S.M. Alzamora’s research while affiliated with University of Buenos Aires and other places

Natural biopolymers have extensively applications in intelligent food packaging due to their renewable nature, easy availability, environmental-friendly, low-cost and excellent processibility. Recently, the integration or embedding of nanocomposites on polymer substrates to improve the multi-faceted performance of packaging materials has attracted widespread attention. Herein, the irregular spherical Co-based metal-organic framework (Co-MOF) loaded with phenol red (PR) and bromothymol blue (BTB) were fabricated, resulting in absorbed nanocomposites Co-MOF/PR and Co-MOF/BTB. Afterward, the nanocomposites were integrated into a sodium carboxymethyl cellulose (CMC-Na) substrate to prepare a CO2-responsive packaging material (CMC-Na/PR/CoMOF and CMC-Na/BTB/Co-MOF) for real-time and in-situ monitoring apple freshness. The synthesis of Co-MOF and the hydrogen-bonding interactions between MOF and pigments adsorption were confirmed. The advantages exhibited by the film with adding Co-MOF, including excellent hydrophobicity and water resistance, improved time-temperature stability and mechanical properties, were explored. Notably, the Co-MOF-based composite film exhibited enhanced UV-visible barrier, anti-migration performance of pigment, and thermal stability. Finally, a significant linear response (R2 = 0.9923 and 0.9781) between the total color difference values (Delta E) of Co-MOFbased film and hardness and total soluble solids (TSS) of fresh-cut Fuji apples at 4 degrees C was demonstrated, respectively. These findings indicate the significant potential of CMC-Na-based composite film containing multifunctional MOF nano-filler as a visual monitoring system, which will pave the way for fresh-cut fruit intelligent packaging.

Dicofol is a highly toxic residual pesticide in tea, which seriously endangers human health. A method for detecting dicofol in tea by combining stoichiometry with surface-enhanced Raman spectroscopy (SERS) technology was proposed in this study. AuNPs were prepared, and silver shells were grown on the surface of AuNPs to obtain core-shell Au@AgNPs. Then, the core-shell Au@AgNPs were attached to the surface of a PDMS membrane by physical deposition to obtain a Au@AgNPs/PDMS substrate. The limit of detection (LOD) of this substrate for 4-ATP is as low as 0.28 × 10-11 mol/L, and the LOD of dicofol in tea is 0.32 ng/kg, showing high sensitivity. By comparing the modeling effects of preprocessing and variable selection algorithms, it is concluded that the modeling effect of Savitzky-Golay combined with competitive adaptive reweighted sampling-partial least squares regression is the best (Rp = 0.9964, RPD = 10.6145). SERS technology combined with stoichiometry is expected to rapidly detect dicofol in tea without labels.

The aim of this study was to explore the use of pulsed light (PL) for inactivating peroxidase (POD), polyphenoloxidase (PP0) and pectin methylesterase (PME) in melon juice. The influence of treatments on the optical, physicochemical and rheological properties of the juice was also evaluated. PL fluences between 3.6 and 71.6 J cm⁻² caused a significant reduction in POD activity from 13% to 96% respectively. On contrary, PPO and PME activities were slightly or not significantly affected by the treatments. POD inactivation curve was successfully fitted with the first‐order and Weibull‐type models. Samples exposed to 35.8 and 71.6 J cm⁻² showed minor changes in pH, titratable acidity and total soluble solids content than non‐treated juice along cold storage. PL treatments also better maintained the original colour of the fresh juice during storage. A slight but significant reduction in the apparent viscosity was observed due to PL exposure. Results indicated that pulsed light could be a useful technique for inhibiting POD activity and preserving the colour of melon juice along cold storage. Other preservation agent(s) in combination would need to be evaluated for better control of enzyme activity.

The aim of the present work was to assess the effect of ozone in aqueous phase (5.1 mg L⁻¹ of ozone for 10 min) on blueberry surface by analysing the changes in epicuticular waxes (EW) by attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectroscopy during storage at 4 °C for 15 d. Besides, colour was studied as a critical quality index for consumers. Ozone treated and controls (untreated fresh fruit and washed fruit without ozone) samples were considered. Among them, three subsets of spectra were acquired: whole fruit, fruit without EW -removed by solvent- and isolated EW. The differences among these sample subsets were much higher than those produced by treatments or storage time as revealed by PCA analysis. Infrared analysis revealed that ozone per se produced chemical modifications on EW of intact fruit, as new bands appeared (such as stretch of C = O at 1701 cm⁻¹, from the oxidation of alcohols to carbonyls) and others shifted. However, no significant changes were observed in colour between treatments or time, showing that neither the alterations in EW nor their partial removal or changes in epidermis ultrastructure (evaluated by microscopy) affected this quality parameter. Further studies are needed to deeply understand the extent of the effect of the chemical alterations produced directly by ozone (and not by the process) in line with consumers demands of minimal processed and extended shelf-life products.

The effect of different doses of UV-C light (5.3, 8.3 and 11.4 kJ/m²) on native mycobiota and Botrytis cinerea incidence, micro and ultrastructure, biomechanical properties and weight loss of blueberry fruit cv. O’Neal during 20 days of storage at 8 ± 1°C was evaluated. Decay incidence was significantly reduced by all UV-C light doses for both, native mycobiota and inoculated B. cinerea. The highest UV-C dose studied (11.4 kJ/m²) was the most effective indelaying the onset of fungal and B. cinerea infection (6 and 4 days, respectively). UV-C irradiation caused some distinctive changes in fruit structure characterized by redistribution, alteration and partial removal of epicuticular waxes, reinforcement of epicarp cell walls, and modifications in the cuticle. Biomechanical parameters were not affected by UV-C treatments excepting at day 15 where irradiated samples showed higher values of rupture force (FR) and deformation (D). Structure changes partially explained the significant increase in weight loss, FR and D values in irradiated fruit after 15 days of storage. UV-C irradiation could be an alternative for delaying and reducing fungal infection. However, postharvest shelf-life of irradiated blueberries could be limited by the negative effect on weight loss.

The aim of this work was to evaluate the effect of the high-pressure assisted-infusion processing on the nutritional and functional properties of mango cubes immersed in a solution of sorbitol and calcium lactate. Three factors were studied: sorbitol concentration (20°Brix-40°Brix-60°Brix), calcium lactate concentration (0% w/w − 1% w/w − 2% w/w) and the pressure level (0.1 MPa–300 MPa-600 MPa). Sugar (sorbitol, glucose and sucrose), calcium and total phenols content and antioxidant capacity were determined. Results showed that the increase of sorbitol concentration from 20°Brix to 40°Brix caused higher sorbitol uptake and lixiviation of the natural compo in mango cubes. However, the increase of sorbitol concentration from 40°Brix to 60°Brix, had no significant effect on the diffusion of solutes. The high-pressure processing (HPP) favored the diffusion of solutes from solution to fruit, while the addition of the calcium counteracted this effect in most cases. Based on these results, the combined effect of 300 MPa and 60°Brix-2% calcium lactate was the most effective at preserving natural compounds of mango and conferred distinctive properties giving an added value to the final product due to its important nutritional implications. Therefore, high-pressure assisted-infusion processing could be considered as an effective method to preserve mango cubes with an acceptable nutritional value. Industrial relevance The present work showed that high-pressure assisted-infusion processing could be considered an alternative to develop mango-based products. Results showed that this process would allow preserving most of the natural compounds of the mango pieces, in addition to achieving distinctive characteristics, as a source of calcium. Therefore, the application of high-pressure assisted-infusion processing could open new opportunities for food industries to develop fresh and value-added products with characteristics similar to fresh fruit.

The effect of mild thermal (TT) and pulsed light (PL) treatments, individually applied or in combination, on fungal spoilage, mechanical properties, weight loss, and microstructure of strawberries (cv. Albion) stored at 5 °C was evaluated. TT (2.5 and 5.0 min in water at 46 ± 0.4 °C) was more effective than PL (fluence: 11.9 J/cm2) to reduce fungal decay. TT for 5 min delayed the onset of infection for 6 days and maintained the lowest percentage of infected fruit along storage, showing the best performance among the strategies evaluated. Combined treatments did not achieve greater fungal inhibition than individual TT. Non significant differences in weight loss among control and treated fruit were observed up to 8 days of storage. TT for 5 min and its combination with PL significantly enhanced firmness, stiffness, and resistance to deformation as compared to untreated fruit, in concordance with the reinforcement of cell walls. This work aimed to compare the effect of mild thermal and pulsed light treatments, individually applied or in combination, on strawberries storage life. The evaluation of the impact of these technologies on selected quality parameters (fungal growth, weight loss, and mechanical properties) and their correlation with modifications at microstructure level, would contribute to the selection of postharvest strategies for prolonging the shelf life of strawberries.