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Minimal sample preparation which does not require labor-intensive procedures and excessive solvent use
Fast, automated sample analysis using a Shimadzu benchtop series linear MALDI-TOF mass spectrometer in positive ion mode
Easy classification of unknown samples by PCA analysis and machine learning with the Shimadzu eMSTAT Solution software
the European Union (EU) provides some analytical methods for
the assessment of olive oil quality and authenticity. Among
these, those based on triacylglycerols (by high-performance
liquid chromatography) and fatty acid and sterol (by gas
chromatography) profiles are quite popular. However, these
methods often have the drawback of requiring time-consuming
extractions, large solvent volumes and long analysis times.
Therefore, simplifying and speeding up analysis methods, while
preserving the quality and robustness of the data, are necessary
steps.
Triacylglycerols (TAGs) account for more than 90% of the
chemical content of edible oils. The TAG composition is unique
for each type of oil, as the fatty acid expression is plant-specific.
Therefore, TAG ‘fingerprints’ are extremely useful for oil typing,
as TAG expression and ratios are a reflection of the fatty acid
abundance.
Here, we propose a simple and powerful analytical method to
tackle the problem of EVOO fraud. Sunflower oil was used as an
example adulterant. The three key steps of the analytical
workflow are: 1) minimal sample treatment; 2) fast, automated
LDI (matrix-free) analyses of TAG profiles carried out on a
Shimadzu benchtop series linear MALDI-TOF mass spectrometer
(MALDI-8020/MALDI-8030) in positive ion mode; 3) multivariate
analysis and machine learning for the classification of unknown
data with the Shimadzu eMSTAT Solution data analysis software
(Figure 1). The EVOO adulteration was simulated by spiking
sunflower oil into EVOO at 5, 10 and 20% amounts.
Introduction
Extra-virgin olive oil (EVOO) is the
highest grade of olive oil due to its
unique production process in which
olive fruits are crushed solely
through mechanical
pressing under cold conditions, thus preserving its chemical
balance and characteristic properties. EVOO has also been
recognised as being nutraceutic, as it provides nutritional and
health benefits due to its optimal balance of saturated,
monounsaturated and polyunsaturated fatty acids, and minor
components such as polyphenols, tocopherols and sterols.
These health benefits, and the higher production costs, result in
a higher value product which is reflected in the price.
For all these reasons, EVOO is a vulnerable target of adulteration
through the addition of alternative, cheaper vegetable oils, in an
attempt by producers and traders to fraudulently sell these
lower quality adulterated oils as genuine, more expensive EVOO
products. Typical vegetable oils which can be found in
adulterated EVOOs are palm, canola, hazelnut, pomace,
sunflower, corn, soybean, peanut, and others. Besides the
economic damage, there are also concerns over the safety of
non-genuine EVOOs for human consumption, due to the
exposure to potentially hazardous allergens, such those in
hazelnut oil.
To combat extra-virgin olive oil frauds, rigorous and efficient
quality control assays have been established to protect the
identity of this unique product. In the EC Regulation 2568/91,
Pure EVOO and
Sunflower oil
EVOO spiked
with 5, 10, 20%
sunflower oil
Add I.S.
Dissolve in
Chloroform
LDI (matrix-free) analysis
Positive ion mode
Multivariate analysis
(PCA)
Machine learning
(RandomForest)
MALDI-8020
a
/
MALDI-8030
b
eMSTAT Solution™
Minimal
sample preparation
Fast, automated
sample analysis
Simple, intuitive
data analysis
Figure 1. Analytical workflow for the analysis of adulterated extra-virgin olive oils.
a
Positive mode only
b
Dual polarity
MALDI-TOF Mass Spectrometry Analysis MALDI-8030
Extra-virgin olive oil authentication: triacylglycerol
profiling and machine learning using the Shimadzu
MALDI-8020/MALDI-8030 and eMSTAT Solution™
S. Salivo (KRATOS ANALYTICAL LTD.)
