LIPIDS

OBJECTIVES Illustrate the role of lipid stability through a series of designed experiments with oils Provide a better understanding of lipid oxidation and its physicochemical consequences in foods (organoleptic and physical) Assess compositional and quality differences between fresh and oxidized lipids Investigate the role of light and dark on lipid oxidation

MATERIAL Oils with varying chemical compositions Pro-oxidants Antioxidants Light and Dark storage conditions Cold vs. ambient vs. hot storage temperature

Part I: Designing the experiment Part II: Analysis Weigh 0.2g of oil into screw test tubes Add 1mL of ethanol to dissolve Add 3mL of TBA, cap tighly and boil (~95°C) for 10min. Observe the yellow, brown/pink color as reaction of TBA with aldehydes take place Cool and record absorbance at 530nm The higher the abs value, the more oxidized the lipid

Sensory changes due to lipid oxidation Report changes in color, odor, appearance and any other aspects (make a table with your observations). Compare and contrast between control and treatments, use of pro-oxidants, antioxidants, as well as the storage conditions to the control of the oils. Were the antioxidants capable of slowing the reaction down? Did the storage conditions affect the oils in a significant way? Why/ why not?

Calculating the TBA value What does this mean???

Results: Interpreting Make a table with the major differences – appearance, color, odor, physical properties, stability and TBARS values – between your oils. Describe the state of your oils from the literature, and determine if this was responsible for your observed results – In terms of physical and TBARS values Compare samples with additions of pro-oxidant, and antioxidants, as well as storage conditions. Discuss the differences…

EXAMPLE CASE FOR APPNOTE Your food company wants to introduce a new line of extra virgin olive-oil based salad dressings. However, they have some concerns about the oxidation and are asking for your advice on the topic and your recommendations for the formulation of a prototype dressing. Be creative!!!

Lipid Oxidation – Part Two Analysis LIPIDS Lipid Oxidation – Part Two Analysis

Analyzing Lipid Oxidation Peroxide Value Hexanal Thiobarbituric acid Reactive Substances

TBARS Assay Measures byproducts of lipid oxidation by the reaction of TBA and malonaldehyde (A product of lipid oxidation).

Part II: Analysis Pipette 0.2mL of oil into screw test tubes Add 1mL of ethanol to dissolve Add 3mL of TBA, cap tightly and boil (~95°C) for 10min Observe the yellow, brown/pink color as reaction of TBA with aldehydes take place Cool and record absorbance at 530nm The higher the abs value, the more oxidized the lipid

Sensory changes due to lipid oxidation Report changes in color, odor, appearance and any other aspects (make a table with your observations). Compare and contrast between control and treatments, use of pro-oxidants, antioxidants, as well as the storage conditions to the control of the oils. Were the antioxidants capable of slowing the reaction down? Did the storage conditions affect the oils in a significant way? Why/ why not?