. ELSD detection or Mass
spectrometry. Elution order based on Equivalent Carbon number. The bigger the ECN,
the longer the retention time.
Oleic acid, linoleic acid and linolenic acids.
Calculation:
with the calculation above:
4. Analysis of oil quality (hydrolysis and lipid oxidation)
Hydrolysis:
Measured by titration with NaOH.
Oxidation:
• Difference between seed and pulp oil:
Seed oil is extracted from Endosperm, low water content, small oil bodies surrounded by
proteins and phospholipids.
Pulp oil is extracted from Mesocarp, higher water content, large oil bodies and almost no
proteins.
• Th effect of high water content of stability during storage of seeds and pulp: Higher aw is a
link to a lower stability. Increase in 3 type reaction: Increase lipid oxidation and lipolysis (non-
3
, enzymatic), increase of enzymatic activity (lipase and lipoxygenase), higher spoilage by
bacteria which grow faster and better with high aw.
• New sources of oils and fats(3.6). Different sources of fat: Vegetable and animal. Difference
between seed oil and pulp oil and interest for new source of oils.
• Extraction steps of seed oils: (3.7-3.9) Cleaning:
• Dehulling: Size reduction:
• Conditioning: Pressing:
4
