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The aim of this work was to evaluate the effect of different variables on osmo-air-dried apple chips processing, in order to identify the most influencing factors on final product crispness. A 23 full factorial design was selected; cultivar (Golden Delicious and Pink Lady®), osmosis time (30, 60 and 90 min) and air drying temperature (70, 80 and 90C), were independent variables; crispness coefficient (E, kNmm−2), relative relaxation stress, water activity, color attribute L*, moisture content (gH2O/100 g solids) and panel score (crispness intensity) were dependent variables. Apple rings were immersed in sucrose, maltose or a mixture of fructose, glucose and sucrose (Aw = 0.90), and air dried to constant weight. Crispness and physico-chemical properties were affected mostly by drying temperature, and less by cultivar and osmosis time. The screening test discriminated pretreated apples from not pretreated ones, the former being evaluated as crispier. Results indicate that the interaction between drying temperature and fruit tissue structure is the key factor optimizing the osmo-air-drying process, aimed at high-level crispy apple chips. PRACTICAL APPLICATIONS A new interest has recently arisen in the field of dried crispy fruits. For snack foods, more than taste, crispness is the sensory attribute that most strongly influence quality evaluation by the consumers. For this reason, it is important to quantify the effects of different variables (apple cultivar, osmosis time and air-drying temperature) on osmo-air-dried apple rings characteristics, especially in terms of crispness. The major interest deals with the possibility to exploit these findings for a more rational manufacturing of such snack product.

Great changes in the structure of vegetal tissue could be produced by both osmotic dehydration and air drying. Texture of material moves from elastic-visco-plastic to rigid, becoming fragile and brittle. These changes are welcomed when the final product is a crispy and crunchy snack food. The aim of this work is to define the combined process, involving the osmodehydration and air-drying techniques, in order to obtain dried and crispy pineapple rings, having high qualitative characteristics. Six mm thick pineapple rings were osmodehydrated for 30 minutes in pineapple juice and sucrose solution, both at 50°Bx. Not pre-treated and pre-osmodehydrated rings were air dried at 70-75-80 °C till constant weight. Dry matter, soluble refractometric residue, pH and titratable acidity of raw and osmodehydrated samples were measured. Solid gain and water loss of the osmotic process were assessed. Dry matter and water activity of dried product were also measured. Changes of colour and surface area due to processing were evaluated by image analysis technique. Final product crispness was determined by bending snapping test. The sensorial characteristics were judged by a panel test. From both instrumental and sensorial aspects air-dehydrated samples resulted crispier than the respective osmo-airdehydrated ones regardless of solution type and temperature. This behaviour could be linked to the higher residual water content of the osmo-airdehydrated pineapple rings. The higher the drying temperature the better the results for instrumental and sensorial crispness. As expected the colour was negatively influenced with the increase in drying temperature. The osmotic pre-treatment in sucrose solution protected the colour during drying but the osmo-dehydration with pineapple juice hadn’t the same positive influence. The best result was obtained with not pre-treated pineapple rings dried at 75 °C: the product was slightly amber- coloured, crispy and not hard and consequently appreciated by the tasters.

Solvent composition, system mobility and viscosity play a central role in the regulation of enzymatic activity. The aim of this study was to investigate the individual and combined effect of water activity (aw), bulk viscosity and glass transition temperature ( T g ′ ) on the activity of horseradish peroxidase (HRP) in buffered solutions. For this purpose, the water activity of the solutions was modulated using both a ionic (sodium chloride) and a non-ionic (sorbitol) ligand and viscosity changed upon the addition of maltodextrin. In viscous solutions characterized by different compositions, the effectiveness of a solute in the inhibition of the HRP activity was dependent both on the chemical properties of the solution, as described by aw, and on the mobility of the system, as described by the inverse of viscosity and T − T g ′ . Viscosity was the most important factor in the inhibition of HRP activity in solutions characterized by the same T g ′ value, but when T g ′ was changed, due to changes in the solutes composition, the latter became a key factor in the regulation of the enzyme activity. In salt–maltodextrin systems the water activity reduction limited HRP activity with higher efficiency at low viscosities whilst in sorbitol–maltodextrin systems, characterised by different T g ′ values, the aw lowering by sorbitol addition resulted in the increase of HRP activity depending on its effect on T g ′ .

Four cultivars of organic sweet cherry were considered in this work. The influence of both a steam and an osmo-blanching step applied to fruit halves before freezing, on colour and on radical-scavenging activity related to the recovery of total phenols and anthocyanins was studied. A 60% (wt/wt) glucose-fructose mixture (2:1) was used for the osmo-blanching, carried out at 87°C for 3 min. Fruit blanching induced a significant recovery increase of total anthocyanins, with a consequently significant increase of radical-scavenging activity. Osmo-blanching proved to be more effective than steam-blanching in 'Adriana'.

Mechanical properties of dried apples rings were studied through two different rapid compression tests. A bending–snapping test and a modified compression–relaxation test were performed in order to differentiate between osmo-air-dried apple rings as a function of variety (Golden Delicious and Pink Lady ® ) and drying temperature (70 °C, 80 °C, 90 °C). Elastic modulus during bending, fracturability indices, peaks density, and relaxation coefficient during compression were taken into consideration. The obtained results reflect primarily the effect of the drying process on the moisture content of both varieties, but also the different changes in the tissues structure related to both the different solid–liquid exchanges during the osmotic pre-treatment and the drying process. Undergoing the same drying treatment, Pink Lady ® rings showed a more rigid and stiff texture than Golden Delicious, which in contrast had a more brittle texture. The obtained results described satisfactorily structural changes of apple tissues, giving the possibility to discriminate, in a rapid way, between different categories of dried apples.

The influence of an osmotic step and the syrup composition on the chemical–physical properties, drying kinetics, structure collapse and colour changes of air dehydrated tomato slices, was studied. Sugar solutions, with reduced sweetening capacity with or without CaCl2 added, were used. During air dehydration, colour attributes and geometric features were evaluated by image analysis, and an electronic nose was used to monitor the changes in aroma profile. The osmotic pre-treatment increased drying rate during the first falling rate phase of the air dehydration step but in the last phase reduced it. Sugar enrichment improved colour stability during subsequent air dehydration and helped to slightly decrease shrinkage during the first phase. The calcium addition improved surface area retention. Image analysis has proved to be a useful tool to study structure evolution during dehydration in combination with conventional analysis. The electronic nose was able to characterize the process aromatic fingerprint, helpful in understanding and parameterizing the degradative events during dehydration.

High-quality standards in blueberry juice can be obtained only taking into account fruit compositional variability and its preservation along the processing chain. In this work, five highbush blueberry cultivars from the same environmental growing conditions were individually processed into juice after an initial blanching step and the influence was studied of the cultivar on juice phenolic content, distribution and relative antioxidant activity, measured as scavenging capacity on the artificial free-radical 2,2-diphenyl-1-picrylhydrazyl (DPPH*). A chromatographic protocol was developed to separate all main phenolic compounds in berries. A total of 15 glycosylated anthocyanins, catechin, galactoside, glucoside, and rhamnoside quercetin 3-derivatives, and main benzoic and cinnamic acids were identified. The total content and relative distribution in anthocyanins, chlorogenic acid, and quercetin of each juice were dependent upon cultivar, and the total content was highly correlated (rxy=0.97) to the antioxidant capacity. A selective protective effect of berry blanching in juice processing can be observed on more labile anthocyanin compounds.

The aim of this work was to investigate the feasibility of near infrared (NIR) spectroscopy both in quantifying the residual water content of osmo-air dehydrated apple rings and in differentiating them on the basis of the sugar solution used in the osmotic pretreatment so identifying the osmotic syrup used. In order to achieve this, a set of products obtained by different processing conditions was created. Apple rings were dipped for different lengths of time (30, 60 and 90 min) in three different sugar solutions at the same water activity (aw = 0.90): sucrose (59% wt /wt), maltose (62% wt /wt) and a mixture (53% wt /wt) of fructose, glucose and sucrose having the same composition as apple. Air drying was then performed at different temperatures (70°, 80°, 90°C) and the obtained osmo-air dehydrated apple rings were packed in polypropylene film under vacuum in order to avoid water absorption phenomena. NIR spectra, in the range 10,000–4000 cm−1, were recorded directly on packed apple rings using a FT-NIR spectrometer equipped with fiber optic probe. In calibrating the residual water content the coefficient of determination (R2) was 0.93, the RPD value was 3.33 and RER value was 13.79, which could be considered, for our purposes, suitable for controlling the dehydration process. Moreover, applying a classification statistic method on NIR data, such as PLS discrimination analysis, it was also possible to identify correctly which sugar solution was used in the osmotic pre-treatment independently of the conditions used. Two-dimensional correlation analysis was also carried out, in order to investigate how the ratios between the main constituents, sugars and water, involved in the osmo-air dehydration varied as a function of the process variable used.

The influence of the type of sugar in the osmotic solution and of the time of processing on the volatile compounds of strawberries was studied, in order to optimize the technique as a pre-treatment to further processing. Strawberries of cultivar ‘Camarosa’, cut into 1 cm thick slices, were subjected to osmotic dehydration at 30 °C for 1, 2, 4 and 6 h using either 60% (w/w) sucrose or 60% (w/w) sorbitol solutions. Volatile compounds of fresh and processed strawberry slices were analyzed by static headspace—gas chromatography. Osmotic treatments provoked a loss in volatile compounds due to the migration, mainly of esters, into the osmotic media. The variations in the volatile pattern depended on both time of treatment and type of osmotic solution. The greater changes occurred after 2 h in sucrose; with a promotion of fermentative volatiles (acetaldehyde, ethyl acetate), and a decrease in the other volatiles. Using sorbitol as osmotic agent, the major variations in the volatile pattern occurred after 4 h of osmosis, and the fermentative process was less important than in sucrose, as sorbitol could be less effective in forming a peripheral layer at the fruit surface and/in reducing tissue porosity.

An electronic nose was used to detect the aroma evolution of strawberry fruits, cultivar “Camarosa,” during the osmotic dehydration in sorbitol and sucrose solutions. Strawberry slices were subjected to osmotic dehydration at 30 °C for 1, 2, 4, and 6 h using either 60% sucrose or 60% sorbitol solutions. Volatile compounds of fresh and processed strawberry slices were analyzed by electronic nose and gas chromatography. Electronic nose was able to reveal changes in the aroma profile during processing and permitted differentiation between dehydrated strawberry samples obtained by different osmotic treatments. The electronic nose has the advantage of being simple, rapid, and nondestructive. Such characteristics and the promising results of this work suggested that this device could be a useful and innovative tool to monitor strawberry aroma changes during osmotic dehydration, providing real-time information about the effects of processing conditions and allowing the optimization of technological parameters.

The effect on strawberry tissue of an osmotic step applied at atmospheric pressure for different lengths of time, was analysed. In this work, the specific influence of osmotic treatments with sucrose solutions at 25 °C on cellular structure, texture, pectin composition and their relationship are discussed. Osmotic dehydration induced a significant texture loss: The longer the immersion time, the higher the texture loss. From 1 h onwards of osmosis there was a gradual disconnection and breakdown of the tissue, with a loss of shape of cellular walls together with loss of turgor pressure. A good agreement was obtained between texture, structure changes and pectic composition modifications. Besides a pectin solubilization, there was an hemicelluloses solubilization, most likely due to an accelerated ripening of strawberry fruit, linked to the anaerobic conditions, caused by a sugar peripheral layer formation.

Osmotic dehydration has been proposed in combination with air dehydration to improve quality attributes of air dried fruit pieces. The influence of the osmotic step and of the syrup composition on the chemical–physical properties, structure collapse and colour changes of osmo-air-dehydrated apricot cubes was studied. The relationship between shrinkage during air dehydration and ‘glass’–‘rubber’ transitions of apricot tissue was also analysed. Colour attributes and geometric features were evaluated by image analysis and mathematical transformations were applied to the image parameters to estimate volume reduction related to absolute moisture content. Sugars added during the osmotic step help to slightly decrease shrinkage during the first phase of the subsequent air dehydration, furthermore the osmo-dehydrated apricot cubes showed the lowest structure collapse, retaining a better superficial appearance. The incorporation of sugars improved the colour stability during air dehydration, with sorbitol showing the highest protective effect.

Water is one of the most critical components in foods and biological systems because it affects several physicochemical properties of these systems with effects on their chemical and enzymatic stability (Bell 2007).

The aim of this study was to develop experience in acquiring water mobility and moisture data that could be used to develop improved models for predicting water loss during osmotic dehydration and/or air-drying. One-dimensional magnetic resonance imaging protocols were used to follow temporal and spatial changes in water mobility via T 2 profiles, water content via M 0 profiles, and structural shrinkage of strawberry slices during osmotic dehydration with 600 g/kg aqueous sucrose over 2 h. Those measurements were also made for 1 h during air-drying of normal and osmotically dried slices at 20, 30, 45 and 60 °C. Air-drying above 20 °C resulted in changes in the strawberry matrix, which suggests the need for a model that incorporates the interaction between the strawberry tissue and the water that diffuses during drying. Modelling of the air-drying of osmotically pretreated slices would be complicated by the variable amounts of sucrose solution remaining after osmotic dehydration.

Over the last few decades wide prospects for osmotic dehydration have arisen as a pre-step to further processing. The distinctive aspect of this process, when compared with other dehydration methods, is the direct formulation achievable through the selective incorporation of solutes, without modifying the food integrity. By balancing the two main osmotic effects, water loss and solid uptake, the functional properties of the fruit could be adapted to many different food systems. The role of an osmotic step mainly related to improvement of processed fruit quality characteristics, such as texture, and pigment, vitamin and aroma content, is analysed.

Among several factors affecting the osmotic dehydration process, the raw material characteristics play a fundamental role. As aroma is one of the major determinants of fruit quality, the influence was studied of both the cultivar and the processing time of dewatering–impregnation–soaking (DIS) on the aroma profiles of muskmelon spheres, in order to optimise the technique as a pre-treatment to further processing. Muskmelon cultivar Mirado and Rony, manually cut into 28 mm diameter spheres, were subjected to osmotic dehydration at 25°C for 1, 2, 4 and 6 h in a 60% (wt/wt) sucrose syrup. Both muskmelon cultivars showed higher uptake of soluble solids when compared with other fruit and there was a higher water loss in cultivar Mirado than cultivar Rony during the whole process. The aroma profile of melon cultivar Rony was less modified by DIS, indicating a better suitability for this type of pre-treatment. `Positive' aroma compounds did not decrease in cultivar Rony, and `negative' ones significantly increased only after 6 h of DIS. Possible differences in tissue structure could account for the different behaviour of the two cultivars.

The influence of both the cultivar and the dehydration method, applied before freezing, on quality characteristics of dehydrofrozen muskmelon spheres has been studied. Water was removed from muskmelon cultivar Mirado and Rony, prior to freezing, by Dewatering–Impregnation–Soaking in concentrated solution (DIS) for 1 h, air dehydration and combined DIS-air dehydration to a final 50% weight reduction. The results of the analysis of exudate loss, texture, colour, aroma composition and sensory characteristics ascertained the crucial importance of the cultivar which had a great influence on the quality of the end products. Moisture reduction prior to freezing reduced exudate loss and improved texture at thawing. All the pre-treatments caused the loss of ethyl esters, namely “positive” aroma compounds, while the alcohols, “negative” aroma compounds, increased in air dehydrated fruits and remained stable in the DIS-treated ones. This finding could explain the higher sensory acceptability of the DIS-treated fruit when compared with those pre-air dehydrated.

In order to optimize the osmotic dehydration process as a pre-treatment to freezing, chemical and structural characteristics of the raw fruit have to be studied together with their influence on the solid liquid exchanges and on the quality of the end products Textural properties of fruits are intimately associated with the cellular structure and pectic composition. So the influence of osmodehydration on the modification of texture and water-soluble, oxalate-soluble and residual protopectin in kiwifruit slices was studied. To determine the optimum firmness level of the raw kiwifruit, the fruits were processed at three instrumentically measured texture levels: firm, medium and soft. Chemical and physical analyses showed that the biggest difference among the three groups of fresh kiwifruit was the protopectin content which was correlated directly with texture. No relationships were found between texture changes and pectic composition during osmodehydration, the slight firmness increase probably bein...

This work forms part of a collaborative research project between members of the EU Concerted Action CT 96-1180 “The preservation of frozen food quality and safety throughout the distribution chain”. The objective was to investigate how added carbohydrates affect the colour stability of frozen strawberry juices stored at high temperature, i.e. above Tg′ the glass transition temperature of the maximally freeze concentrated phase. Differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and dc conductivity measurements were used to determine Tg′. It was found that there was no clear relationship between the anthocyanin loss and the amplitude of the difference between the storage temperature and Tg′ the glass transition temperature of strawberry juices.

Osmodehydrofreezing, a combined process where osmotic dehydration is followed by air-dehydration and freezing, has been proposed to prepare reduced moisture vegetable ingredients, free from preservatives, with a natural and agreeable flavor, color and texture, and with functional properties suitable for different applications. The influence of syrup composition (hydrolyzed lactose syrup from cheese whey ultrafiltration permeate with or without sorbitol) and air-dehydration level on the chemical-physical properties of osmodehydrofrozen red pepper cubes was studied. Owing to the intake of galactose and sorbitol, osmo-air-dehydrated red pepper cubes showed lower water activities and lower consistencies than the air-dehydrated red pepper cubes at the same refractometric index. By incorporating sorbitol, a known humectant, into the vegetable using osmosis, an even softer product can be obtained owing to the higher relative water content at a determined a w , useful as ingredients at reduced a w without rehydration.

Vapor induced puffing during high temperature fluidized bed (HTFB) dehydration of apple cubes was optimized using response surface methodology (RSM). Osmoblanching in sugar syrup prevented enzymatic browning. Successful puffing was achieved by creating a surface barrier to vapor by dipping the cubes in starch solution and manipulating the temperature and time of exposure in the HTFB. Optimum conditions for minimum bulk density with acceptable levels of nonenzymatic browning included dipping osmoblanched apple cubes in 1% starch solution, followed by HTFB drying 11 min at 157 o C. Product bulk density exhibited a minimum' while nonenzymatic browning values did not display an optimum. Minimum value of bulk density predicted by RSM and browning values were very close to those verified experimentally for product processed under the identified optimum conditions

To evaluate the influence of carbohydrate addition on anthocyanin and soluble phenol stability, blueberry juices were added with 20% (wt/wt) of maltose, sorbitol and a mixture (1:1) of glucose and fructose. A juice without addition of carbohydrates was used as a control. The juices were frozen and stored up to six months at −10, −20 and −30 °C. The transition temperatures T m ′ correlated with those of the added sugars. The glass transition was shifted to higher temperatures by addition of maltose and no significant changes in the transition temperatures were noticed with storage time. Anthocyanin and soluble phenol changes were mainly influenced by storage temperature and storage time: the lower the temperature, the shorter the storage time, the lower the changes. Sugar addition had no influence on anthocyanin content.

Maltodextrins influenced the enzymatic activity in aqueous solutions by affecting the water activity (aw) and mobility as described by viscosity and T’g. In diluted solutions, viscosity being equal, (1) maltodextrin with dextrose equivalents (DE) of 33 was more effective than glucose in limiting horseradish peroxidase (HRP) activity; (2) an increase in the maltodextrin chain length from DE 33 to DE 8.7 did not further limited enzymatic activity; (3) the maltodextrin with the highest chain length (DE 2.5) determined the highest enzyme inhibition. In general, the increase of molecular weight negatively affected the HRP activity by increasing the viscosity and T’g (decreasing molecular mobility) but it positively affected the aw and, in some cases, this compensated the HRP activity inhibition. In concentrated solutions (apparent viscosity ≈ 40 mPa s) the HRP activity decreased with the increase of the maltodextrin molecular weight, and it showed a dependence on T’g which could be described by a William, Landel and Ferry (WLF)-type equation. On the contrary, in the solution added with the maltodextrin with the highest chain length (DE 2.5) the HRP activity was much higher than that predicted by the WLF-type equation. The maltodextrin with DE 2.5 contains intact starch fragments and in water forms a suspension. In such a discontinuous system, the viscosity in the vicinity of the protein is lower than the bulk viscosity, and thus, the enzyme activity is higher than expected. Moreover, since T’g is a property of the soluble phase, it does not explain the mobility in discontinuous systems.

The inhibiting effect of ascorbic acid, citric acid and sodium chloride on Polyphenoloxidase (PPO) of Golden Delicious apple cubes was studied. Dipping in ascorbic acid (0.2-10 g/L range) and in NaCl (0.2-1 g/L range) solutions for 5 min increases the PPO activiry. Citric acid solutions (0.2-10 g/L range) have little or no inhibition of PPO. A 90-100% PPO inhibition was obtained with a 5 min dip in mixtures of ascorbic acid and citric acid (10 + 2 g/L), and of ascorbic acid and sodium chloride (I0 + 0.5 g/L).

The basic principles which control osmotic dehydration of fruit and vegetables are reported together with the most important parameters and their influence on the process. The effects of osmosis as a pre-treatment, mainly related to the improvement of nutritional, sensorial and functional properties of the products, are analyzed. The distinctive aspect of this process, when compared to other dehydration methods, is the ‘direct formulation’ achievable through the selective incorporation of solutes, without modifying the food integrity. By balancing the two main osmotic effects, water loss and soluble solids uptake, the functional properties of fruit and vegetables could be adapted to many different food systems. Present applications of the process are shown and problems related to a further industrial development are analyzed.

Fruit pieces of some species have been processed to be used as ingredients in various food systems, either by partial dehydration alone or by osmosis and partial dehydration, to achieve different levels of water activity and solids contents in the final products. The relationships existing among processing, phase composition after processing and functional properties of the products have been assessed within a useful range of water content and water activity. The functional properties are expressed as diagrams relating the phase composition (soluble solids, insoluble solids and water) to the range of consistencies obtainable at various water activities. These diagrams provide a useful tool for preparing fruit ingredients suitable for specific food systems.

The influence of osmotic dehydration on the degradation of pectic substances of apricots (‘San Castrese’ variety) and clingstone peaches (‘Carson’ variety) during processing and storage in flexible pouches was studied. The three pectin fractions, water soluble (WS), oxalate soluble (OS) and residual pectin (protopectin) (RP), were determined in fresh fruits, after blanching, after osmotic dehydration and on packed fruits after 2, 4 and 6 months storage. The anhydrogalacturonic acid content of the three fractions was determined quantitatively by using ion-exchange high-performance liquid chromatography while the methanol was determined by gas chromatography. Textural changes were followed by compression and using penetration tests performed with an Instron and overall preference was determined organoleptically. The analysis of the pectic compositions of the two types of fruits confirmed the role of the protopectin in preserving the fruits' firmness during processing. The differences of composition, highlighted by the distribution of differently soluble fractions of total pectin in the two species of fruits, was sufficiently large to account for the different response to the osmotic dehydration process and storage. The RP fraction of the two fruits and the respective textural and organoleptic values showed a good correlation. The ‘protopectin/soluble pectin’ ratio, introduced here, may prove valuable as an index of the suitability of the fruits for osmotic dehydration. Further investigations of the generality of this correlation for different species of fruits would be a desirable development from this present research.

The exchange of sugar components in cherry, apricot and peach with the osmotic syrup during osmotic dehydration was analyzed. Sugar exchange dynamics between the syrup and the fruits was found to be related not only to the flux of sugars from the syrup into the fruit, but is affected also by the individual sugars originally present in the fruit. The exchange is also dependent on the species of fruit, the relative diffusivity of the sugars and enzymatic activity within the fruit.

The lipid and apoprotein composition of very low density lipoproteins (VLDL) ( d Significant changes are observed in the apoproteins, as well as in the fatty acid composition of cholesterol esters, and in the relative distribution of phospholipids. Apoproteins show a marked increase of peptides with slow mobility (R2 and R3), corresponding to arginine-rich proteins, both in the rabbit and in some types of human hyperlipoproteinemias (hypothyroidism and Fredrickson Type III). VLDL were separated into the two fractions, VLDL-1 and VLDL-2. Peptides of slow mobility were shown to be present in a higher concentration in VLDL-1. Cholererol esters of h.c. VLDL have a very high content of oleic acid, the 18 : 1/18 : 2 ratio being about three times higher than in normal VLDL. Phospholipid distribution in h.c. VLDL is characterized by an increase of sphingomyelin and decrease of phosphatidylethanolamine. The PC/Sph ratio is about one fifth that of normal. These changes in VLDL lipids are very similar to those occurring in the lipid composition of the atherosclerotic plaques in mammals.

Influence of the osmosis time on the stability of processed cherries (“Vittoria”, “Durone Nero I” and “Starking” cultivars) was studied. The cherries were osmo-dehydrated for two, four, six hours, vacuum packed, pasteurized and then analyzed for ascorbic acid, glucose, fructose and maltose content by HPLC, for pH, total titrimetric acidity, dry matter, color and for organoleptic characteristics, during the process and up to six months of storage. The dehydration of the fruit and the exchange with the osmotic syrup took place chiefly during the first two hours of the process. No substantial differences were noted though, in the cherries, processed at different time, both for chemical and organoleptic characteristics. Color data showed the importance of the variety in order to obtain good products. Thus it was concluded that a two hours’osmodehydration process is suitable to achieve very acceptable products.

The type of sugar in the heating and recovery media affected the rate of inactivation and repair capability of a Chablis strain of Saccharomyces cerevisiae. The rate of heat inactivation decreased with decreasing aw in glucose and fructose but not in sucrose solutions. At any aw the order of susceptibility to inactivation of yeast cells was consistently: fructose, glucose, and sucrose. In fructose, a major proportion of the survivors exhibited sublethal injury. When suspended in solutions containing the various sugars after heating and incubated for up to 18 hr prior to plating, the type of sugar in the solution influenced the ability of cells to repair injury.

Vacuum infusion is used to facilitate the peeling of citrus fruit for the fresh-cut market, giving, as a by-product, a peel soaked with water but quite undamaged. Osmotic dehydration, commonly used to remove part of the water content of fruit before further drying, could increase the stability of the colour pigment and minimize the shrinkage phenomenon. The aim of this research is to apply to orange peels the osmodehydration followed by air-drying in order to obtain a high quality food ingredient both from a nutritional and sensorial aspect. Peels from vacuum infused organic oranges, cv Tarocco and cv Navel, were cut into slices (1x2 cm) and then osmodehydrated at 20 °C in sucrose solution (60% w/w) for different times (1-2-3-4-5-6-24 h), followed by air drying at 80 °C up to a constant weight. Solid gain and water loss of the osmotic process were assessed. Changes of colour and shape, due to processing, were evaluated by image analysis technique. The bitterness sensorial characteristic of powders, obtained from grinding the dried peel, was judged by a panel test. The high solid gain of peels, due to the osmotic step, was attributed to the particular structure of pith, which was able to absorb an elevated amount of sugar solution thanks to its wide intercellular spaces and not turgid cells. The solid gain allowed colour attributes of slices after air dehydration to be maintained. The air drying without pre-treatment, caused a structural collapse of peels which looked wrinkled. This effect was noticeably reduced in pre-osmodehydrated slices with a positive progressive trend in function of osmosis time. Furthermore the solid-liquid exchanges and the consequent sucrose intake had a positive effect on sensorial quality of the dried product, decreasing the characteristic bitter perception.