Monitoring vegetable dehydration process by aquaphotomics from lab scale to farm

Solar dehydration processes, implemented with NIR sensors, were studied. The research plan was divided into phases to achieve specific objectives. Phase 1: laboratory tests on micro plants; phase 2: scale transposition tests on small-sized plants - pilot scale; phase 3: tests on commercial systems already in use by Italian SMEs. The realisation of the scheduled activities started with the design, programming, and positioning of NIR sensor for data collection and configuration optimization. NIR spectra were collected in reflectance mode (900-1700 nm) using the MicroNIR1700™ or the MicroNIR On-site W™ (VIAVI Solutions Italia S.r.L., Monza, Italy) portable spectrometers with the MicroNIR Pro ES 1700 software. Spectra were acquired automatically throughout the process by placing the NIR probe over a sample slice, positioned on the intermediate shelf. The probe was thermally insulated to avoid temperature variations. The spectra were first transformed by converting reflectance to absorbance; then the second derivative Savitzky-Golay filter (second order polynomial fit and 21 points) and multiplicative scatter correction were applied to remove potential scatter effects. Aquagrams were calculated from the spectral data. The experiments were carried out with a micro-drying system (45x45x45 cm), and a pilot scale plant available at CREA.IT (Milan). Then, the transfer of the selected configuration was realised using a commercial plant already active in a farm of Pavia area. Different food matrices were tested (pineapple, apple, melon, eggplant, onion). NIR data processing by multivariate analysis was made to prove the reliability of the aquaphotomics approach in detecting the actual end of the drying process. The evaluation of the potential development of dedicated App, easy to consult, to be made available through integration on virtual platform was finally computed.

Improvement of the solar drying process of sludge using thermal storage

Improvement of the drying process of sludge issuing from the coagulation/flocculation of landfill leachate was investigated using thermal storage systems, which consisted of a rock bed with air preheated by a solar air heater passing through the system. Sludge runs were dried inside the solar dryer with and without thermal storage, as well as outside the dryer. The values for the solar energy accumulated per mass of sludge required to obtain a stable sludge mass were 107.5 kJ/kg (with thermal storage), 240 kJ/kg (without thermal storage) and 580.5 kJ/kg, outside the dryer. The values for the energetic efficiency of the drying process were 38.13% and 16.45% for the processes with and without thermal storage, respectively. The net heat input to the storage system during the charging stage was 420 W and 120 W for the discharging stage, resulting in a global energy efficiency in the storage system of 0.28. The thermal efficiency of the solar drying with and without thermal storage system was 37.8% and 22.2%, respectively.

Effect of pre-treatments and drying methods on quality attributes of sweet bell-pepper (Capsicum annum) powder

Pre-treatments and methods of drying for producing good quality dried bell pepper powder for use in the ready-to-eat (RTE) food products were optimized. Out of various pre-treatments used (blanching in boiling water, KMS, CA and combination of KMS + CA at different concentrations), soaking of bell pepper shreds in KMS@ 0.20 % + CA@ 0.50 % after blanching fasten the drying process (19.75 h) compared to control (22.60 h), when dried in mechanical dehydrator at 58 ± 2 °C. Blanching prior to drying improved the rate of drying and produced product with lower acidity (1.25 %). The samples (T7) treated with KMS@ 0.20 % + CA@ 0.50 % significantly (p < 0.05) retained the ascorbic acid content (47.75 mg/100 g) and also attained highest score for colour (8.0), texture (7.5) and overall acceptability (7.5) compared to rest of the treatments. Among different methods of drying, pre-treated bell peppers dried in solar poly tunnel drier produced bright red coloured powder with relatively higher amounts of sugars and ascorbic acid content, hence was optimized. Visual lump formation was observed at 19.75 % and 18.50 % critical moisture contents, which equilibrated at 42 % and 45 % RH for bell pepper powders dried in a mechanical dehydrator and solar poly tunnel drier, respectively.