Researchers from the U.S. FDA developed a novel method to separately extract lipophilic and hydrophilic Cu-CDP and quantify Cu-CDP by UHPLC combined with inductively coupled plasma isotope dilution mass spectrometry (UHPLC-ICP-ID-MS)
Background:
Table olives are a popular food and green colourization is a key feature in the perception of freshness. However, during industrial processing and storage, the green colour of newly harvested olives fades to pale yellow as a result of reactions degrading the chlorophyll. The re-greening of table olives may be achieved by complexation of chloro-phyll degradation products (CDP) with Cu
2+, to form stable bright green copper CDP (Cu-CDP) complexes.
Known colouring substances are the lipophilic food colour E141i composed of Cu-CDP and the hydrophilic food colour E141ii including sodium copper chlorophyllin besides other Cu compounds. However, both colouring substances are not allowed in the EU for the production of table olives. Unfortunately, the detection of E141ii in green table olives and other foods proved challenging. Major obstacles are the poor extraction efficiency from foods containing high fat content and the lack of reliable reference materials.
The new study:Researchers from the U.S. FDA explored the possibilities to quantify Cu-CDP by using ultra-high-performance liquid chromatography with inductively coupled plasma isotope dilution mass spectrometry.
Lipophilic and hydrophilic Cu-CDP complexes were extracted from olives by dedicated liquid extraction procedures. The different complexes were identified by UHPLC-high resolution mass spectrometry (UHPLC-HRMS). For quantification, UHPLC-ICP-S with post column unspecific isotope dilution was applied. This technique can quantify Cu-CDP without species-specific calibration standards, does not suffer from calibration drift or matrix effects, and is a more accurate approach than traditional external calibration strategies. Both types of complexes were quantified separately by UHPLC-ICP-ID-MS.
The content of total elemental Cu and individual Cu-CDP was used to evaluate how the bright green colouration of table olives was achieved. Twenty-four samples of bright green and pale yellow table olives sold in the US ere analysed in this way. Pale yellow olives contained < 1 mg/kg lipophilic Cu-CDP and < 3.5 mg/kg total elemental Cu. Bright green table olives contained 4–22 mg/kg lipophilic Cu-CDP and 14.4–161 mg/kg total elemental Cu in contrast to < 6 mg/kg reported for natural abundance, indicating the formation of Cu-CDP was achieved by addition of copper salts.
The developed methodology seems to be useful for food control, which is required to ensure the complete food safety and the compliance with the current law.
The original study:
Bhakti Petigara Harp, Peter F. Scholl, Patrick J. Gray, Pierluigi Delmonte,
Quantitation of copper chlorophylls in green table olives by ultra-high-performance liquid chromatography with inductively coupled plasma isotope dilution mass spectrometry, J. Chromatogr. A, 1620 (2020) 461008. DOI: 10.1016/j.chroma.2020.461008
Used techniques and instrumentation:
Agilent Technologies Inc. - 8800 - Triple Quad ICP-MS
Agilent Technologies Inc. - Series 1100 HPLC
Related studies (newest first)
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Related EVISA Resources
Link database: Toxicity of copper species Brief summary: Speciation Analysis - Striving for Quality 
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last time modified: September 21, 2024
