The qualification of trade marks of agro-industrial products is consumer
oriented with a growing demand of objective methods to assess production,
preservation and market distribution methods. Monitoring volatile organic
compounds (VOC) in traces it's an approach that requires instrumentation
adequate in sensitivity, selectivity and reliability. Solid state sensors
give only a very limited answer to this demand. Our approach is based on
the development of instrumentation based on mass spectrometry with
chemical ionization (proton transfer) and laser photo-acoustics originally
used in our laboratory to study and characterize supersonic beams of
molecules and clusters used to synthesize thin films (SuMBE). They allow
real time complementary detection of a large number of VOC at very high
sensitivity. CO2 laser based photo-acoustic allows the detection of
ethylene down to a few tens of pptv. Ethylene is the plant gas hormone
that controls very important physiological processes including ripening
and senescence of fruits. On the other hand proton transfer (PTR-MS) is a
ionization process that, drastically reducing fragmentation, allows the
very sensitive mass spectrometric monitoring, for example, of 30 different
VOC, including aldehydes, chetons, esters, alcohols etc., at the pptv
level in a few seconds. This cannot be achieved by any other available
method. In collaboration with the local agronomy institute and the
association of producers, we investigated processes involved in the
production and preservation (including chemical and anoxia treatments
aimed at optimizing the preservation in controlled atmospheres) of apples,
which are a very relevant product in Trentino. The correlation between VOC
and agronomic processes, such as tree production load, chemically or hand
made, and the harvesting at different stages of ripening, have been
studied over the whole preservation period (8 months) in standard storage
cells. Results show clear evidence, over the whole preservation period,
that VOC emitted can be used as markers of both initial and preservation
conditions. Such correlations become stronger during shelf-life after
extraction of apples out of the storage rooms (pathway to market and
consumer). We envisage that these techniques can tailor indices qualifying
evolution and "history" of a product aiming at eliminating passages where
affecting quality and eventually optimizing packaging and storage.
Comparison with standard indices of quality, often rough and destructives
(acidity, sugar content, hardness, colour etc.), shows significant
correlations. Our approach opens a novel and interesting perspective for a
more refined qualification, non destructive and consumer oriented, subject
of a research activity financed by the MIUR and the Province of Trento.
Research in collaboration with "Laser and Molecular Physics" laboratory -
University of Nijmegen (NL) and "Institut fuer IonenPhysik" -University
of Innsbruck (A).
Vedi anche: