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Identification of bioactive compounds as natural antioxidant in smart-packaging materials by Aquaphotomics

Stefania Barzaghi 1 ; Katia Cremonesi 1 ; Tiziana Maria Piera Cattaneo 1
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INTRODUCTION
Food packaging plays an active role in the environment/packaging/ food system and new solutions take into account new concepts of smart, active and/or eco-friendly food packaging materials. On this point of view the active packaging system should be capable of interacting with the food, for instance by the release of active molecules that will provide protection against microbial spoilage, and simultaneously be “natural”. A full exploitation of the antimicrobial and antioxidant properties of propolis, in order to achieve a significant prolongation of the shelf-life, can meet these needs. Moreover fast methods able for classifying, sorting, and identifying the quality and the stability characteristics associated to the different materials are requested along the food chain in order to validated their properties. This study aimed the identification of bioactive compounds from Italian propolis in smart packaging materials by applying the Aquaphotomics approach.
EXPERIMENTAL
Over a three years periods about 360 sheets of paper were collected and analyzed in duplicate. The papers composition was similar to that of those normally used as food packaging, with and without polythene layer.
The active food packaging sheets were obtained adding with an active natural substance, propolis-based, both directly to the paper pulp and by spreading on the sheet surface.
NIR measurements were performed, using a FT-NIR (NIRFlex N500, Büchi Italia srl, Italy) spectrometer equipped with a fibre optic probe over the range from 10,000 cm-1 to 4000 cm–1. Paper sheets, laid on a reflectance material (Spectralon®), were measured directly on the surface. Spectra from 64 scans were collected with 4 cm–1 resolution and converted in absorbance for further calculation; spectra recorded per sheet were averaged (four replicates).
The principal components analysis (PCA) was performed pre-treating the spectra with MSC and a second derivative according to Savitsky–Golay (polynomial order: 2, window: 15 pt) using PLS_Toolbox (Eigenvector Research, Inc., USA) software.
The same pretreated spectra were used for building up the specific Aquagrams.
RESULTS AND DISCUSSION
On the basis of the PCA plot, spectra were grouped according to the presence of polythene layer along the PC1. The full set of spectra were placed, along the PC3, as a function of the presence or the absence of the natural anti-oxidant substance (propolis-based). In particular, the presence of the active compound influenced positively the score values allowing the groups separation. Analysing the Aquagrams results, it was highlighted absorption differences at 1410 nm able to identify the sheets paper obtained by incorporation of the active-compound. A second Aquagrams plot was built up for sheets measured on polythene layer. Results showed different water patterns at 1438, 1440, and from 1474 to 1518 nm. These data support the theory that the water absorption in NIR range can be affected by the presence of chemical groups derived from propolis active compounds, able to interact with water response.