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
- "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
- "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
- "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
- "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
- "Citric acid - good chelator"
- Slows down autoxidation but aren't true antioxidants
- "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
- "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
- "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
- "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
- "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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