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Kiwifruit is an excellent source of vitamin C and other bioactive compounds, which contribute to its high antioxidant activity. However, the fruits with small size and low weight are considered waste and are unprofitable, therefore, the production of healthy kiwifruit-based dried snacks, which contain a lot of health-beneficial ingredients, could be a viable alternative for their use. The aim of this study was to develop formulations and methods to produce attractive and nutritionally valuable dried snacks based on yellow kiwifruit. Three different puree formulations (kiwifruit, fennel, and strawberry, lemon, or spinach) with or without addition of sugar were subjected to two drying methods: freeze-drying (fruit bars) and conventional hot air drying (fruit leathers). The obtained products were analysed for their content of total polyphenols (TPs), flavonoids, and vitamin C, as well as their antioxidant activity. The results showed that snacks prepared by freeze-drying (fruit bars) presented higher TP, vitamin C, and flavonoids content than those prepared by convective drying, however, the antioxidant activity did not always follow this trend. The amount of bioactive compounds depended on the formulation used for the preparation of snacks. The effect of the sugar addition seems to be strictly related to the mix used and specific bioactive compound investigated.

[EN] Recently, some authors have applied pulsed electric fields (PEF) as a pre-treatment of osmotic dehydration, showing a faster kinetics of dehydration. Osmotic dehydration of fruit tissue shows complex mass transfer mechanism associated with active and passive transports of the vegetal matrix, usually driven by electrolytes. The aim of this work was to analyze the effect of different PEF values (100, 250, 400 V/cm) as a pre-treatment of the osmotic dehydration (61.5°Brix, up to 120 min) on mass transport mechanism of organic kiwifruit. A thermodynamic model able to describe the mass transfer and tissue deformation in kiwifruit was developed. It was possible to conclude that pulsed electric field as a pre-treatment, remove a part of the native electrolytes, reducing the activity of protein active pumps, leaving alone the passive protein channels as a main mass transmembrane transport and therefore affecting to the regular functionality of cell homeostasis system., The authors Urszula Tylewicz and Marco Dalla Rosa want to thank for the financial support of this project provided by funding bodies within the FP7 ERA-Net CORE Organic Plus, and with cofunds from the European Commission (this project has received funding from the European Union's 7th Framework Programme under grant agreement No 618107.). The author Marta Castro-Giraldez wants to thank the UPV Postdoctoral Program (PAID-10-14) of the Universidad Politecnica de Valencia for its support. The author Maria Victoria Traffano Schiffo wants to thank the FPI Predoctoral Program of the Universidad Politecnica de Valencia for support her PhD studies, ERASMUS PRACTICAS program to finance her mobility to Italy and also Silvia Tappi and Wei Luo for their cooperation during the experiment.

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.

The aim of this work was to evaluate the influence of the ripening stage on fresh-cut kiwifruit tissues in terms of quality and tissue metabolism, during accelerated storage (AS) in controlled conditions. For this purpose three different ripening stages were selected, corresponding to about 11, 13 and 15 °Brix. For each ripening stage the fruits were peeled and cut into 1 cm thick slices and stored in climatic chambers at 10 °C, 90% RH, for 3 days. During storage, quality indices as soluble solid contents, titrable acidity, colour and texture were monitored. Metabolic assessment was carried out evaluating the endogenous metabolic heat using isothermal calorimetry, and monitoring O2 consumption and CO2 production simultaneously. Differences were found in the evolution of the quality indexes during storage; in particular kiwifruit at the lowest ripening stage showed the slowest quality degradation, both in terms of softening and visual quality modifications. Metabolic heat production results were different at the different ripening levels investigated, evidencing a strict connection between the physiological state of the tissue and the entity of its wounding response.

The effects of osmotic dehydration (OD) on kiwifruit outer pericarp tissue as affected by treatment extent (0–300 min) and raw kiwifruit ripening stage (9 and 14 °Bx) were investigated. Differential scanning calorimetry (DSC) measurements show decomposition of cell wall components (pectins, cellulose and hemi-celluloses). Changes in decomposition parameters (peak temperature lowered and enthalpy increased) were observed related to kiwifruit ripening degree and OD extent increased. Cell wall pectin network disassembly led to the formation of compounds with lower degradation temperature. Raw unripe fruits showed higher firmness values and lower compressibility compared to ripe and OD treated fruits. Isothermal calorimetry revealed metabolic heat production of unripe fruits decreasing linearly with the OD extent. Ripe fruit heat production sharply decreased during the first treatment hour, probably as a consequence of membrane integrity loss. Industrial relevance OD leads to moisture removal and solute uptake in vegetable tissue, providing minimally processed commodities or ingredients for bakery or ice-cream industry. The industrial relevance is the energy-efficiency, since the process does not require water-phase change. OD provokes still unknown collateral alterations on tissue structure and metabolism. The present work applies a new calorimetric approach to evaluate both structure and metabolism changes on kiwifruit as reliant on process extent and raw fruit ripening stage.

Osmotic dehydration is a partial dewatering process by immersion of cellular tissue in a hypertonic solution, which is accompanied by solutes counter-diffusion into the tissue. Low field-nuclear magnetic resonance (LF-NMR) seems to be a promising technique to follow the distribution of water/solutes through the cellular tissue during treatment. The objective of the present study was to evaluate the cellular compartment modifications of kiwifruit (Actinidia deliciosa) outer pericarp tissue caused by osmotic treatment in a 61.5% sucrose solution through the quantification of transversal relaxation time (T2) and water self diffusion coefficient (Dw) obtained by LF-NMR means. Proton T2 of the samples was measured using CPMG sequence. Three T2 were obtained of around 30, 200 and 1000 ms, which could be ascribed to the protons located in the cell walls, in the cytoplasm/ extracellular space, and in vacuoles, respectively and could be directly compared to those described in the literature for several fruits and vegetables. Vacuoles T2 represented around 66% of total kiwifruit protons. The leakage of water leading to vacuoles shrinkage seemed to cause a concentration of solutes, retained by the tonoplast, making the vacuoles T2 decrease at each treatment time. Dw were measured by means of the pulsed field spin-echo (PFSE) sequence. As expected, the kiwifruit Dw values measured in the raw kiwifruit were lower than free water one, as the structures and solutes of raw kiwifruit reduce water mobility, and decrease even more during osmotic treatment, due to the water loss and sugar gain. The coefficient measured by means of PFSE represented an average value of the whole kiwifruit tissue protons. In order to obtain Dw values specific for each cellular compartment, a two compartment fitting was also used. The Dw correspondent to vacuoles was much higher than the average one Dw.

The role of fruit in a healthy diet is growing because fruits are an important source of vitamins, antioxidants and basic ions such as potassium or calcium, which are fundamental in an equilibrated meal. Self life of fruit is short and requires conservation techniques to enhance its commercial life. In this sense, the online control of conservation treatments is essential to preserve the compounds with functionality. Dielectric spectroscopy is a good technique to control polar components such as water and also components with charge such as antioxidants or ions. The aim of this work is to analyze the chemical and structural changes in the osmotic treatment of kiwifruit by using dielectric spectroscopy. The osmotic treatment consisted on immerse the samples into 65% (w/w) sucrose aqueous solution at 30ºC during 60, 90, 120, 180, 250, 320, 400, 720, 1440, 2000 minutes. Some physical-chemical parameters were measured in fresh, treated and reposed (24h at 30ºC) samples. Dielectric spectra were measured in the frequency range from 500 MHz to 20 GHz by an Agilent 85070E Open-ended Coaxial Probe connected to an Agilent E8362B Vector Network Analyzer in the fresh, treated and reposed samples.

Kiwi is an important fruit in the diet because contains vitamins, antioxidants and ions, fundamentals in an equilibrated meal. Self life of this fruit is short and requires conservation techniques to enhance it commercial life. In this sense, modern techniques to analyze how change the product (as SAFES) and how change through the treatment, allow as to develop a new product with the specific characteristics what are looking for. SAFES methodology (Systematic approach in food engineering systems) is a technique to describe the structure of food through any treatment which provides the physicochemical transitions, chemical and biochemical reactions and energy and mass transports. The aim of this work is to explain how change the structure of kiwi through the osmotic dehydration with 61,5% (w/v) sucrose solution at 45ºC, at short times from 0 to 300 minutes. Since the short times of dehydration applied did not allow the equilibration of the system and there were continuous changes of parameters, only one Matrix of changes was indentified. Considering the kiwifruit as a biological system compost of cells, pores and intercellular spaces, two types of tissue (vascular and parenchymatic) were individuated on the basis of cell characteristics that can influence the transport. Moreover the different phases as solid matrix and liquid phase were found in both tissues. One of the main ingredients of kiwifruit is water and its distribution was studied by SAFES application. The water sorption isotherm (Moraga et al., 2006) was used to characterize the adsorbed water in solid matrix, while the sharing out of the liquid water in vascular and parenchymatic tissues was performed by the external volume evaluation.

Osmotic dehydration consists of fruit immersion in hypertonic solution, generally from sugars, and it is one of the most interesting techniques for the shelf-life extension of fresh-cut fruit, as a partial removal of water from the tissues. Aim of this study was to investigate the effect of different times and temperatures of immersion in a specific sugar osmotic solution in the mass transfer phenomena and the main qualitative characteristics of two kiwifruit cultivars, one of them recnognised as "standard" kiwifruit (cv. Hayward) and the other better known as the new "yellow" kiwifruit.