Foodchem Lecture 6 Pictures

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    • "The overall effect of adding an antioxidant is to lengthen the induction period"
    • Antioxidants do not howeer last forever, but are slowly consumed, and eventually the autoxidation reaction predominates and destroys the lipid
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    • "Alpha tocopherol/Vitamin E"
    • Compounds with good antioxidant properties are often phenolic type compounds
    • A typical example is Vitamin E, or alpha-tocopherol, a natural antioxidant found in vegetable oils
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    • "The main synthetic antioxidants utilized for food use:
    • 1. Butylated hydroxy anisole (BHA)
    • 2. Butylated hydroxy toluene (BHT)
    • 3. Propyl gallate (PG)
    • 4. Tert-butyl hydroquinone"
    • These are more effective and cheaper than "natural" antioxidants
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    • "A typical commercial antioxidant mixture is 'Tenox BHA'"
    • Antioxidants are usually used as mixtures because a mixture of antioxidants tend to be more effective than a single antioxidant by itself
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    • "General mechanism of action - BHT"
    • 1. Free radical accepts hydrogen and forms resonance stabilized antioxidant free radical
    • 2. Resonance stabilized antioxidant radical can regenerate antioxidant free radical by reacting with R, reaction can also terminate many other ways, slowly consuming the antioxidant
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    • "Citric acid - good chelator"
    • Slows down autoxidation but aren't true antioxidants
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    • "Chelation of copper ions by 2 citric acid molecules at the juncture of COOH-OH, captures metal ions (M) by making a cyclic structure"
    • Metal ions are powerful catalysts for lipid oxidation
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    • "Metallo-porphyrin compounds allow the formation of very reactive singlet oxygen, which can attack lipids directly, promoting autoxidation"
    • Hence antioxidants are required as a atter of course along with the cheating agents to control the autoxidation process
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    • "Olive oil press"
    • Rarely used in North America - simply involves the ue of a screw press to apply pressure, crush the seed/tissue and squeeze the oil out
    • Preferred method for producing virgin olive oil where we want the flavor and FFAs because it takes time
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    • "Mechanical version of hydraulic pressing which is continuous in nature"
    • An expeller is simplified version of an extruder
    • Archimedes screw ina barrel which tapers toward the end, pressure is increased and the oil is squeezd out continuously
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    • "Expelling process"
    • Throughput is high and process efficient, but the meal/press cake still contains significant levels of oil
    • Expelling is usually followed by solvent extraction
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Foodchem Lecture 6 Pictures
2012-02-13 00:17:22
Foodchem Lecture Pictures

Foodchem Lecture 6 Pictures
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