Linear viscoelasticity of tomato sauce products: influence of previous tomato paste processing

Tomato paste is used as an ingredient for the manufacture of tomato sauce products. This work deals with the influence that some tomato paste processing variables (finisher screen opening and breaking temperature) and tomato variety exert on the linear viscoelastic properties of tomato sauce products. Four tomato varieties (two commercial varieties, one with a lower content of polygalacturonase enzyme, and one with a low content in pectin methylesterase enzyme) have therefore been used. Dynamic viscoelastic tests and particle size distribution (PSD) measurements have been carried out. From the experimental results obtained, we may conclude that the dependence of the linear viscoelastic properties of tomato sauce on the above-mentioned variables is very complex. Nevertheless, the evolution of the viscoelastic characteristics of these products is mainly related to their mean volume diameter and tomato paste water insoluble solids content (WIS). This solid content is mainly controlled by tomato variety and tomato paste processing conditions.     

Rheological Properties of Tomato Paste: Influence of the Addition of Tomato Slurry

ABSTRACT: This article deals with the influence that the addition of tomato slurry into tomato juice exerts on the viscous flow and linear viscoelastic behavior of the final tomato paste. With this aim, 5 tomato paste samples, manufactured at industrial scale, have been studied. Three breaking temperatures and 2 different screen sizes were used to prepare 4 regular tomato paste samples. Moreover, a tomato paste sample with addition of "treated tomato slurry" was manufactured using a breaking temperature of 80 °C and a sieve screen size of 1.2 mm. The results obtained suggest that the addition of treated tomato slurry may be of great interest for tomato paste production.     

Non-linear viscoelasticity modeling of tomato paste products

This paper deals with the characterization and modeling of the non-linear rheological properties of tomato paste samples manufactured under different conditions (sieve pore size and breaking temperature). With this aim, flow measurements, dynamic linear viscoelastic and linear and non-linear stress relaxation tests have been carried out on the above-mentioned tomato paste samples. Different geometries with smooth and serrated surfaces have been used to optimize the viscous flow measurements and avoid wall-depletion phenomena. The viscous flow properties of tomato paste samples depend on water insoluble solids (WIS) content and particle size, which may be highly influenced by processing conditions. In general, viscosity follows a power-law relationship with tomato paste water insoluble content and particle diameter. A factorable non-linear viscoelasticity model, the Wagner integral equation, predicts the non-linear rheological response of these products under shear fairly well. The time-dependent part of this model is described by a continuous linear relaxation spectrum, calculated from regularization techniques. The use of the Soskey–Winter damping function provides the best predictions of the viscous flow curves.     

Factors Influencing Serum Separation of Tomato Ketchup

The effect of tomato cultivar, breaking procedure, starting tomato paste concentration, reconstituted paste, homogenization treatment, percent total and water insoluble solids, and pH on serum separation of tomato ketchup was investigated. Homogenization, as well as increasing the total and/or the water insoluble solids of the ketchup reduced separation. Increasing the total solids of the starting tomato paste decreased the rate of separation, but increased the final amount of serum loss from the resulting ketchup. Among tomato cultivars and breaking procedures included in this study, the Peto 98 cultivar (high water insoluble solids content) and the medium break procedure (at 107.2°C after a 10 min hold at room temperature) gave ketchups with the least serum separation.     

Effect of mechanical and thermal treatments on the microstructure and rheological properties of carrot,broccoli and tomato dispersions

BACKGROUND: The food industry has shown an increased interest in the manufacture of healthier and more natural food products. By tailored processing fruit and vegetables can be used as structurants thus reducing artificial gums and stabilisers. The effect of different thermal and mechanical treatments, including high‐pressure homogenisation, on the microstructural and rheological properties of carrot, broccoli and tomato dispersions was studied. As part of the rheological characterisation small oscillatory deformation as well as shear flow measurements were performed. RESULTS: Carrot and broccoli showed a different behaviour from tomato under the conditions studied. Changing the order of thermal and mechanical treatment led to microstructures with different flow properties. The resulting microstructures differed in the manner of cell wall separation: either breaking across the cell walls or through the middle lamella. High‐pressure homogenisation decreased the viscosity of carrot and broccoli dispersions, while it increased the viscosity of tomato. Cryo‐scanning electron microscopy showed that the cell walls of carrot and broccoli remained as compact structures after homogenisation whereas tomato cell walls were considerably swollen. CONCLUSIONS: Based on the type of vegetable, the different processes applied led to microstructures with different rheological properties. This study shows that particle size distribution, morphology and phase volume are important parameters to explain the complex relationship between rheology and microstructure for these types of systems. Copyright © 2010 Society of Chemical Industry     

Color compensation in nitrite-reduced meat batters incorporating paprika or tomato paste

BACKGROUND: Nitrite is a key ingredient the manufacture of meat products, forming a stable pink color characteristic of cured products, retarding the development of rancidity and off‐odors and flavors during storage, and preventing microbial growth. The negative aspects of nitrite and the demands for healthy foods result in the need to reduce nitrite in cured meat products. Paprika or tomato has been employed as natural pigments in meat products. The objective of this work was to determine the effect of incorporating paprika powder or tomato paste on the texture, rancidity and instrumental and sensory color compensation in nitrite‐reduced meat batters. RESULTS: Addition of tomato paste improved moisture content, resulting in harder but less cohesive samples as compared to control and paprika‐containing meat batters. Color characteristics of reduced nitrite samples obtained higher a* red coloration (8.9 for paprika and 7.7–8.0 for tomato paste), as compared to control samples (5.65). Instrumental color was low in control samples, with high values for tomato paste and paprika samples. Nonetheless, tomato paste used to compensate color in nitrite‐reduced meat batters was ranked closer to the control sample in sensory evaluation. CONCLUSION: Color characteristics—instrumental and sensory—in these kinds of meat products were enhanced by the addition of 2.5–3.0% of tomato paste, presenting results close to the non‐reduced nitrite control. Similarly, antioxidant components of tomato paste or paprika reduced lipid oxidation. Nitrite reduction from 150 to 100 ppm could be achieved employing tomato paste as a natural pigment to improve color and texture. Copyright © 2011 Society of Chemical Industry     

Chemical characterization of tomato pomace

Tomato‐processing by‐product, also known as tomato pomace, consists of peel and seeds and represents around 4% of the fruit weight. If these wastes remain unused, they not only add to the disposal problem but also aggravate environmental pollution. The aim of this paper is to evaluate the chemical composition of tomato pomace collected at different steps during industrial processing in order to assess the quality of this by‐product. Twenty‐one tomato pomace samples were considered for analysis. Samples corresponded to different steps during tomato processing for paste: seven after pulper, five after finisher, six before turbopress and three after turbopress. Samples were analyzed for moisture content, total and soluble sugars, protein, fat, soluble and total fiber, as well as mineral content. From the results obtained we can conclude that tomato pomace composition (in dry weight basis) is as follows: 59.03% fiber, 25.73% total sugars, 19.27% protein, 7.55% pectins, 5.85% total fat and 3.92% minerals. Copyright © 2006 Society of Chemical Industry     

Effect of Break Temperature on Rheological Properties and Microstructure of Tomato Juices and Pastes

The rheological properties and microstructure of canned juices and pastes made from four tomato cultivars at three breaking temperatures of 85°, 96° and 107°C were studied. The apparent viscosities of tomato juices and pastes at a constant shear rate vary with cultivars and processing conditions. The hot break process produced a high viscosity product. The microstructure of tomato pastes and juices were related to their rheology. The microstructure of tomato juice and paste also vary with processing conditions.     

Enzyme inactivation of tomato juice by ohmic heating and its effects on physico‐chemical characteristics of concentrated tomato paste

Fresh juice of fully ripe tomato was subjected to ohmic heat (OH) treatment (90°C for 1 min) and the effectiveness of treatment was compared with conventional hot break (CT) treatment (90°C for 5 min). PG (Polygalacturonase) and PME (Pectin methyl esterase) enzyme inactivation achieved by the OH (1 min.) was similar as compared to CT of 5 min. During the kinetic analysis it was observed that the inactivation of PME & PG enzyme and degradation of ascorbic acid followed first order trend in ohmic as well as conventional treatment of tomato juice, however total color change (DE) was found to follow least‐squares non‐linear parameter algorithm behavior. Thermal treatments leads to the increased release of phyto‐chemicals from the matrix which results in a significant (p<0.01) increase in lycopene content during the early phases of the treatments. The Paste (28±0.5 °Brix) obtained after pre‐treatment was analyzed for lycopene, ascorbic acid content and apparent viscosity and color. OH Paste was found more viscous than CT treatment with maximum viscosity of 2.33×103 mPa‐s. The color of OH treated paste was bright red as compared to CT treatment, however the lycopene and ascorbic acid content of paste were found similar in OH and CT. Based on results of present study it is concluded that the ohmic treatment may be applied as an efficient alternative to the conventional method of enzyme inactivation in tomato juice.     

Evaluation of heat and oxidative damage during storage of processed tomato products. I. Study of heat damage indices

The evolution of heat damage during storage of tomato pulp, puree and paste was studied by accelerated aging tests. Heat damage indices—5‐hydroxymethyl‐2‐furfural (HMF), furosine and colour changes (ΔE)—were evaluated for tomato products stored at 30, 40 and 50 °C for up to 90 days. Furosine and ΔE values increased following pseudo‐zero‐order kinetics, and the higher the solid content of the products, the higher were the rate constant values. HMF formation followed pseudo‐first‐order kinetics in tomato pulp and pseudo‐zero‐order kinetics in puree and paste samples. Data show that heat damage reactions in tomato products proceed even at room temperature, and the kinetic model provided can be used to predict changes occurring during shelf‐life. © 2002 Society of Chemical Industry     

Analysis of cell-wall pectin from hot and cold break tomato preparations

The initial processing of tomatoes includes a break step, which involves rapid heating of the freshly chopped tomatoes to >90 °C for hot break, or 60–77 °C for cold break. It is believed that pectolytic enzyme deactivation is the key element in the hot break step; therefore the pectin content of the different products should be qualitatively distinct. There are two general sources of pectin in a tomato fruit: the middle lamella which is rich in homogalacturonan, and the cell-wall. In this study, a 0-min or 24-min hold time (room temperature) for the chopped tomatoes preceded the break step to replicate hot and cold break, respectively, with minimum variation in the processing. The cell-wall pectin was then isolated and analyzed for the carbohydrate composition, degree of polymerization, and degree of esterification. The results showed no observable differences in pectin isolated from the two preparations, indicating that there is no significant pectolytic activity in the cell wall during the 24 min hold time; thus, the pectolytic enzymes probably act on the lower ester, middle lamella pectin in cold break products.     

Effect of UV-LED irradiation processing on pectolytic activity and quality in tomato (Solanum lycopersicum) juice

The aim of this research was to analyze pectolytic activities (pectinmethylesterase “PME” and polygalacturonase “PG”) and physical qualities in tomato juice treated by UV-LED, Hot Break (HB), and Cold Break (CB) processing. Tomato juice treated by UV-LED (117 mJ/cm²) obtained a residual PME activity similar to that of CB, and tomato juice treated by UV-LED (351 mJ / cm²) had a residual PME activity 28.3% lower than HB (p < 0.05). The effect of UV-LED on PG activity was similar to HB and 49% lower than CB (p < 0.05). Furthermore, UV-LED processing caused a decrease in pH and total acidity and a significant increase in total lycopene content. Antioxidant activity and viscosity for UV-LED processing were similar to CB, total polyphenol content and °Brix were similar to HB (p > 0.05). Therefore, this study provides a promising application of UV-LED technology for controlling enzymatic activity in tomato juice, and an alternative to heat treatment.Industrial relevanceNowadays, the tomato industry uses heat treatments to inactivate pectolytic enzymes. UV-LED technology could have an industrial appreciation, as it was efficient in decrease the activity of these enzymes, in addition, preserved and increased some bioactive compounds. Therfore, it is proposed as an efficient method for processing fruit and vegetable juices. Nevertheless, further studies are needed to clarify the effect of this technology on pectolytic enzymes and quality parameters in liquid fruit and vegetable foods.     

Evaluation of heat and oxidative damage during storage of processed tomato products. II. Study of oxidative damage indices

Tomato products (pulp, puree and paste) submitted to accelerated aging (30, 40 and 50 °C for 3 months) were studied to evaluate variations in the kinetics of the degradation of antioxidants and antioxidant activity. The carotenoids lycopene and β‐carotene, ascorbic acid, rutin and total phenolics were analysed. The antioxidant activity was measured using (a) the xanthine oxidase (XOD)/xanthine system, which generates superoxide radicals and hydrogen peroxide, and (b) the linoleic acid/CuSO₄ system, which promotes lipid peroxidation. The ascorbic acid content decreased even at 30 °C, following pseudo‐first‐order kinetics, with an activation energy of 105 200 J mol^?1 for tomato pulp and 23 600 J mol^?1 for tomato paste. The lower the initial ascorbic acid content, the higher was the degradation rate. Variations in phenolic compounds occurred at 40 °C and higher, following pseudo‐zero order kinetics. The antioxidant activity of the hydrophilic fraction of the tomato products depended on both antioxidant degradation and the Maillard reaction and could not be described by a kinetic model. The β‐carotene content decreased even at 30 °C, whereas the lycopene content was stable in all samples. The antioxidant activity of the lipophilic fraction of the tomato products decreased following pseudo‐first order kinetics, with an activation energy of 22 200 J mol^?1 for tomato pulp and 20 200 J mol^?1 for tomato paste. It is concluded that significant ‘oxidative damage’ can occur in tomato products during their commercial shelf‐life. Copyright © 2003 Society of Chemical Industry     

Effects of industrial tomato paste processing on ascorbic acid, flavonoids and carotenoids and their stability over one-year storage

BACKGROUND : The effects of industrial tomato paste processing and long‐term (12 months) ambient storage on the content and stability of quercetin, kaempferol, ascorbic acid (AA), dehydroascorbic acid (DHAA), β‐carotene and lycopene were evaluated in a commercially produced tomato paste. RESULTS : The initial thermal treatment (hot break; 93 °C for 5 min) resulted in significant reductions in quercetin (54%), kaempferol (61%), AA (63%) and β‐carotene (30%), whereas subsequent processing steps (e.g. evaporation and sterilization) did not result in marked changes in these compounds. Lycopene was stable during hot break but decreased by 20% through evaporation and sterilization. The ratio of DHAA:vitamin C increased during hot break to 23%, whereas the ratio of DHAA:vitamin C remained relatively low in subsequent processing steps, indicating that AA was not oxidized. AA decreased with prolonged storage, with only 13% remaining at 12 months. The carotenoids and quercetin remained stable through 12 months of ambient storage. CONCLUSIONS : Tomato pomace contained significant amounts of carotenoids and flavonoids, indicating that it may be an underutilized processing byproduct. Copyright © 2011 Society of Chemical Industry     

Volatile compounds and changes in flavour‐related enzymes during cold storage of high‐intensity pulsed electric field‐ and heat‐processed tomato juices

BACKGROUND: The effects of high‐intensity pulsed electric field (HIPEF) processing (35 kV cm^?1 for 1500 µs, using 4 µs bipolar pulses at 100 Hz) on the production of volatile compounds and flavour‐related enzymes in tomato juice were investigated and compared with those of thermal processing (90 °C for 30 or 60 s). RESULTS: Tomato juice treated by HIPEF showed lower residual lipoxygenase (LOX) activity (70.2%) than juice heated at 90 °C for 60 s (80.1%) or 30 s (93.2%). In contrast, hydroperoxide lyase (HPL) was almost completely inactivated when the juice was subjected to 90 °C for 60 s, whereas roughly 50% of the control tomato juice was depleted after HIPEF treatment or thermal processing at 90 °C for 30 s. A slight decrease was observed in the initial LOX activity of treated and untreated samples during storage, whereas initial HPL activity was strongly affected over time. CONCLUSION: HIPEF‐treated juice exhibited higher levels of compounds contributing to tomato aroma than untreated and heat‐treated juices throughout storage. Thus HIPEF processing can preserve flavour quality and stability of tomato juice compared with conventional thermal treatments. Copyright © 2010 Society of Chemical Industry     

番茄调味酱的工艺配方优化

本文在分析不同工艺制备的番茄原浆品质优劣基础上,系统研究了白砂糖、酿造食醋、食盐、变性淀粉对番茄调味酱品质的影响,并采用正交试验方法对番茄调味酱的制备工艺进行优化,以期获得高品质的番茄调味酱产品。研究结果表明,本研究优化获得的番茄调味酱最佳工艺配方为:将超冷破原浆番茄酱25 g、热破原浆番酱25 g、白砂糖8 g、酿造食醋5 g、食盐3 g、变性淀粉3 g、水33 g调配混合,经过高温杀菌灌装而制得番茄调味酱。通过与市售5款番茄调味酱感官评价比较,发现本试验组制备的番茄调味酱感官得分最高(92.2分),表明采用本实验配方制备的番茄调味酱在感官品质上具有一定市场竞争力、能满足消费者口感要求。     

In vitro oral processing of raw tomato: Novel insights into the role of endogenous fruit enzymes

During consumption of fruits, the breakdown of the fruit tissue due to oral processing (chewing, mixing with saliva) may activate or increase the rate of endogenous enzyme activities via the disruption of the cell wall, cellular decompartmentalization, and particle size reduction allowing the enzymes to reach their substrates. The aim of this study was to investigate the activity of one such endogenous fruit enzyme (pectin methylesterase [PME] [E.C. 3.1.1.11]) during in vitro oral processing of raw tomatoes and associated changes in viscosity and microstructure. Oral processing of tomatoes purees was examined in the presence of artificial saliva (AS) at 37°C. in vitro oral processing was followed using immunofluorescence microscopy, apparent viscosity measurements, spectrophotometric, and titrimetric techniques. The results demonstrated that PME had slight but significant activity in the tomato fruit during in vitro oral processing generating methanol as a function of oral processing time, which was further evidenced using immunolabeling techniques to detect methylated pectin epitopes. A significant shear‐thinning behavior of the tomato puree was observed due to dilution and/or endogenous fruit enzyme activity. These results suggest that activity of other fruit enzymes, such as polygalacturonase, which catalyzed the depolymerization of unmethylated pectin chains, might have resulted in a decrease in viscosity, which compensated for the increased potential for gel formation (if any) caused by PME. These interesting insights into the role of endogenous fruit enzymes might pave the way to the understanding of fruit viscosity modification occurring in the mouth and help in rational design of new fruit‐based products.     

Characterization of the Red Layer and Pericarp of Processing Tomato using Magnetic Resonance Imaging

Abstract: The characteristics of tomato pericarp are closely associated with peelabililty, an important quality attribute of processing tomatoes. Different types of tissue exist in the pericarp of tomato. The outermost region of the pericarp, the red layer, is removed with the skin during peeling. This study investigated the morphological features and tissue properties of red layer and pericarp for 3 processing tomato cultivars using magnetic resonance imaging (MRI). The red layer can be visualized in MR images with T₂ weighting, indicating the red layer has different properties compared to the rest of the pericarp region. Tomatoes were imaged with a set of MRI sequences with signal intensity dependent on different water proton properties. Principal component analysis (PCA) of the statistical features revealed clustering of fruit by cultivar. The spatial distribution of cultivars in the PCA score plot followed their rank of peeling performance. MRI demonstrated potential as a nondestructive method to characterize tomato pericarp and evaluate the peelability of processing tomatoes. Practical Application: Peelability of tomatoes affects the quality of value‐added whole peel and diced tomato products. The properties of the pericarp of tomato are directly related to the peelability of tomatoes. MRI provided a fast and nondestructive method to characterize the properties of tomato pericarp. The result of this work gives insight into the correlation between tomato pericarp characteristics and peelability.     

Preparation of High‐Grade Powders from Tomato Paste Using a Vacuum Foam Drying Method

We present a rapid and gentle drying method for the production of high‐grade tomato powders from double concentrated tomato paste, comparing results with powders obtained by foam mat air drying and freeze dried powders. The principle of this method consists of drying tomato paste in foamed state at low temperatures in vacuum. The formulations were dried at temperatures of 50, 60, and 70 °C and vacuum of 200 mbar. Foam stability was affected by low serum viscosity and the presence of solid particles in tomato paste. Consequently, serum viscosity was increased by maltodextrin addition, yielding optimum stability at tomato paste:maltodextrin ratio of 2.4:1 (w/w) in dry matter. Material foamability was improved by addition of 0.5% (w/w, fresh weight) egg white. Because of solid particles in tomato paste, foam air filling had to be limited to critical air volume fraction of Φ = 0.7. The paste was first pre‐foamed to Φ = 0.2 and subsequently expanded in vacuo. After drying to a moisture content of 5.6% to 7.5% wet base (w.b.), the materials obtained were in glassy state. Qualities of the resulting powders were compared with those produced by freeze and air drying. Total color changes were the least after vacuum drying, whereas air drying resulted in noticeable color changes. Vacuum foam drying at 50 °C led to insignificant carotenoid losses, being equivalent to the time‐consuming freeze drying method. In contrast, air drying caused lycopene and β‐carotene losses of 18% to 33% and 14% to 19% respectively. Thus, vacuum foam drying enables production of high‐grade tomato powders being qualitatively similar to powders obtained by freeze drying.     

Particle Size Distribution of Natural Peanut Butter and Its Dynamic Rheological Properties

This study compared the dynamic rheological properties of natural peanut butter with commercial peanut butter at 25°C. The natural peanut butter was produced using ultra-high speed grinding (?20,000 rpm) at different grinding times (2–5 min) from peanuts of China and India. Multimodal particle size distribution was observed for all the samples. The linear viscoelastic region obtained from stress sweep test of the peanut butter produced at 2–3 min fell within the linear viscoelastic region of commercial peanut butter of 0.1–11 Pa. Longer grinding time (3.5–5 min) produced a shorter and lower linear viscoelastic region of 0.03–3 Pa. The storage modulus, G′ is an increasing function of particle size distribution. All peanut butter samples exhibited elastic properties.