Description
Parallel transformation tests on pineapple slices, using a drying (with active fan at the top whose ventilation rate depended on the internal temperature: MIRO’ 1), and a dehydration (with continuously working fan at the bottom: MIRO’ 2) micro-plants (45x45x45 cm) operating with solar energy, were carried out.
The performance of the two micro-plants was compared by collecting samples spectra with a microNIR1700 spectrometer (VIAVI Srl, Italy) in reflectance mode, over the range 900 - 1600 nm (50 scans; 125 reading points), at three different times from the beginning of the drying process: 0) process start, 1) during the process [48 hrs]; 2) process end [56 hrs]. Spectra collection took place in triplicates directly on sample slices. The spectral data, converted in absorbance, were pre-treated using the MS Excel® spreadsheet (Office 365, Microsoft Italia, Milan, Italy) to verify the suitability of the Aquaphotomics approach in evaluating process efficiency. Afterwards, spectral data in the wavelength region from 1300 to 1550 nm underwent statistical processing to build the Aquagrams and apply the PCA (95% of confidence level). Data processing was carried out according to Tsenkova R. et al.. The dry matter, the titratable acidity (SH°), pH and the aw (water activity) were measured in parallel.
The Aquagrams, built up at 0, 48, and 56 hrs, highlighted differences among fresh, half-dried, and dried slices. Furthermore, different profiles emerged from different dehydration treatments (MIRO’1; MIRO’2).
The PCA could explain about 90% of the total variance in the PC1-PC2 score plot. The PC1 (75% variance) resulted in the full separation between fresh and dried products while the PC2 pointed out the differences between the two different drying processes.
These preliminary results suggest the applicability of Aquaphotomics for the continuous monitoring of fruit drying processes using an adequate NIR probe. Further experiments are already in progress.
| Consider for full paper in JNIRS | Yes, please |
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