Firmness Of Tomatoes Research Articles

가시광 및 근적외선 분광기법을 이용한 방울토마토의 내부품질 예측에 관한 연구

Although cherry tomato is one of major vegetables consumed in fresh vegetable market, the quality grading method is mostly dependant on size measurement using drum shape sorting machines. Using Visible/Near-infrared spectroscopy, apparatus to be able to acquire transmittance spectrum data was made and used to estimate firmness, sugar content, and acidity of cherry tomatoes grown at hydroponic and soil culture. Partial least square (PLS) models were performed to predict firmness, sugar content, and acidity for the acquired transmittance spectra. To enhance accuracy of the PLS models, several preprocessing methods were carried out, such as normalization, multiplicative scatter correction (MSC), standard normal variate (SNV), and derivatives, etc. The coefficient of determination () and standard error of prediction (SEP) for the prediction of firmness, sugar, and acidity of cherry tomatoes from green to red ripening stages were 0.859 and 1.899 kgf, with a preprocessing of normalization, 0.790 and with a preprocessing of the 1st derivative of Savitzky Golay, and 0.518 and 0.229% with a preprocessing normalization, respectively.

NONDESTRUCTIVE EXAMINATION OF TOMATO DURING THE COURSE OF SHELF LIFE

A nondestructive ultrasonic method was used to monitor the firmness and sugar content of greenhouse tomatoes (cv. 870) during their shelf life. This method is based on measurement of acoustic wave attenuation in the fruit tissue, by means of ultrasonic probes in contact with the fruit peel. The differences in the acoustic signals transmitted through the tissue of fruits of various degrees of firmness were measured and analyzed. The fruits for measurement were transferred from a greenhouse to a controlled-temperature room, and experiments were carried out at intervals throughout the storage period. The fruits were subjected to nondestructive ultrasonic tests and also to destructive penetration measurements of firmness. The results were analyzed statistically to determine the changing relationships between the ultrasonic attenuation measurements and the destructive measurements, during the course of shelf life. The measured attenuation was found to be significantly decreased and the firmness was obviously found to decrease significantly in the course of shelf life. A linear relationship between the attenuation and the firmness was observed until the end of the softening process. This suggests that this ultrasonic method might be used as a nondestructive means of monitoring the firmness of tomatoes during various stages of storage.

Postharvest Ripening Characterization of Greenhouse Tomatoes

The determination of °Brix, pH, titratable acidity and antioxidant composition such as β-carotene, lycopene, and vitamin C was done in greenhouse “Savoura” tomatoes during maturation. The chromatic values L*, a*, b* were determined at the top surface of the tomato, and its strength-deformation curve was tested with a texturometer. Results pointed out that °Brix and titratable acidity did not change during postharvest, while β-carotene, lycopene, and vitamin C contents increased continuously toward the red stage of tomato. The colour values L*, a*, b*, and ratio a*/b* had a good correlation with the maturity stages. Also, a high correlation between lycopene content and (a*/b*) ratio was found, which was well represented with a second order polynomial function (r2 = 0.95). This equation permits to appropriately estimate lycopene content of tomato as a function of its color, without any chemical analysis. During ripening, tomato texture changed from firm turgid to soft and the puncture deformation degree increased. Tomato firmness and chromatic values had a good correlation, and the lycopene content was a logarithm function of firmness (r2 = 0.81). The strength in puncture test increased linearly with deformation until the bioyield point. The measured force was analyzed as the sum of the compression and the shear forces. The two force coefficients can be considered as tomato properties, independent of the puncture probe. These coefficients were found to decrease during tomato maturation.

Prediction of Color and Firmness Changes in Mature Green Tomato (cv. Momotaro) during Ripening by Cumulative Ethylene Production

This study was conducted to determine which index can be used to estimate the pericarp color development and fruit firmness change of mature green tomatoes (cv. Momotaro) during ripening, to determine the optimum harvest stage of mature green tomatoes. The time courses of the changes in CO2 output rate, cumulative CO2 output, ethylene production rate, cumulative ethylene production, pericarp color and firmness of individual tomatoes harvested at the mature green stage were determined during storage at 25℃. Time course analysis revealed a particular pattern of change in each monitored parameter during the investigation period. Moreover, without the effect of individual sample variations, the changes in the pericarp color and fruit firmness of tomatoes correlated well with cumulative ethylene production. Additionally, the pericarp color development of tomatoes obviously coincided with the period of high ethylene production. On the other hand, fruit firmness with decreasing low ethylene production. Thus, the overall results suggest that the ripening of tomatoes can be predicted based on ethylene production.

Morphology, profile and role of chelate-soluble pectin on tomato properties during ripening

To illustrate the role of chelate-soluble pectin (CSP) on fruit properties, neutral sugar composition and morphology of CSP from two tomato cultivars (‘Dongsheng’ and ‘Geruisi’) at two ripening stages (turning and light-red) were investigated by high-performance liquid chromatography (HPLC) and atomic force microscopy (AFM), respectively. Physicochemical properties and firmness of the tomatoes were determined as well. The percentage of wide CSP chains was reduced and the large CSP polymers were found degraded more with lower firmness during ripening. The proportion of galacturonic acid (GalUA) and rhamnose (Rham) increased during tomato ripening in both cultivars. The proportion of xylose (Xyl) and arabinose (Ara) increased in ‘Dongsheng’ tomatoes while decreased in ‘Geruisi’. The results indicate that the morphology and neutral sugar composition of CSP were closely related with firmness of tomatoes.

EVALUATION OF TOMATO QUALITY DURING STORAGE BY ACOUSTIC IMPULSE RESPONSE

ABSTRACT The aim of this research was to evaluate the ability of acoustic impulse response to monitor “Heatwave” tomato quality during storage. The tomato was excited and the response signal is captured using the film sensors. The results showed that acoustic impulse response parameters (dominant frequency, firmness index and elasticity coefficient) of “Heatwave” tomato decreased with storage time. The dominant frequency, firmness index and elasticity coefficient had no correlation with soluble solids contents or pH, but had a good correlation with compression force and puncture force. There was a better correlation between elasticity coefficient and compression force (or puncture force); hence, elasticity coefficient could be a better index of “Heatwave” tomato firmness. The acoustic impulse response is a potential factor in order to determine the firmness of “Heatwave” tomato. PRACTICAL APPLICATIONS Tomato firmness is an important characteristic because firmness of tomato flesh influences the mouth sensory feel. This results showed that acoustic impulse response parameters (dominant frequency, firmness index and elasticity coefficient) of “Heatwave” tomato decreased with storage time. The dominant frequency, firmness index and elasticity coefficient had not correlation with soluble solids contents or pH, but had a good correlation with compression force and puncture force. There were better correlation between elasticity coefficient and compression force (or puncture force), and hence elasticity coefficient could be a better index of “Heatwave” tomato firmness. The acoustic impulse response is potential to determine the firmness of “Heatwave” tomato.

Measurement of the optical properties of fruits and vegetables using spatially resolved hyperspectral diffuse reflectance imaging technique

This paper reports on the measurement of the optical properties of fresh fruits and vegetables over the visible and short-wave near-infrared region (500–1000 nm) using a spatially resolved steady-state diffuse reflectance technique. A hyperspectral imaging system in line scan mode was used to acquire spatially resolved diffuse reflectance images from the samples of apple (three varieties), peach, pear, kiwifruit, plum, cucumber, zucchini squash, and tomato (at three ripeness stages) over the spectral range of 500–1000 nm. The absorption and reduced scattering coefficients of the samples were determined from the spatially resolved scattering profiles using inverse algorithms for a diffusion theory model. Spectra of the absorption coefficient were featured by major pigments (chlorophyll, anthocyanin, and carotenoid) and water in the samples, whereas spectra of the reduced scattering coefficient generally decreased with the increase of wavelength. Values of the absorption and reduced scattering coefficients varied greatly among the test samples. Large differences in the absorption spectra were observed for the tomatoes of three ripeness stages (green, pink, and red), and their ripeness was correctly classified using the ratio of the absorption coefficient at 675 nm (for chlorophyll) to that at 535 nm (for anthocyanin). Values of the reduced scattering coefficient positively correlated with the firmness of tomatoes at individual wavelengths of 500–1000 nm, with the maximum correlation of 0.66 being obtained at 790 nm. Light penetration depths, defined as the depths at which the incident light was reduced by 99%, were estimated to be between 0.97 and 6.52 cm for the fruit and vegetable samples over the wavelength range of 500–1000 nm; they were influenced by major pigments in the plant tissue. The spatially resolved steady-state diffuse reflectance technique provides a convenient and efficient means for measuring the optical properties of turbid food and agricultural products.

Physicochemical properties of cell wall materials from apple, kiwifruit and tomato

Cell wall materials (CWMs) were isolated from the fruit of ripe apple, kiwifruit and tomato using methods of isolation which maximised the water retaining capacity and viscosity generating properties of the CWMs. Aqueous suspensions of all three CWMs were able to form a gel-like matrix at a concentration of 1%. There was a dramatic enhancement in gel firmness of kiwifruit and tomato following a high shear treatment, but no such effect was apparent with apple CWM. Confocal microscopy showed that the shear-induced increase in viscosity was accompanied by fragmentation of the CWMs of kiwifruit and tomato which increased the available surface area for particle–particle and/or particle–solvent interaction. The viscosity of kiwifruit and tomato CWM dispersions was reduced in the presence of electrolytes indicating an important role for the double electrical layer in the gelling properties of the CWMs. The viscosifying properties of apple CWM were however independent of both shear and added electrolyte. This was attributed to the fact that CWM from apple resisted breakup under high shear. The greater connective integrity of the apple cell walls compared to that of kiwifruit and tomato is discussed in relation to differences in ripening induced changes to the pectic polysaccharides of the cell walls.

Nondestructive ultrasonic monitoring of tomato quality during shelf-life storage

A nondestructive ultrasonic method was used to monitor the firmness and sugar content of greenhouse tomatoes (cv. 870) during their shelf-life. This method is based on measurement of acoustic wave attenuation in the fruit tissue, by means of ultrasonic probes in contact with the fruit peel. The fruit for measurement were transferred from the greenhouse to a controlled-temperature room, and were subjected to nondestructive ultrasonic tests and also to destructive penetration measurements of firmness. The results were analyzed statistically to determine the changing relationships between the ultrasonic attenuation measurements and the destructive measurements, during the shelf-life. The differences in the acoustic signals transmitted through the tissue of fruit of various degrees of firmness were measured and analyzed as well. The measured attenuation and the firmness were found to decrease significantly during shelf-life. A linear relationship between the attenuation and the firmness was observed until the end of the softening process. This suggests that this ultrasonic method might be used as a nondestructive means of monitoring the firmness of tomatoes during various stages of storage.

The firmness of stored tomatoes (cv. Tradiro). 1. Kinetic and near infrared models to describe firmness and moisture loss

The aim of this research was to develop practical applicable models capable to describe and to predict the temperature dependent firmness and moisture loss of tomatoes during storage. To gather the required information to develop these models batches of 20 tomatoes (cv. Tradiro), each harvested at two maturity stages, were stored at four different temperatures (3, 12, 20 and 25°C) up to four weeks. One temperature (3°C) is known to cause chilling injury to the product. During storage at these temperatures firmness loss, moisture loss and near infrared spectra were measured on individual tomatoes at regular intervals. The decrease in firmness was measured non-destructively by flat-plate compression, moisture loss was measured by weight loss. The information on firmness and moisture loss was used to develop two types of models. The first type of model was based on fundamental laws of chemical kinetics, assuming plausible chemical reaction mechanisms. These reaction mechanisms describe the processes underlying either firmness, or moisture loss. From these reaction mechanisms a set of differential equations was derived and solved at constant temperature. For these kinetic models, both for firmness, and moisture loss, two independent processes were assumed. One process is mainly expressed at low (<10°C) temperatures and relates to chilling injury; its contribution increases at decreasing temperatures. The other process relates to the normally observed fruit softening and moisture loss process during storage. Throughout the entire temperature range its contribution increases at increasing temperature. The second type of model was based on Partial Least Squares Regression analysis, relating the data on firmness to the near infrared spectral data. Due to their difference in nature the kinetic models describe the firmness change and moisture loss in time at constant external condition. The regression model describes the actual firmness of a homogeneous batch of tomatoes.

The firmness of stored tomatoes (cv. Tradiro). 2. Kinetic and Near Infrared models to describe pectin degrading enzymes and firmness loss

Tomatoes (cv. Tradiro), harvested at two maturity stages, were stored at four different temperatures during up to four weeks. The lowest storage temperature was known to cause chilling injury, the three other temperatures were regarded save. During storage Near Infrared spectra of intact tomatoes were recorded and samples were taken at regular time intervals to determine the activities of the pectolytic enzymes polygalacturonase, pectin methyl esterase and β-galactosidase. The maturity stage of the tomatoes at harvest, followed by storage at the four different temperatures affects the activities of these enzymes. To describe the change in activity of these enzymes kinetic models were built based on fundamental laws of chemical kinetics using assumed, but plausible reaction mechanisms. For the models developed, a fixed and a variable enzyme activity were observed for these three enzymes. For polygalacturonase, this fixed amount of enzyme activity was dependent on maturity stage at harvest. For pectin methyl esterase and β-galactosidase the maturity at harvest had almost no effect on this fixed amount of enzyme activity. The variable part of the enzyme activity could either increase in time (polygalacturonase), followed by denaturation (β-galactosidase), or only decay in time (pectin methyl esterase). For the activity of polygalacturonase, a self-initiated, autocatalytic production of this enzyme was assumed. β-Galactosidase was formed, but inactivated in time. Pectin methyl esterase activity decayed exponentially in time.The models for polygalacturonase and β-galactosidase were integrated into the previously developed model for the firmness loss of tomatoes during storage [Van Dijk, C., Boeriu, C., Peter, F., Stolle-Smits, T., & Tijskens, L. M. M. (2005). The firmness of stored tomatoes (cv. Tradiro). 1. Kinetic and Near Infrared models to describe firmness and moisture loss. Journal of Food Engineering, in press]. It was concluded that any cell wall degrading enzyme, which activity remains within a certain bandwidth, can be integrated into the firmness model to explain the observed firmness decay.Based on Near Infrared spectroscopy, a statistical significant relation was only observed between the polygalacturonase activity and the Near Infrared spectra of intact tomatoes. It is argued that the consequences of the performed polygalacturonase activity are reflected in this relation rather than the amount of this enzyme.Since mutual statistical significant relations exist between Near Infrared spectra, polygalacturonase activity and the tomato firmness it seems reasonable to ascribe a significant role of this enzyme to the firmness decay.

Inheritance of Elastic and Viscoelastic Components of Tomato Firmness Derived from Intra- and Interspecific Genetic Backgrounds

Fruit firmness is a key quality component of tomatoes (Lycopersicon esculentum Mill.) for fresh-market and processed product applications. We characterized inheritance of firmness in processing tomato germplasm developed from interspecific L. esculentum Mill. × L. cheesmanii f. minor (Hook. f.) C.H. Mull. and intraspecific L. esculentum crosses. Although firmness is a key quality attribute of tomato, there is no standard method for measuring it. We measured the elastic portion of firmness by compression (compression Fmax) and puncture (puncture Fmax), and the viscoelastic portion by force-relaxation. The experimental design incorporated six genotypes in a complete 6 × 6 diallel. Compression Fmax and force measurements recorded at 0.5, 1.0, 5.0, and 10.0 seconds of relaxation were strongly related to each other, while relaxation parameters (A, B, C) describing relaxation curve shape were generally independent. Compression Fmax, relaxation curve parameter A, and puncture Fmax were significantly different among hybrids. Significant differences between Maryland and Ohio environments were evident for compression Fmax and relaxation curve parameter A. The patterns of firmness means differed among firmness measurement methods, namely for compression Fmax and puncture Fmax, indicating that they measure different aspects of tomato fruit firmness. Soft-fruited parents generally exerted a negative effect on compression Fmax, whereas firm-fruited parents most often exerted a positive effect on compression Fmax. The force required for fruit compression best approximated subjective assessment of fruit firmness. Force required for fruit puncture was subject to a significant environmental × hybrid influence in the genotypes evaluated. Shape of the force relaxation curve (i.e., parameter A) was not predictive of relative fruit firmness. General combining ability (GCA) and specific combining ability were both significant with GCA being the principal source of genetic variation. In agreement with combining ability estimates, narrow-sense heritability estimates for compression Fmax and puncture Fmax were relatively high.

Modelling of Mooney viscosity relaxation in natural rubber

Better assessment of natural rubber (NR) quality and processability, through the identification of new attributes, is still a major challenge. With this scope, 12 model samples of natural polyisoprene and two of synthetic polyisoprene were characterized in terms of Mooney torque relaxation, using the standardized ISO289 method (ML(1+4) 100, explained later in the Section 1). The main purpose of this study was to identify a model that gave a better fit for the experimental decay of Mooney torque over time (ML( t)=f( t)) than the usual power law model used before ( Y= at − b , [G.M. Bristow, A.G. Sears, The use of novel parameters in the assessment of natural rubber processability, NR Technol. 18 (1987); H.G. Burhin, W. Spreutels, J.M. Campbell, MV2000 Mooney viscometer: Mooney relaxation measurements on raw polymers and compounded rubber stocks, Kautsch. Gummi Kunstst. 43 (1990) 431]). The results showed that a generalized Maxwell model, and the Wu–Abbott empirical model ( Y = 1 − a Ln ( t ) − ( b t / ( c + t ) ) ) [T. Wu, J.A. Abbott, Firmness and force relaxation characteristics of tomatoes stored intact or as slices, Postharvest Biol. Technol. 24 (2002) 59–68], recently used for describing stress relaxation of tomato flesh, allowed a better description of the relaxation curve for the samples studied than the power law or stretched exponential traditionally used. Moreover, the total relaxation time ( τ m) given by the generalized Maxwell model showed good correlation with the total gel content of the samples studied.

Effects of storage temperature and fruit ripening on firmness of fresh cut tomatoes

Tomato fruit (cultivar Belissimo) were harvested at three different stages of ripening, sliced and stored at at 2, 5, 8, 12 and 16 °C. Firmness was measured as the force necessary to cause a deformation of 3 mm, in the outer and the radial pericarp, daily or every two days, depending on the combination of stage of ripening and temperature. For constructing a model, firmness was considered to be built up by a variable part (e.g. pectin based firmness) that changes according to a first order reaction mechanism and a fixed part (e.g. cellulose or structure based firmness) that is invariable under the circumstances under study. The firmness of the tomato slices decreased exponentially during storage, with a reference rate constant of 0.0975 ± 0.0183 J/mol/K for the outer pericarp and 0.0712 ± 0.0328 J/mol/K for the radial pericarp and energy of activation of 87.5 and 94.8 kJ/mol, respectively for outer and radial pericarp. The parameters of the model were estimated using multiple variate non-linear regression analysis with time, temperature and stage of ripening of the fruit at harvest simultaneously as explanatory variables. To combine the information on firmness behaviour during the preharvest and the postharvest period at different temperatures, it was assumed that the process of firmness loss during ripening was the same whether the fruit ripened on the plant or off-vine. So, the initial firmness at the postharvest period depends on the time the tomatoes were allowed to ripen on the plant (stage of ripening). The statistical analysis of the mean values of firmness provided a percentage variance which accounted for 92% and 72% for outer and radial pericarp, respectively. Using a fundamental approach to build the reported model and using all available data and information made it possible to describe and simulate the firmness behaviour of tomato slices as a function of the stage of ripening and the applied storage temperature.

Heritability Patterns of Elastic and Viscoelastic Components of Tomato Firmness Derived from Intra- and Interspecific Genetic Backgrounds

Tomato fruit firmness is a key quality component of tomatoes produced for processing applications. Fruit firmness is generally considered a quantitatively inherited trait. Pericarp firmness of modern tomato cultivars is believed to be derived from a fairly narrow genetic background and is the result of the cumulative effort of numerous breeders over many years. Despite inferior phenotypes, wild species contain loci that can substantially increase tomato fruit quality. In the current study, inheritance of fruit firmness in firm and ultra-firm processing tomato germplasm developed from transgressive segregants of interspecific Lycopersicon esculentum × L. hirsutum and intraspecific L. esculentum crosses was characterized. Large-fruited breeding lines that varied in fruit firmness from soft to firm were identified for genetic analyses. A six-parent diallel of these advanced breeding lines was developed for field trials over multiple locations. Fruit firmness in the resulting 36 lines was determined by measuring fruit elastic properties during fruit puncture and compression. Following loading for compression, stress relaxation was recorded for 15 s. A three-parameter model was used to fit the relaxation curves. There was little correlation between firmness (maximum force) and the three relaxation parameters, i.e., firmness measured the elastic component and the relaxation parameters measured the viscous portions of the texture. General and specific combining ability for firmness derived from the respective genetic backgrounds was determined. Genetic variance components for fruit firmness were estimated using a diallel analysis and narrow sense heritability was measured using parent-offspring regression.

Combined effects of hot water treatment (HWT) and modified atmosphere packaging (MAP) on quality of tomatoes

AbstractEffects of hot water treatment (HWT) and modified atmosphere packaging (MAP) on quality of tomatoes were studied. Prior to packaging with low‐density polyethylene (LDPE) film (0.02 mm in thickness), tomatoes were immersed in hot water (42.5°C) for 30 min. Control tomatoes were not treated and were stored for 2 weeks at 10°C and then for 3 days at 20°C without packaging. Steady states of O2 and CO2 concentrations inside the package were about 5 and 8%, respectively, and were reached after 6 and 4 days of storage, respectively. MAP reduced weight loss of tomatoes to about 41% of that of unpackaged fruit during a 2‐week storage period. The use of a combination of HWT and MAP reduced weight loss and decay, inhibited color development and maintained firmness of tomatoes but had no effect on soluble solids content or titratable acidity. HWT slightly reduced mold growth of tomatoes stored in MAP. Packaging of control fruit in MAP resulted in stimulation of mold growth around the stem end of the fruit after about 1 week of storage and also resulted in cracking and decay. HWT could be used as disinfectant for tomatoes prior to storage in MAP in order to reduce microbial growth, cracking and decay that may be caused by excessive water vapor inside the package. Copyright © 2003 John Wiley &amp; Sons, Ltd.

圧縮空気の吹き付けによって起こるミニトマト表面の変位に基づいた硬度の測定

A method for measuring the firmness of cherry tomatoes based on the displacement of their surface caused by the spraying of compressed air was studied. The main results were as follows : 1) If the air pressure, the inner diameter of the nozzle for spraying the compressed air, and the distance between the tip of the nozzle and the fruit surface were given suitable values, and if the fruit was secured so that it would not shake, the surface of the fruit would be only slightly deformed, and the displacement of the fruit surface could be measured precisely ; 2) The coefficient of correlation between the measurements obtained by this method and measurements obtained by a commercial fruit firmness meter was about -0. 95 ; and 3) When the displacement was calculated from the value that was measured by a laser displacement sensor, 0 mV was the optimal standard value. Thus, it appears that this method can be used to measure the firmness of cherry tomatoes.

Influence of hydroxypropyl methylcellulose edible coating on fresh-keeping and storability of tomato.

The effect of application of cellulose-based edible coating, hydroxypropyl methylcellulose (HPMC) to mature-green tomatoes on the firmness and color was investigated. Tomatoes were stored at 20 degrees C for up to 18 days. Firmness decreased as storage time increased in all treatments. However, application of HPMC edible coating delayed softening of tomatoes during 18 days of storage at 20 degrees C. At days 7, 13 and 18, the firmness of tomatoes coated with HPMC was significantly (P < or = 0.05) greater than the firmness of uncoated tomatoes. The study also confirmed that HPMC coatings could significantly (P < or = 0.05) delay the changes in color of tomatoes stored at 20 degrees C. The ripening of tomatoes from the pink stage to the red stage was successfully retarded. HPMC coating could extend the shelf life of fresh tomatoes. The retardation of the rate of loss of firmness could reduce the economic loss that would result from spoilage by mechanical injury during transportation of tomatoes.

Influence of hydroxypropyl methylcellulose edible coating on fresh-keeping and storability of tomato.

The effect of application of cellulose-based edible coating, hydroxypropyl methylcellulose (HPMC) to mature-green tomatoes on the firmness and color was investigated. Tomatoes were stored at 20°C for up to 18 days. Firmness decreased as storage time increased in all treatments. However, application of HPMC edible coating delayed softening of tomatoes during 18 days of storage at 20°C. At days 7, 13 and 18, the firmness of tomatoes coated with HPMC was significantly (P≦0.05) greater than the firmness of uncoated tomatoes. The study also confirmed that HPMC coatings could significantly (P≦0.05) delay the changes in color of tomatoes stored at 20°C. The ripening of tomatoes from the pink stage to the red stage was successfully retarded. HPMC coating could extend the shelf life of fresh tomatoes. The retardation of the rate of loss of firmness could reduce the economic loss that would result from spoilage by mechanical injury during transportation of tomatoes.

Firmness and force relaxation characteristics of tomatoes stored intact or as slices

Firmness is an important aspect of the quality of fresh tomatoes. Its measurement is necessary for quality control, as well as for postharvest studies to develop procedures for preparation and handling of fresh-cut tomato slices. This study had two objectives, to determine how initial ripeness and cutting affect the textural changes in tomato tissue during storage and to develop a method for measuring textural attributes of tomato slices. Firmness and force relaxation characteristics were compared for tomato flesh harvested at six maturity stages and stored intact or as slices for 0–20 days. Measurements were made at three sites in the outer pericarp and three in columellar tissue on 7-mm thick transverse slices. Following loading, stress relaxation was recorded for 10 s. A 4-mm cylindrical probe provided more consistent firmness measurements (lower% CV) than a 6.4-mm spherical probe at harvest, and distances of 3 mm provided more consistent results than 1 mm. Therefore, stored tomato samples were tested only with the 4-mm cylindrical probe and distance of 3 mm. Fmax (maximum force) of freshly harvested tomatoes ranged from 15 to 2 N for mature green and red tomatoes, respectively. Fmax was closely related to loading energy (area), slope, and yield force; i.e. all four parameters measured elastic behavior. Fmax also was related (r 2 = 0.77–0.97) to forces at specific relaxation times. Tomatoes stored intact generally had lower CVs than those sliced before storage, although there was little difference in average firmness (Fmax) between the two at a given storage time for a given initial ripeness. A three-parameter model was developed to fit the relaxation curves: Y = 1− A ln(1 + t) − Bt/(C + t) where t is relaxation time. There was little correlation between Fmax and the three relaxation parameters (r 2 = 0–0.33), i.e. the relaxation parameters measured a different physical property, presumably viscoelasticity. The responses of the relaxation parameters over storage time were dependent on the initial maturity of the tomatoes; but values usually differed significantly between tomatoes stored intact or sliced, with tomatoes sliced before storage generally having higher values, which we interpret as having lower viscoelasticity. Published by Elsevier Science B.V.