Determination of Chlorophyll in Italian Olive Oils by Scanning VIS-Spectrophotometry

INTRODUCTION:

Olive Oil is made by pressing / extracting the rich Oil from the Olive fruit by various methods. The highest quality (and expensive) grade is EXTRA VIRGIN Olive Oil, which is "cold-pressed" from freshly prepared Olives. It has a greenish-yellow tint and a light fruity aroma, due to the high levels of

Chlorophyll and other volatile materials extracted from the plant. REGULAR Olive Oil is usually made by a "warm extraction", sometimes using water to increase the yield of Oil. This grade is pale yellow and has only a slight aroma because there are very few volatile compounds present at this point. The final grade, called "LIGHT", is very light in color and has no aroma because this material has been "steamed cleaned" under pressure to remove the last traces of Chlorophyll and volatile compounds from the Oil, and this Light Oil is best used for Frying and high-heat uses because there are no reactive chemicals to affect the taste of the fried food product; and it is also much less expensive than the Extra Virgin Oil.

PURPOSE:

To characterize the three grades of Olive Oil, we must do a Wavelength Scan of the VISIBLE Region of the Spectrum to outline the nanometer Position and relative Intensities of the Four (4) ABSORBANCE Peaks that are present in Chlorophyll. Once the "Known" Olive Oil "Standards" have been scanned, an "Unknown" Sample Oil can be evaluated by comparing to these Standards and its grade accurately determined. The complex chemistry of Chlorophyll creates three (3) YELLOW Peaks located at ~413nm., ~454nm. and ~482nm.; and a pair of BLUE Peaks at ~631nm. and ~669nm. All of these appear to be GREEN to the Human Eye, but the different sources of Chlorophylls will have different RATIOS of these Peaks and creates a wide range of green shades (Spinach is Yellow-Green, Parsley is pure Green, and so on).

INSTRUMENTS NEEDED:

· 6405 UV-VIS Spectrophotometer

(from Edu-Chem Innovations) INFO/Buy IT!

· 10mm. square QUARTZ or GLASS Cuvettes

(must be CLEAN to insure accurate ABS readings)

SUPPLIES:

· Disposable plastic pipets/eyedroppers

· Vials of Standard PURE Olive Oils:Regular, Extra Virgin and Light

· Acetone(for cleaning Oil out of Cuvettes)

· Wash-bottles of IPA and DI Water (for rinsing out cuvettes)

SAMPLES:

Vials of Unknown Olive Oil

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