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Attention is drawn to the feasibility of using high sensitivity isothermal heat conduction calorimetry to study metabolic responses of differently processed and stored fresh-cut fruit. The heat production of endogenous (tissue metabolism during 12 h of analysis at 10 °C for kiwifruit and strawberry) and exogenous (microbial growth during 18 d of analysis at 10 °C for cantaloupe) biological processes was investigated. Osmotic dehydration of fresh kiwifruit in sucrose solution (61.5 g/L) at different treatment times (30, 60 and 180 min), resulted in metabolic heat production decrease, confirming the progressive cell death induced by osmotic dehydration. Analysis on strawberry slices under two atmospheric conditions (air and innovative modified atmosphere) seemed to confirm the inhibitory effect of N2O on metabolic activity. Cantaloupe samples immersed in three different syrups (SS: sucrose syrup (20 °Brix); SS1: SS + 0.5 g/L ascorbic acid + 0.5 g/L citric acid; SS2: SS1 + 0.1 g/L potassium sorbate) showed a stability increase when additives with antimicrobial properties were included. Our findings confirm that isothermal calorimetry provides a versatile and high sensitive tool for conducting fundamental metabolic studies on the effect of different processing operations on the quality and shelf life of fresh-cut fruit and vegetables. Fil: Rocculi, Pietro. Università di Bologna; Italia Fil: Panarese, Valentina. Università di Bologna; Italia Fil: Tylewicz, Urszula. Università di Bologna; Italia Fil: Santagapita, Patricio Roman. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentina Fil: Cocci, Emiliano. Università di Bologna; Italia Fil: Gómez Galindo, Federico. Lund University; Suecia Fil: Romani, Santina. Università di Bologna; Italia Fil: Dalla Rosa, Marco. Università di Bologna; Italia

The objective of the present study was to evaluate cellular compartment modifications of kiwifruit (Actinidia deliciosa) outer pericarp tissue caused by osmotic treatment in a 61.5 % sucrose solution, through the quantification of transverse relaxation time (T 2) and water self-diffusion coefficient (D w) obtained by low field nuclear magnetic resonance means. Raw material ripening stage was taken into account as an osmotic dehydration (OD) process variable by analyzing two different kiwifruit groups, low (LB) and high (HB) °Brix. Three T 2 values were obtained of about 20, 310, and 1,250 ms, which could be ascribed to the proton populations, located in the cell walls, in the cytoplasm/extracellular space, and in the vacuoles, respectively. According to T 2 intensity values, vacuole protons represented between 47 and 60 % of the total kiwifruit protons, for LB and HB kiwifruits, respectively. The leakage of water leading to vacuole shrinkage seemed to cause concentration of solutes, retained by the tonoplast, making the vacuole T 2 value decrease along the OD. As expected, the D w values of raw kiwifruits were lower than the value of the free pure water. The water mobility (and hence D w), depending on the kiwifruit distinctive cellular structures and solutes, decreased even more during OD due to water loss and sugar gain phenomena. D w represents an average value of the diffusion coefficient of the whole kiwifruit tissue protons. In order to obtain D w values specific for each cellular compartment, a multiple component model fitting was also used. According to these results, the vacuole water self-diffusion coefficient (D w,v) was much higher than D w.

The present work investigates how ultrasound pretreatment modulates the effects of osmotic dehydration (OD) on the water state and microstructure of kiwifruit. Kiwifruit slices (10 mm thick) were subjected to ultrasonic waves in a water bath at a frequency of 35 kHz for 10, 20 and 30 min. OD process was then carried out by immersing the samples in 61.5% sucrose solution equilibrated at 25 °C for a contact period of 0, 10, 20, 30, 60 and 120 min. The partition of water into the cellular tissue structures (vacuole, cytoplasm, extracellular spaces and cell wall) was investigated by Time Domain Nuclear Magnetic Resonance (TD-NMR). In parallel, the microstructure of kiwifruits slices was examined using a Scanning Electron Microscope. The results showed that US pretreatment performed for more than 10 min had a positive effect on the mass exchange caused by osmotic dehydration. A creation of microchannels and an increase of the average cross-section area of cells were observed when the samples were pretreated with US before OD. TD-NMR showed a slight redistribution of water through the substructures of the cells, as a function of the length of the US pretreatment applied.

UNLABELLED This work reports an experimental study on the permeability and thermal behavior of commercial polypropylene (PP) film used for fresh-cut potatoes packaging. The permeability was tested using oxygen, carbon dioxide, nitrogen, mix of these 3 gases, normally used for modified atmosphere packaging (MAP) and Air, to understand if it would be possible to extend the shelf life of this food product designed for the catering field in respect to the packaging behavior. The temperature influence on permeability data, from 5 to 40 °C, was analyzed, before and after 4, 8, 12, 15, and 20 d of food contact, pointing out the dependence between temperature and gas transmission rate (GTR), solubility (S), diffusion coefficient (D), and time lag (t(L)) parameters. The activation energies (E) of the permeation process were determined with the different gases used in the experiments. The thermal behavior of PP film was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) to well understand its thermal stability. Fourier transformed-infrared with attenuated total reflectance (FT-IR/ATR) spectroscopy was also performed in order to study the influence of the food contact on the chemical characteristics of the polymer film. The results obtained were discussed and compared each other. Studied samples showed, for all investigated gases, an increase of gas permeability and S values at higher temperature. Heat resistance classification among the sample as it is and stored in modified atmospheres was made. Finally all performed experiments have showed good polymer stability for the shelf-life storage potatoes under study. PRACTICAL APPLICATION Study of packaging material was performed in a range of temperature, which can simulate the service condition to assess the suitability of a commercial polymer film for modified atmosphere packaging of fresh-cut potatoes minimally processed designed for catering purpose.

Poly(lactic acid) (PLA) is now a very attractive polymer for food packaging application because in addition of being thermoplastic, biodegradable, compostable, and produced from renewable resources, it shows same behavior in mechanical, thermal, and barrier properties comparable to the most used synthetic polymers like polystyrene and poly(ethylene terephthalate). In this work, we take into consideration four commercial PLA films, natural- and surface-modified, to make a correlation between mechanical, thermal, and barrier properties due to the surface modification, to well understand whether PLA is adapt to packaging application, especially in the food field. Films were studied by tensile testing, simultaneous differential thermal analysis/thermogravimetry, differential scanning calorimetry, permeation to carbon dioxide and oxygen at different temperature (7 and 23°C) and FTIR spectroscopic analysis. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

This study investigated mass transfer and water state changes promoted by osmotic dehydration on two kiwifruit species, Actinidia deliciosa and Actinidia chinensis. Osmotic treatment was performed in a 61.5% w/v sucrose solution at three different temperatures (25, 35 and 45 °C), with treatment time from 0 to 300 min. Treatment time positively influenced kiwifruit water loss and solid gain while temperature significantly affected only water loss. Peleg’s model highlighted that the main response differences between the two species occurred during the initial phase of the osmotic treatment. Thermal properties and relaxation time measurements offered a complementary view concerning the effects of osmotic dehydration on kiwifruit. DSC parameters appeared to be sensitive to water and solid exchange between fruit and osmotic solution. LF-NMR proton T2 revealed the consequences of the water– solid exchange on the cell compartments, namely vacuole, cytoplasm plus extracellular space and cell wall. During the osmotic treatment, the initial freezing temperature and the freezable water content decrease was dependent on time and treatment temperature, showing a similar tendency for both the kiwifruit species. They evidenced the same treatment response also concerning the reduction of vacuole and the increase of cytoplasm plus extracellular space T2 values.

[EN] Shelf life of kiwifruit is short and requires conservation techniques to increase its commercial life. In this sense, the modern techniques used to analyze the changes of the product through the treatment allow developing new products with the specific quality characteristics required. In this work, the structural and physico-chemical changes of kiwifruit through the osmotic dehydration treatment with 61.5% (w/w) sucrose solution at short times from 0 to 300 min were explained. The SAFES (systematic approach to food engineering systems) methodology applied in kiwifruit is useful to obtain the internal composition of each phase, to control the fruit changes through the process, and to determine the behaviors involved in transports. Moreover, the Gibbs free energy, the enthalpy and the entropy estimation of each phase was calculated in order to analyze the irreversibility of the process. (C) 2011 Elsevier Ltd. All rights reserved.

[EN] Osmotic dehydration experiments of kiwifruit (Actinidiadeliciosa cv Hayward) were carried out in order to apply a nonlinear irreversible thermodynamic model. Samples were immersed into 65% (w/w) sucrose aqueous solution at 30 degrees C during 5, 10, 15, 20, 30, 45, 60, 90, 120, 180, 250, 320, 400, 720, 1440 min. Some physical-chemical parameters were measured in fresh, treated and reposed (24 h at 30 degrees C) samples. It was possible to apply the enthalpy-entropy compensation coupled to a nonlinear thermodynamic model, obtaining the apparent bulk modulus and explaining the elastic answer of the tissue throughout the osmotic process. The osmotic dehydration also produces losses in the native compounds of kiwifruit such as citric acid and Calcium and Potassium. (C) 2011 Elsevier Ltd. All rights reserved.

The aim of this study was to compare some physico-chemical properties (O 2 and CO 2 in the package headspace, weight loss, pH, albumen and yolk water content and colour, Haugh unit) of non packed eggs and eggs packed in high barrier plastic pouches with three atmospheres (air, 100% N 2 , 100% CO 2 ) during 28 days of storage at 25 °C. Modified atmosphere packaging (MAP) permitted a strong reduction of the weight loss from the product. While the greatest quality decline was observed for the control eggs (not packed), eggs packed in CO 2 maintained the initial values of Haugh unit during storage and the albumen pH was about 2 units lower than in the control group. Nevertheless, the light yellow colour of CO 2 sample albumen deepened and the shell gradually developed a powdery surface. MAP with 100% N 2 did not promote any additional benefits to the eggs in comparison with the product packed in air.