soap production

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(soap production)
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Fats solid at room temperature (animal
origin) Oils liquid at room temperature (plant
origin)
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Major Membrane Phospholipids
Phosphatidylcholine (PC)
Phosphatidylethanolamine (PE)
Phosphatidylserine (PS)
Phosphatidylinositol (PI)
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Lipid Rancidity

• Hydrolytic
• release of short chain volatile fatty acids
• from TGs and PLs (chemical or enzymatic)
• Oxidative
• oxidation of long chain fatty acids
• (free or esterified to TGs and PLs)

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Accelerators of Oxidative Rancidity
Heat Light (U.V.) Salts (e.g., NaCl) Heavy metals
(copper, iron) Heme compounds (myoglobin) Oxygen P
rocessing (e.g., dehydration)
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Effects of Lipid Oxidation

• Flavor Quality Loss
• Rancid flavor
• Changes of color and texture
• Consumer Acceptance
• Economic loss
• Nutritional Quality Loss
• Essential Fatty Acids
• Vitamins
• Health Risks
• Growth Retardation
• Heart Diseases

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Fatty Acid Structures
1,4-pentadiene system
1,4-pentadiene system
1,4-pentadiene system
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Initiation
Initiation of autoxidation occurs when hydrogen
atom at ?-methylene group in double bonds of
unsaturated fatty acids is removed to form an
alkyl radical (R?).
RH
R?
H?

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Propagation
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Termination
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Characteristics of Free Radicals in Oxidation
H Hydrogen atom The simplest free
radical O2 - Superoxide anion An
oxygen-centered radical. Limited
reactivity HO Hydroxyl A highly reactive
oxygen-centered radical. Indeed attacks all
molecules in human body RO2 Peroxyl Oxygencen
tered radicals formed during the RO Alkoxy
breakdown of organic peroxides
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Products of Lipid Oxidation
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Pentane from Linoleic Acid by Triplet Oxygen
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Tests for Lipid Oxidation

• TBA test
• reaction of 2-thiobarbituric acid and aldehyde
• Peroxide value
• ROOH KI ? free Iodine
• Gas chromatography
• measure volatile fatty acids (pentane)
• Distillation
• high MW polymers dont distill

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Lipid Oxidation Stability Tests

• Active Oxygen Method (bubble air through oil at
  100 C)
• Oven Stability Method (sample placed in oven (65
  C)
• Oxygen Bomb Test (add oxygen to sample and
  measure
• pressure over time

(used to measure effectiveness of antioxidants)
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Functions of Antioxidants

• Inhibits or slows the formation of free alkyl
  
• radicals in the initiation step
• Interrupts the propagation of free radical chain
  
• Delays the start or slows the chemical reaction
• rate of lipid oxidation.

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Types of Antioxidants

• Hydrogen donating compounds
• Singlet oxygen quenchers
• Metal chelators
• Enzymes
• Oxygen scavengers and Reducing agents

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Hydrogen Donating Antioxidants
The major hydrogen donating antioxidants are
monohydroxy or polyhydroxy phenolic compounds
with various ring substitutions. The
antioxidant free radical does not initiate
another free radical due to the stabilization of
delocalization of radical.
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Reaction of Antioxidants with Radicals
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Termination Reactions






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Synthetic Antioxidants
Butylatedhydroxyanisole (BHA)
Butylatedhydroxytoluene (BHT)
Tertiary butylhydroquionone (TBHQ)
Propyl gallate
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Natural Antioxidants

• Benefits
• Health implication
• Stability in food system
• Limits
• Characteristic flavor
• Safety test required

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Tocopherol
delta-tocopherol has highest antioxidant
activity, alpha-tocpherol has highest vitamin
activity
A chain breaking antioxidant competes with
polyunsaturated lipid for the lipid peroxyl
radicals.
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Ascorbic Acid

• Hydrogen donation to lipid radicals
• Quenching of singlet oxygen
• Removal of molecular oxygen
• Regenerate tocopherol radicals
• Prooxidant Reduce ferric iron to ferrous
  iron

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Metal Chelators

• Phosphoric acid
• Citric acid
• Ascorbic acid
• Ethylenediamine Tetraacetate (EDTA)
• Proteins such as Transferrin, Ovotransferrin
• Amino acids and Peptides

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Flavonoids

• Secondary products of plant metabolism
• Metal chelating ability
• Superoxide anion scavengers
• Anthocyanines, catechins, flavones, flavonols,
  isoflavone, and proanthocyanidins

(fruits, tea, herbs, spices)
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• Synergism When antioxidants are added in
• combination their effects are enhanced (e.g.,
• BHA/BHT
• Synergists Compounds (not diphenols) that
• when added in combination with an antioxidant
• improve the capacity of the antioxidant
• reducing agents can regenerate antioxidants
• (citric acid, ascorbic acid,
  phosphoric acid)
• chelating agents can tie up pro-oxidants (EDTA)

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Oil and Fat Production
Mechanical Crushing and disruption of plant
tissue. The oil is pressed out of the plant (hot
or cold). High quality, but low yield
product Solvent Extraction Solvents (e.g.,
hexane) are used to extract oil from plant
tissue. High yield, but lower quality. Must
remove solvent from product Rendering Heat
adipose tissue to disrupt cells and liquefy TGs.
Fat globules are separated dry or wet.
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Refining Fats and Oils

• Remove insoluble material filtration or
  centrifugation
• Deodorization steam distillation
• Bleaching remove color
• physical (e.g., use diatomaceous earth)
• solvent extraction
• Remove free fatty acids
• react with base to produce soap
• Winterization Remove high molecular weigh
  compounds (waxes, long chain saturated fatty
  acids). Hold at low temperature and allow for
  their crystallization.

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Physical Properties of Triglycerides

• Melting point
• Fatty acid residues
• unsaturated FA have lower MP than
• saturated FA
• short chain FA have lower MP than
• long chain FA
• Arrangement of fatty acids on the
• TG molecule
• Crystalline structure of TGs

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Crystalline Structures of Triglycerides
The same TG can have 3 melting points because of
its crystalline structures