Lycopene degradation and isomerization in tomato dehydration

Lycopene is an important nutrient, since it appears to provide protection against a broad range of epithelial cancers. Tomatoes and tomato products are the major source of lycopene, and are considered to be an important source of carotenoids in the human diet. Biodegradation of lycopene not only affects the attractive color of the final products, but also their nutritive value. The main cause of lycopene degradation in tomato dehydration is isomerization and oxidation. The objectives of this study were to determine the retention of total lycopene and isomerization in different dehydration methods, and to optimize processing technology for the retention of lycopene biological potency in the tomato products. Experiments were carried out to compare the effect of osmotic treatment, vacuum-drying, air-drying and their combination on the retention of lycopene bioactivity. Firstly a skin treatment was applied to the tomatoes, following an osmotic treatment at 25°C in 65°Brix sucrose solution for 4 h, then vacuum-drying at 55°C for 4–8 h, or air-drying at 95°C for 6–10 h. In the fresh tomato samples, lycopene content is 75.5 μg/100 g on dry weight basis. Lycopene occurs in nature primarily in the more stable all-trans form. A significant increase in the cis-isomers with simultaneous decrease in the all-trans isomers can be observed in the dehydrated tomato samples in the different dehydration methods. The cis-isomers increased with temperature and processing time. In the osmotic treatment, the predominating mechanism is isomerization of lycopene. Since the total lycopene content remained essentially constant, but the distribution of trans- and cis-isomers changed. In the air-drying processing, isomerization and oxidation (autoxidation) as two strong factors affected simultaneously the decrease of total lycopene content, distribution of trans-and cis-isomers, and biological potency. A possible explanation of this result is that sugar enters the tomato matrix and strengthen the binding force on lycopene in the tomato matrix. Osmotic solution (sugar) remaining on the surface layer of the tomato prevents oxygen from penetrating and oxidizing lycopene. The osmotic treatment could reduce lycopene losses in comparison with other dehydration methods.     

Preserving Melons by Osmotic Dehydration in a Ternary System Followed by Air-Drying

In this study, the effect of different osmotic solution concentrations (20–60% w/w of sucrose with 10% w/w NaCl salt), fruit to solution ratios (1:9–1:3), immersion times (0.5–4 h), and temperatures (15–55°C) on the mass transfer kinetics during osmotic dehydration of melons (Curcumis melo L.) in ternary solution namely sucrose–salt–water followed by air-drying were investigated. The effective diffusion coefficients for sucrose and water during osmotic dehydration were determined, assuming osmotic dehydration to be governed by Fickian diffusion. The estimated parameters allowed optimizing the system to reduce total processing time. The optimum treatments were with 50% sucrose and 10% NaCl salt concentration, fruit to solution ratio of 1:4 for 1 h at 45°C. Samples non-treated and pre-treated in optimized conditions were dried in a hot-air dryer at 60°C until equilibrium was achieved after 2.5 h. Pre-treatment reduced the air-drying period in up to 6.8 h.     

Volatile profile of dehydrated cherry tomato: Influences of osmotic pre-treatment and microwave power

Vegetable flavour is a quality characteristic for consumer acceptability. Sun and air are traditionally used for drying tomatoes; however, the optimal combination of techniques such as osmotic dehydration or microwave-assisted air-drying could lead to high quality self-stable products. The aim of this paper was to study the influence of different process variables on the volatile profile of dehydrated cherry tomato halves. The analysed variables were: air-drying temperature (40 and 55 °C), microwave power (0 and 1 W/g) and previous osmotic dehydration with a 55 Brix binary sucrose solution at 30 °C for 120 min (OD1) or ternary solution of 27.5% sucrose + 10% NaCl (w/w) at 40 °C for 60 min (OD2). Twenty major volatile compounds were identified in fresh tomatoes. Among them, 2-isobutylthiazole and 6-methyl-5-hepten-2-one stand out as impact volatile compounds. Dehydration modified the volatile profile, mainly due to the changes induced in some typical fresh-like tomato compounds, but also due to the generation of five new compounds: 1-butanol, 2-methyl-2-butenal, 3-hydroxy-2-butanone, furfural, acetonitrile, related to Maillard reactions, and the catabolism of carotenoids and polyunsaturated fatty acids. Principal component analysis showed the possibility of obtaining dried cherry tomatoes with different volatile profiles, depending on drying conditions.     

Magnetic Resonance Imaging of Strawberry (Fragaria vesca) Slices During Osmotic Dehydration and Air Drying

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 T₂ profiles, water content via M₀ 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.     

Mass transfer evaluation of ultrasonic osmotic dehydration of cherry tomatoes in sucrose and salt solutions

In order to elaborate dehydration and osmotic equilibrium characteristics of cherry tomatoes and to analyse the applicability of Peleg model in prediction of equilibrium moisture content and the methodology of Crank’s solution to Fick’s diffusion law in calculation of effective diffusivity, cherry tomatoes were osmotically treated in ternary solution (water, sucrose and NaCl) with or without ultrasound at 30 °C. Results indicated that, a time cumulative effect of ultrasound occurred about 30 min for water loss (WL), while for sugar gain it happened after 45 min, which made the dehydration efficiency index best at the ultrasonic power of 150 W for 40 min. As a function of salt content, the equilibrium WL followed well the first order exponential decay model, and the equilibrium salt content followed well the second order polynomial. A great relative error (29.13%) between the practical determination and the predicted value indicated that Peleg model was not suitable for prediction of equilibrium moisture content. A great truncation error (865%) occurred when moisture effective diffusivity (6.66 × 10^?9 m² s^?1) was calculated with Crank’s solution to Fick’s diffusion law by letting n = 1 as compared to that (0.77 × 10^?9 m² s^?1) by letting n = 100.     

Use of Ultrasound for Dehydration of Papayas

This work evaluated the production of dehydrated papayas (Carica papaya L.) with low sugar content. The product was obtained applying ultrasonic waves to enhance the loss of sugar from the fruit. To achieve this goal, this paper examined the influence of the ultrasonic pre-treatment before air-drying on dehydration of papaya. Ultrasonic pre-treatment for air-drying of fruits was studied and compared with osmotic dehydration. This study allowed estimate of the effective diffusivity water in the air-drying process for papayas submitted to ultrasonic pretreatment. Results show that the water effective diffusivity increases after application of ultrasound causing a reduction of about 16% in the drying time. During ultrasonic treatment the papayas lost sugar (13.8% in 30 min), so such a pre-treatment stage can be a practical process to produce dried fruits with lower sugar content.     

Image analysis of osmotically dehydrated fruits: melons dehydration in a ternary system

Osmotic dehydration represents a technological alternative to reduce post-harvest losses of fruits. In this work, the osmotic dehydration of a ternary system (water/sugar/salt) was investigated for melon (Curcumis melo L.) dehydration using image analysis. Three kinds of sugars were used to formulate the osmotic solutions: sucrose, glucose and manitol. The process of osmotic dehydration was studied and the effects of the ternary osmotic system on the fruit shrinkage were investigated using image analysis technique. The experimental study allowed estimating the process parameters of the osmotic dehydration. The results showed the advantage of using high sugar and salt concentrations for the osmotic solution, mild temperatures, and the use of the osmotic treatment to reduce the total processing time to dry the fruit. Image analysis enabled to show how far the solid penetrates inside the fruit and to estimate the shrinkage factor of the fruit during the osmotic dehydration.     

Comparative evaluation of the effects of pulsed electric field and freezing on cell membrane permeabilisation and mass transfer during dehydration of red bell peppers

The extent of cell membrane permeabilisation due to high intensity electric field pulses (HELP) varying number of pulses (1–50) using electric field of 2 kV/cm, 400 μs pulse duration and freezing on mass transfer and vitamin C content during osmotic (50° Brix sucrose at 40 °C) and convective air (60 °C, 1 m/s for 5 h) dehydration of red bell peppers was studied. Total pore area due to HELP increased with number of pulses while freezing resulted in total pore area of almost 6 times as greater as the highest value from the HELP process. Higher water loss was observed for all HELP treated than for prefrozen samples while slow freezing provided samples with the highest solids uptake. The correlation coefficient (R²) of linear regression between water loss and solids gain estimated from either total solids or soluble solids measurement ranged from 0.954 to 0.998 suggesting the possibility of using the soluble solids method in evaluating mass transfer kinetics during osmotic dehydration process. Drying rate during convective air-drying was more enhanced by HELP than by freezing. Electrical conductivity of the osmotic solution increased with the degree of permeabilisation to a given medium value after which no further increase in the release of the intracellular ions was observed. Minimal vitamin C depletion was observed immediately after HELP treatment. The order of magnitude of vitamin C retention was untreated>frozen>HELP pretreated samples with 1 pulse>5 pulses>50 pulses>10 pulses>20 pulses after osmotic dehydration. The reduction in vitamin C content of HELP treated samples after convective drying ranged from approximately 11 to 24% while freezing resulted in approximately 24% decrease compared to the untreated samples.     

Dehydrofreezing of pineapple

Dehydrofreezing technique involves one step of partial dehydration before freezing, in order to diminish the tissue damage by removing part of water from vegetable tissue prior to freezing. The objective of the present study was to evaluate the effect of osmotic dehydration and hot air-drying, applied previous to the freezing process, on the end quality of pineapple slices. Quality loss was quantified through drip loss, ascorbic acid content and mechanical properties changes of tissue. Freezing was carried out in a conventional air-blast tunnel at −31.5 ± 2 °C. Mechanical properties of fresh and dehydrated fruit, with and without the later process of freezing, were evaluated through compression tests. Ascorbic acid content was quantified by liquid chromatography. Osmotic dehydration and hot air-drying have the beneficial effect of reducing the time necessary for pineapple samples freezing. The freezing–thawing process affects the values of pineapple samples mechanical properties. Ascorbic acid losses were somewhat greater during the osmotic dehydration than with air dehydration.     

Quality and Nutritional Status of Fresh-Cut Tomato as Affected by Spraying of Delactosed Whey Permeate Compared to Industrial Washing Treatment

The aim of this study was to examine the applicability of delactosed whey permeate (DWP) treatment on preserving the quality and antioxidant attributes of fresh-cut tomato. Tomatoes were treated with 3% DWP by dipping, spraying and a combination of both, stored at 4?°C for 10?days and compared with the industrial standard, chlorine. The combination of dipping and spraying of DWP showed the best results for all the markers tested. The combined treatment of dipping and spraying of DWP significantly lowered total counts (??1.0 log cfu/g), yeast and moulds (??1.2 log cfu/g), inhibited the loss of firmness (25%) and reduced POD activity (15%) of the tomato slices after 10?days compared to the chlorine treatment. Moreover, DWP-treated tomatoes maintained significantly (p?<?0.05) higher levels of vitamin C, total phenols and antioxidant activity (DPPH) than the chlorine-treated samples during storage. Sensory scores confirmed that DWP-treated tomatoes retained better aroma and texture. Also, the appearance and overall acceptability were higher than chlorine-treated tomatoes. Thus DWP treatment has potential to extend the shelf life of fresh-cut tomatoes.     

Effects of brine concentration and temperature on equilibrium distribution coefficients during osmotic dehydration of sardine sheets

Effects of brine concentration (0.15-0.27 gNaCl/g) and temperature (32-38°C) on equilibrium distribution coefficients of sardine sheets were studied during osmotic dehydration. The equilibrium distribution coefficients of water and salt were determined using the mass transfer dynamic. The distribution coefficient for water and salt ranged from 0.5008 to 0.6254 and from 0.5286 to 0.7783, respectively. At a constant brine concentration, distribution coefficient of water decreased and distribution coefficient of salt increased with the increasing temperature. At a constant temperature, distribution coefficients of water and salt decreased with the increase in brine concentration. A multiple linear regression fitted (P=0.001; R²=0.877-0.966) distribution coefficient as a function of brine concentration and temperature.     

CONTROLLED ATMOSPHERE STORAGE AND EDIBLE COATING EFFECTS ON STORAGE LIFE AND QUALITY OF TOMATOES

Tomatoes at pink stage maturities were coated with Semperfresh^TM edible fruit coating which is composed of sucrose esters of fatty acids, sodium carboxymethyl cellulose and mono-diglycerides of fatty acids. One group of coated and uncoated tomatoes were stored at 23 × 2C under air atmosphere, another group was stored at 12C under air atmosphere and third group was stored at 12C, 93–95% RH in a controlled atmosphere (CA) containing 3% CO₂, 3% O₂ and 94% N₂. Samples of tomatoes were analyzed for firmness, weight loss, titratable acidity, pH, soluble solids, sugars, ascorbic acid and lycopene to examine changes in quality during storage. Semperfresh^TM edible fruit coating was found to be significantly effective at both storage temperatures (23 × 2C and 12C) in air to delay changes in firmness, titratable acidity, pH, soluble solids, sugars, ascorbic acid and lycopene. Semperfresh^TM fruit coating reduced fruit weight loss as compared to fruit without coating but the difference between coated and uncoated tomatoes was not significant. Shelf-life of pink tomatoes was increased 3 days at 23 × 2C and 6 days at 12C in air by coating. CA storage delayed compositional changes in tomatoes significantly as compared to air storage of coated and uncoated tomatoes. CA storage also had a significant potential for reducing weight loss and microbial spoilage. Tomatoes were stored 40 days in CA. Coated and uncoated tomatoes exhibited the same results in CA.     

Effect of Maltodextrin,Sodium Chloride,and Liquid Smoke on the Mass Transfer Kinetics and Storage Stability of Osmotically Dehydrated Beef Meat

Osmotic dehydration is a non-thermal process for water removal from foods. The aim of the present study was (i) to investigate the effect of binary (NaCl and water) and ternary (maltodextrin, NaCl, and water) osmotic solutions with or without 0.5% liquid smoke on moisture loss, solids gain, and salt content during osmotic dehydration of beef meat and (ii) to evaluate the microbiological and oxidative stability of the processed meat. Osmotic processing resulted in 8.01–13.15% water loss and 3.53–7.59% solids gain depending on the concentration of the osmotic medium. Liquid smoke did not affect mass transfer phenomena (P > 0.05), except for the treatment with 25% NaCl. The applied models for the estimation of the apparent coefficients demonstrated a good fit with experimental data. The simplified Fick’s equations produced the best results. Osmotic treatment with binary and ternary osmotic solutions reduced total aerobic viable microbial counts (P > 0.05) of meat during storage at 4 °C for 9 days. Liquid smoke did not affect microbial counts, but it was very effective in inhibiting lipid oxidation during storage. The results demonstrate that osmotic dehydration with the addition of liquid smoke could effectively increase the shelf life of beef meat by at least 2 days.     

Colour and flavour changes during osmotic dehydration of fruits

Andes berry (Rubus glaucus Benth.) and tamarillo (Solanum betaceum Cav., dark-red strain) fruit were separately submitted to osmotic dehydration with three different osmotic agents: sucrose (70%), sucrose (70%)-glycerol (65%) 1:1, and ethanol. This process decreased the water activity in the fruits and promoted the transfer of main pigments (anthocyanins) and flavour constituents to the osmotic solutions. Tristimulus colorimetry was applied to qualitatively evaluate the process of obtaining colour- and flavour-enriched osmotic solutions. It was found that after successive DIS (Dewatering–Impregnation–Soaking) cycles, it is advisable to obtain high C_ab colour parameter values, as criteria for the evaluation of osmotic solutions. Based on colour parameters, anthocyanin content, and volatile analysis, the ethanol and sucrose osmotic solutions from Andes berry were selected as promising raw materials for developing natural additives.Industrial relevanceOsmotic dehydration is one of the processes used to reduce or avoid detrimental phenomena in fruit and vegetables without a sensorial and nutritional quality loss. Its economic viability depends on the possibility of reusing the osmotic solution in successive DIS cycles. The present work demonstrates that the osmotic solutions, usually considered waste material of osmotic dehydration, could be used as a source of natural pigments and flavours, furthermore exhibiting antioxidant properties. At a large scale, this finding is most significant because it would render this environmentally friendly process more economical.     

The effect of delactosed whey permeate on phytochemical content of canned tomatoes

The effect of delactosed whey permeate (DWP) treatment on antioxidant and phyto-chemical components of canned Irish plum tomatoes were investigated. Tomatoes were sterilised for 5 min (F₀) at 120 °C and stored for 6 months. The DWP treatment retained significantly (p < 0.05) higher levels of ascorbic acid and lycopene of tomatoes. The antioxidant activity of DWP treated tomatoes was higher (7%) than the control at the end of storage. The firmness in DWP-treated fruits was around 40% higher than that in control. All the parameters decreased significantly (p < 0.05) during storage except lycopene and total phenols. Lycopene content showed no significant change and total phenols increased during storage. The changes in ascorbic acid, antioxidant activity and texture were fitted well to Weibull kinetic models with high coefficients of determination (R²) and low RMSE (root mean sum of squared error). The results clearly indicate that DWP enhanced the retention of antioxidant compounds in tomatoes during storage.     

Acceleration of mass transfer rates in osmotic dehydration of elephant foot yam (Amorphophallus paeoniifolius) applying pulsed-microwave-vacuum

The elephant foot yam slices were processed with combined pulsed-microwave-vacuum osmotic drying. Osmotic dehydration at ambient (28 °C and 45% RH) was carried out using different levels of sucrose concentration (30, 40, 50 and 60% w/w), salt concentration (5, 7.5, 10 and 12.5% w/w) and dehydration time (10, 20, 30, 50, 70, 90 and 120 min). During the osmotic dehydration, pulsed microwave vacuum (15 kPa pressure, 1 W/g power density and 1.853 pulsating ratio) was maintained for 2 min over the sample and solution to enhance the mass transfer. For this purpose, the osmotic dehydration experiments were conducted in the microwave-vacuum cavity. Azuara model predicted the moisture loss and solid gain by elephant foot yam slices during osmosis. It was observed that both the moisture loss and the solid gain increased with increasing concentration of the osmotic solution. The optimum conditions found in the process were 40% w/w sucrose concentration, 6% w/w salt concentration and 70 min osmotic dehydration time, resulting in to 42.80% moisture loss (initial weight) and 14.65% solid gain (initial weight). Further, samples were dried using microwave vacuum dryer up to moisture content of 5–6% d.b. by varying microwave power density (2, 4, 6 and 8 W/g) and pulsating ratio (1.312, 1.625, 1.983 and 2.250). Page model was fitted to the data to study the microwave vacuum drying kinetics. The microwave vacuum drying at 1.625 pulsating ratio with microwave power density 4 W/g yielded a product with the highest overall acceptability score. Guggenheim, Anderson and deBoer (GAB) model was used in the study of the sorption behavior of dehydrated elephant foot yam and shelf life prediction.Industrial relevanceThe production of elephant foot yam in India and South East Asia is comparatively higher than other vegetables. Although, it is nutritious product and good source of energy, food industries are not interested to process elephant foot yam using a time consuming traditional osmotic dehydration process followed by hot air drying. Therefore, present research work was undertaken from industry suggestion to develop accelerated osmotic dehydration process for elephant foot yam using novel pulsed-microwave-vacuum combination followed by finish drying by microwave-vacuum. This research has been carried out to decrease industrial processing time, energy consumption and improving quality of the product. Industry will start adopting this new hybrid process of drying elephant foot yam on large scale.     

Effects of Pseudomonas chlororaphis and gaseous chlorine dioxide on the survival of Salmonella enterica on tomatoes

Control of Salmonella enterica on tomatoes is important for food safety. The aim of this research was to evaluate the survival of Salmonella enterica serovars Montevideo (SM) and Typhimurium (ST) on tomatoes exposed to gaseous chlorine dioxide and Pseudomonas chlororaphis (Pc). Pc was applied to stem scars of tomatoes prior to inoculations with SM and ST. Tomatoes were treated with gaseous ClO₂ at 0.4 mg L^?1 for 2 and 4 h (90% R.H. 13 °C), respectively. At 4 h of ClO₂ treatment, SM and ST populations were reduced to 0.82 and <0.30 log CFU g^?1, respectively. Tomatoes treated with SM and ST had 5.42 and 5.37 log CFU g^?1 of Salmonella. Tomatoes treated with Pc + Salmonella count was 2.59 (treated) and 5.83 log CFU g^?1 (control). Salmonella survival was similar at 2 and 4 h of ClO₂ treatment. Application of ClO₂ and Pc may reduce contamination of tomatoes by Salmonella serovars.     

Ascorbic acid degradation kinetics in tomatoes at different drying conditions

High temperatures and long drying times used in hot air drying can negatively affect the nutritional quality of the final product. It is generally observed that, if ascorbic acid is well retained, other components are also well retained. Hence, ascorbic acid can be taken as an index of nutrient quality of foods. The interest in dried tomato has increased since its use as ingredients for pizza and various vegetable and spicy dishes has became popular. Tomatoes are usually dried in slices or halves, after seeds and parenchyma removal with a resulting large amount of wastes and an important nutrient loss. The objective of this work was to investigate the effects of drying temperatures on ascorbic acid degradation kinetics in caustic-peeled whole tomatoes (with or without osmotic pre-treatment) and in halved and drained tomatoes. The degradation rates were dependent on samples treatment before drying, as well as on drying temperature. Lower degradation rates were observed in osmotically pre-treated whole tomatoes, whereas higher degradation rates occurred in halved tomatoes. Increasing drying temperature led to higher degradation rates.     

Changes in respiration rate and physical properties of strawberries due to osmotic dehydration and storage

The effect of osmotic dehydration on the respiration rate (R) and the mechanical and optical properties of strawberry halves were evaluated throughout six days at 10 °C. Two different dehydration levels (15 and 20 °Brix) were considered, by applying (PVOD) or not (OD) a vacuum pulse and with and without calcium addition. Dehydrated samples showed a faster drop in R than non-treated samples, thus indicating a faster development of senescence. PVOD implied a greater reduction of O₂ consumption. Calcium addition slightly reduced R. Osmotic treatments provoked a decrease in the puncture forces, especially in samples with 20 °Brix, as a consequence of the structural collapse caused by treatments. After storage, calcium addition and PVOD treatments had beneficial effects on the maintenance of the sample texture. Colour of treated strawberries was modified, mainly in the parenchyma zone, when changes in the sample porosity were greater due to the treatment (vacuum impregnation).     

Changes in phenolic profile and antioxidant activity during production of diced tomatoes

Tomatoes and tomato-based products are rich in antioxidants such as carotenoids, vitamin C and polyphenols. The industrial processing of diced tomatoes involves heat treatments in which these antioxidant compounds may be potentially affected. In this study, we evaluate the effect of each separate step in the dice-making process. Three technological processes were investigated: Hot, Cold and Cold treated with calcium salt (CaCl₂). Four stages were monitored in each process: (1) fresh tomatoes; (2) peeled tomatoes; (3) diced tomatoes; and (4) final product after sauce addition. The main tool for minimising or counteracting the eventual processing damage was the strategy of ‘reconstitution’, achieved by adding a sauce rich in seeds and peels with high levels of antioxidants and phenolics to the diced tomatoes. Different analyses were carried out in order to evaluate the effect of each processing step. First, total polyphenols (TP) were evaluated using Folin–Ciocalteau (F–C) assay and antioxidant activity using ABTS⁺ and DPPH assays. Flavonols, flavanones, hydroxycinnamic and phenolic acids were then quantified using liquid chromatography/electrospray ionisation tandem mass spectrometry (HPLC–ESI–MS/MS). The combination of principal component analysis (PCA) and analysis of variance (ANOVA) revealed that each processing step induces alterations in the antioxidant and phenolic profile, and in particular sauce addition and calcium treatment significantly affected the levels of antioxidants and phenolics during the dice-making process.