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fbtwitterlinkedinvimeoflicker grey 14rssslideshare1
Languages: English
Types: Doctoral thesis
Subjects:
The past decade has seen an influx of speciality plant seed oils arriving into the market place. The need to characterise these oils has become an important aspect of the oil industry. The characterisation of the oils allows for the physical and chemical properties of the oil to be determined. Speciality oils were characterised based on their lipid and fatty acid profiles and categorised as monounsaturated rich (oleic acid as the major acyl components e.g. Moringa and Marula oil), linoleic acid rich (Grape seed and Evening Primrose oil) or linolenic acid rich (Flaxseed and Kiwi oil). The quality of the oils was evaluated by determining the free fatty acid content, the peroxide value (that measures initial oxidation) and p-anisidine values (that determines secondary oxidation products containing the carbonyl function). A reference database was constructed for the oils in order to compare batches of oils for their overall quality including oxidative stability. For some of the speciality oils, the stereochemistry of the triacylglycerols was determined. Calophyllum, Coffee, Poppy and Sea Buckthorn oils stereochemistry was determined. The oils were enriched with saturated and/or a monounsaturated fatty acids at position sn-1 and sn-3. The sn-2 position of the four oils was esterified with a polyunsaturated and/or a monounsaturated fatty acid indicating that they follow a typical acylation pathway and no novel acylation activity was evident from these studies (e.g enrichment of saturates at the sn-2 position). The oxidative stability of the oils was evaluated at 18oC and 60oC and the effect of adding a-tocopherol at commercially used level i.e 750ppm was assessed. The addition of 750ppm of a-tocopherol at 18oC increased the oxidative stability of Brown flax, Moringa, Wheat germ and Yangu oils. At 60oC Brown Flax, Manketti and Pomegranate oil polymerised after 48 hours. The addition of 750ppm a-tocopherol delayed the onset of polymerisation by up to 48 hours in Brown Flax seed oil. Pomegranate oil showed a high resistance to oxidation, and was blended into other speciality oils at 1%. Pomegranate oil increased the oxidative stability of Yangu oil at 18oC. The addition of Pomegranate oil to Wheat germ oil at 60oC, decreased the peroxide content by 10%. In Manketti and Brown Flaxseed oil at elevated temperatures, Pomegranate oil delayed the onset of polymerisation. Preliminary studies of Pomegranate oil blending to Moringa and Borage oil showed it to be more effective than a-tocopherol for certain oils. The antioxidant effects observed following the addition of Pomegranate oil may be due to its conjugated linolenic acid fatty acid, punicic acid.
  • The results below are discovered through our pilot algorithms. Let us know how we are doing!

    • 1.3.1 Lipid Oxidation
    • 1.3.2 Free Radical Oxidation
    • 1.3.3 Hydroperoxide Formation
    • 1.3.4 Lipid Oxidation Detection Methods
    • 1.3.5 Oxidative Stability
    • 1.4 Antioxidants
    • 1.4.1 An Introduction to Antioxidants
    • 1.4.2 Antioxidant Mechanism
    • 1.4.3 Synthetic and Natural Antioxidants
    • 1.5 Vitamin E
    • 1.5.1 Vitamin E, Tocopherols and Tocotrienols
    • 1.5.2 The Effects of Tocopherols on lipid Peroxidation:
    • 1.5.3 Tocopherols as Proxidants
    • 1.5.4 Major Factors Affecting Tocopherol Antioxidant Potency
    • Aims of PhD Research Chapter 2 Materials and Methods
    • 2.1 Materials
    • 2.2 Methods
    • 2.2.1 Fatty Acid Methyl Esters
    • 2.2.2 Punicic Acid Fatty Acid Methyl Ester
    • 2.2.3 Peroxide Value
    • 2.2.4 Free Fatty Acid Value
    • 3.3.9 Stereochemical Analysis
    • 3.3.10 Punicic Acid Methylation
    • 3.4 Conclusions Chapter 4 Evaluating the Oxidative Stability of Plant Seed Oils
    • 4.1 Introduction
    • 4.2 Results
    • 4.3 Results and Discussion
    • 4.3.1 Oxidative Stability of Plant Seed Oils
    • 4.3.2 Peroxide Accumulation in MUFA Rich Oil
    • 4.3.3 Peroxide Accumulation in PUFA Rich Oils
    • 4.3.4 Assays to Evaluate Oxidation
    • 4.3.5 Oxidation of Oils Rich in Oleic Acid
    • 4.3.6 Oxidation of Oils Rich in Linoleic Acid
    • 4.3.7 Oxidation of Oils Rich in Linolenic Acid
    • 4.4 Conclusions Chapter 5 Preliminary Blending of Pomegranate Oil
    • 5.1 Introduction
    • 5.2 Results
    • 5.3 Results and Discussion
    • 5.3.1 Percentage Addition of Pomegranate Oil
    • 5.3.2 Pomegranate and α-Tocopherol
    • 5.3.3 Borage Oil Blended with 1% Pomegranate Oil
    • 5.3.4 Radical Scavenging Properties of Punicic acid
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