Lecture 4: UV absorption

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C. Olive oil Quality2. Olive oil categories and
types

• 4. UV absorption

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UV absorption spectrum (part I)

•  it is another indicator used to determine the
  quality of the oil
• This measurement provides information about the
  quality of the oil situation and in particular to
  determine the extent of oxidative deterioration.
  It is measured at two wavelengths, 232 and 270
  nm.

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UV absorption spectrum (part II)

• In the first wavelength primary oxidation
  products (conjugated peroxides) are absorbed,
  while in the second, the secondary oxidation
  products (aldehydes, ketones)

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UV absorption spectrum (part III)

• The difference (DK) absorption gives information
  on the state of oxidation of the oil

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UV absorption spectrum (part III)

• The lower the value, the higher the quality of
  the oil, with a maximum value 0.01 for the extra
  virgin olive oil

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Spectrophotometric examination in the
ultraviolet (part I)

• the value of the absorption coefficient K232 is
  increased when the olives are stored for several
  days until the elision and the oil is stored in
  unsuitable conditions
• the value of the absorption coefficient K270
  depends on how fresh the oil is

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Spectrophotometric examination in the
ultraviolet (part II)

• Old oils or blends with old oil have increased
  rates of K270.
• the price of K270 is very low immediately after
  bottling and increased with advancing age of the
  oil
• the exposure of the oil to sunlight or high
  temperatures accelerate the progress of aging

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Factors influencing UV absorption

• air
• light
• temperature and
• trace of metals

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UV absorption and olive oil
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Summary of 4th Lecture

• UV absorption and olive oil